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NanoArt is a novel art discipline related to science and technology . It depicts natural or synthetic structures with features sized at the nanometer scale, which are observed by electron or scanning probe microscopy techniques in scientific laboratories. The recorded two or three dimensional images and movies are processed for artistic appeal and presented to the general audience.
One of the aims of NanoArt is to familiarize people with nanoscale objects and advances in their synthesis and manipulation. NanoArt has been presented at traditional art exhibitions around the world. Besides, online competitions have been launched in the 2000s such as the “NANO” 2003 show at Los Angeles County Museum of Art and “Nanomandala”, the 2004 and 2005 installations in New York and Rome by Victoria Vesna and James Gimzewski , [ 1 ] and the regular "Science as Art" section launched at the 2006 Materials Research Society Meeting. [ 2 ] [ 3 ]
A characteristic example of nanoart is A Boy and His Atom , a one-minute stop-motion animated film created in 2012 by IBM Research from 242 images sized by 45×25 nm, which were recorded with a scanning tunneling microscope . The movie tells the story of a boy and a wayward atom who meet and become friends. The film was accepted into the Tribeca Online Film Festival and shown at the New York Tech Meet-up and the World Science Festival.
Earlier in 2007 a book Teeny Ted from Turnip Town was created at the Simon Fraser University in Canada using a gallium -ion beam with a diameter of ~7 nanometers. The book contains 30 silicon -based pages sized by 0.07×0.10 mm; it was published in 100 copies and has an ISBN .
In 2015, Jonty Hurwitz pioneered a new technique for creating nanosculpture using multiphoton lithography and photogrammetry . His work Trust was prepared in collaboration with Karlsruhe Institute of Technology and set a Guinness World Record as the "Smallest Sculpture of a Human Form". [ 4 ] | https://en.wikipedia.org/wiki/Nanoart |
Nanobama is the name of microminiature portraits of United States President Barack Obama . They were created by Professor John Hart of University of Michigan 's Mechanical Engineering department to celebrate the election of Obama. The portrait, which considered the world's smallest presidential portrait, measures 500 μm across (about the size of a period in the average printed text).
The portrait is composed of some 150 million carbon nanotubes representing the number of people who voted for him in the 2009 presidential election. [ 1 ] Each nanotube is 10,000 times smaller than a human hair. [ 2 ] These were grown together on a silicon substrate, with the 3D artwork produced using photolithography . [ 1 ] Hart actually created the portraits before the election's outcome was known, and he let the secret out to the world in early November 2008. There are several Nanobamas extant, but they all reside on a silicon wafer in the professor's office.
Aside from serving as homage to Obama, nanobama was also created to draw attention to the growing capabilities of nanotechnology . According to Hart, the nanotubes are the strongest molecule known to man and, although it has fantastic electrical and thermal properties, effective methods of organizing large numbers of these nanotubes are needed. [ 3 ]
This nanotechnology-related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Nanobama |
A nanobe ( / ˈ n æ n oʊ b , ˈ n eɪ n oʊ b / ) [ 1 ] is a tiny filamental structure first found in some rocks and sediments . Some scientists hypothesize that nanobes are the smallest form of life , 1 / 10 the size of the smallest known bacteria . [ 2 ]
No conclusive evidence exists that these structures are, or are not, living organisms, so their classification is controversial.
The 1996 discovery of nanobes was published in 1998 [ 3 ] by Uwins et al. , [ 4 ] from the University of Queensland , Australia . They were found growing from rock samples (both full-diameter and sidewall cores) of Jurassic and Triassic sandstones, originally retrieved from an unspecified number of oil exploration wells off Australia's west coast. Depths of retrieval were between 3,400 metres (2.1 mi) and 5,100 metres (3.2 mi) below the sea bed. While Uwins et al. [ 3 ] present assertions against it, they do not exclude the possibility that the nanobes are from a surface contaminant, not from the rock units cited.
The smallest are just 20 nanometers in diameter. Some researchers believe that these structures are crystal growths, but the staining of these structures with dyes that bind to DNA might indicate that they are living organisms. [ 5 ]
They are similar to the structures found in ALH84001 , a Mars meteorite found in the Antarctic . A 2022 study concluded that ALH84001 did not contain Martian life; the discovered organic molecules were found to be associated with abiotic processes (ie, "serpentinization and carbonation reactions that occurred during the aqueous alteration of basalt rock by hydrothermal fluids") produced on the very early Mars four billion years ago instead. [ 6 ] [ 7 ]
Nanobes are similar in size to nanobacteria , which are also structures that had been proposed to be extremely small living organisms. However, these two should not be confused: Nanobacteria were thought to be cellular organisms, while nanobes are hypothesized (by some) to be a previously unknown form of life or protocells . [ citation needed ]
A review in Microbes and Environments [ 9 ] of the various ultra-small forms of proposed life states that the main criticism of nanobes is that they appear too small to contain the biochemical machinery needed to sustain life. The review also states that there is no evidence that nanobes are organisms in themselves and not fragments of larger organisms.
Tony Taylor was one of the authors of the original nanobe paper. [ 3 ] He argues that the conspicuous lack of phosphorus in the X-ray spectroscopy data and the failure to find DNA using various DNA amplification techniques demonstrates that nanobes do not have any DNA or RNA. He also argues that they may have a completely different mechanism for heredity, which would account for many of their unusual chemical and physical properties. | https://en.wikipedia.org/wiki/Nanobe |
Nanobiomechanics (also bionanomechanics ) is a field in nanoscience and biomechanics that combines the powerful tools of nanomechanics to explore fundamental science of biomaterials and biomechanics.
Since the introduction by its founder Yuan-Cheng Fung , the field of biomechanics has become one of the branches of mechanics and bioscience. For many years, biomechanics has examined tissue . Through advancements in nanoscience, the scale of the forces that could be measured and also the scale of observation of biomaterials was reduced to "nano" and "pico" level. Consequently, it became possible to measure the mechanical properties of biological materials at nanoscale . This is relevant to improve tissue engineering processes and cellular therapy. [ 1 ]
Most of the biological materials have different hierarchical levels, and the smallest ones refer to the nanoscale. For example, bone has up to seven levels of biological organization , and the smallest level, i.e., single collagen fibril and hydroxylapatite minerals have dimensions well below 100 nm. Therefore, being able to probe properties at this small scales provides a great opportunity for better understanding the fundamental properties of these materials. For example, measurements have shown that nanomechanical heterogeneity exists even within single collagen fibrils as small as 100 nm. [ 2 ]
One of the other most relevant topics in this field is measurement of tiny forces on living cells to recognize changes caused by different diseases , including disease progression. [ 1 ] [ 3 ] For example, it has been shown that red blood cells infected by malaria are 10 times stiffer than normal cells. [ 4 ] Likewise, it has been shown that cancer cells are 70 percent softer than normal cells. [ 3 ] Early signs of aging cartilage and osteoarthritis has been shown by looking at the changes in the tissue at the nanoscale. [ 5 ]
The common methods in nanobiomechanics include atomic force microscopy (AFM), nanoindentation , and application of nanoparticles . [ 6 ] [ 7 ] [ 8 ] These and other methods may be applied to relevant materials, for example: bone [ 6 ] and its hierarchical constituents such as single collagen fibrils, single living cells, actin filaments and microtubules . [ 9 ]
For a description of atomic force microscopy (AFM), see atomic force microscopy .
AFM has been used to study the nanoscale level of the cytoskeleton and its components, the extracellular matrix , and the cell's environment. Understanding the cell's mechanics, including at a nanoscale level, is highly connected to understanding these molecules and structures. As all of this affects how the cell behaves, it is beneficial for tissue engineering. [ 7 ] One example of this is when researchers applied tapping mode AFM to study repair bone from genetically modified mesenchymal cells. Via this method, they were able to image structures in the bone on a nano scale that suggested collagen was present. [ 6 ]
AFM has also been applied to measure the mechanical properties of proteins and other biomolecules in a variety of conditions through extension and compression experiments. [ 10 ] Further, it has been applied to the mapping of cells' and membranes' mechanical properties, mechanotransduction , how cells adhere or detach based on the surface they are on and their own molecules, and the stiffness of cells. [ 7 ]
As metastatic cells have been shown to be softer than benign cells using AFM, the mechanics of cancer cells may be useful to diagnose cancer. [ 11 ] [ 7 ]
For a description of nanoindentation, see nanoindentation .
Nanoindentation has been applied to biomechanical studies. One example studied repair bone from genetically modified mesenchymal cells. They compressed a probe with a nanometer radius into both native and repair bone and used it to study the deformability of the tissue . This gave them insight into mechanical properties of the bone, including its stiffness. Nanoindentation also allowed them to study the bone's compressibility through loading and unloading curves. [ 6 ]
Further, nanoindentation may be combined with other methods in specific studies. One example is AFM nanoindentation, which has been applied to study subcellular components in living cells . [ 1 ]
For a description of nanoparticles, see nanoparticles .
Nanoparticles both affect cells on a nanoscale level, and are one method of studying the mechanical properties of cells and biomaterials on the nanoscale level. Nanoparticles affect how cells adhere to substrates, and the cell's stiffness. They also impact components of the cell's cytoskeleton which in turn affect cell motility as they bind and interact with structures such as receptors and RNA . [ 8 ]
As these nanoparticles affect the nanobiomechanics of cells , they are valuable tools to study them. For example, nanoparticles have been embedded on the surfaces of structures to alter the nanotopographical environment, and affected how the cell behaved. This included how cells spread, how cytoskeletal components assemble, and how cells attach. Some included nanoparticles have magnetic properties , and have been used in conjunction with magnetic fields for detailed control of cellular surfaces and other studies. [ 8 ]
Nanoparticles are useful in studying the ways cells adapt physical forces into biochemical signals, and the mechanical properties of cellular constituents. They have also been used in processes such as particle tracking microrheology . [ 8 ] | https://en.wikipedia.org/wiki/Nanobiomechanics |
Nanobiotechnology , bionanotechnology , and nanobiology are terms that refer to the intersection of nanotechnology and biology . [ 1 ] Given that the subject is one that has only emerged very recently, bionanotechnology and nanobiotechnology serve as blanket terms for various related technologies.
This discipline helps to indicate the merger of biological research with various fields of nanotechnology. Concepts that are enhanced through nanobiology include: nanodevices (such as biological machines ), nanoparticles , and nanoscale phenomena that occurs within the discipline of nanotechnology. This technical approach to biology allows scientists to imagine and create systems that can be used for biological research. Biologically inspired nanotechnology uses biological systems as the inspirations for technologies not yet created. [ 2 ] However, as with nanotechnology and biotechnology , bionanotechnology does have many potential ethical issues associated with it.
The most important objectives that are frequently found in nanobiology involve applying nanotools to relevant medical/biological problems and refining these applications. Developing new tools, such as peptoid nanosheets , for medical and biological purposes is another primary objective in nanotechnology. New nanotools are often made by refining the applications of the nanotools that are already being used. The imaging of native biomolecules , biological membranes , and tissues is also a major topic for nanobiology researchers. Other topics concerning nanobiology include the use of cantilever array sensors and the application of nanophotonics for manipulating molecular processes in living cells. [ 3 ]
Recently, the use of microorganisms to synthesize functional nanoparticles has been of great interest. Microorganisms can change the oxidation state of metals. [ citation needed ] These microbial processes have opened up new opportunities for us to explore novel applications, for example, the biosynthesis of metal nanomaterials. In contrast to chemical and physical methods, microbial processes for synthesizing nanomaterials can be achieved in aqueous phase under gentle and environmentally benign conditions. This approach has become an attractive focus in current green bionanotechnology research towards sustainable development. [ 4 ]
The terms are often used interchangeably. When a distinction is intended, though, it is based on whether the focus is on applying biological ideas or on studying biology with nanotechnology. Bionanotechnology generally refers to the study of how the goals of nanotechnology can be guided by studying how biological "machines" work and adapting these biological motifs into improving existing nanotechnologies or creating new ones. [ 5 ] [ 6 ] Nanobiotechnology, on the other hand, refers to the ways that nanotechnology is used to create devices to study biological systems. [ 7 ]
In other words, nanobiotechnology is essentially miniaturized biotechnology , whereas bionanotechnology is a specific application of nanotechnology. For example, DNA nanotechnology or cellular engineering would be classified as bionanotechnology because they involve working with biomolecules on the nanoscale. Conversely, many new medical technologies involving nanoparticles as delivery systems or as sensors would be examples of nanobiotechnology since they involve using nanotechnology to advance the goals of biology.
The definitions enumerated above will be utilized whenever a distinction between nanobio and bionano is made in this article. However, given the overlapping usage of the terms in modern parlance, individual technologies may need to be evaluated to determine which term is more fitting. As such, they are best discussed in parallel.
Most of the scientific concepts in bionanotechnology are derived from other fields. Biochemical principles that are used to understand the material properties of biological systems are central in bionanotechnology because those same principles are to be used to create new technologies. Material properties and applications studied in bionanoscience include mechanical properties (e.g. deformation, adhesion, failure), electrical/electronic (e.g. electromechanical stimulation, capacitors , energy storage/batteries), optical (e.g. absorption, luminescence , photochemistry ), thermal (e.g. thermomutability, thermal management), biological (e.g. how cells interact with nanomaterials, molecular flaws/defects, biosensing, biological mechanisms such as mechanosensation ), nanoscience of disease (e.g. genetic disease, cancer, organ/tissue failure), as well as biological computing (e.g. DNA computing ) and agriculture (target delivery of pesticides, hormones and fertilizers. [ 8 ] [ 9 ] [ 10 ] [ 11 ] The impact of bionanoscience, achieved through structural and mechanistic analyses of biological processes at nanoscale, is their translation into synthetic and technological applications through nanotechnology.
Nanobiotechnology takes most of its fundamentals from nanotechnology. [ clarification needed ] Most of the devices designed for nano-biotechnological use are directly based on other existing nanotechnologies. [ citation needed ] Nanobiotechnology is often used to describe the overlapping multidisciplinary activities associated with biosensors , particularly where photonics , chemistry, biology, biophysics , nanomedicine , and engineering converge. Measurement in biology using wave guide techniques, such as dual-polarization interferometry , is another example.
Applications of bionanotechnology are extremely widespread. Insofar as the distinction holds, nanobiotechnology is much more commonplace in that it simply provides more tools for the study of biology. Bionanotechnology, on the other hand, promises to recreate biological mechanisms and pathways in a form that is useful in other ways.
Nanomedicine is a field of medical science whose applications are increasing.
The field includes nanorobots and biological machines , which constitute a very useful tool to develop this area of knowledge. In the past years, researchers have made many improvements in the different devices and systems required to develop functional nanorobots – such as motion and magnetic guidance. [ 12 ] [ 13 ] This supposes a new way of treating and dealing with diseases such as cancer; thanks to nanorobots, side effects of chemotherapy could get controlled, reduced and even eliminated, so some years from now, cancer patients could be offered an alternative to treat such diseases instead of chemotherapy, [ citation needed ] which causes secondary effects such as hair loss, fatigue or nausea killing not only cancerous cells but also the healthy ones. Nanobots could be used for various therapies, surgery, diagnosis, and medical imaging [ 14 ] – such as via targeted drug-delivery to the brain (similar to nanoparticles ) and other sites. [ 15 ] [ 16 ] [ 17 ] Programmability for combinations of features such as "tissue penetration, site-targeting, stimuli responsiveness, and cargo-loading" makes such nanobots promising candidates for " precision medicine ". [ 18 ]
At a clinical level, cancer treatment with nanomedicine would consist of the supply of nanorobots to the patient through an injection that will search for cancerous cells while leaving the healthy ones untouched. Patients that are treated through nanomedicine would thereby not notice the presence of these nanomachines inside them; the only thing that would be noticeable is the progressive improvement of their health. [ citation needed ] Nanobiotechnology may be useful for medicine formulation. [ clarification needed ]
"Precision antibiotics" has been proposed to make use of bacteriocin -mechanisms for targeted antibiotics. [ 19 ] [ 20 ]
Nanoparticles are already widely used in medicine. Its applications overlap with those of nanobots and in some cases it may be difficult to distinguish between them. They can be used to for diagnosis and targeted drug delivery , encapsulating medicine. [ 21 ] Some can be manipulated using magnetic fields and, for example, experimentally, remote-controlled hormone release has been achieved this way. [ 22 ]
One example advanced application under development are "Trojan horse" designer-nanoparticles that makes blood cells eat away – from the inside out – portions of atherosclerotic plaque that cause heart attacks [ 23 ] [ 24 ] [ 25 ] and are the current most common cause of death globally . [ 26 ] [ 27 ]
Artificial cells such as synthetic red blood cells that have all or many of the natural cells ' known broad natural properties and abilities could be used to load functional cargos such as hemoglobin , drugs, magnetic nanoparticles , and ATP biosensors which may enable additional non-native functionalities. [ 28 ] [ 29 ]
Nanofibers that mimic the matrix around cells and contain molecules that were engineered to wiggle was shown to be a potential therapy for spinal cord injury in mice. [ 30 ] [ 31 ] [ 32 ]
Technically, gene therapy can also be considered to be a form of nanobiotechnology or to move towards it. [ 33 ] An example of an area of genome editing related developments that is more clearly nanobiotechnology than more conventional gene therapies, is synthetic fabrication of functional materials in tissues. Researcher made C. elegans worms synthesize, fabricate, and assemble bioelectronic materials in its brain cells. They enabled modulation of membrane properties in specific neuron populations and manipulation of behavior in the living animals which might be useful in the study and treatments for diseases such as multiple sclerosis in specific and demonstrates the viability of such synthetic in vivo fabrication. [ 34 ] [ 35 ] [ 36 ] Moreover, such genetically modified neurons may enable connecting external components – such as prosthetic limbs – to nerves. [ 37 ]
Nanosensors based on e.g. nanotubes, nanowires, cantilevers, or atomic force microscopy could be applied to diagnostic devices/sensors [ 21 ]
Nanobiotechnology (sometimes referred to as nanobiology) in medicine may be best described as helping modern medicine progress from treating symptoms to generating cures and regenerating biological tissues .
Three American patients have received whole cultured bladders with the help of doctors who use nanobiology techniques in their practice. Also, it has been demonstrated in animal studies that a uterus can be grown outside the body and then placed in the body in order to produce a baby . Stem cell treatments have been used to fix diseases that are found in the human heart and are in clinical trials in the United States. There is also funding for research into allowing people to have new limbs without having to resort to prosthesis. Artificial proteins might also become available to manufacture without the need for harsh chemicals and expensive machines. It has even been surmised that by the year 2055, computers may be made out of biochemicals and organic salts . [ 38 ]
Another example of current nanobiotechnological research involves nanospheres coated with fluorescent polymers. Researchers are seeking to design polymers whose fluorescence is quenched when they encounter specific molecules. Different polymers would detect different metabolites. The polymer-coated spheres could become part of new biological assays, and the technology might someday lead to particles which could be introduced into the human body to track down metabolites associated with tumors and other health problems . Another example, from a different perspective, would be evaluation and therapy at the nanoscopic level, i.e. the treatment of nanobacteria (25-200 nm sized) as is done by NanoBiotech Pharma. [ citation needed ]
"Nanoantennas" made out of DNA – a novel type of nano-scale optical antenna – can be attached to proteins and produce a signal via fluorescence when these perform their biological functions, in particular for their distinct conformational changes . This could be used for further nanobiotechnology such as various types of nanomachines, to develop new drugs, for bioresearch and for new avenues in biochemistry. [ 39 ] [ 40 ]
It may also be useful in sustainable energy : in 2022, researchers reported 3D-printed nano-"skyscraper" electrodes – albeit micro-scale , the pillars had nano-features of porosity due to printed metal nanoparticle inks – (nanotechnology) that house cyanobacteria for extracting substantially more sustainable bioenergy from their photosynthesis (biotechnology) than in earlier studies. [ 41 ] [ 42 ] [ 43 ] [ 44 ] [ 45 ]
While nanobiology is in its infancy, there are a lot of promising methods that may rely on nanobiology in the future. Biological systems are inherently nano in scale; nanoscience must merge with biology in order to deliver biomacromolecules and molecular machines that are similar to nature. Controlling and mimicking the devices and processes that are constructed from molecules is a tremendous challenge to face for the converging disciplines of nanobiotechnology. [ 46 ] All living things, including humans , can be considered to be nanofoundries . Natural evolution has optimized the "natural" form of nanobiology over millions of years. In the 21st century, humans have developed the technology to artificially tap into nanobiology. This process is best described as "organic merging with synthetic". Colonies of live neurons can live together on a biochip device; according to research from Gunther Gross at the University of North Texas . Self-assembling nanotubes have the ability to be used as a structural system. They would be composed together with rhodopsins ; which would facilitate the optical computing process and help with the storage of biological materials. DNA (as the software for all living things) can be used as a structural proteomic system – a logical component for molecular computing. Ned Seeman – a researcher at New York University – along with other researchers are currently researching concepts that are similar to each other. [ 47 ]
Broadly, bionanotechnology can be distinguished from nanobiotechnology in that it refers to nanotechnology that makes use of biological materials/components – it could in principle or does alternatively use abiotic components. It plays a smaller role in medicine (which is concerned with biological organisms). It makes use of natural or biomimetic systems or elements for unique nanoscale structures and various applications that may not be directionally associated with biology rather than mostly biological applications. In contrast, nanobiotechnology uses biotechnology miniaturized to nanometer size or incorporates nanomolecules into biological systems. In some future applications, both fields could be merged. [ 48 ] [ 49 ] [ 50 ] [ additional citation(s) needed ]
DNA nanotechnology is one important example of bionanotechnology. [ 51 ] The utilization of the inherent properties of nucleic acids like DNA to create useful materials or devices – such as biosensors [ 52 ] – is a promising area of modern research.
DNA digital data storage refers mostly to the use of synthesized but otherwise conventional strands of DNA to store digital data, which could be useful for e.g. high-density long-term data storage [ 53 ] that isn't accessed and written to frequently as an alternative to 5D optical data storage or for use in combination with other nanobiotechnology.
Another important area of research involves taking advantage of membrane properties to generate synthetic membranes. Proteins that self-assemble to generate functional materials could be used as a novel approach for the large-scale production of programmable nanomaterials. One example is the development of amyloids found in bacterial biofilms as engineered nanomaterials that can be programmed genetically to have different properties. [ 54 ]
Lipid nanotechnology is another major area of research in bionanotechnology, where physico-chemical properties of lipids such as their antifouling and self-assembly is exploited to build nanodevices with applications in medicine and engineering. [ 55 ] Lipid nanotechnology approaches can also be used to develop next-generation emulsion methods to maximize both absorption of fat-soluble nutrients and the ability to incorporate them into popular beverages. [ 56 ]
" Memristors " fabricated from protein nanowires of the bacterium Geobacter sulfurreducens which function at substantially lower voltages than previously described ones may allow the construction of artificial neurons which function at voltages of biological action potentials . The nanowires have a range of advantages over silicon nanowires and the memristors may be used to directly process biosensing signals , for neuromorphic computing (see also: wetware computer ) and/or direct communication with biological neurons . [ 57 ] [ 58 ] [ 59 ]
Protein folding studies provide a third important avenue of research, but one that has been largely inhibited by our inability to predict protein folding with a sufficiently high degree of accuracy. Given the myriad uses that biological systems have for proteins, though, research into understanding protein folding is of high importance and could prove fruitful for bionanotechnology in the future. [ citation needed ]
In the agriculture industry, engineered nanoparticles have been serving as nano carriers, containing herbicides, chemicals, or genes, which target particular plant parts to release their content. [ 60 ] [ 61 ]
Previously nanocapsules containing herbicides have been reported to effectively penetrate through cuticles and tissues, allowing the slow and constant release of the active substances. Likewise, other literature describes that nano-encapsulated slow release of fertilizers has also become a trend to save fertilizer consumption and to minimize environmental pollution through precision farming. These are only a few examples from numerous research works which might open up exciting opportunities for nanobiotechnology application in agriculture. Also, application of this kind of engineered nanoparticles to plants should be considered the level of amicability before it is employed in agriculture practices. Based on a thorough literature survey, it was understood that there is only limited authentic information available to explain the biological consequence of engineered nanoparticles on treated plants. Certain reports underline the phytotoxicity of various origin of engineered nanoparticles to the plant caused by the subject of concentrations and sizes . At the same time, however, an equal number of studies were reported with a positive outcome of nanoparticles, which facilitate growth promoting nature to treat plant. [ 62 ] In particular, compared to other nanoparticles, silver and gold nanoparticles based applications elicited beneficial results on various plant species with less and/or no toxicity. [ 63 ] [ 64 ] Silver nanoparticles (AgNPs) treated leaves of Asparagus showed the increased content of ascorbate and chlorophyll. Similarly, AgNPs-treated common bean and corn has increased shoot and root length, leaf surface area, chlorophyll, carbohydrate and protein contents reported earlier. [ 65 ] The gold nanoparticle has been used to induce growth and seed yield in Brassica juncea. [ 66 ]
Nanobiotechnology is used in tissue cultures . [ 67 ] The administration of micronutrients at the level of individual atoms and molecules allows for the stimulation of various stages of development, initiation of cell division , and differentiation in the production of plant material, which must be qualitatively uniform and genetically homogeneous. The use of nanoparticles of zinc (ZnO NPs) and silver (Ag NPs) compounds gives very good results in the micropropagation of chrysanthemums using the method of single-node shoot fragments. [ 67 ]
This field relies on a variety of research methods, including experimental tools (e.g. imaging, characterization via AFM /optical tweezers etc.), x-ray diffraction based tools, synthesis via self-assembly, characterization of self-assembly (using e.g. MP-SPR , DPI , recombinant DNA methods, etc.), theory (e.g. statistical mechanics , nanomechanics, etc.), as well as computational approaches (bottom-up multi-scale simulation , supercomputing ).
As of 2009, the risks of nanobiotechnologies are poorly understood and in the U.S. there is no solid national consensus on what kind of regulatory policy principles should be followed. [ 33 ] For example, nanobiotechnologies may have hard to control effects on the environment or ecosystems and human health. The metal-based nanoparticles used for biomedical prospectives are extremely enticing in various applications due to their distinctive physicochemical characteristics, allowing them to influence cellular processes at the biological level. The fact that metal-based nanoparticles have high surface-to-volume ratios makes them reactive or catalytic. Due to their small size, they are more likely to be able to penetrate biological barriers such as cell membranes and cause cellular dysfunction in living organisms. Indeed, the high toxicity of some transition metals can make it challenging to use mixed oxide NPs in biomedical uses. It triggers adverse effects on organisms, causing oxidative stress, stimulating the formation of ROS, mitochondrial perturbation, and the modulation of cellular functions, with fatal results in some cases. [ 68 ]
Bonin notes that "Nanotechnology is not a specific determinate homogenous entity, but a collection of diverse capabilities and applications" and that nanobiotechnology research and development is – as one of many fields – affected by dual-use problems. [ 69 ] | https://en.wikipedia.org/wiki/Nanobiotechnology |
The nanocar is a molecule designed in 2005 at Rice University by a group headed by Professor James Tour . Despite the name, the original nanocar does not contain a molecular motor , hence, it is not really a car. Rather, it was designed to answer the question of how fullerenes move about on metal surfaces; specifically, whether they roll or slide (they roll).
The molecule consists of an H-shaped 'chassis' with fullerene groups attached at the four corners to act as wheels.
When dispersed on a gold surface, the molecules attach themselves to the surface via their fullerene groups and are detected via scanning tunneling microscopy . One can deduce their orientation as the frame length is a little shorter than its width.
Upon heating the surface to 200 °C the molecules move forward and back as they roll on their fullerene "wheels". The nanocar is able to roll about because the fullerene wheel is fitted to the alkyne "axle" through a carbon-carbon single bond . The hydrogen on the neighboring carbon is no great obstacle to free rotation. When the temperature is high enough, the four carbon-carbon bonds rotate and the car rolls about. Occasionally the direction of movement changes as the molecule pivots. The rolling action was confirmed by Professor Kevin Kelly, also at Rice, by pulling the molecule with the tip of the STM .
The concept of a nanocar built out of molecular "tinkertoys" was first hypothesized by M.T. Michalewicz at the Fifth Foresight Conference on Molecular Nanotechnology (November 1997). [ 2 ] Subsequently, an expanded version was published in Annals of Improbable Research . [ 3 ] These papers were supposed to be a not-so-serious contribution to a fundamental debate on the limits of bottom-up Drexlerian nanotechnology and conceptual limits of how far mechanistic analogies advanced by Eric Drexler could be carried out. The important feature of this nanocar concept was the fact that all molecular component tinkertoys were known and synthesized molecules (alas, some very exotic and only recently discovered, e.g. staffanes , and notably – ferric wheel, 1995), in contrast to some Drexlerian diamondoid structures that were only postulated and never synthesized; and the drive system that was embedded in a ferric wheel and driven by inhomogeneous or time-dependent magnetic field of a substrate – an "engine in a wheel" concept.
The Nanodragster , dubbed the world's smallest hot rod , is a molecular nanocar. [ 1 ] [ 4 ] The design improves on previous nanocar designs and is a step towards creating molecular machines . The name comes from the nanocar's resemblance to a dragster , as its staggered wheel fitment has a shorter axle with smaller wheels in the front and a larger axle with larger wheels in the back.
The nanocar was developed at Rice University’s Richard E. Smalley Institute Nanoscale Science and Technology by the team of James Tour , Kevin Kelly and other colleagues involved in its research. [ 5 ] [ 6 ] The previous nanocar developed was 3 to 4 nanometers which was a little over [the width of?] a strand of DNA and was around 20,000 times thinner than a human hair. [ 7 ] These nanocars were built with carbon buckyballs as their four wheels, and the surface on which they were placed required a temperature of 400 °F (200 °C) to get it moving. On the other hand, a nanocar which utilized p- carborane wheels moves as if sliding on ice, rather than rolling. [ 8 ] Such observations led to the production of nanocars which had both wheel designs.
The nanodragster is 50,000 times thinner than a human hair and has a top speed of 0.014 millimeters per hour (0.0006 in/h or 3.89×10 −9 m/s). [ 4 ] [ 9 ] [ 10 ] The rear wheels are spherical fullerene molecules, or buckyballs, composed of sixty carbon atoms each, which are attracted to a dragstrip that is made up of a very fine layer of gold . This design also enabled Tour’s team to operate the device at lower temperatures.
The nanodragster and other nano-machines are designed for use in transporting items. The technology can be used in manufacturing computer circuits and electronic components, or in conjunction with pharmaceuticals inside the human body. [ 11 ] Tour also speculated that the knowledge gained from the nanocar research would help build efficient catalytic systems in the future.
Kudernac et al. described a specially designed molecule that has four motorized "wheels". By depositing the molecule on a copper surface and providing them with sufficient energy from electrons of a scanning tunnelling microscope they were able to drive some of the molecules in a specific direction, much like a car, being the first single molecule capable to continue moving in the same direction across a surface. Inelastic electron tunnelling induces conformational changes in the rotors and propels the molecule across a copper surface. By changing the direction of the rotary motion of individual motor units, the self-propelling molecular 'four-wheeler' structure can follow random or preferentially linear trajectories. This design provides a starting point for the exploration of more sophisticated molecular mechanical systems, perhaps with complete control over their direction of motion. [ 12 ] This electrically driven nanocar was built under supervision of University of Groningen chemist Bernard L. Feringa , who was awarded the Nobel Prize for Chemistry in 2016 for his pioneering work on nanomotors (together with Jean-Pierre Sauvage and J. Fraser Stoddart ), [ 13 ] and served as inspiration for the development of the next generation of electrically driven nanocars, [ 14 ] some of which were showcased at the Nanocar Race .
A future nanocar with a synthetic molecular motor has been developed by Jean-Francois Morin et al. [ 15 ] It is fitted with carborane wheels and a light-powered helicene synthetic molecular motor. Although the motor moiety displayed unidirectional rotation in solution, light-driven motion on a surface has yet to be observed. Mobility in water and other liquids can be also realized by a molecular propeller in the future. | https://en.wikipedia.org/wiki/Nanocar |
Nanocar Race is an international scientific competition with the aim of testing the performance of getting a large molecule suspended over a solid surface to cover the largest distance with the use of a scanning tunneling microscope .
The first race consisted of overcoming a distance of 100 nanometers and was held for the first time in Toulouse on 28 and 29 April 2017. A second race was held in 2022 with the winners covering multiple hundreds of nanometers.
The idea for the race was formulated by scientists Christian Joachim and Gwénaël Rapenne [ fr ] in Toulouse , France in January 2013 in the ACS Nano journal. [ 1 ] A call for applications was launched to give the participating teams time to prepare appropriate nanocars. [ 1 ] The race is officially announced by the French National Centre for Scientific Research (CNRS) in November 2015 in Toulouse during Futurapolis1. [ 2 ] On this occasion, five teams presented their prototype projects on November 27, 2015. [ 3 ]
The first race in the world of this type, [ 4 ] between four vehicles, started on the 28 April 2017 [ 5 ] at the CEMES-CNRS in Toulouse [ 6 ] and lasted 36 hours. The Toulouse organizers also agreed on the competition of two more vehicles, which will then be remotely controlled via Internet from the CEMES-CNRS race room on the microscope of their own laboratory. These relates to the vehicles from Ohio and Graz-Rice.
The track of the first competition is a gold surface, equipped with grooves to define race lanes in order to avoid losing vehicles. It is about 100 nanometres long, and includes two bends. [ 6 ] It is located in a small enclosure cooled to -269°C under a primary vacuum of 10 −10 mbar and is observed simultaneously by four scanning tunneling microscopes (STM) [ 6 ] miniaturized for this event and operating on the same surface. Each microscope is responsible for driving a single vehicle (a single nanocar).
During this competition, the nanocars should move as far as possible on the gold track during the 36 hours race. Speeds of 5 nanometers per hour were expected. [ 7 ]
Nanocars are a new class of molecular machines that can roll across solid surfaces with structurally defined direction. [ 8 ] They are molecules essentially composed of a few tens or hundreds of hydrogen and carbon atoms and are measuring one to three nanometers .
The nanocar is propelled step by step by electrical impulses and electron transfer from the tip of the STM. The resulting tunnel current flows through the nanocar between the tip of the microscope and the common metal track. There is no direct mechanical contact with the tip. The nanocar is therefore neither pushed nor deformed by the tip of the microscope during the race. Some of the electrons that pass through the nanocar release energy as small intramolecular vibrations that activate the nanocar's motor.
For instance, the NANOHISPA team nanocar was designed with an anthracene-based chassis and four aromatic rings that slightly lift it off the Au(111) surface. The molecule is remotely driven in a controlled manner by its attraction to the STM tip, which arises from the electrical dipole induced by electrons flowing through its molecular structure when a voltage is applied. [ 9 ]
The race on the gold surface was won by the Swiss team that crossed the finish line first after covering a distance of 133 nanometers. [ 10 ]
On the silver surface, the vehicle of the Austrian-American team from Rice University and the University of Graz set the first speed record with a peak speed of 95 nanometers per hour, [ 11 ] and was ranked equally with the Swiss team which raced on the gold surface, given that motion of the same nanocar on silver surfaces are slower than on gold surfaces. [ 12 ] This vehicle was remotely controlled from the Toulouse race hall on the University of Graz microscope. [ citation needed ] Specific properties of the chemical structure as well as a completely new manipulation technique (without time-consuming imaging steps) rendered this nanocar very fast. [ 13 ] These properties even allowed it to complete a distance of more than 1000 nm after completion of the official race track.
The American team from Ohio University turned back for no apparent reason after 20 nanometers, the German team broke 2 vehicles without being able to restart, and the Japanese team ended up giving up. [ 11 ] The French team lost sight of its vehicle on its surface area, and was also obliged to abandon, comforting itself with the symbolic prize of "the most elegant car in the competition". [ 11 ]
Sources: [ 14 ] [ 15 ]
NANOHISPA and NIMS-MANA were both ranked first, both making about 54 turns and covering 678 nm and 1054 nm, respectively. The first demonstrated a change of lane for overpassing while the latter crossed a trench and go back. StrasNanocar ranked third covering 476 nm and performing 28 turns. [ 15 ]
Among the benefits, the CNRS cites the development molecular motors and Tech-Atoms, that will make possible in the future the preparation of quantum electronic circuits on the surface of an insulator, atom by atom, whose calculating parts will measure less than 1 nm. To make this kind of race possible, a considerable number of problems had to be solved beforehand, such as the choice of the track and its preparation, the improvement of monitoring and control devices, in particular the sensitivity of current measurements, the evaporation of a large number of very different molecules on the same surface and microscope validation. [ 16 ] | https://en.wikipedia.org/wiki/Nanocar_Race |
Nanocellulose is a term referring to a family of cellulosic materials that have at least one of their dimensions in the nanoscale . Examples of nanocellulosic materials are microfibrilated cellulose , cellulose nanofibers or cellulose nanocrystals . Nanocellulose may be obtained from natural cellulose fibers through a variety of production processes. This family of materials possesses interesting properties suitable for a wide range of potential applications.
Micro cellulose (MFC) is a type of nanocellulose that is more heterogeneous than cellulose nanofibers or nanocrystals as it contains a mixture of nano- and micron-scale particles. The term is sometimes misused to refer to cellulose nanofibers instead. [ 1 ] [ 2 ]
Cellulose nanofibers (CNF), also called nanofibrillated cellulose (NFC), are nanosized cellulose fibrils with a high aspect ratio (length to width ratio). Typical fibril widths are 5–20 nanometers with a wide range of lengths, typically several micrometers .
The fibrils can be isolated from natural cellulose, generally wood pulp , through high-pressure, high temperature and high velocity impact homogenization , grinding or microfluidization (see manufacture below). [ 3 ] [ 4 ] [ 5 ]
Cellulose nanocrystals (CNCs), or nanocrystalline cellulose (NCC), are highly crystalline , rod-like nanoparticles. [ 6 ] [ 7 ] They are usually covered by negatively charged groups that render them colloidally stable in water. They are typically shorter than CNFs, with a typical length of 100 to 1000 nanometers. [ 8 ]
Some cellulose producing bacteria have also been used to produce nanocellulosic materials that are then referred to as bacterial nanocellulose . [ 9 ] The most common examples being Medusomyces gisevii (the bacteria involved in the making of Kombucha ) and Komagataeibacter xylinus (involve in the fabrication of Nata de coco ), see bacterial cellulose for more details. This naming distinction might arise from the very peculiar morphology of these materials compared to the more traditional ones made of wood or cotton cellulose. In practice, bacterial nanocellulosic materials are often larger than their wood or cotton counterparts.
The discovery of nanocellulosic materials can be traced back to late 1940s studies on the hydrolysis of cellulose fibers. [ 2 ] Eventually it was noticed that cellulose hydrolysis seemed to occur preferentially at some disordered intercrystalline portions of the fibers. [ 10 ] This led to the obtention of colloidally stable and highly crystalline nanorods particles. [ 11 ] [ 12 ] [ 13 ] These particles were first referred to as micelles, before being given multiple names including cellulose nanocrystals (CNCs), nanocrystalline cellulose (NCC), or cellulose (nano)whiskers , though this last term is less used today. [ 2 ] Later studies by O. A. Battista showed that in milder hydrolysis conditions, the crystalline nanorods stay aggregated as micron size objects. [ 14 ] [ 15 ] This material was later referred to as microcrystalline cellulose (MCC) and commercialised under the name Avicel by FMC Corporation . [ 16 ]
Microfibrillated cellulose (MFC) was discovered later, in the 1980s, by Turbak, Snyder and Sandberg at the ITT Rayonier labs in Shelton , Washington. [ 17 ] [ 18 ] [ 19 ] This terminology was used to describe a gel-like material prepared by passing wood pulp through a Gaulin type milk homogenizer at high temperatures and high pressures followed by ejection impact against a hard surface. In later work, F. W. Herrick at ITT Rayonier Eastern Research Division (ERD) Lab in Whippany also published work on making a dry powder form of the gel. [ 20 ] [ 19 ] Rayonier, as a company, never pursued scale-up and gave free license to whoever wanted to pursue this new use for cellulose. [ citation needed ] Rather, Turbak et al. pursued 1) finding new uses for the MFC, including using as a thickener and binder in foods, cosmetics, paper formation, textiles, nonwovens, etc. and 2) evaluate swelling and other techniques for lowering the energy requirements for MFC production. [ 21 ] The first MFC pilot production plant of MFC was established in 2010 by Innventia AB (Sweden). [ 22 ]
Nanocellulose materials can be prepared from any natural cellulose source including wood , cotton , agricultural [ 23 ] or household wastes, [ 24 ] algae , [ 25 ] bacteria or tunicate . Wood , in the form of wood pulp is currently the most commonly used starting material for the industrial production of nanocellulosic materials.
Nanocellulose fibrils (MFC and CNFs) may be isolated from the cellulose fibers using mechanical methods that expose the fibers to high shear forces, delaminating them into nano-fibers. For this purpose, high-pressure homogenizers, grinders or microfluidizers can be used. [ citation needed ] This process consumes very large amounts of energy and values over 30 MWh/ tonne are not uncommon. [ citation needed ]
To address this problem, sometimes enzymatic/mechanical pre-treatments and introduction of charged groups for example through carboxymethylation or TEMPO-mediated oxidation are used. [ 26 ] These pre-treatments can decrease energy consumption below 1 MWh/tonne. [ citation needed ] "Nitro-oxidation" has been developed to prepare carboxycellulose nanofibers directly from raw plant biomass. Owing to fewer processing steps to extract nanocellulose, the nitro-oxidation method has been found to be a cost-effective, less-chemically oriented and efficient method to extract carboxycellulose nanofibers. [ 27 ] [ 28 ] Functionalized nanofibers obtained using nitro-oxidation have been found to be an excellent substrate to remove heavy metal ion impurities such as lead , [ 29 ] cadmium , [ 30 ] and uranium . [ 31 ]
A chemo-mechanical process for production of nanocellulose from cotton linters has been demonstrated with a capacity of 10 kg per day. [ 32 ]
Cellulose nanocrystals (CNC) are formed by the acid hydrolysis of native cellulose fibers, most commonly using sulfuric or hydrochloric acid . Disordered sections of native cellulose are hydrolysed and after careful timing, the remaining crystalline sections can be retrieved from the acid solution by centrifugation and dialysis against water. Their final dimensions depend on the cellulose source, its history, the hydrolysis conditions and the purification procedures. [ 33 ] CNCs are commercialised by various companies that use different sources and processes, leading to a range of available products. [ 34 ] [ 35 ]
Spherical shaped carboxycellulose nanoparticles prepared by nitric acid - phosphoric acid treatment are stable in dispersion in its non-ionic form. [ 36 ]
The ultrastructure of nanocellulose derived from various sources has been extensively studied. Techniques such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM), wide angle X-ray scattering (WAXS), small incidence angle X-ray diffraction and solid state 13 C cross-polarization magic angle spinning (CP/MAS), nuclear magnetic resonance (NMR) and spectroscopy have been used to characterize typically dried nanocellulose morphology. [ citation needed ]
A combination of microscopic techniques with image analysis can provide information on fibril widths, it is more difficult to determine fibril lengths, because of entanglements and difficulties in identifying both ends of individual nanofibrils. [ 37 ] [ 38 ] Also, nanocellulose suspensions may not be homogeneous and can consist of various structural components, including cellulose nanofibrils and nanofibril bundles. [ 39 ]
In a study of enzymatically pre-treated nanocellulose fibrils in a suspension the size and size-distribution were established using cryo-TEM. The fibrils were found to be rather mono-dispersed mostly with a diameter of ca. 5 nm although occasionally thicker fibril bundles were present. [ 40 ] By combining ultrasonication with an "oxidation pretreatment", cellulose microfibrils with a lateral dimension below 1 nm has been observed by AFM. The lower end of the thickness dimension is around 0.4 nm, which is related to the thickness of a cellulose monolayer sheet. [ 41 ]
Aggregate widths can be determined by CP/MAS NMR developed by Innventia AB , Sweden, which also has been demonstrated to work for nanocellulose (enzymatic pre-treatment). An average width of 17 nm has been measured with the NMR-method, which corresponds well with SEM and TEM. Using TEM, values of 15 nm have been reported for nanocellulose from carboxymethylated pulp. However, thinner fibrils can also be detected. Wågberg et al. reported fibril widths of 5–15 nm for a nanocellulose with a charge density of about 0.5 meq./g. [ 42 ] The group of Isogai reported fibril widths of 3–5 nm for TEMPO-oxidized cellulose having a charge density of 1.5 meq./g. [ 43 ]
Pulp chemistry has a significant influence on nanocellulose microstructure. Carboxymethylation increases the numbers of charged groups on the fibril surfaces, making the fibrils easier to liberate and results in smaller and more uniform fibril widths (5–15 nm) compared to enzymatically pre-treated nanocellulose, where the fibril widths were 10–30 nm. [ 44 ] The degree of crystallinity and crystal structure of nanocellulose. Nanocellulose exhibits cellulose crystal I organization and the degree of crystallinity is unchanged by the preparation of the nanocellulose. Typical values for the degree of crystallinity were around 63%. [ 44 ]
The rheology of nanocellulose dispersions has been investigated. [ 45 ] [ 40 ] and revealed that the storage and loss modulus were independent of the angular frequency at all nanocellulose concentrations between 0.125% to 5.9%. The storage modulus values are particularly high (104 Pa at 3% concentration) [ 40 ] compared to results for CNCs (102 Pa at 3% concentration). [ 45 ] There is also a strong concentration dependence as the storage modulus increases 5 orders of magnitude if the concentration is increased from 0.125% to 5.9%. Nanocellulose gels are also highly shear thinning (the viscosity is lost upon introduction of the shear forces). The shear-thinning behaviour is particularly useful in a range of different coating applications. [ 40 ]
It is pseudo-plastic and exhibits thixotropy , the property of certain gels or fluids that are thick (viscous) under normal conditions, but become less viscous when shaken or agitated. When the shearing forces are removed the gel regains much of its original state.
Crystalline cellulose has a stiffness about 140–220 GPa, comparable with that of Kevlar and better than that of glass fiber, both of which are used commercially to reinforce plastics. Films made from nanocellulose have high strength (over 200 MPa ), high stiffness (around 20 GPa ) [ 46 ] but lack of high strain [ clarification needed ] (12%). Its strength/weight ratio is 8 times that of stainless steel. [ 47 ] Fibers made from nanocellulose have high strength (up to 1.57 GPa) and stiffness (up to 86 GPa). [ 48 ]
In semi-crystalline polymers, the crystalline regions are considered to be gas impermeable. Due to relatively high crystallinity, [ 44 ] in combination with the ability of the nanofibers to form a dense network held together by strong inter-fibrillar bonds (high cohesive energy density), it has been suggested that nanocellulose might act as a barrier material. [ 43 ] [ 49 ] [ 50 ] Although the number of reported oxygen permeability values are limited, reports attribute high oxygen barrier properties to nanocellulose films. One study reported an oxygen permeability of 0.0006 (cm 3 μm)/(m 2 day kPa) for a ca. 5 μm thin nanocellulose film at 23 °C and 0% RH. [ 49 ] In a related study, a more than 700-fold decrease in oxygen permeability of a polylactide (PLA) film when a nanocellulose layer was added to the PLA surface was reported. [ 43 ]
The influence of nanocellulose film density and porosity on film oxygen permeability has been explored. [ 51 ] Some authors have reported significant porosity in nanocellulose films, [ 52 ] [ 46 ] [ 53 ] which seems to be in contradiction with high oxygen barrier properties, whereas Aulin et al. [ 49 ] measured a nanocellulose film density close to density of crystalline cellulose (cellulose Iß crystal structure, 1.63 g/cm 3 ) [ 54 ] indicating a very dense film with a porosity close to zero.
Changing the surface functionality of the cellulose nanoparticle can also affect the permeability of nanocellulose films. Films constituted of negatively charged CNCs could effectively reduce permeation of negatively charged ions, while leaving neutral ions virtually unaffected. Positively charged ions were found to accumulate in the membrane. [ 55 ]
Multi-parametric surface plasmon resonance is one of the methods to study barrier properties of natural, modified or coated nanocellulose. The different antifouling, moisture, solvent, antimicrobial barrier formulation quality can be measured on the nanoscale. The adsorption kinetics as well as the degree of swelling can be measured in real-time and label-free. [ 56 ] [ 57 ]
Owed to their anisotropic shape and surface charge, nanocelluloses (mostly rigid CNCs) have a high excluded volume and self-assemble into cholesteric liquid crystals beyond a critical volume fraction. [ 58 ] Nanocellulose liquid crystals are left-handed due to the right-handed twist on particle level. [ 59 ] Nanocellulose phase behavior is susceptible to ionic charge screening . An increase in ionic strength induces the arrest of nanocellulose dispersions into attractive glasses. [ 60 ] At further increasing ionic strength, nanocelluloses aggregate into hydrogels . [ 61 ] The interactions within nanocelluloses are weak and reversible, wherefore nanocellulose suspensions and hydrogels are self-healing and may be applied as injectable materials [ 62 ] or 3D printing inks. [ 63 ]
Nanocellulose can also be used to make aerogels /foams, either homogeneously or in composite formulations. Nanocellulose-based foams are being studied for packaging applications in order to replace polystyrene -based foams. Svagan et al. showed that nanocellulose has the ability to reinforce starch foams by using a freeze-drying technique. [ 64 ] The advantage of using nanocellulose instead of wood-based pulp fibers is that the nanofibrils can reinforce the thin cells in the starch foam. Moreover, it is possible to prepare pure nanocellulose aerogels applying various freeze-drying and super critical CO 2 drying techniques. Aerogels and foams can be used as porous templates. [ 65 ] [ 66 ] Tough ultra-high porosity foams prepared from cellulose I nanofibril suspensions were studied by Sehaqui et al. a wide range of mechanical properties including compression was obtained by controlling density and nanofibril interaction in the foams. [ 67 ] CNCs could also be made to gel in water under low power sonication giving rise to aerogels with the highest reported surface area (>600m2/g) and lowest shrinkage during drying (6.5%) of cellulose aerogels. [ 66 ] In another study by Aulin et al., [ 68 ] the formation of structured porous aerogels of nanocellulose by freeze-drying was demonstrated. The density and surface texture of the aerogels was tuned by selecting the concentration of the nanocellulose dispersions before freeze-drying. Chemical vapour deposition of a fluorinated silane was used to uniformly coat the aerogel to tune their wetting properties towards non-polar liquids/oils. The authors demonstrated that it is possible to switch the wettability behaviour of the cellulose surfaces between super-wetting and super-repellent, using different scales of roughness and porosity created by the freeze-drying technique and change of concentration of the nanocellulose dispersion. Structured porous cellulose foams can however also be obtained by utilizing the freeze-drying technique on cellulose generated by Gluconobacter strains of bacteria, which bio-synthesize open porous networks of cellulose fibers with relatively large amounts of nanofibrils dispersed inside. Olsson et al. [ 69 ] demonstrated that these networks can be further impregnated with metalhydroxide/oxide precursors, which can readily be transformed into grafted magnetic nanoparticles along the cellulose nanofibers. The magnetic cellulose foam may allow for a number of novel applications of nanocellulose and the first remotely actuated magnetic super sponges absorbing 1 gram of water within a 60 mg cellulose aerogel foam were reported. Notably, these highly porous foams (>98% air) can be compressed into strong magnetic nanopapers, which may find use as functional membranes in various applications.
Nanocelluloses can stabilize emulsions and foams by a Pickering mechanism, i.e. they adsorb at the oil-water or air-water interface and prevent their energetic unfavorable contact. Nanocelluloses form oil-in-water emulsions with a droplet size in the range of 4-10 μm that are stable for months and can resist high temperatures and changes in pH. [ 70 ] [ 71 ] Nanocelluloses decrease the oil-water interface tension [ 72 ] and their surface charge induces electrostatic repulsion within emulsion droplets. Upon salt-induced charge screening the droplets aggregate but do not undergo coalescence , indicating strong steric stabilization. [ 73 ] The emulsion droplets even remain stable in the human stomach and resist gastric lipolysis , thereby delaying lipid absorption and satiation. [ 74 ] [ 75 ] In contrast to emulsions, native nanocelluloses are generally not suitable for the Pickering stabilization of foams, which is attributed to their primarily hydrophilic surface properties that results in an unfavorable contact angle below 90° (they are preferably wetted by the aqueous phase). [ 76 ] Using hydrophobic surface modifications or polymer grafting, the surface hydrophobicity and contact angle of nanocelluloses can be increased, allowing also the Pickering stabilization of foams. [ 77 ] By further increasing the surface hydrophobicity, inverse water-in-oil emulsions can be obtained, which denotes a contact angle higher than 90°. [ 78 ] [ 79 ] It was further demonstrated that nanocelluloses can stabilize water-in-water emulsions in presence of two incompatible water-soluble polymers. [ 80 ]
A bottom up approach can be used to create a high-performance bulk material with low density, high strength and toughness, and great thermal dimensional stability: cellulose nanofiber plate (CNFP). Cellulose nanofiber hydrogel is created by biosynthesis. The hydrogels can then be treated with a polymer solution or by surface modification and then are hot-pressed at 80 °C. The result is bulk material with excellent machinability. “The ultrafine nanofiber network structure in CNFP results in more extensive hydrogen bonding, the high in-plane orientation, and “three way branching points” of the microfibril networks”. [ 81 ] This structure gives CNFP its high strength by distributing stress and adding barriers to crack formation and propagation. The weak link in this structure is bond between the pressed layers which can lead to delamination. To reduce delamination, the hydrogel can be treated with silicic acid , which creates strong covalent cross-links between layers during hot pressing. [ 81 ]
The surface modification of nanocellulose is currently receiving a large amount of attention. [ 82 ] Nanocellulose displays a high concentration of hydroxyl groups at the surface which can be reacted. However, hydrogen bonding strongly affects the reactivity of the surface hydroxyl groups. In addition, impurities at the surface of nanocellulose such as glucosidic and lignin fragments need to be removed before surface modification to obtain acceptable reproducibility between different batches. [ 83 ]
Processing of nanocellulose does not cause significant exposure to fine particles during friction grinding or spray drying. No evidence of inflammatory effects or cytotoxicity on mouse or human macrophages can be observed after exposure to nanocellulose. The results of toxicity studies suggest that nanocellulose is not cytotoxic and does not cause any effects on inflammatory system in macrophages. In addition, nanocellulose is not acutely toxic to Vibrio fischeri in environmentally relevant concentrations. [ 84 ]
Despite intensified research on oral food or pharmaceutical formulations containing nanocelluloses they are not generally recognized as safe . Nanocelluloses were demonstrated to exhibit limited toxicity and oxidative stress in in vitro intestinal epithelium [ 85 ] [ 86 ] [ 87 ] or animal models. [ 88 ] [ 89 ] [ 90 ]
The properties of nanocellulose (e.g. mechanical properties, film-forming properties, viscosity etc.) makes it an interesting material for many applications. [ 91 ]
In the area of paper and paperboard manufacture, nanocelluloses are expected to enhance the fiber-fiber bond strength and, hence, have a strong reinforcement effect on paper materials. [ 94 ] [ 95 ] [ 96 ] Nanocellulose may be useful as a barrier in grease-proof type of papers and as a wet-end additive to enhance retention, dry and wet strength in commodity type of paper and board products. [ 97 ] [ 98 ] [ 99 ] [ 100 ] It has been shown that applying CNF as a coating material on the surface of paper and paperboard improves the barrier properties, especially air resistance [ 101 ] and grease/oil resistance. [ 101 ] [ 102 ] [ 97 ] It also enhances the structure properties of paperboards (smoother surface). [ 103 ] Very high viscosity of MFC/CNF suspensions at low solids content limits the type of coating techniques that can be utilized to apply these suspensions onto paper/paperboard. Some of the coating methods utilized for MFC surface application onto paper/paperboard have been rod coating, [ 98 ] size press, [ 102 ] spray coating, [ 104 ] foam coating [ 105 ] and slot-die coating. [ 101 ] Wet-end surface application of mineral pigments and MFC mixture to improve barrier, mechanical and printing properties of paperboard are also being explored. [ 106 ]
Nanocellulose can be used to prepare flexible and optically transparent paper. Such paper is an attractive substrate for electronic devices because it is recyclable, compatible with biological objects, and easily biodegrades . [ 93 ]
As described above the properties of the nanocellulose makes an interesting material for reinforcing plastics. Nanocellulose can be spun into filaments that are stronger and stiffer than spider silk. [ 48 ] [ 107 ] Nanocellulose has been reported to improve the mechanical properties of thermosetting resins, starch -based matrixes, soy protein , rubber latex , poly(lactide) . Hybrid cellulose nanofibrils-clay minerals composites present interesting mechanical, gas barrier and fire retardancy properties. [ 108 ] The composite applications may be for use as coatings and films, [ 109 ] paints, foams, packaging.
Nanocellulose can be used as a low calorie replacement for carbohydrate additives used as thickeners, flavour carriers, and suspension stabilizers in a wide variety of food products. [ 110 ] It is useful for producing fillings, crushes, chips, wafers, soups, gravies, puddings etc. The food applications arise from the rheological behaviour of the nanocellulose gel.
Applications in this field include: super water absorbent material (e.g. for incontinence pads material), nanocellulose used together with super absorbent polymers, nanocellulose in tissue, non-woven products or absorbent structures and as antimicrobial films. [ citation needed ]
Nanocellulose has potential applications in the general area of emulsion and dispersion applications in other fields. [ 111 ] [ 112 ]
The use of nanocellulose in cosmetics and pharmaceuticals has been suggested:
Nanocellulose can pave the way for a new type of "bio-based electronics" where interactive materials are mixed with nanocellulose to enable the creation of new interactive fibers, films, aerogels, hydrogels and papers. [ 114 ] E.g. nanocellulose mixed with conducting polymers such as PEDOT:PSS show synergetic effects resulting in extraordinary [ 115 ] mixed electronic and ionic conductivity, which is important for energy storage applications. Filaments spun from a mix of nanocellulose and carbon nanotubes show good conductivity and mechanical properties. [ 116 ] Nanocellulose aerogels decorated with carbon nanotubes can be constructed into robust compressible 3D supercapacitor devices. [ 117 ] [ 118 ] Structures from nanocellulose can be turned into bio-based triboelectric generators [ 119 ] and sensors .
In April 2013 breakthroughs in nanocellulose production, by algae, were announced at an American Chemical Society conference, by speaker R. Malcolm Brown, Jr., Ph.D, who has pioneered research in the field for more than 40 years, spoke at the First International Symposium on Nanocellulose, part of the American Chemical Society meeting. Genes from the family of bacteria that produce vinegar, Kombucha tea and nata de coco have become stars in a project — which scientists said has reached an advanced stage - that would turn algae into solar-powered factories for producing the “wonder material” nanocellulose. [ 9 ]
Cellulose nanocrystals have shown the possibility to self organize into chiral nematic structures [ 120 ] with angle-dependent iridescent colours. It is thus possible to manufacture totally bio-based pigments and glitters , films including sequins having a metallic glare and a small footprint compared to fossil-based alternatives.
Nano chitin is similar in its nanostructure to cellulose nanocrystals but extracted from chitin. | https://en.wikipedia.org/wiki/Nanocellulose |
Nanochannel glass materials are an experimental mask technology that is an alternate method for fabricating nanostructures , although optical lithography is the predominant patterning technique. [ 1 ]
Nanochannel glass materials are complex glass structures containing large numbers of parallel hollow channels. In its simplest form, the hollow channels are arranged in geometric arrays with packing densities as great as 10 11 channels/cm 2 . Channel dimensions are controllable from micrometers to tens of nanometers, while retaining excellent channel uniformity. Exact replicas of the channel glass can be made from a variety of materials. This is a low cost method for creating identical structures with nanoscale features in large numbers. [ 2 ] [ 3 ]
These materials have high density of uniform channels with diameters from 15 micrometres to 15 nanometers. These are rigid structures with serviceable temperatures to at least 300 °C, with potential up to 1000 °C. Furthermore, these are optically transparent photonic structures with high degree of reproducibility.
The materials can be fabricated using methods in nanolithography such as electron beam lithography (EBL), focused ion beam (FIB), and nanoimprint lithography (NIL). [ 4 ] [ irrelevant citation ] [ 5 ] [ irrelevant citation ]
These can be used as a material for chromatographic columns , unidirectional conductors , Microchannel plate and nonlinear optical devices . They are used in sensors for chemical and biological processes. [ 6 ] [ irrelevant citation ] Other uses are as masks for semiconductor development, including ion implantation, optical lithography, and reactive ion etching . [ 2 ] [ 3 ] [ 7 ] | https://en.wikipedia.org/wiki/Nanochannel_glass_materials |
Nanochemistry is an emerging sub-discipline of the chemical and material sciences that deals with the development of new methods for creating nanoscale materials. [ 1 ] The term "nanochemistry" was first used by Ozin in 1992 as 'the uses of chemical synthesis to reproducibly afford nanomaterials from the atom "up", contrary to the nanoengineering and nanophysics approach that operates from the bulk "down"'. [ 2 ] Nanochemistry focuses on solid-state chemistry that emphasizes synthesis of building blocks that are dependent on size, surface, shape, and defect properties, rather than the actual production of matter. Atomic and molecular properties mainly deal with the degrees of freedom of atoms in the periodic table. However, nanochemistry introduced other degrees of freedom that controls material's behaviors by transformation into solutions. [ 3 ] Nanoscale objects exhibit novel material properties, largely as a consequence of their finite small size. Several chemical modifications on nanometer-scaled structures approve size dependent effects. [ 2 ]
Nanochemistry is used in chemical, materials and physical science as well as engineering, biological, and medical applications. Silica , gold , polydimethylsiloxane , cadmium selenide , iron oxide , and carbon are materials that show its transformative power. Nanochemistry can make the most effective contrast agent of MRI out of iron oxide (rust) which can detect cancers and kill them at their initial stages. [ 4 ] Silica (glass) can be used to bend or stop lights in their tracks. [ 5 ] Developing countries also use silicone to make circuits for the fluids used in pathogen detection. [ 6 ] Nano-construct synthesis leads to the self-assembly of the building blocks into functional structures that may be useful for electronic, photonic , medical, or bioanalytical problems. Nanochemical methods can be used to create carbon nanomaterials such as carbon nanotubes , graphene , and fullerenes which have gained attention in recent years due to their remarkable mechanical and electrical properties. [ 7 ]
One of the first scientific reports is the colloidal gold particles synthesized by Michael Faraday as early as 1857. By the early 1940’s, precipitated and fumed silica nanoparticles were being manufactured and sold in USA and Germany as substitutes for ultrafine carbon black for rubber reinforcements. [ 8 ]
Over the past two decades, iron oxide nanoparticles for biomedical use had increased dramatically, largely due to its ability of non-invasive imaging, targeting and triggering drug release, or cancer therapy. Stem or immune cell could be marked with iron oxide nanoparticles to be detected by Magnetic resonance imaging (MRI). However, the concentration of iron oxide nanoparticles needs to be high enough to enable the significant detection by MRI. [ 4 ] Due to the limited understanding of physicochemical nature of iron oxide nanoparticles in biological systems, more research is needed to ensure nanoparticles can be controlled under certain conditions for medical usage without posing harm to humans. [ 9 ]
Emerging methods of drug delivery involving nanotechnological methods can be useful by improving bodily response, specific targeting, and non-toxic metabolism. Many nanotechnological methods and materials can be functionalized for drug delivery. Ideal materials employ a controlled-activation nanomaterial to carry a drug cargo into the body. Mesoporous silica nanoparticles (MSN) have increased in research popularity due to their large surface area and flexibility for various individual modifications while maintaining high-resolution performance under imaging techniques. [ 10 ] Activation methods greatly vary across nanoscale drug delivery molecules, but the most commonly used activation method uses specific wavelengths of light to release the cargo. Nanovalve-controlled cargo release uses low-intensity light and plasmonic heating to release the cargo in a variation of MSN containing gold molecules. [ 11 ] The two-photon activated photo-transducer (2-NPT) uses near infrared wavelengths of light to induce the breaking of a disulfide bond to release the cargo. [ 12 ] Recently, nanodiamonds have demonstrated potential in drug delivery due to non-toxicity, spontaneous absorption through the skin, and the ability to enter the blood–brain barrier .
The unique structure of carbon nanotubes also gives rise to many innovative inventions of new medical methods. As more medicine is made at the nano level to revolutionize the ways for human to detect and treat diseases, carbon nanotubes become a stronger candidate in new detection methods [ 13 ] and therapeutic strategies. [ 14 ] Specially, carbon nanotubes can be transformed into sophisticated biomolecule and allow its detection through changes in the carbon nanotube fluorescence spectra. [ 15 ] Also, carbon nanotubes can be designed to match the size of small drug and endocitozed by a target cell, hence becoming a delivery agent. [ 16 ]
Cells are very sensitive to nanotopographical features, so optimization of surfaces in tissue engineering has pushed towards implantation. Under appropriate conditions, a carefully crafted 3-dimensional scaffold is used to direct cell seeds toward artificial organ growth. The 3-D scaffold incorporates various nanoscale factors that control the environment for optimal and appropriate functionality. [ 17 ] The scaffold is an analog of the in vivo extracellular matrix in vitro , allowing for successful artificial organ growth by providing the necessary, complex biological factors in vitro .
For abrasions and wounds, nanochemistry has demonstrated applications in improving the healing process. Electrospinning is a polymerization method used biologically in tissue engineering but can also be used for wound dressing and drug delivery. This produces nanofibers that encourage cell proliferation , antibacterial properties, in controlled environment. [ 18 ] These properties appear macroscopically, however, nanoscale versions may show improved efficiency due to nanotopographical features. Targeted interfaces between nanofibers and wounds have higher surface area interactions and are advantageous in vivo . [ 19 ] There is evidence that certain nanoparticles of silver are useful to inhibit some viruses and bacteria . [ 20 ]
Materials in certain cosmetics such as sun cream, moisturizer, and deodorant may have potential benefits from the use of nanochemistry. Manufacturers are working to increase the effectiveness of various cosmetics by facilitating oil nanoemulsion. [ 21 ] These particles have extended the boundaries in managing wrinkling, dehydrated, and inelastic skin associated with aging. In sunscreen , titanium dioxide and zinc oxide nanoparticles prove to be effective UV filters but can also penetrate through skin. [ 22 ] These chemicals protect the skin against harmful UV light by absorbing or reflecting the light and prevent the skin from retaining full damage by photoexcitation of electrons in the nanoparticle. [ 23 ]
Scientists have devised a large number of nanowire compositions with controlled length, diameter, doping, and surface structure by using vapor and solution phase strategies. These oriented single crystals are being used in semiconductor nanowire devices such as diodes , transistors , logic circuits , lasers , and sensors. Since nanowires have a one-dimensional structure, meaning a large surface-to-volume ratio, the diffusion resistance decreases. In addition, their efficiency in electron transport which is due to the quantum confinement effect, makes their electrical properties be influenced by minor perturbation. [ 24 ] Therefore, the use of these nanowires in nanosensor elements increases the sensitivity in electrode response. As mentioned above, the one-dimensionality and chemical flexibility of the semiconductor nanowires make them applicable in nanolasers. Peidong Yang and his co-workers have done some research on the room-temperature ultraviolet nanowires used in nanolasers. They have concluded that using short wavelength nanolasers has applications in different fields such as optical computing, information storage, and microanalysis. [ 25 ]
The small size of nanoenzymes (or nanozymes) (1–100 nm) has provided them with unique optical, magnetic, electronic, and catalytic properties. [ 26 ] Moreover, the control of surface functionality of nanoparticles and the predictable nanostructure of these small-sized enzymes have allowed them to create a complex structure on their surface that can meet the needs of specific applications [ 27 ]
Fluorescent nanoparticles are highly sought after. They have broad applications, but their use in macroscopic arrays allows them efficient in applications of plasmonics , photonics , and quantum communications. While there are many methods in assembling nanoparticles array, especially gold nanoparticles , they tend to be weakly bonded to their substrate so they can't be used for wet chemistry processing steps or lithography . Nanodiamonds allow for greater variability in access that can subsequently be used to couple plasmonic waveguides to realize quantum plasmonic circuitry .
Nanodiamonds can be synthesized by employing nanoscale carbonaceous seeds created in a single step by using a mask-free electron beam-induced position technique to add amine groups. This assembles nanodiamonds into an array. The presence of dangling bonds at the nanodiamond surface allows them to be functionalized with a variety of ligands . The surfaces of these nanodiamonds are terminated with carboxylic acid groups, enabling their attachment to amine-terminated surfaces through carbodiimide coupling chemistry. [ 28 ] This process affords a high yield that relies on covalent bonding between the amine and carboxyl functional groups on amorphous carbon and nanodiamond surfaces in the presence of EDC. Thus unlike gold nanoparticles, they can withstand processing and treatment, for many device applications.
Fluorescent properties in nanodiamonds arise from the presence of nitrogen-vacancy (NV) centers, nitrogen atoms next to a vacancy. Fluorescent nanodiamond (FND) was invented in 2005 and has since been used in various fields of study. [ 29 ] The invention received a US patent in 2008 States7326837 B2 United States 7326837 B2 , Chau-Chung Han; Huan-Cheng Chang & Shen-Chung Lee et al., "Clinical applications of crystalline diamond particles", issued February 5, 2008, assigned to Academia Sinica, Taipei (TW) , and a subsequent patent in 2012 States8168413 B2 United States 8168413 B2 , Huan-Cheng Chang; Wunshian Fann & Chau-Chung Han, "Luminescent Diamond Particles", issued May 1, 2012, assigned to Academia Sinica, Taipei (TW) . NV centers can be created by irradiating nanodiamonds with high-energy particles (electrons, protons, helium ions), followed by vacuum-annealing at 600–800°C. Irradiation forms vaccines in the diamond structure while vacuum-annealing migrates these vacancies, which will get trapped by nitrogen atoms within the nanodiamond. This process produces two types of NV centers. Two types of NV centers are formed—neutral (NV0) and negatively charged (NV–)—and these have different emission spectra. The NV– the center is of particular interest because it has an S = 1 spin ground state that can be spin-polarized by optical pumping and manipulated using electron paramagnetic resonance. [ 30 ] Fluorescent nanodiamonds combine the advantages of semiconductor quantum dots (small size, high photostability, bright multicolor fluorescence) with biocompatibility, non-toxicity, and rich surface chemistry, which means that they have the potential to revolutionize Vivo imaging applications. [ 31 ]
Nanodiamonds can self-assemble and a wide range of small molecules, proteins antibodies, therapeutics, and nucleic acids can bind to its surface allowing for drug delivery, protein-mimicking, and surgical implants. Other potential biomedical applications are the use of nanodiamonds as support for solid-phase peptide synthesis and as sorbents for detoxification and separation and fluorescent nanodiamonds for biomedical imaging. Nanodiamonds are capable of biocompatibility, the ability to carry a broad range of therapeutics, dispersibility in water and scalability, and the potential for targeted therapy all properties needed for a drug delivery platform. The small size, stable core, rich surface chemistry, ability to self-assemble, and low cytotoxicity of nanodiamonds have led to suggestions that they could be used to mimic globular proteins . Nanodiamonds have been mostly studied as potential injectable therapeutic agents for generalized drug delivery, but it has also been shown that films of Parylene nanodiamond composites can be used for localized sustained release of drugs over periods ranging from two days to one month. [ 32 ]
Nanolithography is the technique to pattern materials and build devices under nano-scale. Nanolithography is often used together with thin-film-deposition, self-assembly, and self-organization techniques for various nanofabrications purpose. Many practical applications make use of nanolithography, including semiconductor chips in computers. There are many types of nanolithography, which include:
Each nanolithography technique has varying factors of the resolution, time consumption, and cost. There are three basic methods used by nanolithography. One involves using a resist material that acts as a "mask", known as photoresists, to cover and protect the areas of the surface that are intended to be smooth. The uncovered portions can now be etched away, with the protective material acting as a stencil. The second method involves directly carving the desired pattern. Etching may involve using a beam of quantum particles , such as electrons or light, or chemical methods such as oxidation or Self-assembled monolayers . The third method places the desired pattern directly on the surface, producing a final product that is ultimately a few nanometers thicker than the original surface. To visualize the surface to be fabricated, the surface must be visualized by a nano-resolution microscope, which includes the scanning probe microscopy and the atomic force microscope . Both microscopes can also be engaged in processing the final product.
Photoresists are light-sensitive materials, composed of a polymer, a sensitizer, and a solvent. Each element has a particular function. The polymer changes its structure when it is exposed to radiation. The solvent allows the photoresist to be spun and to form thin layers over the wafer surface. Finally, the sensitizer, or inhibitor, controls the photochemical reaction in the polymer phase. [ 33 ]
Photoresists can be classified as positive or negative. In positive photoresists, the photochemical reaction that occurs during exposure, weakens the polymer, making it more soluble to the developer so the positive pattern is achieved. Therefore, the masks contains an exact copy of the pattern, which is to remain on the wafer, as a stencil for subsequent processing. In the case of negative photoresists, exposure to light causes the polymerization of the photoresist so the negative resist remains on the surface of the substrate where it is exposed, and the developer solution removes only the unexposed areas. Masks used for negative photoresists contain the inverse or photographic “negative” of the pattern to be transferred. Both negative and positive photoresists have their own advantages. The advantages of negative photoresists are good adhesion to silicon, lower cost, and a shorter processing time. The advantages of positive photoresists are better resolution and thermal stability. [ 33 ]
Monodisperse, nanometer-size clusters (also known as nanoclusters ) are synthetically grown crystals whose size and structure influence their properties through the effects of quantum confinement . One method of growing these crystals is through inverse micellar cages in non-aqueous solvents. [ 34 ] Research conducted on the optical properties of MoS 2 nanoclusters compared them to their bulk crystal counterparts and analyzed their absorbance spectra. The analysis reveals that size dependence of the absorbance spectrum by bulk crystals is continuous, whereas the absorbance spectrum of nanoclusters takes on discrete energy levels. This indicates a shift from solid-like to molecular-like behavior which occurs at a reported cluster the size of 4.5 – 3.0 nm. [ 34 ]
Interest in the magnetic properties of nanoclusters exists due to their potential use in magnetic recording , magnetic fluids, permanent magnets , and catalysis . Analysis of Fe clusters shows behavior consistent with ferromagnetic or superparamagnetic behavior due to strong magnetic interactions within clusters. [ 34 ]
Dielectric properties of nanoclusters are also a subject of interest due to their possible applications in catalysis, photocatalysis , micro capacitors, microelectronics , and nonlinear optics . [ 35 ]
The idea of nanothermodynamics was initially proposed by T. L. Hill in 1960, theorizing the differences between differential and integral forms of properties due to small sizes. The size, shape, and environment of a nanoparticle affect the power law , or its proportionality, between nano and macroscopic properties. Transitioning from macro to nano changes the proportionality from exponential to power. [ 36 ] Therefore, nanothermodynamics and the theory of statistical mechanics are related in concept. [ 37 ] Building on these ideas, recent research has shown that, in finite nanosystems, the spatial dependence of intensive variables persists even in the thermodynamic limit. [ 38 ]
There are several researchers in nanochemistry that have been credited with the development of the field. Geoffrey A. Ozin , from the University of Toronto, is known as one of the "founding fathers of Nanochemistry" due to his four and a half decades of research on this subject. [ 39 ] This research includes the study of matrix isolation laser Raman spectroscopy, naked metal clusters chemistry and photochemistry , nanoporous materials, hybrid nanomaterials , mesoscopic materials, and ultrathin inorganic nanowires . [ 40 ]
Another chemist who is also viewed as one of the nanochemistry's pioneers is Charles M. Lieber at Harvard University . He is known for his contributions to the development of nano-scale technologies, particularly in the field of biology and medicine. [ 41 ] The technologies include nanowires, a new class of quasi-one-dimensional materials that have demonstrated superior electrical, optical, mechanical, and thermal properties and can be used potentially as biological sensors. Research under Lieber has delved into the use of nanowires mapping brain activity. [ 42 ]
Shimon Weiss, a professor at the University of California, Los Angeles , is known for his research of fluorescent semiconductor nanocrystals, a subclass of quantum dots , for biological labeling. [ 43 ]
Paul Alivisatos , from the University of California, Berkeley , is also notable for his research on the fabrication and use of nanocrystals. This research has the potential to develop insight into the mechanisms of small-scale particles such as the process of nucleation, cation exchange, and branching. A notable application of these crystals is the development of quantum dots. [ 44 ]
Peidong Yang , another researcher from the University of California, Berkeley , is also notable for his contributions to the development of 1-dimensional nanostructures. The Yang group has active research projects in the areas of nanowire photonics, nanowire-based solar cells, nanowires for solar to fuel conversion, nanowire thermoelectrics, nanowire-cell interface, nanocrystal catalysis, nanotube nanofluidics, and plasmonics . [ 45 ] | https://en.wikipedia.org/wiki/Nanochemistry |
Nanochondria are hypothetical nanomachines that are meant to live inside or with biological cells . [ 1 ] [ 2 ] They are named after mitochondria , due to their similarities in working inside the cell, and their reproduction.
Nanochondria would be able to replicate themselves within the body, even to the point where a mother would pass them on to her children, reducing the need for them to be implanted after the first generation. [ 2 ] Even a single nanochondrion inside of an egg cell would be able to replicate to the point where the person that was born from the egg would have nanochondria in every cell in their body. They would interact with and modify cells in the body, [ 1 ] potentially allowing people to modify or even make copies of themselves. [ 2 ] Due to this, they have been criticized for their ability to make synthetic humans, or even "natural robots", as well as their potential to damage DNA . [ 3 ] Nanochondria would even allow a person to exhale a utility fog , allowing them to in effect "breathe" a needed tool. [ 2 ]
Nanochondria would have to be incredibly small, which would limit their computational power. To remedy this, they would be likely be able to communicate with each other, as well as other devices inside and outside the body, in an internalnet , in a distributed computing network. This would be likely to be accomplished by acoustic wave communication, or using wires composed of single electrons. [ 2 ] Anders Sandberg has commented saying that "mitochondria ... just react on local conditions and indirectly cooperate". and that "It might be hard to make those pipes reliable", although he conceded that "linked nanochondria will be much more versatile". [ 4 ] Nanochondria could be used to perform a diagnostic test on a person's own body, and then used to fix or even modify cells. [ 2 ]
This nanotechnology-related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Nanochondrion |
Nanocomposite is a multiphase solid material where one of the phases has one, two or three dimensions of less than 100 nanometers (nm) or structures having nano-scale repeat distances between the different phases that make up the material.
In the broadest sense this definition can include porous media , colloids , gels and copolymers , but is more usually taken to mean the solid combination of a bulk matrix and nano-dimensional phase(s) differing in properties due to dissimilarities in structure and chemistry. The mechanical, electrical, thermal, optical, electrochemical, catalytic properties of the nanocomposite will differ markedly from that of the component materials. Size limits for these effects have been proposed: [ 1 ]
Nanocomposites are found in nature, for example in the structure of the abalone shell and bone. The use of nanoparticle-rich materials long predates the understanding of the physical and chemical nature of these materials. Jose-Yacaman et al. [ 2 ] investigated the origin of the depth of colour and the resistance to acids and bio-corrosion of Maya blue paint, attributing it to a nanoparticle mechanism. From the mid-1950s nanoscale organo-clays have been used to control flow of polymer solutions (e.g. as paint viscosifiers) or the constitution of gels (e.g. as a thickening substance in cosmetics, keeping the preparations in homogeneous form). By the 1970s polymer/ clay composites were the topic of textbooks, [ 3 ] [ 4 ] although the term "nanocomposites" was not in common use.
In mechanical terms, nanocomposites differ from conventional composite materials due to the exceptionally high surface to volume ratio of the reinforcing phase and/or its exceptionally high aspect ratio . The reinforcing material can be made up of particles (e.g. minerals), sheets (e.g. exfoliated clay stacks) or fibres (e.g. carbon nanotubes or electrospun fibres). [ 5 ] The area of the interface between the matrix and reinforcement phase(s) is typically an order of magnitude greater than for conventional composite materials. The matrix material properties are significantly affected in the vicinity of the reinforcement. Ajayan et al. [ 6 ] note that with polymer nanocomposites, properties related to local chemistry, degree of thermoset cure, polymer chain mobility, polymer chain conformation, degree of polymer chain ordering or crystallinity can all vary significantly and continuously from the interface with the reinforcement into the bulk of the matrix.
This large amount of reinforcement surface area means that a relatively small amount of nanoscale reinforcement can have an observable effect on the macroscale properties of the composite. For example, adding carbon nanotubes improves the electrical and thermal conductivity . Other kinds of nanoparticulates may result in enhanced optical properties , dielectric properties , heat resistance or mechanical properties such as stiffness , strength and resistance to wear and damage. In general, the nano reinforcement is dispersed into the matrix during processing. The percentage by weight (called mass fraction ) of the nanoparticulates introduced can remain very low (on the order of 0.5% to 5%) due to the low filler percolation threshold , especially for the most commonly used non-spherical, high aspect ratio fillers (e.g. nanometer-thin platelets, such as clays, or nanometer-diameter cylinders, such as carbon nanotubes). The orientation and arrangement of asymmetric nanoparticles, thermal property mismatch at the interface, interface density per unit volume of nanocomposite, and polydispersity of nanoparticles significantly affect the effective thermal conductivity of nanocomposites. [ 7 ]
Ceramic matrix composites (CMCs) consist of ceramic fibers embedded in a ceramic matrix. The matrix and fibers can consist of any ceramic material, including carbon and carbon fibers. The ceramic occupying most of the volume is often from the group of oxides, such as nitrides, borides, silicides, whereas the second component is often a metal . Ideally both components are finely dispersed in each other in order to elicit particular optical, electrical and magnetic properties [ 8 ] as well as tribological, corrosion-resistance and other protective properties. [ 9 ]
The binary phase diagram of the mixture should be considered in designing ceramic-metal nanocomposites and measures have to be taken to avoid a chemical reaction between both components. The last point mainly is of importance for the metallic component that may easily react with the ceramic and thereby lose its metallic character. This is not an easily obeyed constraint because the preparation of the ceramic component generally requires high process temperatures. The safest measure thus is to carefully choose immiscible metal and ceramic phases. A good example of such a combination is represented by the ceramic-metal composite of TiO 2 and Cu , the mixtures of which were found immiscible over large areas in the Gibbs’ triangle of ' Cu-O-Ti. [ 10 ]
The concept of ceramic-matrix nanocomposites was also applied to thin films that are solid layers of a few nm to some tens of μm thickness deposited upon an underlying substrate and that play an important role in the functionalization of technical surfaces. Gas flow sputtering by the hollow cathode technique turned out as a rather effective technique for the preparation of nanocomposite layers. The process operates as a vacuum-based deposition technique and is associated with high deposition rates up to some μm/s and the growth of nanoparticles in the gas phase. Nanocomposite layers in the ceramics range of composition were prepared from TiO 2 and Cu by the hollow cathode technique [ 11 ] that showed a high mechanical hardness , small coefficients of friction and a high resistance to corrosion .
Metal matrix nanocomposites can also be defined as reinforced metal matrix composites. This type of composites can be classified as continuous and non-continuous reinforced materials. One of the more important nanocomposites is Carbon nanotube metal matrix composites , which is an emerging new material that is being developed to take advantage of the high tensile strength and electrical conductivity of carbon nanotube materials. [ 12 ] Critical to the realization of CNT-MMC possessing optimal properties in these areas are the development of synthetic techniques that are (a) economically producible, (b) provide for a homogeneous dispersion of nanotubes in the metallic matrix, and (c) lead to strong interfacial adhesion between the metallic matrix and the carbon nanotubes. In addition to carbon nanotube metal matrix composites, boron nitride reinforced metal matrix composites and carbon nitride metal matrix composites are the new research areas on metal matrix nanocomposites. [ 13 ]
A recent study, comparing the mechanical properties (Young's modulus, compressive yield strength, flexural modulus and flexural yield strength) of single- and multi-walled reinforced polymeric (polypropylene fumarate—PPF) nanocomposites to tungsten disulfide nanotubes reinforced PPF nanocomposites suggest that tungsten disulfide nanotubes reinforced PPF nanocomposites possess significantly higher mechanical properties and tungsten disulfide nanotubes are better reinforcing agents than carbon nanotubes. [ 14 ] Increases in the mechanical properties can be attributed to a uniform dispersion of inorganic nanotubes in the polymer matrix (compared to carbon nanotubes that exist as micron sized aggregates) and increased crosslinking density of the polymer in the presence of tungsten disulfide nanotubes (increase in crosslinking density leads to an increase in the mechanical properties). These results suggest that inorganic nanomaterials , in general, may be better reinforcing agents compared to carbon nanotubes.
Another kind of nanocomposite is the energetic nanocomposite, generally as a hybrid sol–gel with a silica base, which, when combined with metal oxides and nano-scale aluminum powder, can form superthermite materials. [ 15 ] [ 16 ] [ 17 ] [ 18 ]
In the simplest case, appropriately adding nanoparticulates to a polymer matrix can enhance its performance, often dramatically, by simply capitalizing on the nature and properties of the nanoscale filler [ 19 ] (these materials are better described by the term nanofilled polymer composites [ 19 ] ). This strategy is particularly effective in yielding high performance composites, when uniform dispersion of the filler is achieved and the properties of the nanoscale filler are substantially different or better than those of the matrix. The uniformity of the dispersion is in all nanocomposites is counteracted by thermodynamically driven phase separation. Clustering of nanoscale fillers produces aggregates that serve as structural defects and result in failure. Layer-by-layer (LbL) assembly when nanometer scale layers of nanoparticulates and a polymers are added one by one. LbL composites display performance parameters 10-1000 times better that the traditional nanocomposites made by extrusion or batch-mixing.
Nanoparticles such as graphene, [ 20 ] carbon nanotubes, [ 21 ] molybdenum disulfide and tungsten disulfide are being used as reinforcing agents to fabricate mechanically strong biodegradable polymeric nanocomposites for bone tissue engineering applications. The addition of these nanoparticles in the polymer matrix at low concentrations (~0.2 weight %) cause significant improvements in the compressive and flexural mechanical properties of polymeric nanocomposites. [ 22 ] [ 23 ] [ 24 ] Potentially, these nanocomposites may be used as a novel, mechanically strong, light weight composite as bone implants. The results suggest that mechanical reinforcement is dependent on the nanostructure morphology, defects, dispersion of nanomaterials in the polymer matrix, and the cross-linking density of the polymer. In general, two-dimensional nanostructures can reinforce the polymer better than one-dimensional nanostructures, and inorganic nanomaterials are better reinforcing agents than carbon based nanomaterials. In addition to mechanical properties, polymer nanocomposites based on carbon nanotubes or graphene have been used to enhance a wide range of properties, giving rise to functional materials for a wide range of high added value applications in fields such as energy conversion and storage, sensing and biomedical tissue engineering. [ 25 ] For example, multi-walled carbon nanotubes based polymer nanocomposites have been used for the enhancement of the electrical conductivity. [ 26 ]
An alternative route to synthesis of nanocomposites is sequential infiltration synthesis , in which inorganic nanomaterials are grown within polymeric substrates using vapor-phase precursors that diffuse into the matrix. Furthermore, nanocomposites can be prepared via in situ generation of nanoparticles on and within polymeric materials, an approach that relies on the chemical transformation of suitable precursors to targeted nanoparticles synchronous with the build-up of the nanohybrid systems. [ 27 ] The in situ -generated nanoparticles tend to nucleate and grow on the active sites of the macromolecular chains, showing strong adhesion on the polymeric host.
Nanoscale dispersion of filler or controlled nanostructures in the composite can introduce new physical properties and novel behaviors that are absent in the unfilled matrices. This effectively changes the nature of the original matrix [ 19 ] (such composite materials can be better described by the term genuine nanocomposites or hybrids [ 19 ] ). Some examples of such new properties are fire resistance or flame retardancy, [ 28 ] and accelerated biodegradability .
A range of polymeric nanocomposites are used for biomedical applications such as tissue engineering, drug delivery, cellular therapies. [ 29 ] [ 30 ] Due to unique interactions between polymer and nanoparticles, a range of property combinations can be engineered to mimic native tissue structure and properties. A range of natural and synthetic polymers are used to design polymeric nanocomposites for biomedical applications including starch, cellulose, alginate, chitosan, collagen, gelatin, and fibrin, poly(vinyl alcohol) (PVA), poly(ethylene glycol) (PEG), poly(caprolactone) (PCL), poly(lactic-co-glycolic acid) (PLGA), and poly(glycerol sebacate) (PGS). A range of nanoparticles including ceramic, polymeric, metal oxide and carbon-based nanomaterials are incorporated within polymeric network to obtain desired property combinations. [ 31 ]
Nanocomposites that can respond to an external stimulus are of increased interest due to the fact that, because of the large amount of interaction between the phase interfaces, the stimulus response can have a larger effect on the composite as a whole. The external stimulus can take many forms, such as a magnetic, electrical, or mechanical field. Specifically, magnetic nanocomposites are useful for use in these applications due to the nature of magnetic material's ability to respond both to electrical and magnetic stimuli. The penetration depth of a magnetic field is also high, leading to an increased area that the nanocomposite is affected by and therefore an increased response. In order to respond to a magnetic field, a matrix can be easily loaded with nanoparticles or nanorods The different morphologies for magnetic nanocomposite materials are vast, including matrix dispersed nanoparticles, core-shell nanoparticles,
colloidal crystals, macroscale spheres, or Janus-type nanostructures. [ 32 ] [ 33 ]
Magnetic nanocomposites can be utilized in a vast number of applications, including catalytic, medical, and technical. For example, palladium is a common transition metal used in catalysis reactions. Magnetic nanoparticle-supported palladium complexes can be used in catalysis to increase the efficiency of the palladium in the reaction. [ 34 ]
Magnetic nanocomposites can also be utilized in the medical field, with magnetic nanorods embedded in a polymer matrix can aid in more precise drug delivery and release. Finally, magnetic nanocomposites can be used in high frequency/high-temperature applications. For example, multi-layer structures can be fabricated for use in electronic applications. An electrodeposited Fe/Fe oxide multi-layered sample can be an example of this application of magnetic nanocomposites. [ 35 ]
In applications such as power micro-inductors where high magnetic permeability is desired at high operating frequencies. [ 36 ] The traditional micro-fabricated magnetic core materials see both decrease in permeability and high losses at high operating frequency. [ 37 ] In this case, magnetic nano composites have great potential for improving the efficiency of power electronic devices by providing relatively high permeability and low losses. For example, As Iron oxide nano particles embedded in Ni matrix enables us to mitigate those losses at high frequency. [ 38 ] The high resistive iron oxide nanoparticles helps to reduce the eddy current losses where as the Ni metal helps in attaining high permeability. DC magnetic properties such as Saturation magnetization lies between each of its constituent parts indicating that the physical properties of the materials can be altered by creating these nanocomposites. | https://en.wikipedia.org/wiki/Nanocomposite |
A nanocrystalline ( NC ) material is a polycrystalline material with a crystallite size of only a few nanometers . These materials fill the gap between amorphous materials without any long range order and conventional coarse-grained materials. Definitions vary, but nanocrystalline material is commonly defined as a crystallite (grain) size below 100 nm. Grain sizes from 100 to 500 nm are typically considered "ultrafine" grains.
The grain size of a NC sample can be estimated using x-ray diffraction . In materials with very small grain sizes, the diffraction peaks will be broadened. This broadening can be related to a crystallite size using the Scherrer equation (applicable up to ~50 nm), a Williamson-Hall plot , [ 1 ] or more sophisticated methods such as the Warren-Averbach method or computer modeling of the diffraction pattern. The crystallite size can be measured directly using transmission electron microscopy . [ 1 ]
Nanocrystalline materials can be prepared in several ways. Methods are typically categorized based on the phase of matter the material transitions through before forming the nanocrystalline final product.
Solid-state processes do not involve melting or evaporating the material and are typically done at relatively low temperatures. Examples of solid state processes include mechanical alloying using a high-energy ball mill and certain types of severe plastic deformation processes.
Nanocrystalline metals can be produced by rapid solidification from the liquid using a process such as melt spinning . This often produces an amorphous metal, which can be transformed into an nanocrystalline metal by annealing above the crystallization temperature .
Thin films of nanocrystalline materials can be produced using vapor deposition processes such as MOCVD . [ 2 ]
Some metals, particularly nickel and nickel alloys , can be made into nanocrystalline foils using electrodeposition . [ 3 ]
Nanocrystalline materials show exceptional mechanical properties relative to their coarse-grained varieties. Because the volume fraction of grain boundaries in nanocrystalline materials can be as large as 30%, [ 4 ] the mechanical properties of nanocrystalline materials are significantly influenced by this amorphous grain boundary phase. For example, the elastic modulus has been shown to decrease by 30% for nanocrystalline metals and more than 50% for nanocrystalline ionic materials. [ 5 ] This is because the amorphous grain boundary regions are less dense than the crystalline grains, and thus have a larger volume per atom, Ω {\displaystyle \Omega } . Assuming the interatomic potential, U ( Ω ) {\displaystyle U(\Omega )} , is the same within the grain boundaries as in the bulk grains, the elastic modulus, E ∝ ∂ 2 U / ∂ Ω 2 {\displaystyle E\propto \partial ^{2}U/\partial \Omega ^{2}} , will be smaller in the grain boundary regions than in the bulk grains. Thus, via the rule of mixtures , a nanocrystalline material will have a lower elastic modulus than its bulk crystalline form.
The exceptional yield strength of nanocrystalline metals is due to grain boundary strengthening , as grain boundaries are extremely effective at blocking the motion of dislocations. Yielding occurs when the stress due to dislocation pileup at a grain boundary becomes sufficient to activate slip of dislocations in the adjacent grain. This critical stress increases as the grain size decreases, and these physics are empirically captured by the Hall-Petch relationship,
where σ y {\displaystyle \sigma _{y}} is the yield stress, σ 0 {\displaystyle \sigma _{0}} is a material-specific constant that accounts for the effects of all other strengthening mechanisms, K {\displaystyle K} is a material-specific constant that describes the magnitude of the metal's response to grain size strengthening, and d {\displaystyle d} is the average grain size. [ 6 ] Additionally, because nanocrystalline grains are too small to contain a significant number of dislocations, nanocrystalline metals undergo negligible amounts of strain-hardening , [ 5 ] and nanocrystalline materials can thus be assumed to behave with perfect plasticity.
As the grain size continues to decrease, a critical grain size is reached at which intergranular deformation, i.e. grain boundary sliding, becomes more energetically favorable than intragranular dislocation motion. Below this critical grain size, often referred to as the “reverse” or “inverse” Hall-Petch regime, any further decrease in the grain size weakens the material because an increase in grain boundary area results in increased grain boundary sliding. Chandross & Argibay modeled grain boundary sliding as viscous flow and related the yield strength of the material in this regime to material properties as
where L {\displaystyle L} is the enthalpy of fusion , ρ L / M {\displaystyle \rho _{L}/M} is the atomic volume in the amorphous phase, T m {\displaystyle T_{m}} is the melting temperature, and f g {\displaystyle f_{g}} is the volume fraction of material in the grains vs the grain boundaries, given by f g = ( 1 − δ / d ) 3 {\displaystyle f_{g}=(1-\delta /d)^{3}} , where δ {\displaystyle \delta } is the grain boundary thickness and typically on the order of 1 nm. The maximum strength of a metal is given by the intersection of this line with the Hall-Petch relationship, which typically occurs around a grain size of d {\displaystyle d} = 10 nm for BCC and FCC metals. [ 4 ]
Due to the large amount of interfacial energy associated with a large volume fraction of grain boundaries, nanocrystalline metals are thermally unstable. In nanocrystalline samples of low-melting point metals (i.e. aluminum , tin , and lead ), the grain size of the samples was observed to double from 10 to 20 nm after 24 hours of exposure to ambient temperatures. [ 5 ] Although materials with higher melting points are more stable at room temperatures, consolidating nanocrystalline feedstock into a macroscopic component often requires exposing the material to elevated temperatures for extended periods of time, which will result in coarsening of the nanocrystalline microstructure. Thus, thermally stable nanocrystalline alloys are of considerable engineering interest. Experiments have shown that traditional microstructural stabilization techniques such as grain boundary pinning via solute segregation or increasing solute concentrations have proven successful in some alloy systems, such as Pd-Zr and Ni-W. [ 7 ]
While the mechanical behavior of ceramics is often dominated by flaws, i.e. porosity, instead of grain size, grain-size strengthening is also observed in high-density ceramic specimens. [ 8 ] Additionally, nanocrystalline ceramics have been shown to sinter more rapidly than bulk ceramics, leading to higher densities and improved mechanical properties, [ 5 ] although extended exposure to the high pressures and elevated temperatures required to sinter the part to full density can result in coarsening of the nanostructure.
The large volume fraction of grain boundaries associated with nanocrystalline materials causes interesting behavior in ceramic systems, such as superplasticity in otherwise brittle ceramics. The large volume fraction of grain boundaries allows for a significant diffusional flow of atoms via Coble creep , analogous to the grain boundary sliding deformation mechanism in nanocrystalline metals. Because the diffusional creep rate scales as d − 3 {\displaystyle d^{-3}} and linearly with the grain boundary diffusivity, refining the grain size from 10 μm to 10 nm can increase the diffusional creep rate by approximately 11 orders of magnitude. This superplasticity could prove invaluable for the processing of ceramic components, as the material may be converted back into a conventional, coarse-grained material via additional thermal treatment after forming. [ 5 ]
While the synthesis of nanocrystalline feedstocks in the form of foils, powders, and wires is relatively straightforward, the tendency of nanocrystalline feedstocks to coarsen upon extended exposure to elevated temperatures means that low-temperature and rapid densification techniques are necessary to consolidate these feedstocks into bulk components. A variety of techniques show potential in this respect, such as spark plasma sintering [ 9 ] or ultrasonic additive manufacturing , [ 10 ] although the synthesis of bulk nanocrystalline components on a commercial scale remains untenable. | https://en.wikipedia.org/wiki/Nanocrystalline_material |
A nanodomain is a nanometer-sized cluster of proteins found in a cell membrane. They are associated with the signal which occurs when a single calcium ion channel opens on a cell membrane , allowing an influx of calcium ions (Ca 2+ ) which extend in a plume a few tens of nanometres from the channel pore. [ 1 ] In a nanodomain, the coupling distance, that is, the distance between the calcium-binding proteins which sense the calcium, and the calcium channel, is very small, less than 100 nm (3.9 × 10 −6 in), which allows rapid signalling. [ 2 ] The formation of a nanodomain signal is virtually instantaneous following the opening of the calcium channel, as calcium ions move rapidly into the cell along a steep concentration gradient . [ 3 ] The nanodomain signal collapses just as quickly when the calcium channel closes, as the ions rapidly diffuse away from the pore. [ 3 ] Formation of a nanodomain signal requires the influx of only approximately 1000 calcium ions. [ 4 ]
Coupling distances greater than 100 nm (3.9 × 10 −6 in), mediated by a larger number of channels, are referred to as microdomains. [ 2 ] nanodomain
Nanodomain signals are thought to improve the temporal precision of fast exocytosis of vesicles due to two specific properties: [ 5 ]
Single channels are able to cause vesicular release, however, the cooperativity of different calcium channels is synapse-specific. The release driven by a single calcium ion channel minimizes the total calcium ion influx, overlapping domains can provide greater reliability and temporal fidelity. [ 5 ]
This molecular biology article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Nanodomain |
Nanoelectrochemistry is a branch of electrochemistry that investigates the electrical and electrochemical properties of materials at the nanometer size regime. Nanoelectrochemistry plays significant role in the fabrication of various sensors , and devices for detecting molecules at very low concentrations.
Two transport mechanisms are fundamental for nanoelectrochemistry: electron transfer and mass transport . The formulation of theoretical models allows to understand the role of the different species involved in the electrochemical reactions.
The electron transfer between the reactant and the nanoelectrode can be explained by the combination of various theories based on the Marcus theory .
Mass transport, that is the diffusion of the reactant molecules from the electrolyte bulk to the nanoelectrode, is influenced by the formation of a double electric layer at the electrode/electrolyte interface. At the nanoscale it is necessary to theorize a dynamic double electric layer which takes into account an overlap of the Stern layer and the diffuse layer . [ 1 ]
Knowledge of the mechanisms involved allows to build computational models that combine the density functional theory with electron transfer theories and the dynamic double electric layer. [ 2 ] In the field of molecular modelling, accurate models could predict the behaviour of the system as reactants, electrolyte or electrode change.
The role of the surface is strongly reaction-specific: in fact, one site can catalyze certain reactions and inhibit other ones. According to TSK model , surface atoms in nanocrystals can occupy terrace, step or kink positions: each site has a different tendency to adsorb reactants and to let them move along the surface. Generally, sites having lower coordination number (steps and kinks) are more reactive due to their high free energy. High energy sites, however, are less thermodynamically stable and nanocrystals have a tendency to transform to their equilibrium shape .
Thanks to the progress in nanoparticles synthesis it is now possible to have a single-crystal approach to surface science, allowing more precise research on the effect of a given surface. Studies have been conducted on nanoelectrodes exposing a (100), (110) or (111) plane to a solution containing the reactants, in order to define the surface effect on reaction rate and selectivity of the most common electrochemical reactions. [ 3 ]
Nanoelectrodes are tiny electrodes made of metals or semiconducting materials having typical dimensions of 1-100 nm.
Various forms of nanoelectrodes have been developed taking advantage of the different possible fabrication techniques: among the most studied are the nanoband, disk, hemispherical, nanopore geometries as well as the different forms of carbon nanostructures. [ 4 ] [ 5 ]
It is necessary to characterize each produced electrode: size and shape determine its behavior. The most used characterization techniques are: [ 4 ] [ 6 ]
There are mainly two properties that distinguish nanoelectrodes from electrodes: smaller RC constant and faster mass transfer. The former allows measurements to be made in high-resistance solutions because they offer less resistance, the latter, due to radial diffusion, allows much faster voltammetry responses. Due to these and other properties, nanoelectrodes are used in various applications: [ 1 ] [ 4 ]
The main advantages of using nanoelectrodes and arrays of nanoelectrodes include enhanced mass transport, lower capacitance, ability to work in smaller volumes and smaller overall device footprints. [ 7 ]
The electrical current generated at an electrode is proportional to the electrode's geometric area. A disadvantage of using a single nanoelectrode is that it generates a small current output, which puts pressure on the instrumentation, and in turn, the reliability of the measurements recorded. One way to overcome this is the use an array of nanoelectrodes. The arrays produce a current, which is proportional with the number of electrodes in the array. This method has been used extensively in electroanalysis. Through the careful and accurate fabrication of arrays of nanoelectrodes, the electrochemical instrumentation is more reliable for sensitive measurement that enables implementation of a range of electroanalytical techniques. [ 8 ]
There are two main types of arrangements; nanoelectrode arrays (NEAs) where the nanoelectrodes are spaced in an ordered arrangement and nanoelectrode ensembles (NEEs), where the individual nanoelectrodes are distributed randomly. | https://en.wikipedia.org/wiki/Nanoelectrochemistry |
A nanoelectromechanical ( NEM ) relay is an electrically actuated switch that is built on the nanometer scale using semiconductor fabrication techniques. They are designed to operate in replacement of, or in conjunction with, traditional semiconductor logic. While the mechanical nature of NEM relays makes them switch much slower than solid-state relays , they have many advantageous properties, such as zero current leakage and low power consumption , which make them potentially useful in next generation computing.
A typical NEM relay requires a potential on the order of the tens of volts in order to "pull in" and have contact resistances on the order of gigaohms. Coating contact surfaces with platinum can reduce achievable contact resistance to as low as 3 kΩ. [ 1 ] Compared to transistors, NEM relays switch relatively slowly, on the order of nanoseconds. [ 2 ]
A NEM relay can be fabricated in two, three, or four terminal configurations. A three terminal relay is composed of a source (input), drain (output), and a gate (actuation terminal). Attached to the source is a cantilevered beam that can be bent into contact with the drain in order to make an electrical connection. When a significant voltage differential is applied between the beam and gate, and the electrostatic force overcomes the elastic force of the beam enough to bend it into contact with the drain, the device "pulls in" and forms an electrical connection. In the off position, the source and drain are separated by an air gap. This physical separation allows NEM relays to have zero current leakage, and very sharp on/off transitions. [ 3 ]
The nonlinear nature of the electric field, and adhesion between the beam and drain cause the device to "pull out" and lose connection at a lower voltage than the voltage at which it pulls in. This hysteresis effect means there is a voltage between the pull in voltage, and the pull out voltage that will not change the state of the relay, no matter what its initial state is. This property is very useful in applications where information needs to be stored in the circuit, such as in static random-access memory . [ 1 ]
NEM relays are usually fabricated using surface micromachining techniques typical of microelectromechanical systems (MEMS). [ 4 ] Laterally actuated relays are constructed by first depositing two or more layers of material on a silicon wafer . The upper structural layer is photolithographically patterned in order to form isolated blocks of the uppermost material. The layer below is then selectively etched away, leaving thin structures, such as the relay's beam, cantilevered above the wafer, and free to bend laterally. [ 1 ] A common set of materials used in this process is polysilicon as the upper structural layer, and silicon dioxide as the sacrificial lower layer.
NEM relays can be fabricated using a back end of line compatible process, allowing them to be built on top of CMOS . [ 1 ] This property allows NEM relays to be used to significantly reduce the area of certain circuits. For example, a CMOS-NEM relay hybrid inverter occupies 0.03 μm 2 , one-third the area of a 45 nm CMOS inverter. [ 5 ]
The first switch made using silicon micro-machining techniques was fabricated in 1978. [ 6 ] Those switches were made using bulk micromachining processes and electroplating . [ 7 ] In the 1980s, surface micromachining techniques were developed [ 8 ] and the technology was applied to the fabrication of switches, allowing for smaller, more efficient relays. [ 9 ]
A major early application of MEMS relays was for switching radio frequency signals at which solid-state relays had poor performance. [ 10 ] The switching time for these early relays was above 1 μs. By shrinking dimensions below one micrometer, [ 11 ] and moving into the nano scale, MEMS switches have achieved switching times in the ranges of hundreds of nanoseconds. [ 5 ]
Due to transistor leakage, there is a limit to the theoretical efficiency of CMOS logic. This efficiency barrier ultimately prevents continued increases in computing power in power-constrained applications. [ 12 ] While NEM relays have significant switching delays, their small size and fast switching speed when compared to other relays means that mechanical computing utilizing NEM Relays could prove a viable replacement for typical CMOS based integrated circuits , and break this CMOS efficiency barrier. [ 3 ] [ 2 ]
A NEM relay switches mechanically about 1000 times slower than a solid-state transistor takes to switch electrically. While this makes using NEM relays for computing a significant challenge, their low resistance would allow many NEM relays to be chained together and switch all at once, performing a single large calculation. [ 2 ] On the other hand, transistor logic has to be implemented in small cycles of calculations, because their high resistance does not allow many transistors to be chained together while maintaining signal integrity. Therefore, it would be possible to create a mechanical computer using NEM relays that operates at a much lower clock speed than CMOS logic, but performs larger, more complex calculations during each cycle. This would allow a NEM relay based logic to perform to standards comparable to current CMOS logic. [ 2 ]
There are many applications, such as in the automotive , aerospace , or geothermal exploration businesses, in which it would be beneficial to have a microcontroller that could operate at very high temperatures. However, at high temperatures, semiconductors used in typical microcontrollers begin to fail as the electrical properties of the materials they are made of degrade, and the transistors no longer function. NEM relays do not rely on the electrical properties of materials to actuate, so a mechanical computer utilizing NEM relays would be able to operate in such conditions. NEM relays have been successfully tested at up to 500 °C, but could theoretically withstand much higher temperatures. [ 13 ]
The zero leakage current, low energy usage, and ability to be layered on top of CMOS properties of NEM relays make them a promising candidate for usage as routing switches in field-programmable gate arrays (FPGA). A FPGA utilizing a NEM relay to replace each routing switch and its corresponding static random-access memory block could allow for a significant reduction in programming delay, power leakage, and chip area compared to a typical 22nm CMOS based FPGA. [ 14 ] This area reduction mainly comes from the fact that the NEM relay routing layer can be built on top of the CMOS layer of the FPGA. | https://en.wikipedia.org/wiki/Nanoelectromechanical_relay |
Nanoengineering is the practice of engineering on the nanoscale . It derives its name from the nanometre , a unit of measurement equalling one billionth of a meter.
Nanoengineering is largely a synonym for nanotechnology , but emphasizes the engineering rather than the pure science aspects of the field.
The first nanoengineering program was started at the University of Toronto within the Engineering Science program as one of the options of study in the final years. In 2003, the Lund Institute of Technology started a program in Nanoengineering. In 2004, the College of Nanoscale Science and Engineering at the University at Albany, SUNY was founded as the first of its kind in the United States. The college later merged with SUNY Poly , but will rejoin the University at Albany in 2023. In 2005, the University of Waterloo established a unique program which offers a full degree in Nanotechnology Engineering. [ 2 ] Louisiana Tech University started the first program in the U.S. in 2005. In 2006 the University of Duisburg-Essen started a Bachelor and a Master program NanoEngineering. [ 3 ] Unlike early NanoEngineering programs, the first NanoEngineering Department in the world, offering both undergraduate and graduate degrees, was established by the University of California, San Diego in 2007.
In 2009, the University of Toronto began offering all Options of study in Engineering Science as degrees, bringing the second nanoengineering degree to Canada. Rice University established in 2016 a Department of Materials Science and NanoEngineering (MSNE).
DTU Nanotech - the Department of Micro- and Nanotechnology - is a department at the Technical University of Denmark established in 1990.
In 2013, Wayne State University began offering a Nanoengineering Undergraduate Certificate Program, which is funded by a Nanoengineering Undergraduate Education (NUE) grant from the National Science Foundation . The primary goal is to offer specialized undergraduate training in nanotechnology. Other goals are: 1) to teach emerging technologies at the undergraduate level, 2) to train a new adaptive workforce, and 3) to retrain working engineers and professionals. [ 4 ] | https://en.wikipedia.org/wiki/Nanoengineering |
Nanofiber Seeding is a process to control the bulk morphology of chemically synthesized conducting polymers.
Typically, catalytic amount of nanofiber seeds are added in prior to onset of nanofiber seeding polymerization (reaction), where seeds are served as the 'morphology directing agent' rather than conventional templates (see hard or soft templating methods).
A new synthetic approach, called nanofiber seeding, 1 was developed to control the bulk morphology of chemically synthesized electronic organic polymers. Bulk quantities of nanofibers of conducting polymers such as polyaniline , can be synthesized in one step without the need for conventional templates, surfactants, polymers, or organic solvents. 3
Conventional oxidative polymerization approaches to nanostructured conducting polymers include the use of hard template zeolites, opals, and controlled pore-size membranes, or soft template such as polymers and surfactants. A “template-free” approach has also been described in which the use of large organic anions results in polyaniline nanofibers and nanotubes having average diameters in the 650-80 nm range. 1
Standard synthesis of polyaniline yields granular morphology. However, if the conventional reaction is seeded by 1-4 mg (seed quantities) of added pre-synthesized polyaniline nanofibers , (nanofiber seeds could be prepared from interfacial polymerization) the bulk morphology changes dramatically from granular to nano-fibrillar. Furthermore, increased capacitance values were observed in polyaniline nanofibers synthesized by the nanofiber seeding approach. Oxidative polymerization can be also seeded by other nanostructure materials such as vanadium pentoxide nanofibers, where V2O5 nanofibers (i) Rapidly initiate fibrillar polymer growth (ii) Slowly dissolve in aq. 1.0 M HCl, which eliminates template removal steps. Hence only catalytic amounts (4mg) V2O5 nanofibers are needed prior to onset of polymerization, which significantly change the bulk morphology of the polymer precipitate. Moreover, single-walled carbon nanotube and nano fibrous hexapeptide can be also used as templating seeds. This method can be extended to all major classes of conducting polymers, including polypyrrole , PEDOT and other polythiophenes etc. 2 3
Nanofiber seeding is a convenient approach to obtain thin, substrate-supported, transparent films of nanofibers of conducting polymers without requiring any bulk processing steps. 3 | https://en.wikipedia.org/wiki/Nanofiber_seeding |
Nanofilms are thin films ranging from 1 to 100 nanometers in thickness. These materials exhibit unique chemical and physical properties, largely influenced by quantum behavior and surface effects. Their low surface energy, reduced friction coefficient, and high selectivity make them valuable across various industries, including solar energy, medicine, and food packaging. The properties of nanofilms are highly dependent on their chemical composition and molecular structure. [ 1 ] [ 2 ] [ 3 ] [ 4 ] [ 5 ]
Nanofilms are characterized using a range of instrumental techniques, including scanning electron microscopy (SEM], X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), Raman spectroscopy, and UV-Vis absorption spectroscopy. [ 2 ] [ 4 ] [ 6 ]
The nanofilm market has gained significant economic importance, with a market size of $2.06 billion, projected to grow to $7.09 billion by 2027. This growth is primarily driven by technological applications. Leading companies in the global nanofilm market include Nano Therapeutics Pvt. Ltd., Nanofilm, Cosmo Films Limited , Smart Source Technologies, Nano Foam Technology Private Limited, Advanced Thin Film, and MetaTechnica. [ 3 ]
Various methods are employed to synthesize nanofilms, with the chosen technique directly influencing the physicochemical properties and therefore applications of the films.
Layer by layer (LbL) assembly is the most widely used method for nanofilm synthesis due to its simplicity, versatility, and precise control over film characteristics. Additionally, LBL offers an extensive choice of usable material for coating both planar and particulate substrates.Various molecules, including polymeric, organic, inorganic, and biomolecules, can be used to achieve desired functionalities. Generally, in LbL assembly, a charged material is adsorbed onto a substrate, followed by the deposition of an oppositely charged material on top of the first layer, forming a bilayer. Substrates can vary greatly in shape, size, or porosity and include surfaces, fibres, particles, and membranes. Five primary LbL assembly techniques exist. [ 2 ] [ 7 ]
In this method, substrates are manually immersed in a solution of the desired composition, followed by washing and centrifugation to deposit layers. This process can be repeated to achieve the desired thickness and properties. In some circumstances, the substrate can be removed to create a free-standing film. Layering materials include polymers, colloids, and charged polymers. The resulting film is rough with interpenetrated layers. While effective, immersive methods require large amounts of material, leading to waste management challenges in industrial use. Innovations such as automation of labor-intensive steps and real-time monitoring using quartz crystal microbalances to enable computer monitored feedback loops are being explored to improve efficiency. [ 2 ] [ 8 ]
Spin methods involve depositing materials onto a spinning substrate. This method is generally used for flat substrates due to inherent limitations of spin coaters. This method can be applied to polymers and colloids. Compared to immersive LbL methods, spin coating offers rapid assembly and improved film organization. The resulting film is smooth and stratified, making it ideal for optical coatings, transparent films, and LED applications. [ 8 ]
Aerosolized polymer solutions are sprayed onto a substrate, making this method efficient and suitable for nonplanar surfaces. This method is organized, quick, and adaptable to a range of morphologies. Due to its speed and versatility, spray coating is particularly attractive for industrial-scale production. [ 8 ]
This technique employs electric or magnetic fields to deposit nanofilms onto substrates, resulting in densely packed films with greater thickness. There are three main types of electromagnetic LbL methods including electrodeposition, magnetic, and electro-immobilization methods. This method can be applied to polymers, colloids, and charged polymers. [ 8 ] [ 9 ]
Film thickness is directly related to the voltage used during assembly, with the optimal voltage depending on the pH of the polymer solution. Higher voltages can cause film desorption, as the electrode repels the previously deposited layer, and the resulting films tend to be more interpenetrated than those produced via the immersive method. Generally, films produced with the electromagnetic method are thicker and more densely packed than films created using other LbL methods. Moreover, this technique requires specialized equipment and expertise. [ 8 ]
Using pressure or vacuum-driven channels, this method enables nanofilm deposition on surfaces that are otherwise difficult to access, such as the interiors of capillaries. Fluidic assembly is used primarily for polymers, but can also be applied to colloids. [ 8 ]
Electrospinning utilizes an external electric field to collect nanofibers on a plate acting as an electrode. The polymer solution or melt used can be manipulated to achieve specific functionalities and morphologies on the surface of the film. Electrospinning enables the creation of ultrathin, high-porosity films and can be created using both synthetic and natural polymer materials. [ 7 ] [ 10 ]
Atomic layer deposition (ALD) is a vapor-phase technique used to produce films with high conformality and precise thickness control. The process relies on self-limiting surface reactions, where only one monolayer is deposited during each cycle. This is achieved through sequential, alternating pulses of gaseous precursors that react with the substrate. The individual gas-surface reactions, or half-reaction, is followed by an inert gas purge to remove byproducts before the introduction of a counter-reactant. The cycle is repeated until the desired film thickness is reached. ALD is versatile, enabling the deposition of a wide range of materials, including metals, insulators, and semiconductors in both crystalline and amorphous forms. Common elements used to create the material are oxides, nitrides, and sulfides. ALD is widely applied in photovoltaics, fuel cells, and semiconductor manufacturing. [ 11 ]
Thermal evaporation is a form of physical vapor deposition (PVD) technique that employs a heat source to vaporize a solid material typically in the form of a rod or wire within a vacuum chamber. The resulting vapor is thermally transported through the vacuum and condenses onto a substrate, creating a thin film. Benefits of thermal evaporation include controlled thickness and uniform, reproducible coatings. This method also features minimal contamination, simplicity, versatility, and cost-effectiveness. It is capable of depositing a wide range of materials such as metals, alloys, and organic compounds, making it suitable for diverse applications in the semiconductor industry, optics, photovoltaics, OLED displays, and sensors. [ 12 ] [ 13 ]
There are many promising applications of nanofilms in medicine, including coatings for medical implant devices, scaffolds for tissue engineering, coatings for targeted drug delivery, artificial cells for oxygen therapeutics, and artificial viruses for immunization [5,8]. Cell coatings can be applied for diagnosis and cell studies due to nanofilms’ ability to attach to biomolecules and replicate molecule diffusion. For example, by layering polymers and nanoparticles on a cell wall, one can create cell-based biosensors . Applying a polymer film onto a cell with attached functional molecules results in targeted molecule delivery. [ 14 ]
By controlling the composition of the film, protein-inspired polypeptide films are being investigated for the development of artificial cells. These films have successfully encapsulated glucose oxidase and hemoglobin. Further research is aimed at applying polypeptide films to encapsulate different drugs for targeted and sustained-release delivery. [ 9 ] [ 14 ]
Carbon nanotubes are used to form nanofilm materials in implants. These films act as antimicrobial agents. The nanofilm is capable of destroying pathogens without the use of antibiotic or other biochemical agents, instead they act through disruption of the cell wall. A nanofilm coating comes in direct contact with the cell wall causing disruption of the cell. [ 5 ]
Nanofilms offer significant potential for improving the efficiency in photovoltaic-thermal collectors. Hybrid photovoltaic-thermal (PV-T) collectors are capable of generating thermal energy and electricity and offer significantly higher overall efficiency compared to independent photovoltaic panels. Nanofilms selectively filter light, allowing only specific parts of the light spectrum to pass through the films. This selectivity allows the light to either be absorbed or reflected to match characteristics of respective solar cells. A glass substrate coated with the nanofilm layers comprises the selectively reflective layer. This ultimately results in increased efficiency. [ 15 ] [ 16 ]
The spectral fraction absorbed by the thermal absorber (Gₜₕ(λ)) can be calculated using the following equation:
Gₜₕ(λ)=Gᵢₙ(λ)𝜏ₙ(λ)
Meanwhile, spectral fraction reflected to the PV cells (Gₚᵥ(λ)) can be calculated using the following equation:
Gₚᵥ(λ)=Gᵢₙ(λ)Ƴₙ(λ)
Where 𝜏ₙ(λ) is the transmissivity of the nanofilm filter, Ƴₙ(λ) is the reflectivity of the filter, and Gᵢₙ(λ) is the incident spectral energy distribution [ 15 ]
TiO₂/SiO₂ is a common stack of nanofilms that significantly reduce absorption loss and can offer high selectivity of cut-off wavelength. Layer thickness ranges from 10 to 110 nm. The cut off wavelength can be adjusted by changing the film material, thickness and number of layers. [ 15 ]
Nanofilms can be used as edible packaging on food surfaces. This emerging application has anti-browning, antioxidant, and antimicrobial properties. In addition, by acting as a moisture barrier, nanoedible films decrease the use of plastic packaging. Edible polymer films are laid within an edible matrix and can be made from a range of different organic materials ranging from polysaccharide-based to protein-based films. [ 17 ] [ 18 ]
Chitosan-based nanofilms, for example, offer microbial resistance as well as a slowed ripening process. Furthermore, the film itself is nontoxic, biodegradable, and biocompatible. [ 17 ] [ 19 ]
While nanofilms offer numerous benefits, concerns regarding their toxicity and environmental impact persist. The mechanisms underlying their toxic effects remain poorly understood due to variations in experimental conditions, such as nanoparticle concentration and structuring methods. [ 5 ]
Further research is necessary to assess the degradability, safety, and environmental footprint of nanofilms, particularly as their use expands across industries. Regulatory frameworks and standardized toxicity testing methods will be essential in ensuring their safe and sustainable implementation. [ 20 ] | https://en.wikipedia.org/wiki/Nanofilm |
Nanofiltration is a membrane filtration process that uses nanometer sized pores through which particles smaller than about 1–10 nanometers pass through the membrane. Nanofiltration membranes have pore sizes of about 1–10 nanometers, smaller than those used in microfiltration and ultrafiltration , but a slightly bigger than those in reverse osmosis . Membranes used are predominantly polymer thin films. [ 1 ] It is used to soften, disinfect, and remove impurities from water, and to purify or separate chemicals such as pharmaceuticals.
Membrane materials that are commonly used are polymer thin films such as polyethylene terephthalate or metals such as aluminium . [ 2 ] Pore dimensions are controlled by pH , temperature and time during development with pore densities ranging from 1 to 106 pores per cm 2 .
Membranes made from polyethylene terephthalate (PET) and other similar materials, are referred to as "track-etch" membranes, named after the way the pores on the membranes are made. [ 3 ] "Tracking" involves bombarding the polymer thin film with high energy particles. This results in making tracks that are chemically developed into the membrane, or "etched" into the membrane, which are the pores.
Membranes created from metal such as alumina membranes, are made by electrochemically growing a thin layer of aluminum oxide from aluminum in an acidic medium. [ citation needed ]
Historically, nanofiltration and other membrane technology used for molecular separation was applied entirely on aqueous systems. The original uses for nanofiltration were water treatment and in particular water softening . [ 4 ] Nanofilters "soften" water by retaining scale-forming divalent ions (e.g. Ca 2+ , Mg 2+ ). [ 5 ] [ 6 ]
Nanofiltration has been extended into other industries such as milk and juice production as well as pharmaceuticals , fine chemicals, and flavour and fragrance industries. [ 5 ]
Room temperature solvent exchange
Purification of gas condensates
Continuous recovery of homogeneous catalysts
Enrichment of natural compounds
Gentle Separations
One of the main advantages of nanofiltration as a method of softening water is that during the process of retaining calcium and magnesium ions while passing smaller hydrated monovalent ions, filtration is performed without adding extra sodium ions, as used in ion exchangers. [ 7 ] Many separation processes do not operate at room temperature (e.g. distillation ), which greatly increases the cost of the process when continuous heating or cooling is applied. Performing gentle molecular separation is linked with nanofiltration that is often not included with other forms of separation processes ( centrifugation ). These are two of the main benefits that are associated with nanofiltration.
Nanofiltration has a very favorable benefit of being able to process large volumes and continuously produce streams of products. Still, Nanofiltration is the least used method of membrane filtration in industry as the membrane pores sizes are limited to only a few nanometers. Anything smaller, reverse osmosis is used and anything larger is used for ultrafiltration. Ultrafiltration can also be used in cases where nanofiltration can be used, due to it being more conventional.
A main disadvantage associated with nanotechnology, as with all membrane filter technology, is the cost and maintenance of the membranes used. [ 8 ] Nanofiltration membranes are an expensive part of the process. Repairs and replacement of membranes is dependent on total dissolved solids, flow rate and components of the feed. With nanofiltration being used across various industries, only an estimation of replacement frequency can be used. This causes nanofilters to be replaced a short time before or after their prime usage is complete. [ citation needed ]
Industrial applications of membranes require hundreds to thousands of square meters of membranes and therefore an efficient way to reduce the footprint by packing them is required. Membranes first became commercially viable when low cost methods of housing in 'modules' were achieved. [ 9 ] Membranes are not self-supporting. They need to be stayed by a porous support that can withstand the pressures required to operate the NF membrane without hindering the performance of the membrane. To do this effectively, the module needs to provide a channel to remove the membrane permeation and provide appropriate flow condition that reduces the phenomena of concentration polarisation. A good design minimises pressure losses on both the feed side and permeate side and thus energy requirements. [ 10 ]
Concentration polarization describes the accumulation of the species being retained close to the surface of the membrane which reduces separation capabilities. It occurs because the particles are convected towards the membrane with the solvent and its magnitude is the balance between this convection caused by solvent flux and the particle transport away from the membrane due to the concentration gradient (predominantly caused by diffusion .) Although concentration polarization is easily reversible, it can lead to fouling of the membrane. [ 10 ] [ 11 ]
Spiral wound modules are the most commonly used style of module and are 'standardized' design, available in a range of standard diameters (2.5", 4" and 8") to fit standard pressure vessel that can hold several modules in series connected by O-rings. The module uses flat sheets wrapped around a central tube. The membranes are glued along three edges over a permeate spacer to form 'leaves'. The permeate spacer supports the membrane and conducts the permeate to the central permeate tube. Between each leaf, a mesh like feed spacer is inserted. [ 11 ] [ 12 ] The reason for the mesh like dimension of the spacer is to provide a hydrodynamic environment near the surface of the membrane that discourages concentration polarisation. Once the leaves have been wound around the central tube, the module is wrapped in a casing layer and caps placed on the end of the cylinder to prevent 'telescoping' that can occur in high flow rate and pressure conditions [ 13 ]
Tubular modules look similar to shell and tube heat exchangers with bundles of tubes with the active surface of the membrane on the inside. Flow through the tubes is normally turbulent , ensuring low concentration polarisation but also increasing energy costs. The tubes can either be self-supporting or supported by insertion into perforated metal tubes. This module design is limited for nanofiltration by the pressure they can withstand before bursting, limiting the maximum flux possible. [ 9 ] [ 10 ] Due to both the high energy operating costs of turbulent flow and the limiting burst pressure, tubular modules are more suited to 'dirty' applications where feeds have particulates such as filtering raw water to gain potable water in the Fyne process. The membranes can be easily cleaned through a ' pigging ' technique with foam balls are squeezed through the tubes, scouring the caked deposits. [ 14 ]
These strategies work to reduce the magnitude of concentration polarisation and fouling. There is a range of techniques available however the most common is feed channel spacers as described in spiral wound modules. All of the strategies work by increasing eddies and generating a high shear in the flow near the membrane surface. Some of these strategies include vibrating the membrane, rotating the membrane, having a rotor disk above the membrane, pulsing the feed flow rate and introducing gas bubbling close to the surface of the membrane. [ 10 ] [ 11 ] [ 12 ]
Retention of both charged and uncharged solutes and permeation measurements can be categorised into performance parameters since the performance under natural conditions of a membrane is based on the ratio of solute retained/ permeated through the membrane. [ citation needed ]
For charged solutes, the ionic distribution of salts near the membrane-solution interface plays an important role in determining the retention characteristic of a membrane. If the charge of the membrane and the composition and concentration of the solution to be filtered is known, the distribution of various salts can be found. This in turn can be combined with the known charge of the membrane and the Gibbs–Donnan effect to predict the retention characteristics for that membrane. [ 10 ]
Uncharged solutes cannot be characterised simply by Molecular Weight Cut Off (MWCO,) although in general an increase in molecular weight or solute size leads to an increase in retention. The charge and structure, pH of the solute, influence the retention characteristics. [ 1 ]
The morphology of a membrane is usually established by microscopy. Atomic force microscopy (AFM) is one method used to characterise the surface roughness of a membrane by passing a small sharp tip (<100 Ă) across the surface of a membrane and measuring the resulting Van der Waals force between the atoms in the end of the tip and the surface. [ 10 ] This is useful as a direct correlation between surface roughness and colloidal fouling has been developed. Correlations also exist between fouling and other morphology parameters, such as hydrophobe , showing that the more hydrophobic a membrane is, the less prone to fouling it is. See membrane fouling for more information. [ citation needed ]
Methods to determine the porosity of porous membranes have also been found via permporometry , making use of differing vapour pressures to characterise the pore size and pore size distribution within the membrane. Initially all pores in the membrane are completely filled with a liquid and as such no permeation of a gas occurs, but after reducing the relative vapour pressure some gaps will start to form within the pores as dictated by the Kelvin equation . Polymeric (non-porous) membranes cannot be subjected to this methodology as the condensable vapour should have a negligible interaction within the membrane. [ 10 ]
Unlike membranes with larger and smaller pore sizes, passage of solutes through nanofiltration is significantly more complex. [ citation needed ]
Because of the pore sizes, there are three modes of transport of solutes through the membrane. These include 1) diffusion (molecule travel due to concentration potential gradients, as seen through reverse osmosis membranes), 2) convection (travel with flow, like in larger pore size filtration such as microfiltration), and 3) electromigration (attraction or repulsion from charges within and near the membrane). [ citation needed ]
Additionally, the exclusion mechanisms in nanofiltration are more complex than in other forms of filtration. Most filtration systems operate solely by size (steric) exclusion, but at small length scales seen in nanofiltration, important effects include surface charge and hydration ( solvation shell ). The exclusion due to hydration is referred to as dielectric exclusion, a reference to the dielectric constants (energy) associated with a particles precense in solution versus within a membrane substrate. Solution pH strongly impacts surface charge, [ 15 ] providing a method to understand and better control rejection.
The transport and exclusion mechanisms are heavily influenced by membrane pore size, solvent viscosity, membrane thickness, solute diffusivity, solution temperature, solution pH, and membrane dielectric constant. The pore size distribution is also important. Modeling rejection accurately for NF is very challenging. It can be done with applications of the Nernst–Planck equation , although a heavy reliance on fitting parameters to experimental data is usually required. [ 1 ]
In general, charged solutes are much more effectively rejected in NF than uncharged solutes, and multivalent solutes like SO 2− 4 (valence of 2) experience very high rejection. [ citation needed ]
Keeping in mind that NF is usually part of a composite system for purification, a single unit is chosen based on the design specifications for the NF unit. For drinking water purification many commercial membranes exist, coming from chemical families having diverse structures, chemical tolerances and salt rejections. [ citation needed ]
NF units in drinking water purification range from extremely low salt rejection (<5% in 1001A membranes) to almost complete rejection (99% in 8040-TS80-TSA membranes.) Flow rates range from 25 to 60 m 3 /day for each unit, so commercial filtration requires multiple NF units in parallel to process large quantities of feed water. The pressures required in these units are generally between 4.5 and 7.5 bar. [ 10 ]
For seawater desalination using a NF-RO system a typical process is shown below. [ citation needed ]
Because NF permeate is rarely clean enough to be used as the final product for drinking water and other water purification, is it commonly used as a pre treatment step for reverse osmosis (RO) [ 8 ] as is shown above.
As with other membrane based separations such as ultrafiltration , microfiltration and reverse osmosis , post-treatment of either permeate or retentate flow streams (depending on the application) – is a necessary stage in industrial NF separation prior to commercial distribution of the product. The choice and order of unit operations employed in post-treatment is dependent on water quality regulations and the design of the NF system. Typical NF water purification post-treatment stages include aeration and disinfection & stabilisation. [ citation needed ]
A Polyvinyl chloride (PVC) or fibre-reinforced plastic (FRP) degasifier is used to remove dissolved gases such as carbon dioxide and hydrogen sulfide from the permeate stream. [ 16 ] This is achieved by blowing air in a countercurrent direction to the water falling through packing material in the degasifier. The air effectively strips the unwanted gases from the water. [ citation needed ]
The permeate water from a NF separation is demineralised and may be disposed to large changes in pH, thus providing a substantial risk of corrosion in piping and other equipment components. To increase the stability of the water, chemical addition of alkaline solutions such as lime and caustic soda is employed. Furthermore, disinfectants such as chlorine or chloroamine are added to the permeate, as well as phosphate or fluoride corrosion inhibitors in some cases. [ 16 ]
Challenges in nanofiltration (NF) technology include minimising membrane fouling and reducing energy requirements. Thin film composite membranes (TFC), which consist of a number of extremely thin selective layers interfacially polymerized over a microporous substrate, have had commercial success in industrial membrane applications. [ 17 ] Electrospunnanofibrous membrane layers (ENMs) enhances permeate flux. [ 18 ] Energy-efficient alternatives to the commonly used spiral wound arrangement are hollow fibre membranes, which require less pre-treatment. [ 19 ] Titanium Dioxide nanoparticles have been used to minimize for membrane fouling. [ 20 ] | https://en.wikipedia.org/wiki/Nanofiltration |
Nanofluidic circuitry is a nanotechnology aiming for control of fluids in nanometer scale. Due to the effect of an electrical double layer within the fluid channel, the behavior of nanofluid is observed to be significantly different compared with its microfluidic counterparts. Its typical characteristic dimensions fall within the range of 1–100 nm. At least one dimension of the structure is in nanoscopic scale . Phenomena of fluids in nano-scale structure are discovered to be of different properties in electrochemistry and fluid dynamics .
With the development of microfabrication and nanotechnology, the study of microfluidics and nanofluidics is drawing more attention. [ 1 ] Research on microfluidic found its advantages in DNA analysis, lab-on-a-chip, and micro-TAS. Devices in a microfluidic system include channels, valves, mixers, and pumps. Integration of these microfluidic devices enables sorting, transporting, and mixing of substances within fluids. However, the failure of moving parts in these systems is usually the critical issue and the main drawback. Mechanisms to control flow without using mechanical parts are always desired for reliability and lifetime. [ 2 ]
In 1997, Wei, Bard and Feldberg discovered that ion rectification occurs at the tip of a nano-sized pipe. [ 3 ] They observed that the surface charge at the wall of a nano-pipet induced a non-neutral electrical potential within the orifice. The electrical potential then modifies the concentration of ion species, resulting in an asymmetric current-voltage characteristic for the current through the pipet.
Transport of ions in the electrolyte can be adjusted by tuning the pH value in a dilute ionic solution, or by introducing an external electrical potential to change the surface charge density of the wall. [ 4 ] As an analogy to semiconductor devices, the mechanism to control charge carrier transport in electronic devices was established in the area of nanofluidics. In nanofluidics, the active control of ion transport is realized using nano-scale channels or pores.
Research efforts on micro-scaled fluidic systems started to focus on the rectifying phenomena, which can be seen only in nano-scaled systems. In 2006, Professor Majumdar and Professor Yang in University of California, Berkeley built the first "nanofluidic" transistor. The transistor can be turn on or off by an external electrical signal, allowing the control of ionic fluids in a nano-scaled channel. Their work implies a possibility to create a nanofluidic circuitry with logic functions.
The main researchers in the area of nanofluidic devices include Arun Majumdar and Peidong Yang in University of California - Berkeley, Harold Craighead and Brian Kirbyat Cornell University, Juan Santiago at Stanford University, Albert van den Berg in University of Twente , Zuzanna Siwy in University of California - Irvine, and Mark Shannon in University of Illinois - Urbana-Champaign.
For electrolyte solution in a channel with a macro- or micro-scaled radius, surface charges at the wall attract counterions and repel co-ions due to electrostatic force. Therefore, an electrical double layer exists between the wall of channel and the solution. The dimension of the electrical double layer is determined by the Debye length in this system, which is typically much smaller than the channel radius. Most of the solution in the channel is electrically neutral due to the shielding effect of the electrical double layer.
In a nanochannel, however, the solution is charged when the dimension of channel radius is smaller than the Debye length . Therefore, it is possible to manipulate the flow of ions inside the nanochannel by introducing surface charges on the wall or by applying an external electrical potential.
Ionic concentration of solution has an important effect on the ion transport. Because a higher concentration leads to a shorter Debye length for the electrical double layer at the channel wall. Its rectifying effect decreases with increasing ionic concentration. On the other hand, ion rectification can be improved by having a dilute solution.
To analyze the transport of ions in the channel, behaviors of system in electrochemistry as well as fluid mechanics need to be considered. The Poisson–Nernst–Planck (PNP) equations are utilized to describe ionic current flowing through a channel, and the Navier–Stokes (NS) equations are used to represent the fluid dynamics in the channel.
The PNP equations consist of the Poisson equation : [ 5 ] [ 6 ]
∇ 2 ϕ = − 1 ε 0 ε ∑ a z a e n a {\displaystyle \nabla ^{2}\phi =-{\frac {1}{\varepsilon _{0}\varepsilon }}\displaystyle \sum _{a}z_{a}en_{a}}
and the Nernst–Planck equations , which gives the particle flux of ion species a {\displaystyle a} due to a concentration gradient and electric potential gradient:
J a = − D a ( ∇ n a + z a e n a k T ∇ ϕ ) {\displaystyle {\boldsymbol {J}}_{a}=-D_{a}(\nabla n_{a}+{\frac {z_{a}en_{a}}{kT}}\nabla \phi )}
where ϕ {\displaystyle \phi } is the electrostatic potential, e {\displaystyle e} is the unit charge of electron, ε 0 {\displaystyle \varepsilon _{0}} is the permittivity in vacuum, and ε {\displaystyle \varepsilon } is the dielectric constant of solution; D a {\displaystyle D_{a}} , n a {\displaystyle n_{a}} and z a {\displaystyle z_{a}} are the diffusivity, the number density of ions, and the valence of ion species a {\displaystyle a} .
The solution in steady-state satisfies the continuity equation. To describe fluid velocity field in the channel, using Navier–Stokes equations :
∇ ⋅ ( n a u + J a ) = 0 {\displaystyle \nabla \cdot (n_{a}{\boldsymbol {u}}+{\boldsymbol {J}}_{a})=0}
∇ ⋅ u = 0 {\displaystyle \nabla \cdot {\boldsymbol {u}}=0}
u ⋅ ∇ u = 1 ρ [ − ∇ p + μ ∇ 2 u − ( ∑ a z a e n a ) ∇ ϕ ] {\displaystyle {\boldsymbol {u}}\cdot \nabla {\boldsymbol {u}}={\frac {1}{\rho }}[-\nabla p+\mu \nabla ^{2}{\boldsymbol {u}}-(\displaystyle \sum _{a}z_{a}en_{a})\nabla \phi ]}
where p {\displaystyle p} , u {\displaystyle {\boldsymbol {u}}} , μ {\displaystyle \mu } , and ρ {\displaystyle \rho } are pressure, velocity vector, viscosity, and density of fluid, respectively. The equations above are usually solved with numerical algorithm to determine the velocity, pressure, electric potential, and ionic concentration in the fluid, as well as the electric current flow through the channel.
Ionic selectivity is defined to evaluate the performance of a nano-channel for ionic flow control. [ 7 ] Ionic selectivity is the ratio of the difference in currents of majority and minority carriers to the total current carried by both positive and negative ions, I {\displaystyle I} . For a nanochannel with perfect control over cation and anion, the selectivity is unity. For a nanochannel without ionic flow control, the selectivity is zero.
S = I + − I − I + + I − {\displaystyle S={\frac {I^{+}-I^{-}}{I^{+}+I^{-}}}}
Nanofluidic diodes are utilized for rectification of ionic transport. [ 8 ] [ 9 ] [ 10 ] A diode in electronic circuits limits the flow of electric current to one direction. A nanofluidic diode has the same function to restrict the ionic flow in one direction. A nanofluidic diode is a channel with its radius dimension of several nanometers. The inner surface of the channel is coated with surface charges. Current rectification can occur when the surface charges at the wall are of the same sign. It is also observed that, when a half of the channel is coated with opposite sign or electrically neutral, the rectification will be enhanced.
When the wall of the channel is coated with positive charges, the negative charged ions in the electrolyte will be attracted and accumulated within the channel. In this case, the flow of positive charges passing through the channel is not favorable, resulting in a decrease in ionic current. Therefore, the ionic current becomes asymmetric if the biasing voltage is reversed.
By applying an additional electrode on a nanochannel as the gate electrode, it is possible to adjust the electrical potential inside the channel. [ 11 ] [ 12 ] A nanofluidic field-effect transistor can be made of silica nanotubes with an oxide as the dielectric material between the metal gate electrode and the channel. [ 13 ] The tuning of the ionic current, therefore, can be achieved by changing the voltage applied on the gate. The gate bias and the source-drain bias are applied to adjust the cation and anion concentration within the nanochannel, therefore tuning the ionic current flowing through it. [ 14 ]
This concept is an analogy to the structure of a metal-oxide semiconductor field-effect transistor (MOSFET) in electronic circuits. Similar to a MOSFET, a nanofluidic transistor is the fundamental element for building a nanofluidic circuitry. There is possibility to achieve a nanofluidic circuitry, which is capable of logic operation and manipulation for ionic particles.
Since the conductance of ionic current flow is controlled by the gate voltage, using a material with high dielectric constant as the wall of the channel is desired. In this case, there is a stronger field seen within the channel due to a higher gate capacitance . A channel surface with a low surface charge is also desired in order to strengthen the effect of potential tuning by gate electrode. This increases the ability to spatially and temporally tune the ionic and electrostatic environment in the channel.
By introducing an asymmetric field effect along the nanochannel, a field-effect reconfigurable nanofluidic diode is feasible, [ 16 ] which features post-fabrication reconfiguration of the diode functions, such as the forward/reverse directions and the rectification degrees. Unlike the nanofluidic field-effect transistor, where only the amount of ions/molecules is regulated by an electrostatic potential, the field-effect reconfigurable diode can be used to control both directions and magnitudes of ion/molecule transport. This device could be deemed as the building blocks for ionic counterpart of the electronic field-programmable gate array.
Ionic bipolar transistors can be made from two conical channels with the smallest opening in nano-scaled dimension. By introducing opposite surface charges at each side, it is able to rectify ionic current as an ionic diode. An ionic bipolar transistor is built by combining two ionic diodes and forming a PNP junction along the inner surface of the channel. While the ionic current is from emitter end to collector end, the strength of the current can be modulated by the base electrode. The surface charge at the channel wall can be modified using chemical methods, by changing the electrolyte concentration or pH value.
Nanofuidic triode is a three-terminal double junction nanofluidic device composed of positive-charged alumina and negative-charged silica nanochannels. [ 17 ] The device is essentially a three-terminal bipolar junction transistor. By controlling the voltage across emitter and collector terminals, one can regulate the ion current from base terminal to one of the other two terminals, functioning as an ionic single-pole, double-throw switch.
When surface charges present at the wall of a channel of micro-scaled width, counterions are attracted and co-ions are repelled by electrostatic force. The counterions form a shielding area near the wall. This region penetrate into solution to a certain distance called Debye length until the electric potential decays to the bulk value of neutrality. The Debye length is ranging typically from 1 nm to 100 nm for aqueous solutions.
In nano-channels, the Debye length is usually comparable with the channel width, therefore solution within the channel is charged. Ions inside the fluid is no longer shielded from surface charge. Instead, surface charge affect the dynamics of ions within a nano-channel.
It requires a channel to be narrow and long for it to have a good selectivity. In other words, a channel with a high aspect ratio has a better selectivity. To further increase its selectivity, it is required to have a highly charged wall. [ 7 ]
The performance of ionic selectivity also largely related to the applied bias. With a low bias, a high selectivity is observed. With the increase of the bias voltage, there is an apparent decrease in the selectivity. For a nanochannel with a low aspect ratio, high selectivity is possible when the bias voltage is low.
The advantage of nanofluidic devices is from its feasibility to be integrated with electronic circuitry. Because they are built using the same manufacturing technology, it is possible to make a nanofluidic system with digital integrated circuit on a single chip. Therefore, the control and manipulation of particles in the electrolyte can be achieved in a real-time. [ 19 ]
Fabrication of nano-channels is categorized into top-down and bottom-up methods. Top-down methods are the conventional processes utilized in the IC industry and Microelectromechanical systems research. It begins with photolithography on a bulk silicon wafer. Bottom-up methods, in contrast, starts with atoms or molecules with intrinsic nano-scaled dimension. By organize and combine these building blocks together, it is able to form a nanostructures as small as only a few nanometers.
A typical method of top-down fabrication includes photolithography to define the geometry of channels on a substrate wafer. The geometry is created by several thin-film deposition and etching steps to form trenches. The substrate wafer is then bonded to another wafer to seal the trenches and form channels. Other technologies to fabricate nano-channels include surface micromachining with sacrificial layers, nano-imprinting lithography, and soft-lithography.
The most common method utilized for bottom-up fabrication is self-assembled monolayers (SAM). This method usually use biological materials to form a molecular monolayer on the substrate. Nano-channels can also be fabricated from the growth of carbon nanotubes (CNT) and quantum wires. The bottom-up methods usually give well-defined shapes with characteristic length about few nanometers. For these structures to be utilized as nanofluidic devices, the interconnection between nano-channels and microfluidic systems becomes an important issue.
There exist several ways to coat the inner surface with specific charges. Diffusion-limited patterning can be utilized because a bulk solution only penetrate the entrance of a nanochannel within a certain distance. Because the diffusion speed is different for each reactant. By introducing several steps of reactants flowing into the nanochannel, it is possible to pattern the surface with different surface charges inside the channel. [ 20 ]
Nanofluidic devices have been built for application in chemistry, molecular biology and medicine. The main purposes to use nanofluidic devices are separation and measurement of solutions containing nanoparticles for drug delivery, gene therapy and nanoparticle toxicology on a micro-total-analysis system. [ 21 ] An important advantage of micro- and nano-scaled systems is the small amount of sample or reagent used in analysis. This reduces the time required for sample processing. It is also possible to achieve analysis in an array, which further speeds up processes and increases throughput of analysis.
Nanochannels are utilized to achieve single-molecule sensing and diagnosis, as well as DNA separation. In many cases, nanofluidic devices are integrated within a microfluidic system to facilitate logic operation of fluids. The future of nanofluidic systems will be focused on several areas such as analytical chemistry and biochemistry, liquid transport and metering, and energy conversion.
In nanofluidics, the valence numbers of the ions determines their net electrophoretic velocities. In other words, the velocity of an ion in the nano-channel is related not only to its ion mobility but also its ion valence. This enables the sorting function of nanofluidics, which cannot be done in a micro-channel. Therefore, it is possible to do sorting and separation for short strand DNA by using a nanochannel. For the single-molecule DNA application, the final goal is to sequence a strand of genomic DNA in a reproducible and precise result. Similar application can also be found in chromatography , or separation of various ingredients in the solution.
Application also can be found in synthesis of fibers. Polymer fibers can be created by electrospinning the monomers at an interface between liquid and vacuum. An organized polymer structure is formed from a flow of monomers aligning on a substrate.
There is also an attempt to bring nanofluidic technology into energy conversion. In this case, the electrical charged wall behaves as the stator, while the flowing solution as the rotor. It is observed that when the pressure-driven solvent flowing through a charged nanochannel, it can generate a streaming current and a streaming potential. This phenomenon can be used in electrical energy harvesting.
Advances in nanofabrication techniques and concerns about energy shortage make people interested in this idea. The main challenge is to increase efficiency, which is now only a few percent, compared with efficiencies of up to about 95 per cent for standard rotational electromagnetic generators.
Recent studies focus on the integration of nanofluidic devices into microsystems. An interface should be created for the connection between two length-scales. A system with solely nanofluidic devices standalone is impractical because it would requires a large driving pressure to make fluids flow into the nano-channel. [ 22 ]
Nanofluidic devices are powerful in their high sensitivity and accurate manipulation of sample materials even down to a single molecule. Nevertheless, the drawback of nanofuidic separation systems is the relatively low sample throughput and its result in detection. One possible approach to deal with the problem is to use parallel separation channels with parallel detection in each channel. In addition, a better approach for detection needs to be created in view of the very small quantities of molecules present.
One of the biggest challenges in this research area are due to the peculiar size-effect. Researchers try to solve the problems caused by the extremely high surface-to-volume ratios. Under this condition, adsorption of molecules can lead to large losses and can also change the surface properties.
Another issue arises when the sample for detection is a relatively large molecule, such as DNA or protein. In the application for large molecule, clogging is a concern because the small size of the nanochannel makes it easy to happen. A low friction coating at inner surface of the channel is desired to avoid blocking of fluid channels in this application. | https://en.wikipedia.org/wiki/Nanofluidic_circuitry |
Nanofluidics is the study of the behavior, manipulation, and control of fluids that are confined to structures of nanometer (typically 1–100 nm) characteristic dimensions (1 nm = 10 −9 m). Fluids confined in these structures exhibit physical behaviors not observed in larger structures, such as those of micrometer dimensions and above, because the characteristic physical scaling lengths of the fluid, ( e.g. Debye length , hydrodynamic radius ) very closely coincide with the dimensions of the nanostructure itself.
When structures approach the size regime corresponding to molecular scaling lengths, new physical constraints are placed on the behavior of the fluid. For example, these physical constraints induce regions of the fluid to exhibit new properties not observed in bulk, e.g. vastly increased viscosity near the pore wall; they may effect changes in thermodynamic properties and may also alter the chemical reactivity of species at the fluid-solid interface . A particularly relevant and useful example is displayed by electrolyte solutions confined in nanopores that contain surface charges , i.e. at electrified interfaces, as shown in the nanocapillary array membrane (NCAM) in the accompanying figure.
All electrified interfaces induce an organized charge distribution near the surface known as the electrical double layer . In pores of nanometer dimensions the electrical double layer may completely span the width of the nanopore, resulting in dramatic changes in the composition of the fluid and the related properties of fluid motion in the structure. For example, the drastically enhanced surface-to-volume ratio of the pore results in a preponderance of counter-ions ( i.e. ions charged oppositely to the static wall charges) over co-ions (possessing the same sign as the wall charges), in many cases to the near-complete exclusion of co-ions, such that only one ionic species exists in the pore. This can be used for manipulation of species with selective polarity along the pore length to achieve unusual fluidic manipulation schemes not possible in micrometer and larger structures.
In 1965, Rice and Whitehead published the seminal contribution to the theory of the transport of electrolyte solutions in long (ideally infinite) nanometer-diameter capillaries. [ 1 ] Briefly, the potential , ϕ , at a radial distance, r , is given by the Poisson-Boltzmann equation ,
where κ is the inverse Debye length ,
determined by the ion number density , n , the dielectric constant , ε , the Boltzmann constant , k , and the temperature, T . Knowing the potential, φ(r) , the charge density can then be recovered from the Poisson equation , whose solution may be expressed as a modified Bessel function of the first kind, I 0 , and scaled to the capillary radius, a . An equation of motion under combined pressure and electrically-driven flow can then be written,
where η is the viscosity, dp/dz is the pressure gradient, and F z is the body force driven by the action of the applied electric field , E z , on the net charge density in the double layer.
When there is no applied pressure, the radial distribution of the velocity is given by,
From the equation above, it follows that fluid flow in nanocapillaries is governed by the κa product, that is, the relative sizes of the Debye length and the pore radius.
By adjusting these two parameters and the surface charge density of the nanopores, fluid flow can be manipulated as desired.
Nanostructures can be fabricated as single cylindrical channels, nanoslits, or nanochannel arrays from materials such as silicon, glass, polymers (e.g. PMMA , PDMS , PCTE) and synthetic vesicles. [ 3 ] Standard photolithography , bulk or surface micromachining, replication techniques (embossing, printing, casting and injection molding), and nuclear track or chemical etching, [ 4 ] [ 5 ] [ 6 ] [ 7 ] [ 8 ] are commonly used to fabricate structures which exhibit characteristic nanofluidic behavior.
Because of the small size of the fluidic conduits, nanofluidic structures are naturally applied in situations demanding that samples be handled in exceedingly small quantities, including Coulter counting, [ 9 ] analytical separations and determinations of biomolecules, such as proteins and DNA, [ 2 ] [ 10 ] and facile handling of mass-limited samples. One of the more promising areas of nanofluidics is its potential for integration into microfluidic systems, i.e. micrototal analytical systems or lab-on-a-chip structures. For instance, NCAMs, when incorporated into microfluidic devices, can reproducibly perform digital switching, allowing transfer of fluid from one microfluidic channel to another, [ 11 ] [ 12 ] selectivity separate and transfer analytes by size and mass, [ 11 ] [ 13 ] [ 14 ] [ 15 ] [ 16 ] mix reactants efficiently, [ 17 ] and separate fluids with disparate characteristics. [ 11 ] [ 18 ] In addition, there is a natural analogy between the fluid handling capabilities of nanofluidic structures and the ability of electronic components to control the flow of electrons and holes. This analogy has been used to realize active electronic functions such as rectification [ 19 ] [ 20 ] and field-effect [ 21 ] [ 22 ] [ 23 ] and bipolar transistor [ 24 ] [ 25 ] action with ionic currents. Application of nanofluidics is also to nano-optics for producing tuneable microlens array [ 26 ] [ 27 ]
Nanofluidics have had a significant impact in biotechnology , medicine and clinical diagnostics with the development of lab-on-a-chip devices for PCR and related techniques. [ 28 ] [ 29 ] Attempts have been made to understand the behaviour of flowfields around nanoparticles in terms of fluid forces as a function of Reynolds and Knudsen number using computational fluid dynamics . [ 30 ] [ 31 ] [ 32 ] The relationship between lift, drag and Reynolds number has been shown to differ dramatically at the nanoscale compared with macroscale fluid dynamics.
There are a variety of challenges associated with the flow of liquids through carbon nanotubes and nanopipes. A common occurrence is channel blocking due to large macromolecules in the liquid. Also, any insoluble debris in the liquid can easily clog the tube. A solution for this researchers are hoping to find is a low friction coating or channel materials that help reduce the blocking of the tubes. Also, large polymers, including biologically relevant molecules such as DNA, often fold in vivo, causing blockages. Typical DNA molecules from a virus have lengths of approx. 100–200 kilobases and will form a random coil of the radius some 700 nm in aqueous solution at 20%. This is also several times greater than the pore diameter of even large carbon pipes and two orders of magnitude the diameter of a single walled carbon nanotube. | https://en.wikipedia.org/wiki/Nanofluidics |
Nanofoams are a class of nanostructured, porous materials ( foams ) containing a significant population of pores with diameters less than 100 nm . Aerogels are one example of nanofoam. [ 1 ]
Metallic nanofoams are a subcategorization of nanofoams; more specifically, there are nanofoams consisting of metals, often pure, that form interconnected networks of ligaments that make up the structure of the foam. A variety of metals are used, including copper , nickel , gold , and platinum . [ 2 ] Metallic nanofoams may offer certain advantages over alternative polymer nanofoams; structurally, they retain the electrical conductivity of metals, offer increased ductility , as well as the higher surface area and nano-architecture properties offered by nanofoams. [ 2 ]
Synthesis of metallic nanofoams may be accomplished through a variety of methods. In 2006, researchers produced metal nanofoams by igniting pellets of energetic metal bis(tetrazolato)amine complexes. Nanofoams of iron , cobalt , nickel , copper , silver , and palladium have been prepared through this technique. These materials exhibit densities as low as 11 mg/cm 3 , and surface areas as high as 258 m 2 /g. These foams are effective catalysts [ 3 ] and electrocatalyst supports. [ 4 ] Also, metal nanofoams can be made by electrodeposition of metals inside templates with interconnected pores, such as 3D-porous anodic aluminum oxide (AAO). [ 5 ] [ 6 ] [ 7 ] Such method gives nanofoams with an organized structure and allows to control the surface area and porosity of the fabricated material. [ 8 ] [ 9 ] [ 10 ]
A 2016 study discussed a low temperature/pressure microwave solvothermal method for fabricating pure copper, silver, and nickel metal nanofoams. The process claims to be non-hazardous, novel, as well as facile, with an emphasis on its low-waste and low-cost method of manufacturing. [ 11 ]
Additionally, a 2020 publication discussed successful synthesis of nanofoam films from silver, gold, copper, and palladium through the use of a modified vacuum thermal evaporation method. [ 12 ]
Metallic nanofoams have seen a broad variety of applications, including catalysts, [ 13 ] hydrogen storage , [ 14 ] as well as fuel cells . [ 15 ] Additionally, applications of metallic nanofoam as an electrocatalyst have been fruitful; a nickel-iron nanofoam catalyst has proven to exhibit exceptional electrocatalytic performance, as well as water-splitting to isolate hydrogen atoms. [ 16 ] Applications to the clean energy industry, specifically for lithium-ion batteries and other fuel cells, have been discussed as well. [ 11 ]
Through literature discussing the fabrication of a completely porous nanofoam biopolymer is scarce, recent endeavors have resulted in the formation of nanofoam surfaces on biopolymers. [ 17 ] In these instances, biopolymers such as collagen and gelatine, [ 18 ] chitosan, [ 19 ] and pure curcumin [ 17 ] have been used to varying degrees.
A 2008 study explored the usage of femtosecond laser irradiation to create permanent spatial arrangements in transparent materials, particularly in its usage to form a singular foamed layer upon biopolymers such as collagen or curcumin. [ 17 ] Foaming these surfaces results in a variety of surface modifications that may improve the material's ability for cell adhesion, permeability of fluids due to cell structure, and the formation of nanoscopic fibers. [ 19 ]
Additionally, an iron-nitrogen co-doped carbon nanofoam was purposed to be fabricated through the acile salt-assisted pyrolysis process of chitooligosaccharides. [ 20 ]
Foamed biopolymers have multiple purported applications in the biomedical and pharmaceuticals industry due to their modified surface properties. Gelatine films with curcumin dropped upon the surface, for instance, displayed a higher tolerance for ablation following its foaming; this tolerance is suspected to arise from curcumin's binding to proteins to protect from free radicals, as well as its anti-oxidant properties. [ 17 ] These findings present implications for greater cellular surgery, as well as the manufacturing of biopolymers as a whole, due to these modifications from plasma irradiation. [ 17 ]
Silver nanofoams are specific metal nanofoams consisting of mainly silver that are uniquely regarded for their antibacterial and electrical properties. Many of these silver nanofoams are alloys of silver and another metal such as aluminum. [ 21 ] They are unique for their hierarchical porous structure are a current point of modern research and development. They have many applications in the fields of mechanical, chemical, and biomedical engineering, including filtration, air management, and use in electrical systems.
The underlying principle is to merge pores of different sizes into a material with a large surface area (thanks to smaller pores), which in turn allows efficient molecular transport (which requires larger pores). The process used to produce these materials is a combination of the replication method, typically used to produce large-pore foams, and the selective dissolution method, generally used to manufacture small-pore foams. [ 21 ]
Ag foams with hierarchical porous structures are prepared by the following three-step method: [ 21 ]
(i) Packing large spherical NaCl particles to create a hard template, with a distinct perform network of negative space. Then this network is filled with liquid Al-25Ag.
(ii) Removing the NaCl template by water dissolution to form Al−25Ag macro-porous foam.
(iii) Dissolving the Al-rich phase by a chemical attack with aqueous solutions of HCl or NaOH to form the final Ag foam. This creates the nanoscale pores of the foam.
Silver ions have been shown to have potent antibacterial activity, and have been shown to affect the growth of Gram-positive and Gram-negative bacteria. This is due to their ability to form ligand complexes with proteins or enzymes in bacterial cells. [ 21 ] Due to this unique property, these nanofoams create excellent air filters designed to filter out bacteria and other microorganisms, this level of filtration was shown to be more effective than tradition HCl analogues. [ 21 ]
These silver nanofoams have also been used as electrocatalysts for the reduction reaction of CO 2 to CO. It was found that on average silver nanofoams can maintain over 90% FECO in a wide potential window (−0.5 to −1.2 VRHE), enabling the maximum CO selective current density of 33 mA cm−2 and the mass activity of 23.5 A gAg−1, which are the highest values among recently reported metal foam-based electrocatalysts. [ 22 ]
Carbon nanofoam is an allotrope of carbon discovered in 1997. [ 23 ] Its structure consists of a cluster-assembly of carbon atoms strung together in a loose three-dimensional web, similar to an aerogel. The material has a density of 2–10 mg/cm 3 (0.0012 lb/ft 3 ), which is among the lightest materials to date. [ 23 ] [ 24 ] [ 25 ] [ 26 ] [ 27 ]
There are multiple formation methods for carbon nanofoams. Pulsed Laser Deposition (PLD) has been the first technique used for the synthesis of carbon nanofoam, [ 23 ] and is considered one of the most versatile approach for the production of carbon nanofoams with controlled density and morphology. [ 27 ] The process of nanofoam growth via the Pulsed Laser Deposition has been described in terms of a " snowfall-like " mechanism: [ 26 ]
(i) Carbon nanoparticles are generated upon laser ablation of a graphite target, either directly of because of the presence of a background atmosphere
(ii) Nanoparticles stick together in micrometric-sized, fractal-like aggregates that grow in-flight within the deposition chamber
(iii) fractal-like aggregates land on a suitable substrate, much like snowflakes land on the ground
(iv) a void-rich, web-like nanofoam is obtained by the layering of fractal-like aggregates
Two of the most common alternatives to PLD synthesis are described below:
Cellulose nanofibers (CNF) were constructed into nanofoams by: [ 28 ]
(i) Recycled milk container board was pretreated with deep eutectic solvent (DES) to fibrillate it.
(ii) The pretreated board was put through a simple freezing drying procedure to form a nanofoam shape.
(iii) Fibers are then modified for increased hydrophobicity and reinforced structure by sialylation agents.
A porous carbon nanofoam was created by: [ 29 ]
(i) Pitch and CaCO 3 (in a 1:14 ratio) were dissolved in methylene chloride . 10mL of NaCl was added. Mixture was stirred continuously.
(ii) Sample was naturally air dried at room temperature.
(iii) Sample was carbonized at 600 °C for 2 hours. The heating rate was 2 °C per minute.
(iv) Carbonized structure is washed in 1M HCl to remove excess CaCO 3 nanoparticles.
Carbon Nanofoams have been shown to have great application as solar steam generators . They possess excellent light absorption, good thermal stability, low density, and low thermal conductivity, all factors important to solar generators. In experiments done, carbon nanofoams showed superior solar photo-thermal performance with an evaporation rate of 1.68 kg m−2 h−1 achieved under 1 sun irradiation. [ 29 ]
Additionally, carbon nanofoams have also been used to create extremely efficient aerosol filters . Using cellulose nanofibers collected from recycled milk jugs, researchers were able to develop a carbon nanofoam that achieved a very high filtration efficacy (>99.5%) in tests run with 0.7 wt% nanofoam sample for particles smaller than 360 nm. This efficiency value even meets the standard requirements of the N95 respirator face masks. The structure of the nanofoam filter gives it an advantage in performance over normal filters when dealing with high particle bearing [ 28 ]
In 2014, researchers also fabricated glass nanofoam via femtosecond laser ablation. Their work consisted of raster scanning femtosecond laser pulses over the surface of glass to produce glass nanofoam with ~70 nm diameter wires. [ 30 ] | https://en.wikipedia.org/wiki/Nanofoam |
A nanofoundry is considered to be a foundry that performs on a scale similar to nanotechnology . This concept makes it similar to the role that the nanofactory would play because it is considered to be a factory that operates on that same scale model. The closest thing that nature has to a nanofoundry is the simple biological cell . [ 1 ]
In silico biology attempts to duplicate nature by creating a virtual cell with the complete cycle of metabolism. [ 1 ] The idea of creating an artificial cell along with working nanofoundries is highlighted in the phenomena of bioconvergence ; which may advance us from the Information Age to the "Nanotechnology Age. [ 1 ] " Nanofoundries and artificial cells are creating a world where health care , the very definition of "medicine", along with life itself is entering a state of transition. [ 1 ] This phenomenon is directly in parallel with changes in the procedures used in agriculture , managing our bioresources, ultimately leading up to the de facto equivalent of bio-engineering entire ecosystems from scratch. [ 1 ]
As of 2011 [update] the latest area of research involved using both micro- and nano-focused ion beams is found using nanomachining . [ 2 ] Preliminary studies have indicated that tissues can be successfully grown on three-dimensional structures while using ion beams on a substrate. [ 2 ]
On a larger scale, materials that appear to be smooth still have an abrasive appearance to them. [ 3 ] Using the nanoscale, however, atoms rub off one a time. [ 3 ] This creates new challenges for researchers who build their devices that are only 10 atoms wide. [ 3 ]
One of the first nanofoundries has been set up at the University of Madras in Chennai , Tamil Nadu , India . [ 4 ] Knowledge about nanotechnology would be converted into useful consumer goods through the usage of nanofoundries. [ 4 ] Scientists do not want nanotechnology to be confined to publishing research papers in journals when it could be useful for creating nanotechnology-enhanced consumer products that would be beneficial in our 21st century society. [ 4 ] By converting the nanotechnology curriculum of the major universities into a more industry-oriented format, it makes the technology more practical for employers as well as consumers. [ 4 ]
The ability to grow more complex structures with a high ratio allows for drug release devices, biosensors , nanoreactors , and other countless discoveries. [ 2 ] During the following decades to come, researchers will scramble to construct the world's first nuclear nanobeam complex. [ 2 ] This facility would offer state-of-the-art facilities to a wide range of disciplines; including the conventional sciences. [ 2 ]
Commercial manufacturing could easily be scaled up thanks to nanofoundries. [ 3 ] Nanofactories will most likely use metal nanoparticles instead of glass, plastic or rare earth minerals that are currently used to make most of our products. [ 5 ] | https://en.wikipedia.org/wiki/Nanofoundry |
A nanofountain probe ( NFP ) is a device for 'drawing' micropatterns of liquid chemicals at extremely small resolution. An NFP contains a cantilevered micro-fluidic device terminated in a nanofountain. The embedded microfluidics facilitates rapid and continuous delivery of molecules from the on-chip reservoirs to the fountain tip. When the tip is brought into contact with the substrate, a liquid meniscus forms, providing a path for molecular transport to the substrate . By controlling the geometry of the meniscus through hold time and deposition speed, various inks and biomolecules could be patterned on a surface, with sub 100 nm resolution.
The advent of dip-pen nanolithography (DPN) in recent years represented a revolution in nanoscale patterning technology. With sub-100-nanometer resolution and an architecture conducive to massive parallelization, DPN is capable of producing large arrays of nanoscale features. As such, conventional DPN and other probe-based techniques are generally limited in their rate of deposition and by the need for repeated re-inking during extended patterning.
To address these challenges, nanofountain probe was developed by Espinosa et al. where microchannels were embedded in AFM probes to transport ink or bio-molecules from reservoirs to substrates, realizing continuous writing at the nanoscale. [ 1 ] Integration of continuous liquid ink feeding within the NFP facilitates more rapid deposition and eliminates the need for repeated dipping, all while preserving the sub-100-nanometer resolution of DPN.
Nano fountain probes (NFPs) are fabricated on the wafer-scale using microfabrication techniques allowing for batch fabrication of numerous chips. [ 2 ] Through the different generations of devices, design and experimentation improved the device yielding to a robust fabrication process. The highly enhanced feature dimension and shapes is expected to improve the performance in writing and imaging.
NFP is used in the development of a to scale, direct-write nanomanufacturing platform. The platform is capable of constructing complex, highly-functional nanoscale devices from a diverse suite of materials (e.g., nanoparticles, catalysts (increase rate of reaction), biomolecules, and chemical solutions). [ 3 ] Demonstrated nanopatterning capabilities include:
• Biomolecules (proteins, DNA ) for biodetection assays or cell adhesion studies
• Functional nanoparticles for drug delivery studies and nanosystems making (fabrication)
• Catalysts for carbon nanotube growth in nanodevice fabrication
• Thiols for directed self-assembly of nanostructures.
Taking advantage of the unique tip geometry of the NFP nanomaterials are directly injected into live cells with minimal invasiveness. [ 4 ] This enables unique studies of nanoparticle -mediated delivery, as well as cellular pathways and toxicity. Whereas typical in vitro studies are limited to cell populations, these broadly-applicable tools enable multifaceted interrogation at a truly single cell level. | https://en.wikipedia.org/wiki/Nanofountain_probe |
A nanogenerator is a compact device that converts mechanical or thermal energy into electricity, serving to harvest energy for small, wireless autonomous devices. It uses ambient energy sources like solar, wind, thermal differentials, and kinetic energy . Nanogenerators can use ambient background energy in the environment, such as temperature gradients from machinery operation, electromagnetic energy , or even vibrations from motions.
Energy harvesting from the environment has a very long history, dating back to early devices such as watermills , windmills and later hydroelectric plants . More recently there has been interest in smaller systems. While there was some work in the 1980s on implantable piezoelectric devices, [ 1 ] [ 2 ] more devices were developed in the 1990s including ones based upon the piezoelectric effect , [ 3 ] [ 4 ] electrostatic forces , [ 5 ] thermoelectric effect [ 6 ] and electromagnetic induction [ 7 ] [ 8 ] —see Beeby et al for a 2006 review. [ 9 ] Very early on it was recognized that these could use energy sources such as from walking in shoes, [ 10 ] and could have important medical applications, [ 4 ] be used for in vivo MEMS devices [ 11 ] or be used to power wearable computing. [ 12 ] Many more recent systems have built onto this work, for instance triboelectric generators, [ 13 ] bistable systems, [ 14 ] pyroelectric materials [ 15 ] and continuing work on piezoelectric systems [ 16 ] as well as those described in more general overviews [ 17 ] including applications in wireless electronic devices [ 18 ] and other areas.
There are three classes of nanogenerators: piezoelectric , triboelectric , both of which convert mechanical energy into electricity, and pyroelectric nanogenerators, which convert heat energy into electricity. [ 19 ]
A piezoelectric nanogenerator is an energy-harvesting device capable of converting external kinetic energy into electrical energy via action by a nano-structured piezoelectric material. It is generally used to indicate kinetic energy harvesting devices utilizing nano-scaled piezoelectric material, like in thin-film bulk acoustic resonators . [ 20 ] [ 21 ]
The working principle of the nanogenerator will be explained in two different cases: the force exerted perpendicular to and parallel to the axis of the nanowire . [ 22 ] When a piezoelectric structure is subjected to the external force of the moving tip, deformation occurs throughout the structure. The piezoelectric effect will create an electrical field inside the nanostructure ; the stretched part with the positive strain will exhibit positive electrical potential, whereas the compressed part with negative strain will show the negative electrical potential. This is due to the relative displacement of cations with respect to anions in their crystalline structure. As a result, the tip of the nanowire will have an electrical potential distribution on its surface, while the bottom of the nanowire is neutralized since it is grounded. The maximum voltage generated in the nanowire can be calculated using the following equation: [ 23 ]
V max = ± 3 4 ( κ 0 + κ ) [ e 33 − 2 ( 1 + ν ) e 15 − 2 ν e 31 ] a 3 l 3 ν max {\displaystyle V_{\text{max}}=\pm {\frac {3}{4(\kappa _{0}+\kappa )}}[e_{\text{33}}-2(1+\nu )e_{\text{15}}-2\nu e_{\text{31}}]{\frac {a^{3}}{l^{3}}}\nu _{\text{max}}} ,
where κ 0 is the permittivity in vacuum, κ is the dielectric constant, e 33 , e15, and e 31 are the piezoelectric coefficients, ν is the Poisson ratio, a is the radius of the nanowire, l is the length of the nanowire, and ν max is the maximum deflection of the nanowire's tip.
The Schottky contact must be formed between the counter electrode and the tip of the nanowire since the ohmic contact will neutralize the electrical field generated at the tip. ZnO nanowire with an electron affinity of 4.5 eV, Pt ( φ = 6.1 eV ), is a metal sometimes used to construct the Schottky contact. By constructing the Schottky contact, the electrons will pass to the counter electrode from the surface of the tip when the counter electrode is in contact with the regions of the negative potential, whereas no current will be generated when it is in contact with the regions of the positive potential, in the case of the n-type semiconductive nanostructure (the p-type semiconductive structure will exhibit the reversed phenomenon since the hole is mobile in this case).
For the second case, a model with a vertically grown nanowire stacked between the ohmic contact at its bottom and the Schottky contact at its top is considered. When the force is applied toward the tip of the nanowire, the uniaxial compressive force is generated in the nanowire. Due to the piezoelectric effect, the tip of the nanowire will have a negative piezoelectric potential, increasing the Fermi level at the tip. Since the electrons will then flow from the tip to the bottom through the external circuit, positive electrical potential will be generated at the tip. The Schottky contact will stop electrons from being transported through the interface, therefore maintaining the potential at the tip. As the force is removed, the piezoelectric effect diminishes, and the electrons will be flowing back to the top in order to neutralize the positive potential at the tip. The second case will generate an alternating-current output signal. [ 24 ]
Depending on the configuration of the piezoelectric nanostructure, the nanogenerator can be categorized into 3 types: VING, LING, and NEG.
VING is a 3-dimensional configuration consisting of a stack of 3 layers, which are the base electrode, the vertically grown piezoelectric nanostructure, and the counter electrode. The piezoelectric nanostructure is usually grown on the base electrode, which is then integrated with the counter electrode in full or partial mechanical contact with its tip.
The first VING was developed in 2007 [ 25 ] with a counter electrode with the periodic surface grating resembling the arrays of the AFM tip as a moving electrode. Since the counter electrode is not in full contact with the tips of the piezoelectric nanowire, its motion in-plane or out-of-plane caused by the external vibration induces the deformation of the piezoelectric nanostructure, leading to the generation of the electrical potential distribution inside each individual nanowire. The counter electrode is coated with metal, forming a Schottky contact with the tip of the nanowire. Zhong Lin Wang's group has generated counter electrodes composed of ZnO nanorods. Sang-Woo Kim's group at Sungkyunkwan University (SKKU) and Jae-Young Choi's group at Samsung Advanced Institute of Technology (SAIT) introduced a bowl-shaped transparent counter electrode by combining anodized aluminum and electroplating technology. [ 26 ] They have also developed the other type of counter electrode by using networked single-walled carbon nanotube ( SWNT ). [ 27 ]
LING is a 2-dimensional configuration consisting of three parts: the base electrode, the laterally grown piezoelectric nanostructure, and the metal electrode for schottky contact. In most cases, the thickness of the substrate film is thicker than the diameter of the piezoelectric nanostructure. LING is an expansion of the single wire generator (SWG).
NEG is a 3-dimensional configuration consisting of three main parts: the metal plate electrodes, the vertically grown piezoelectric nanostructure, and the polymer matrix, which fills in between the piezoelectric nanostructure. NEG was introduced by Momeni et al. [ 28 ] A fabric-like geometrical configuration has been suggested where a piezoelectric nanowire is grown vertically on the two microfibers in their radial direction, and they are twined to form a nanogenerator. [ 29 ] One of the microfibers is coated with the metal to form a Schottky contact, serving as the counter electrode for VINGs.
Among the various piezoelectric materials studied for the nanogenerator, much of the research has focused on materials with a wurtzite structure , such as ZnO , CdS [ 30 ] and GaN . [ 31 ] Zhong Lin Wang of the Georgia Institute of Technology introduced p-type ZnO nanowires. [ 32 ] Unlike the n-type semiconductive nanostructure, the mobile particle in the p-type is a hole, thus, the schottky behavior is reversed from that of the n-type case; the electrical signal is generated from the portion of the nanostructure where the holes are accumulated.
From the idea that the material with a perovskite structure is known to have more effective piezoelectric characteristics compared to that with a wurtzite structure, barium titanate nanowire has also been studied by Min-Feng Yu of the University of Illinois at Urbana -Champaign. [ 33 ] The output signal was found to be more than 16 times that of a similar ZnO nanowire. Liwei Lin of the University of California, Berkeley , has suggested that PVDF can also be applied to form a nanogenerator. [ 34 ]
A comparison of the reported materials as of 2010 is given in the following table:
In 2010, the Zhong Lin Wang group developed a self-powered pH or UV sensor integrated with VING with an output voltage of 20–40 mV on the sensor. Zhong Lin Wang's group has also generated an alternating current voltage of up to 100 mV from the flexible SWG attached to a device for running hamster . [ 39 ]
Some of the piezoelectric nanostructure can be formed on various kinds of substrates, such as transparent organic substrates. The research groups in SKKU (Sang-Woo Kim's group) and SAIT (Jae-Young Choi's group) have developed a transparent and flexible nanogenerator. Their research substituted an indium-tin-oxide (ITO) electrode with a graphene layer. [ 40 ]
A triboelectric nanogenerator is an energy-harvesting device that converts mechanical energy into electricity using the triboelectric effect . They were first demonstrated by Zhong Lin Wang 's group at the Georgia Institute of Technology in 2012. [ 41 ] [ 42 ]
Ever since the first report of the TENG in January 2012, the output power density of the TENG has improved, reaching 313 W/m 2 , the volume density reaches 490 kW/m 3 , and conversion efficiencies of ~60% [ 43 ] –72% [ 44 ] have been demonstrated. Ramakrishna Podila's group at Clemson University also demonstrated the first truly wireless triboelectric nanogenerators, [ 45 ] which were able to charge energy storage devices (e.g., batteries and capacitors) without the need for any external amplification or boosters. [ 46 ]
The triboelectric nanogenerator has three basic operation modes: vertical contact-separation mode, in-plane sliding mode, and single-electrode mode. They have different characteristics and are suitable for different applications.
The periodic change in the potential difference induced by the cycled separation and re-contact of the opposite triboelectric charges on the inner surfaces of the two sheets. When mechanical agitation is applied to the device to bend or press it, the inner surfaces will come into close contact, leaving one side of the surface with positive charges and the other with negative charges.
When the deformation is released, the two surfaces with opposite charges will separate automatically, so that these opposite triboelectric charges will generate an electric field and induce a potential difference across the top and bottom electrodes. The electrons will flow from one electrode to the other through the external load. The electricity generated in this process will continue until the potentials of the two electrodes are the same. Subsequently, when the two sheets are pressed towards each other again, the triboelectric-charge-induced potential difference will begin to decrease to zero, so that the transferred charges will flow back through the external load to generate another current pulse in the opposite direction.
When this periodic mechanical deformation lasts, the alternating current signals will be continuously generated. [ 47 ] [ 48 ] As for the pair of materials getting into contact and generating triboelectric charges, at least one of them needs to be an insulator so that the triboelectric charges cannot be conducted away but will remain on the inner surface of the sheet.
There are two basic friction processes: normal contact and lateral sliding. One TENG is designed based on the in-plane sliding between the two surfaces in a lateral direction. [ 49 ] With triboelectrification from sliding, a periodic change in the contact area between two surfaces leads to a lateral separation of the charge centers, which creates a voltage driving the flow of electrons in the external load. The mechanism of in-plane charge separation can work in either one-directional sliding between two plates [ 50 ] or in rotation mode. [ 51 ]
A single-electrode-based triboelectric nanogenerator is introduced as a more practical design for some applications, such as fingertip-driven triboelectric nanogenerators. [ 52 ] [ 53 ] According to the triboelectric series, electrons were injected from the skin into the PDMS since the PDMS is more triboelectrically negative than the skin. When negative triboelectric charges on the PDMS are fully screened from the induced positive charges on the ITO electrode by increasing the separation distance between the PDMS and skin, no output signals can be observed.
TENG is a physical process of converting mechanical agitation to an electric signal through triboelectrification (in the inner circuit) and electrostatic induction processes (in the outer circuit). Harvesting vibration energy might be used to power mobile electronics. TENG has been demonstrated for harvesting ambient vibration energy based on the contact-separation mode. [ 54 ] A three-dimensional triboelectric nanogenerator (3D-TENG) has been designed based on a hybridization mode of conjunction between the vertical contact-separation mode and the in-plane sliding mode.
In 2013, Zhonglin Wang's group reported a rotary triboelectric nanogenerator for harvesting wind energy . [ 55 ] Subsequently, various types of triboelectric nanogenerators for harvesting ambient energy have been proposed, like 3D spiral structure triboelectric nanogenerators to collect wave energy, [ 56 ] fully enclosed triboelectric nanogenerators applied in water and harsh environments, [ 57 ] and multi-layered disk nanogenerators for harvesting hydropower . [ 58 ] However, due to the limitations of the nanogenerator's working models, the friction generated between layers of the triboelectric nanogenerator will reduce the energy conversion efficiency and the durability of the device. Researchers have designed an all-weather droplet-based triboelectric nanogenerator that relies on the contact electrification effect between liquid and solid to generate electricity. [ 59 ]
The term "self-powered sensors" can refer to a system that powers all the electronics responsible for measuring detectable movement. For example, the self-powered triboelectric encoder, integrated into a smart belt-pulley system, converts friction into usable electrical energy by storing the harvested energy in a capacitor and fully powering the circuit, which includes a microcontroller and an LCD. [ 60 ]
A pyroelectric nanogenerator is an energy-harvesting device that converts external thermal energy into electrical energy by using nano-structured pyroelectric materials. The pyroelectric effect is about the spontaneous polarization in certain anisotropic solids as a result of temperature fluctuation. [ 61 ] The first pyroelectric nanogenerator was introduced by Zhong Lin Wang at the Georgia Institute of Technology in 2012. [ 62 ]
The working principle of a pyroelectric nanogenerator can be explained by the primary pyroelectric effect and the secondary pyroelectric effect.
The primary pyroelectric effect describes the charge produced in a strain-free case. The primary pyroelectric effect dominates the pyroelectric response in PZT , BTO , and some other ferroelectric materials. [ 63 ] The mechanism is based on the thermally induced random wobbling of the electric dipole around its equilibrium axis, the magnitude of which increases with increasing temperature. [ 64 ] Due to thermal fluctuations at room temperature, the electric dipoles will randomly oscillate within a degree from their respective aligning axes.
Under a fixed temperature, the spontaneous polarization from the electric dipoles is constant. If the temperature in the nanogenerator changes from room temperature to a higher temperature, it will result in the electric dipoles oscillating within a larger degree of spread around their respective aligning axes. The quantity of induced charges in the electrodes is thus reduced, resulting in a flow of electrons. If the nanogenerator is cooled, the electric dipoles oscillate within a smaller degree of spread angle due to the lower thermal activity.
In the second case, the obtained pyroelectric response is explained by the secondary pyroelectric effect, which describes the charge produced by the strain induced by thermal expansion. The secondary pyroelectric effect dominates the pyroelectric response in ZnO , CdS , and some other wurzite-type materials. The thermal deformation can induce a piezoelectric potential difference across the material, which can drive the electrons to flow in the external circuit.
In 2012, Zhong Lin Wang used a pyroelectric nanogenerator as a self-powered temperature sensor for detecting a change in temperature, where the response time and reset time of the sensor are about 0.9 and 3 s, respectively. [ 65 ] | https://en.wikipedia.org/wiki/Nanogenerator |
Nanoholes are a class of nanostructured material consisting of nanoscale voids in a surface of a material. Not to be confused with nanofoam or nanoporous materials which support a network of voids permeating throughout the material (often in a disordered state), nanohole materials feature a regular hole pattern extending through a single surface. These can be thought of as the inverse of a nanopillar or nanowire structure.
Nanohole structures have been used for a variety of applications, ranging from superlenses produced from a metal nanohole array, [ 1 ] to structured photovoltaic devices used to improve carrier extraction, [ 2 ] and light absorption. [ 3 ]
Nanohole structures are also extensively utilized for the creation of photonic crystals , particularly for creating photonic crystal waveguides . | https://en.wikipedia.org/wiki/Nanohole |
A nanoindenter is the main component for indentation hardness tests used in nanoindentation . Since the mid-1970s nanoindentation has become the primary method for measuring and testing very small volumes of mechanical properties. Nanoindentation, also called depth sensing indentation or instrumented indentation , gained popularity with the development of machines that could record small load and displacement with high accuracy and precision. [ 1 ] [ 2 ] The load displacement data can be used to determine modulus of elasticity , hardness, yield strength , fracture toughness , scratch hardness and wear properties . [ 3 ]
There are many types of nanoindenters in current use differing mainly on their tip geometry. Among the numerous available geometries are three and four sided pyramids , wedges , cones , cylinders , filaments, and spheres . Several geometries have become a well established common standard due to their extended use and well known properties; such as Berkovich, cube corner, Vickers , and Knoop nanoindenters. To meet the high precision required, nanoindenters must be made following the definitions of ISO 14577-2, [ 4 ] and be inspected and measured with equipment and standards traceable to the National Institute of Standards and Technology (NIST). The tip end of the indenter can be made sharp, flat, or rounded to a cylindrical or spherical shape. The material for most nanoindenters is diamond and sapphire , although other hard materials can be used such as quartz , silicon , tungsten , steel , tungsten carbide and almost any other hard metal or ceramic material . Diamond is the most commonly used material for nanoindentation due to its properties of hardness, thermal conductivity , and chemical inertness . In some cases electrically conductive diamond may be needed for special applications and is also available.
Nanoindenters are mounted on holders which could be the standard design from a manufacturer of nanoindenting equipment, or custom design. The holder material can be steel, titanium , machinable ceramic , other metals or rigid materials. In most cases the indenter is attached to the holder using a rigid metal bonding process. The metal forms a molecular bond with both material be it diamond-steel, diamond-ceramic, etc.
Nanoindenter dimensions are very small, some less than 50 micrometres (0.0020 in), and made with precise angular geometry in order to achieve the highly accurate readings required for nanoindentation. Instruments that measure angles on larger objects such as protractors or comparators are neither practical nor precise enough to measure nanoindenter angles even with help of microscopes . For precise measurements a laser goniometer is used to measure diamond nanoindenter angles. Nanoindenter faces are highly polished and reflective which is the basis for the laser goniometer measurements. The laser goniometer can measure within a thousandth of a degree to specified or requested angles. [ 5 ] | https://en.wikipedia.org/wiki/Nanoindenter |
Nanoinformatics is the application of informatics to nanotechnology . It is an interdisciplinary field that develops methods and software tools for understanding nanomaterials, their properties, and their interactions with biological entities, and using that information more efficiently. It differs from cheminformatics in that nanomaterials usually involve nonuniform collections of particles that have distributions of physical properties that must be specified. The nanoinformatics infrastructure includes ontologies for nanomaterials, file formats, and data repositories.
Nanoinformatics has applications for improving workflows in fundamental research, manufacturing, and environmental health , allowing the use of high-throughput data-driven methods to analyze broad sets of experimental results. Nanomedicine applications include analysis of nanoparticle-based pharmaceuticals for structure–activity relationships in a similar manner to bioinformatics .
While conventional chemicals are specified by their chemical composition , and concentration , nanoparticles have other physical properties that must be measured for a complete description, such as size , shape , surface properties , crystallinity , and dispersion state . In addition, preparations of nanoparticles are often non-uniform , having distributions of these properties that must also be specified. These molecular-scale properties influence their macroscopic chemical and physical properties, as well as their biological effects. They are important in both the experimental characterization of nanoparticles and their representation in an informatics system. [ 1 ] [ 2 ] The context of nanoinformatics is that effective development and implementation of potential applications of nanotechnology requires the harnessing of information at the intersection of safety, health, well-being, and productivity; risk management ; and emerging nanotechnology. [ 3 ] [ 4 ]
One working definition of nanoinformatics developed through the community-based Nanoinformatics 2020 Roadmap [ 5 ] and subsequently expanded [ 3 ] is:
Although nanotechnology is the subject of significant experimentation, much of the data are not stored in standardized formats or broadly accessible. Nanoinformatics initiatives seek to coordinate developments of data standards and informatics methods. [ 5 ]
In the context of information science, an ontology is a formal representation of knowledge within a domain , using hierarchies of terms including their definitions, attributes, and relations. Ontologies provide a common terminology in a machine-readable framework that facilitates sharing and discovery of data. Having an established ontology for nanoparticles is important for cancer nanomedicine due to the need of researchers to search, access, and analyze large amounts of data. [ 6 ] [ 7 ]
The NanoParticle Ontology is an ontology for the preparation, chemical composition, and characterization of nanomaterials involved in cancer research. It uses the Basic Formal Ontology framework and is implemented in the Web Ontology Language . It is hosted by the National Center for Biomedical Ontology and maintained on GitHub . [ 6 ] The eNanoMapper Ontology is more recent and reuses wherever possible already existing domain ontologies. As such, it reuses and extends the NanoParticle Ontology, but also the BioAssay Ontology, Experimental Factor Ontology , Unit Ontology, and ChEBI . [ 8 ]
ISA-TAB-Nano is a set of four spreadsheet-based file formats for representing and sharing nanomaterial data, [ 9 ] [ 10 ] based on the ISA-TAB metadata standard. [ 11 ] In Europe, other templates have been adopted that were developed by the Institute of Occupational Medicine , [ 12 ] and by the Joint Research Centre for the NANoREG project. [ 13 ]
Nanoinformatics is not limited to aggregating and sharing information about nanotechnologies, but has many complementary tools, some originating from chemoinformatics and bioinformatics . [ 14 ] [ 15 ]
Over the last couple of years, various databases have been made available. [ 16 ]
caNanoLab, developed by the U.S. National Cancer Institute , focuses on nanotechnologies related to biomedicine. [ 17 ] The NanoMaterials Registry, maintained by RTI International , is a curated database of nanomaterials, and includes data from caNanoLab. [ 18 ]
The eNanoMapper database, a project of the EU NanoSafety Cluster, is a deployment of the database software developed in the eNanoMapper project. [ 19 ] It has since been used in other settings, such as the EU Observatory for NanoMaterials (EUON). [ 20 ] [ 21 ]
Other databases include the Center for the Environmental Implications of NanoTechnology's NanoInformatics Knowledge Commons (NIKC) [ 22 ] and NanoDatabank, [ 23 ] PEROSH 's Nano Exposure & Contextual Information Database (NECID), [ 24 ] Data and Knowledge on Nanomaterials (DaNa), [ 25 ] and Springer Nature 's Nano database. [ 26 ]
Nanoinformatics has applications for improving workflows in fundamental research, manufacturing, and environmental health , allowing the use of high-throughput data-driven methods to analyze broad sets of experimental results. [ 5 ]
Nanoinformatics is especially useful in nanoparticle-based cancer diagnostics and therapeutics. They are very diverse in nature due to the combinatorially large numbers of chemical and physical modifications that can be made to them, which can cause drastic changes in their functional properties. This leads to a combinatorial complexity that far exceeds, for example, genomic data. [ 6 ] Nanoinformatics can enable structure–activity relationship modelling for nanoparticle-based drugs. [ 6 ] Nanoinformatics and biomolecular nanomodeling provide a route for effective cancer treatment. [ 27 ] Nanoinformatics also enables a data-driven approach to the design of materials to meet health and environmental needs. [ 28 ]
Viewed as a workflow process, [ 2 ] nanoinformatics deconstructs experimental studies using data, metadata , controlled vocabularies and ontologies to populate databases so that trends, regularities and theories will be uncovered for use as predictive computational tools. Models are involved at each stage, some material (experiments, reference materials , model organisms ) and some abstract (ontology, mathematical formulae), and all intended as a representation of the target system. Models can be used in experimental design, may substitute for experiment or may simulate how a complex system changes over time. [ 29 ]
At present, nanoinformatics is an extension of bioinformatics due to the great opportunities for nanotechnology in medical applications, as well as to the importance of regulatory approvals to product commercialization. In these cases, the models target, their purposes, may be physico-chemical, estimating a property based on structure (quantitative structure–property relationship, QSPR); or biological, predicting biological activity based on molecular structure ( quantitative structure–activity relationship , QSAR) or the time-course development of a simulation ( physiologically based toxicokinetics , PBTK). [ 30 ] [ 31 ] Each of these has been explored for small molecule drug development with a supporting body of literature.
Particles differ from molecular entities, especially in having surfaces that challenge nomenclature system and QSAR/PBTK model development. For example, particles do not exhibit an octanol–water partition coefficient , which acts as a motive force in QSAR/PBTK models; and they may dissolve in vivo or have band gaps. [ 32 ] Illustrative of current QSAR and PBTK models are those of Puzyn et al. [ 33 ] and Bachler et al. [ 34 ] The OECD has codified regulatory acceptance criteria, [ 35 ] and there are guidance roadmaps [ 5 ] [ 12 ] with supporting workshops [ 36 ] to coordinate international efforts.
Communities active in nanoinformatics include the European Union NanoSafety Cluster , [ 37 ] The U.S. National Cancer Institute National Cancer Informatics Program's Nanotechnology Working Group, [ 38 ] [ 39 ] and the US–EU Nanotechnology Communities of Research. [ 40 ]
Individuals who engage in nanoinformatics can be viewed as fitting across four categories of roles and responsibilities for nanoinformatics methods and data: [ 4 ] [ 41 ] [ 42 ]
In some instances, the same individuals perform all four roles. More often, many individuals must interact, with their roles and responsibilities extending over significant distances, organizations, and time. Effective communication is important across each of the twelve links (in both directions across each of the six pairwise interactions) that exist among the various customers, creators, curators, and analysts. [ 4 ]
One of the first mentions of nanoinformatics was in the context of handling information about nanotechnology. [ 43 ]
An early international workshop with substantial discussion of the need for sharing all types of information on nanotechnology and nanomaterials was the First International Symposium on Occupational Health Implications of Nanomaterials held 12–14 October 2004 at the Palace Hotel, Buxton , Derbyshire, UK. [ 44 ] The workshop report [ 44 ] included a presentation on Information Management for Nanotechnology Safety and Health [ 45 ] that described the development of a Nanoparticle Information Library (NIL) and noted that efforts to ensure the health and safety of nanotechnology workers and members of the public could be substantially enhanced by a coordinated approach to information management. The NIL subsequently served as an example for web-based sharing of characterization data for nanomaterials. [ 46 ]
The National Cancer Institute prepared in 2009 a rough vision of, what was then still called, nanotechnology informatics, [ 47 ] outlining various aspects of what nanoinformatics should comprise. This was later followed by two roadmaps, detailing existing solutions, needs, and ideas on how the field should further develop: the Nanoinformatics 2020 Roadmap [ 5 ] and the EU US Roadmap Nanoinformatics 2030 . [ 12 ]
A 2013 workshop on nanoinformatics described current resources, community needs and the proposal of a collaborative framework for data sharing and information integration. [ 48 ] | https://en.wikipedia.org/wiki/Nanoinformatics |
Nanoinjection is the process of using a microscopic lance and electrical forces to deliver DNA to a cell. It is claimed to be more effective than microinjection because the lance used is ten times smaller than a micropipette and the method uses no fluid. The nanoinjector mechanism is operated while submerged in a pH buffered solution. Then, a positive electrical charge is applied to the lance, which accumulates negatively charged DNA on its surface. The nanoinjector mechanism then penetrates the zygotic membranes, and a negative charge is applied to the lance, releasing the accumulated DNA within the cell. The lance is required to maintain a constant elevation on both entry and exit of the cell. [ 1 ]
Nanoinjection results in a long-term cell viability of 92% following the electrophoretic injection process with a 100 nm diameter nanopipette , the typical diameter of nanoinjection pipet. [ 2 ]
Single cell transfections are used to virtually transfer any type of mammalian cell into another using a syringe which creates an entry for DNA to be released. A nano needle is used as a mechanical vector for plasmid DNA. The method can be improved further with Atomic Force Microscopy or AFM. In order to avoid causing permanent damage to the cell or provoke cellular leaking of intracellular fluid, AFM is a tool of choice, as it allows for precise positioning of the DNA, allowing for tip penetration into the cytosol , which is critical for viable DNA transfer into the cell. [ 3 ]
Reasons to use nanoinjection include the insertion of genetic material into the genome of a zygote. This method is a critical step in understanding and developing gene functions.
Nanoinjection is also used to genetically modify animals to aid in the research of cancer , Alzheimer’s disease, and diabetes. [ 2 ]
The lance is made using the polyMUMPs fabrication technology. It creates a gold layer, and two structural layers that are 2.0 and 1.5 μm thick respectively. It is a simple process, which makes it good as a platform to prototype polysilicon MEMS devices at a low commercial cost of fabrication. The lance has a solid, tapered body, that is 2 μm thick, with a tip width of 150 nm. The taper is set at 7.9°, coming to a maximum width of 11 μm. Two highly folded electrical connections provide an electrical path between the lance and two equivalent bond pads, with a gold wire connecting one of the bond pads to an integrated circuit chip carrier’s pin. The carrier is then placed into a custom built electrical socket. [ 4 ]
In the situation of fertilizing eggs, the lance is incorporated into a kinematic mechanism consisting of a change-point parallel-guiding six-bar mechanism and a compliant parallel-guiding folded-beam suspension.
Electrophoretic injection remains the most common form of nanoinjection. Just as with the other methods, a lance ten times smaller than that of microinjection is used. Preparing the lance for injection, a positive charge is applied, attracting the negatively-charged DNA to its tip. After the lance has reached a desired depth within the cell, the charge is reversed, repelling the DNA into the cell. [ 1 ] The typical injection voltages are ±20 V, but can be as low as 50-100 mV.
A manual force is applied to a center fixture of the injection device, moving the lances through cell membranes and into the cytoplasm or nucleus of adhered cells. The magnitude of the force is measured using a force plate on a small number of injections to obtain an estimate of the manual force. The force plate is arranged to measure the force actually applied to the injection chip (that is, not including the stiffness of the support spring). After holding the force for five seconds, the force is released and the injection device is removed from the cell. The diffusion protocol presented data for comparison against other variations in the injection process. [ 5 ]
By delivering certain particles into cells, diseases can be treated or even cured. Gene therapy is possibly the most common field of foreign material delivery into cells and has great implications for curing human genetic diseases.
For example, two monkeys colorblind from birth were given gene therapy treatment in a recent experiment. As a result of gene therapy, both animals had their color vision restored with no apparent side effects. Traditionally, gene therapy has been divided into two categories: biological (viral) vectors and chemical or physical (nonviral) approaches. Although viral vectors are currently the most effective approach to delivering DNA into cells, they have certain limitations, including immunogenicity , toxicity , and limited capacity to carry DNA. [ 5 ]
One factor critical to successful gene therapy is the development of efficient delivery systems. Although advances in gene transfer technology, including viral and non-viral vectors, have been made, an ideal vector system has not yet been constructed. [ 6 ]
Microinjection is the predecessor to nanoinjection. Still used in biological research, microinjection is useful in the examination of non-living cells or in cases where cell viability does not matter. Using a glass pipette 0.5-1.0 micrometers in diameter, the cell has its membrane damaged upon puncture. As opposed to nanoinjection, microinjection uses DNA-filled liquid driven into the cell under pressure. Depending on factors such as the skill of the operator, survival rates of cells undergoing this procedure can be as high as 56% or as low as 9%. [ 2 ]
Other methods exist that target groups of cells, such as electroporation . These methods are incapable of targeting specific cells, and are therefore not usable where efficiency and cell viability are a concern. | https://en.wikipedia.org/wiki/Nanoinjection |
A nanoknife is a carbon nanotube -based prototype compression cutting tool intended for sectioning of biological cells. [ 1 ] Working principle is similar to that of a 'cheese slicer' [ citation needed ] , a nanometer-thin individual carbon nanotube strung between two tungsten needles would allow sectioning of very thin slices of biological matter for imaging under an electron microscope . Tests are currently being performed by scientists at Virginia Tech , CU-Boulder and other universities. [ 2 ] [ 3 ] A successful development of this new tool will allow scientists and biologists to make 3D images of cells and tissues for electron tomography , which typically requires samples less than ~300 nanometers in thickness. [ 2 ] In 2009, the nano-knife was used to create indentation marks on biological cell plasticizer (epoxy resin). [ 4 ] The whole cutting process is currently limited by electron charging of polymeric specimen in the SEM , which makes it difficult to observe any small cut or mark as the carbon nanotube is pressed against the specimen.
Nanoknife Procedure
Doctors use a special medical device designed for the specific purpose of performing irreversible electroporation . The device implements a direct current generator which emits short pulses of high voltage electric current through electrodes into the cell membrane. The doctor inserts thin needles into the area, using ultrasound imaging to guide the placement of the needles. In nanoknife treatment, strong electric fields cause cells to die without exposing the tissue to radiation or heating it. [ 5 ] Most patients don’t feel anything at all during the procedure.
This cell biology article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Nanoknife |
Nanolamination is the production of materials that are fully dense, ultra-fine grained solids that exhibit a high concentration of interface defects. The properties of fabricated nanolaminates depend on their compositions and thicknesses. [ 1 ]
Nanolaminates can be grown using atom-by-atom deposition techniques that are designed with different stacking sequences and layer thicknesses.
Electrolytic reduction allows the production of metals and metal alloys in sub- μm -thick layers. It can be employed to create alloys with properties such as improved toughness, strength, thermal properties and corrosion that are a function of the interfaces in the nanolayers. They can be created using a bath containing multiple metal ion elements. By changing the current at precise moments to select a different element, it can create a layered structure. Coatings of up to a centimeter thick have been created. [ 2 ]
It is claimed to offer the benefits of high-cost materials at much lower costs, because such materials can coat lower-cost materials that have other necessary properties such as strength. [ 3 ]
Commercial production was introduced in the 2010s by a new company named Modumetal. [ 4 ]
Many hybrid thin film oxides can be created using atomic layer deposition (ALD) with unique physical, chemical, and electronic properties. For example, a rough oxide layer can be further coated with a smooth oxide layer to provide a required surface texture. Properties may also depend on deposition temperature and the stratum to which the nanolaminate is applied. [ 5 ]
In autoclave testing, some nanolaminated alloys have shown 8 times the resistance of carbon steels to degradation and in some cases, no measurable degradation. [ 3 ]
Application include those that take advantage of enhanced mechanical properties or for devices such as energy storage and memory storage capacitors. [ 1 ]
Corrosion-resistant, structural tubulars and casings are important infrastructure assets in the oil and gas industry. Tubulars and casings are subject to aggressive well conditions, serving to permit operations across extreme formation and production pressure differentials, in high temperatures and in highly corrosive environments that contain hydrogen sulfide ( H 2 S ), carbon dioxide ( CO 2 ) and chlorides. [ 4 ]
Modumetal produces pumps, valves and tubulars that for launch customers. The products are claimed to offer corrosion and wear protection through a durable, high toughness, nanolaminated metal alloy cladding. [ 4 ]
Nanolaminate dielectrics can have efficient dielectric constant and high insulation characteristics. Dielectric materials with giant dielectric constants can be fabricated as modified single, binary and perovskite oxides. [ 1 ] | https://en.wikipedia.org/wiki/Nanolamination |
A nanolattice is a synthetic porous material consisting of nanometer-size members patterned into an ordered lattice structure, like a space frame . The nanolattice is a material class that emerged after 2015. Nanolattices redefine the limits of the material property space. Despite consisting of 50-99% air, nanolattices are mechanically robust because they take advantage of size-dependent properties generally seen in nanoparticles, nanowires, and thin films. The most typical mechanical properties of nanolattices include strength, damage tolerance, and stiffness. Thus, nanolattices have a wide range of potential applications.
Driven by the evolution of 3D printing techniques, nanolattices aiming to exploit beneficial material size effects through miniaturized lattice designs were first developed in the mid-2010s,. [ 2 ] [ 3 ] [ 4 ] [ 5 ] Nanolattices are the smallest man-made lattice truss structures [ 2 ] [ 6 ] [ 1 ] and a class of metamaterials that derive their properties from both their geometry (general metamaterial definition) and their elements' small size. [ 5 ] Therefore, they can possess effective properties not found in nature, and that may not be achieved with larger-scale lattices.
Polymer templates are manufactured by 3D printing processes, such as multiphoton lithography , self-assembly , self-propagating photopolymer waveguides, and direct laser writing techniques. Those methods can produce a unit cell size on the order of 50 nanometers . Genetic engineering also has potential in synthesizing nanolattice. Ceramic , metal or composite material nanolattices are formed by post-treatment of the polymer templates with techniques including pyrolysis , atomic layer deposition , electroplating and electroless plating . [ 5 ] Pyrolysis, can additionally shrink lattices by up to 90%, creating the smallest structures, whereby the polymeric template material transforms into carbon, [ 1 ] or other ceramics [ 7 ] and metals, [ 8 ] through thermal decomposition in inert atmosphere or vacuum.
At the nanoscale, size effects and different dimensional constraints, like grain boundaries, dislocations, and distribution of voids, can change material properties. Nanolattices possess unparalleled mechanical properties. Nanolattices are the strongest existing cellular materials despite their light weight. Though 50%-99% air, nanolattice can be as strong as steel. [ 2 ] [ 5 ] [ 1 ] Its effective strength can reach up to 1 GPa . On the order of 50nm, the volume of individual elements, such as walls, nodes, and trusses, thereby statistically nearly eliminate the material flaw population. The base material of nanolattices can reach mechanical strengths on the order of the theoretical strength of an ideal, perfect crystal. While such effects are typically limited to individual, geometrically primitive structures such as nanowires , the specific architecture allows nanolattices to exploit them in complex, three-dimensional structures of notably larger overall size. Nanolattices can be designed to be highly deformable and recoverable, [ 4 ] [ 9 ] even with ceramic base materials. Nanolattices are able to undergo 80% compressive strain without catastrophic failure and then still recover to 100% original shape. Nanolattices can possess mechanical metamaterial properties like auxetic (negative Poisson's ratio ) or meta-fluidic behavior (large bulk modulus ). [ 1 ] Nanolattices can combine mechanical resilience and ultra-low thermal conductivity and can have electromagnetic metamaterial characteristics such as optical cloaking . [ 10 ] However, one challenge in nanolattice research is how to retain the robust properties while increasing object size. It is challenging to keep nanoscale size effects in bulk structure. The straightforward workaround to overcome this challenge is to combine bulk processes with thin film deposition techniques to retain the frame space hollow structure. [ citation needed ]
The first market for nanolattices may be small-scale, small-lot components for biomedical, electrochemical, microfluidic, and aerospace applications, which require customizable property combinations. In the aerospace industry, nanolattices could make aircraft lighter and save energy. | https://en.wikipedia.org/wiki/Nanolattice |
Nanomanufacturing is both the production of nanoscaled materials, which can be powders or fluids, and the manufacturing of parts "bottom up" from nanoscaled materials or "top down" in smallest steps for high precision, used in several technologies such as laser ablation , etching and others. Nanomanufacturing differs from molecular manufacturing , which is the manufacture of complex, nanoscale structures by means of nonbiological mechanosynthesis (and subsequent assembly). [ 1 ]
The term "nanomanufacturing" is widely used, e.g. by the European Technology Platform MINAM [ 2 ] and the U.S. National Nanotechnology Initiative (NNI). [ 3 ] The NNI refers to the sub-domain of nanotechnology as one of its five "priority areas." [ 4 ] There is also a nanomanufacturing program at the U.S. National Science Foundation , through which the National Nanomanufacturing Network (NNN) has been established. The NNN is an organization that works to expedite the transition of nanotechnologies from laboratory research to production manufacturing and it does so through information exchange, [ 5 ] strategic workshops, and roadmap development.
The NNI has defined nanotechnology very broadly, [ 6 ] to include a wide range of tiny structures, including those created by large and imprecise tools. However, nanomanufacturing is not defined in the NNI's recent report, Instrumentation and Metrology for Nanotechnology . In contrast, another "priority area," nanofabrication , is defined as "the ability to fabricate, by directed or self-assembly methods, functional structures or devices at the atomic or molecular level" (p. 67). Nanomanufacturing appears to be the near-term, industrial-scale manufacture of nanotechnology-based objects, with emphasis on low cost and reliability. Many professional societies have formed Nanotechnology technical groups. The Society of Manufacturing Engineers , for example, has formed a Nanomanufacturing Technical Group to both inform members of the developing technologies and to address the organizational and IP (intellectual property) legal issues that must be addressed for broader commercialization.
In 2014 the Government Accountability Office noted that America's leadership in nanotechnology was put at risk by a failure of the government to invest in preparing basic research for commercial application. [ 7 ]
The realization of the numerous applications and benefits of nano-scale systems in everyday materials, electronics, medicine, energy conservation, sustainability, and transportation has led to research in developing techniques to produce these nano-systems on a larger-scale and at higher rates. [ 8 ] Programs and organizations like the NNI and NNN are currently funding research towards designing economic, sustainable and reliable industry-scale nanomanufacturing techniques. [ 9 ] [ 10 ]
An example of such technology is the Nanoscale Offset Printing System (NanoOps) which was developed by researchers at the Center of High-rate Nanomanufacturing (CHN) in Northeastern University. [ 11 ] The NanoOps is a form of directed assembly which is faster and more economic than traditional 3D printing of nanosystems. Ahmed Busnaina, who was the head lead of the project and featured in the film From Lab to Fab: Pioneers in Nano-manufacturing describes the system as a printing press. An etched template with nano wires is dipped in a solution with nano particles which acts as the ink for the press. [ 12 ] The nanoparticles adhere to the template when electricity is applied to the solution. [ 11 ] The template with the attached nano particles can then be taken out of the solution and pressed onto any material of choice. According to Busnaina, the whole process only costs 1% of conventional manufacturing and can reduce manufacturing time from days to minutes. [ 11 ]
Another illustrative example is the soft-template infiltration manufacturing technique developed by Nazanin Bassiri-Gharb at Georgia Institute of Technology . This is a bottom-up nanomanufacturing technique for the fabrication of ferroelectric, piezoelectrically-active nanotubes. The method uses electron beam lithography to draw a vacuum on the precursor sol-gel solution, thereby creating a polymeric template. Via this highly scalable and practical manufacturing process the user can produce custom patterns and shapes for numerous applications. [ 13 ] [ 14 ]
Nanomanufacturing refers to manufacturing processes of objects or material with dimensions between one and one hundred nanometers . [ 15 ] These processes results in nanotechnology , extremely small devices, structures, features, and systems that have applications in organic chemistry, molecular biology , aerospace engineering , physics , and beyond. [ 16 ] Nanomanufacturing enables the creation of new materials and products that have applications such as material removal processes, device assembly, medical devices , electrostatic coating and fibers , and lithography . [ 16 ] Nanomanufacturing is a relatively recent branch of manufacturing that represents both a new field of science and also a new marketplace. Research in nanomanufacturing, unlike tradition manufacturing, requires collective effort across typical engineering divides, such as collaboration between mechanical engineers , physicists, biologists , chemists , and material scientists . [ 16 ]
Nanomanufacturing can generally be broken down into two categories: top-down and bottom-up approaches.
In 2009, $91 billion was in US products that incorporate nanoscale components. [ 17 ] More than 60 countries established nanomanufacturing industry related programs at a national level between 2001 and 2004. [ 17 ] Cumulative funding since 2000 for National Nanotechnology Initiative (NNI) is more than $12 billion. [ 17 ]
For sustainability point of view, Atomic Layer Deposition (ALD) is a Nano-scale manufacturing technology using bottom-up and chemical vapor deposition (CVD) manufacturing method. [ 19 ] ALD replaces SiO 2 dielectric film with Al 2 O 3 dielectric film. [ 19 ] ALD industry is already in use in Semiconductor industry and promising in solar cells, fuel cells, medical device, sensor, polymer industries. [ 19 ] Nanomanufacturing technology allow improvements in food packaging. [ 18 ] For example, improvement in plastic material barrier allow customers to identify relevant information. [ 18 ] Longer food life and safer food is aimed with self repairing functions as well. [ 18 ] Performance of traditional construction materials; steel and concrete improves with nanotechnology. Reinforcing concrete with metal oxide nanoparticle reduces permeability and increase strength. [ 20 ] Property of high tensile strength and Young’s modulus of Nanocarbon additions such as Carbon nanotubes (CNTs) and Carbon nanofibers (CNFs), creates denser and less porous material. [ 20 ]
The transitioning of nanotechnology from lab demonstrations to industrial-scale manufacturing has a number of challenges, some of which include: | https://en.wikipedia.org/wiki/Nanomanufacturing |
Nanomaterial-based catalysts are usually heterogeneous catalysts based upon metal nanoparticles . Metal nanoparticles have high surface area , which can increase catalytic activity. Nanoparticle catalysts can be easily separated and recycled. [ 1 ] [ 2 ] [ 3 ] They are typically used under mild conditions to prevent decomposition or agglomeration of the nanoparticles. [ 4 ] In many cases they are supported on substrates, sometimes they are not.
Functionalized metal nanoparticles are more stable toward solvents compared to non-functionalized metal nanoparticles. [ 5 ] [ 6 ] In liquids, the metal nanoparticles can be affected by van der Waals force . Particle aggregation can sometimes decrease catalytic activity by lowering the surface area. [ 7 ] Nanoparticles can also be functionalized with polymers or oligomers to sterically stabilize the nanoparticles by providing a protective layer that prevents the nanoparticles from interacting with each other. [ 8 ] Alloys of two metals, called bimetallic nanoparticles, are used to create synergistic effects on catalysis between the two metals. [ 9 ]
Nanoparticle catalysts are active for the hydrogenolysis of C-Cl bonds such as polychlorinated biphenyls . [ 5 ] [ 6 ] Another reaction is hydrogenation of halogenated aromatic amines is also important for the synthesis of herbicides and pesticides as well as diesel fuel . [ 5 ] In organic chemistry , hydrogenation of a C-Cl bond with deuterium is used to selectively label the aromatic ring for use in experiments dealing with the kinetic isotope effect .
Buil et al. created rhodium complexes that generated rhodium nanoparticles. These nanoparticles catalyzed the dehalogenation of aromatic compounds as well as the hydrogenation of benzene to cyclohexane . [ 6 ] Polymer-stabilized nanoparticles can also be used for the hydrogenation of cinnamaldehyde and citronellal . [ 5 ] [ 7 ] [ 10 ] [ 9 ] Yu et al. found that the ruthenium nanocatalysts are more selective in the hydrogenation of citronellal compared to the traditional catalysts used. [ 9 ]
The Reduction of gold , cobalt , nickel , palladium , or platinum organometallic complexes with silanes produces metal nanoparticle that catalyze the hydrosilylation reaction. [ 11 ] BINAP -functionalized palladium nanoparticles and gold nanoparticles have been used for the hydrosilylaytion of styrene under mild conditions; they were found to be more catalytically active and more stable than non-nanoparticle Pd-BINAP complexes. [ 11 ] [ 12 ] The reaction may also be catalyzed by a nanoparticle that consists of two metals. [ 5 ] [ 13 ]
An oxidation reaction to form adipic acid is shown in figure 3 and it can be catalyzed by cobalt nanoparticles. [ 5 ] This is used in an industrial scale to produce the nylon 6,6 polymer.
Other examples of oxidation reactions that are catalyzed by metallic nanoparticles include the oxidation of cyclooctane , the oxidation of ethene , and glucose oxidation. [ 5 ]
Metallic nanoparticles can catalyze C–C coupling reactions such as the hydroformylation of olefins , [ 5 ] the synthesis of vitamin E and the Heck coupling and Suzuki coupling reactions. [ 5 ]
Palladium nanoparticles were found to efficiently catalyze Heck coupling reactions. It was found that increased electronegativity of the ligands on the palladium nanoparticles increased their catalytic activity. [ 5 ] [ 14 ]
The compound Pd 2 (dba) 3 is a source of Pd(0), which is the catalytically active source of palladium used for many reactions, including cross coupling reactions. [ 4 ] Pd2(dba)3 was thought to be a homogeneous catalytic precursor, but recent articles suggest that palladium nanoparticles are formed, making it a heterogeneous catalytic precursor. [ 4 ]
Iron oxide and cobalt nanoparticles can be loaded onto various surface active materials like alumina to convert gases such as carbon monoxide and hydrogen into liquid hydrocarbon fuels using the Fischer-Tropsch process. [ 15 ] [ 16 ]
Much research on nanomaterial-based catalysts has to do with maximizing the effectiveness of the catalyst coating in fuel cells. Platinum is currently the most common catalyst for this application, however, it is expensive and rare, so a lot of research has been going into maximizing the catalytic properties of other metals by shrinking them to nanoparticles in the hope that someday they will be an efficient and economic alternative to platinum. Gold nanoparticles also exhibit catalytic properties , despite the fact that bulk gold is unreactive.
Yttrium stabilized zirconium nanoparticles were found to increase the efficiency and reliability of a solid oxide fuel cell . [ 17 ] [ 18 ] Nanomaterial ruthenium/platinum catalysts could potentially be used to catalyze the purification of hydrogen for hydrogen storage . [ 19 ] Palladium nanoparticles can be functionalized with organometallic ligands to catalyze the oxidation of CO and NO to control air pollution in the environment . [ 17 ] Carbon nanotube supported catalysts can be used as a cathode catalytic support for fuel cells and metal nanoparticles have been used to catalyze the growth of carbon nanotubes . [ 17 ] Platinum-cobalt bimetallic nanoparticles combined with carbon nanotubes are promising candidates for direct methanol fuel cells since they produce a higher stable current electrode . [ 17 ]
In magnetic chemistry , nanoparticles can be used for catalyst support for medicinal use.
Besides conventional catalysis, nanomaterials have been explored for mimicking natural enzymes. The nanomaterials with enzyme mimicking activities are termed as nanozymes . [ 20 ] Many nanomaterials have been used to mimic varieties of natural enzymes, such as oxidase, peroxidase, catalase, SOD, nuclease, etc. The nanozymes have found wide applications in many areas, from biosensing and bioimaging to therapeutics and water treatment.
Nanocatalysts are of wide interest in fuel cells and electrolyzers, where the catalyst strongly affects efficiency.
In fuel cells, nanoporous materials are widely used to make cathodes. Porous nanoparticles of platinum have good activity in nanocatalysis but are less stable and their lifetime is short. [ 21 ]
One drawback to the use of nanoparticles is their tendency to agglomerate. The problem can be mitigated with the correct catalyst support . Nanoparticles are optimal structures to be used as nanosensors because they can be tuned to detect specific molecules. Examples of Pd nanoparticles electrodeposited on multi-walled carbon nanotubes have shown good activity towards catalysis of cross-coupling reactions. [ 22 ]
Nanowires are very interesting for electrocatalytic purpose because they are easier to produce and the control over their characteristics in the production process is quite precise. Also, nanowires can increase faradaic efficiency due to their spatial extent and thus to greater availability of reactants on the active surface. [ 23 ]
The nanostructures involved in electrocatalysis processes can be made up of different materials. Through the use of nanostructured materials, electrocatalysts can achieve good physical-chemical stability, high activity, good conductivity and low cost.
Metallic nanomaterials are commonly made up of transition metals (mostly iron, cobalt, nickel, palladium, platinum).
Multi-metal nanomaterials show new properties due to the characteristics of each metal. The advantages are the increase in activity, selectivity and stability and the cost reduction. Metals can be combined in different ways such as in the core-shell bimetallic structure: the cheapest metal forms the core and the most active one (typically a noble metal) constitutes the shell. By adopting this design, the use of rare and expensive metals can be reduced down to 20%. [ 24 ]
One of the future challenges is to find new stable materials, with good activity and especially low cost. Metallic glasses , polymeric carbon nitride (PCN) and materials derived from metal-organic frameworks (MOF) are just a few examples of materials with electrocatalytic properties on which research is currently investing. [ 25 ] [ 26 ] [ 27 ]
Many of the photocatalytic systems can benefit from the coupling with a noble metal; the first Fujishima-Honda cell made use of a co-catalyst plate as well. For instance, the essential design of a disperse photocatalytic reactor for water splitting is that of a water sol in which the dispersed phase is made up of semiconductor quantum dots each coupled to a metallic co-catalyst: the QD converts the incoming electromagnetic radiation into an exciton whilst the co-catalyst acts as an electron scavenger and lowers the overpotential of the electrochemical reaction. [ 28 ]
Some techniques that can be used to characterize functionalized nanomaterial catalysts include X-ray photoelectron spectroscopy , transmission electron microscopy , circular dichroism spectroscopy , nuclear magnetic resonance spectroscopy , UV-visible spectroscopy and related experiments. | https://en.wikipedia.org/wiki/Nanomaterial-based_catalyst |
Nanomechanics is a branch of nanoscience studying fundamental mechanical (elastic, thermal and kinetic) properties of physical systems at the nanometer scale. Nanomechanics has emerged on the crossroads of biophysics , classical mechanics , solid-state physics , statistical mechanics , materials science , and quantum chemistry . As an area of nanoscience, nanomechanics provides a scientific foundation of nanotechnology .
Nanomechanics is that branch of nanoscience which deals with the study and application of fundamental mechanical properties of physical systems at the nanoscale, such as elastic, thermal and kinetic material properties.
Often, nanomechanics is viewed as a branch of nanotechnology , i.e., an applied area with a focus on the mechanical properties of engineered nanostructures and nanosystems (systems with nanoscale components of importance). Examples of the latter include nanomachines , nanoparticles , nanopowders, nanowires , nanorods , nanoribbons, nanotubes , including carbon nanotubes (CNT) and boron nitride nanotubes (BNNTs); nanoshells , nanomembranes, nanocoatings, nanocomposite /nanostructured materials, (fluids with dispersed nanoparticles); nanomotors , etc. [ citation needed ]
Some of the well-established fields of nanomechanics are: nanomaterials , nanotribology ( friction , wear and contact mechanics at the nanoscale ), nanoelectromechanical systems (NEMS), and nanofluidics .
As a fundamental science, nanomechanics is based on some empirical principles (basic observations), namely general mechanics principles and specific principles arising from the smallness of physical sizes of the object of study.
General mechanics principles include:
Due to smallness of the studied object, nanomechanics also accounts for:
These principles serve to provide a basic insight into novel mechanical properties of nanometer objects. Novelty is understood in the sense that these properties are not present in similar macroscale objects or much different from the properties of those (e.g., nanorods vs. usual macroscopic beam structures). In particular, smallness of the subject itself gives rise to various surface effects determined by higher surface-to-volume ratio of nanostructures , and thus affects mechanoenergetic and thermal properties (melting point, heat capacitance, etc.) of nanostructures . Discreteness serves a fundamental reason, for instance, for the dispersion of mechanical waves in solids , and some special behavior of basic elastomechanics solutions at small scales. Plurality of degrees of freedom and the rise of thermal fluctuations are the reasons for thermal tunneling of nanoparticles through potential barriers, as well as for the cross- diffusion of liquids and solids . Smallness and thermal fluctuations provide the basic reasons of the Brownian motion of nanoparticles. Increased importance of thermal fluctuations and configuration entropy at the nanoscale give rise to superelasticity , entropic elasticity ( entropic forces ), and other exotic types of elasticity of nanostructures . Aspects of configuration entropy are also of great interest in the context self-organization and cooperative behavior of open nanosystems.
Quantum effects determine forces of interaction between individual atoms in physical objects, which are introduced in nanomechanics by means of some averaged mathematical models called interatomic potentials .
Subsequent utilization of the interatomic potentials within the classical multibody dynamics provide deterministic mechanical models of nano structures and systems at the atomic scale/resolution. Numerical methods of solution of these models are called molecular dynamics (MD), and sometimes molecular mechanics (especially, in relation to statically equilibrated (still) models). Non-deterministic numerical approaches include Monte Carlo , Kinetic More-Carlo (KMC), and other methods. Contemporary numerical tools include also hybrid multiscale approaches allowing concurrent or sequential utilization of the atomistic scale methods (usually, MD) with the continuum (macro) scale methods (usually, field emission microscopy ) within a single mathematical model. Development of these complex methods is a separate subject of applied mechanics research.
Quantum effects also determine novel electrical, optical and chemical properties of nanostructures , and therefore they find even greater attention in adjacent areas of nanoscience and nanotechnology , such as nanoelectronics , advanced energy systems, and nanobiotechnology . | https://en.wikipedia.org/wiki/Nanomechanics |
Nanomedicine is the medical application of nanotechnology . [ 1 ] Nanomedicine ranges from the medical applications of nanomaterials and biological devices , to nanoelectronic biosensors, and even possible future applications of molecular nanotechnology such as biological machines . Current problems for nanomedicine involve understanding the issues related to toxicity and environmental impact of nanoscale materials (materials whose structure is on the scale of nanometers, i.e. billionths of a meter ). [ 2 ] [ 3 ]
Functionalities can be added to nanomaterials by interfacing them with biological molecules or structures. The size of nanomaterials is similar to that of most biological molecules and structures; therefore, nanomaterials can be useful for both in vivo and in vitro biomedical research and applications. Thus far, the integration of nanomaterials with biology has led to the development of diagnostic devices, contrast agents, analytical tools, physical therapy applications, and drug delivery vehicles.
Nanomedicine seeks to deliver a valuable set of research tools and clinically useful devices in the near future. [ 4 ] [ 5 ] The National Nanotechnology Initiative expects new commercial applications in the pharmaceutical industry that may include advanced drug delivery systems, new therapies, and in vivo imaging. [ 6 ] Nanomedicine research is receiving funding from the US National Institutes of Health Common Fund program, supporting four nanomedicine development centers. [ 7 ] The goal of funding this newer form of science is to further develop the biological, biochemical, and biophysical mechanisms of living tissues. [ 7 ] More medical and drug companies today are becoming involved in nanomedical research and medications. These include Bristol-Myers Squibb, which focuses on drug delivery systems for immunology and fibrotic diseases; Moderna known for their COVID-19 vaccine and their work on mRNA therapeutics; and Nanobiotix, a company that focuses on cancer and currently has a drug in testing that increases the effect of radiation on targeted cells. More companies include Generation Bio, which specializes in genetic medicines and has developed the cell-targeted lipid nanoparticle, and Jazz Pharmaceuticals, which developed Vyxeos , a drug that treats acute myeloid leukemia, and concentrates on cancer and neuroscience. Cytiva is a company that specializes in producing delivery systems for genomic medicines that are non-viral, including mRNA vaccines and other therapies utilizing nucleic acid and Ratiopharm is known for manufacturing Pazenir, a drug for various cancers. Finally, Pacira specializes in pain management and is known for producing ZILRETTA for osteoarthritis knee pain, the first treatment without opioids. [ 8 ]
Nanomedicine sales reached $16 billion in 2015, with a minimum of $3.8 billion in nanotechnology R&D being invested every year. Global funding for emerging nanotechnology increased by 45% per year in recent years, with product sales exceeding $1 trillion in 2013. [ 9 ] In 2023, the global market was valued at $189.55 billion and is predicted to exceed $ 500 billion in the next ten years. [ 8 ] As the nanomedicine industry continues to grow, it is expected to have a significant impact on the economy.
Nanotechnology has provided the possibility of delivering drugs to specific cells using nanoparticles. [ 10 ] [ 11 ] This use of drug delivery systems was first proposed by Gregory Gregoriadis in 1974, who outlined liposomes as a drug delivery system for chemotherapy. [ 12 ] The overall drug consumption and side-effects may be lowered significantly by depositing the active pharmaceutical agent in the diseased region only and in no higher dose than needed. Targeted drug delivery is intended to reduce the side effects of drugs in tandem decreases in consumption and treatment expenses. Additionally, targeted drug delivery reduces the side effects of crude or naturally occurring drugs by minimizing undesired exposure to healthy cells. Drug delivery focuses on maximizing bioavailability both at specific places in the body and over a period of time. This can potentially be achieved by molecular targeting by nanoengineered devices. [ 13 ] [ 14 ] A benefit of using nanoscale for medical technologies is that smaller devices are less invasive and can possibly be implanted inside the body, plus biochemical reaction times are much shorter. These devices are faster and more sensitive than typical drug delivery. [ 15 ] The efficacy of drug delivery through nanomedicine is largely based upon: a) efficient encapsulation of the drugs, b) successful delivery of drug to the targeted region of the body, and c) successful release of the drug. [ 16 ] Several nano-delivery drugs were on the market by 2019. [ 17 ]
Drug delivery systems, lipid- [ 18 ] or polymer-based nanoparticles, can be designed to improve the pharmacokinetics and biodistribution of the drug. [ 19 ] [ 20 ] [ 21 ] However, the pharmacokinetics and pharmacodynamics of nanomedicine is highly variable among different patients. [ 22 ] When designed to avoid the body's defense mechanisms, [ 23 ] nanoparticles have beneficial properties that can be used to improve drug delivery. Complex drug delivery mechanisms are being developed, including the ability to get drugs through cell membranes and into cell cytoplasm . Triggered response is one way for drug molecules to be used more efficiently. Drugs are placed in the body and only activate on encountering a particular signal. For example, a drug with poor solubility will be replaced by a drug delivery system where both hydrophilic and hydrophobic environments exist, improving the solubility. [ 24 ] Drug delivery systems may also be able to prevent tissue damage through regulated drug release; reduce drug clearance rates; or lower the volume of distribution and reduce the effect on non-target tissue. However, the biodistribution of these nanoparticles is still imperfect due to the complex host's reactions to nano- and microsized materials [ 23 ] and the difficulty in targeting specific organs in the body. Nevertheless, a lot of work is still ongoing to optimize and better understand the potential and limitations of nanoparticulate systems. While advancement of research proves that targeting and distribution can be augmented by nanoparticles, the dangers of nanotoxicity become an important next step in further understanding of their medical uses. [ 25 ] The toxicity of nanoparticles varies, depending on size, shape, and material. These factors also affect the build-up and organ damage that may occur. Nanoparticles are made to be long-lasting, but this causes them to be trapped within organs, specifically the liver and spleen, as they cannot be broken down or excreted. This build-up of non-biodegradable material has been observed to cause organ damage and inflammation in mice. [ 26 ] Delivering magnetic nanoparticles to a tumor using uneven stationary magnetic fields may lead to enhanced tumor growth. In order to avoid this, alternating electromagnetic fields should be used. [ 27 ]
Nanoparticles are under research for their potential to decrease antibiotic resistance or for various antimicrobial uses. [ 28 ] [ 29 ] [ 30 ] [ 31 ] Nanoparticles might also be used to circumvent multidrug resistance (MDR) mechanisms. [ 10 ]
Advances in lipid nanotechnology were instrumental in engineering medical nanodevices and novel drug delivery systems, as well as in developing sensing applications. [ 32 ] Another system for microRNA delivery under preliminary research is nanoparticles formed by the self-assembly of two different microRNAs to possibly shrink tumors . [ 33 ] One potential application is based on small electromechanical systems, such as nanoelectromechanical systems being investigated for the active release of drugs and sensors for possible cancer treatment with iron nanoparticles or gold shells. [ 34 ] Another system of drug delivery involving nanoparticles is the use of aquasomes , self-assembled nanoparticles with a nanocrystalline center, a coating made of a polyhydroxyl oligomer , covered in the desired drug, which protects it from dehydration and conformational change . [ 12 ]
Some nanotechnology-based drugs that are commercially available or in human clinical trials include:
In vivo imaging is another area where tools and devices are being developed. [ 38 ] Using nanoparticle contrast agents , images such as ultrasound and MRI have a better distribution and improved contrast. In cardiovascular imaging, nanoparticles have potential to aid visualization of blood pooling, ischemia, angiogenesis , atherosclerosis , and focal areas where inflammation is present. [ 38 ]
The small size of nanoparticles gives them with properties that can be very useful in oncology , particularly in imaging. [ 10 ] Quantum dots (nanoparticles with quantum confinement properties, such as size-tunable light emission), when used in conjunction with MRI (magnetic resonance imaging), can produce exceptional images of tumor sites. Nanoparticles of cadmium selenide ( quantum dots ) glow when exposed to ultraviolet light. When injected, they seep into cancer tumors . The surgeon can see the glowing tumor, and use it as a guide for more accurate tumor removal. These nanoparticles are much brighter than organic dyes and only need one light source for activation. This means that the use of fluorescent quantum dots could produce a higher contrast image and at a lower cost than today's organic dyes used as contrast media . The downside, however, is that quantum dots are usually made of quite toxic elements, but this concern may be addressed by use of fluorescent dopants, substances added to create fluorescence. [ 39 ]
Tracking movement can help determine how well drugs are being distributed or how substances are metabolized. It is difficult to track a small group of cells throughout the body, so scientists used to dye the cells. These dyes needed to be excited by light of a certain wavelength in order for them to light up. While different color dyes absorb different frequencies of light, there was a need for as many light sources as cells. A way around this problem is with luminescent tags. These tags are quantum dots attached to proteins that penetrate cell membranes. [ 39 ] The dots can be random in size, can be made of bio-inert material, and they demonstrate the nanoscale property that color is size-dependent. As a result, sizes are selected so that the frequency of light used to make a group of quantum dots fluoresce is an even multiple of the frequency required to make another group incandesce. Then both groups can be lit with a single light source. They have also found a way to insert nanoparticles [ 40 ] into the affected parts of the body so that those parts of the body will glow showing the tumor growth or shrinkage or also organ trouble. [ 41 ]
Nanotechnology-on-a-chip is one more dimension of lab-on-a-chip technology. Magnetic nanoparticles, bound to a suitable antibody, are used to label specific molecules, structures or microorganisms. Silica nanoparticles, in particular, are inert from a photophysical perspective and can accumulate a large number of dye(s) within their shells. [ 42 ] Gold nanoparticles tagged with short DNA segments can be used to detect genetic sequences in a sample. Multicolor optical coding for biological assays has been achieved by embedding different-sized quantum dots into polymeric microbeads . Nanopore technology for analysis of nucleic acids converts strings of nucleotides directly into electronic signatures. [ 43 ]
Sensor test chips containing thousands of nanowires, able to detect proteins and other biomarkers left behind by cancer cells, could enable the detection and diagnosis of cancer in the early stages from a few drops of a patient's blood. [ 44 ] Nanotechnology is helping to advance the use of arthroscopes , which are pencil-sized devices that are used in surgeries with lights and cameras so surgeons can do the surgeries with smaller incisions. The smaller the incisions the faster the healing time which is better for the patients. It is also helping to find a way to make an arthroscope smaller than a strand of hair. [ 45 ]
Research on nanoelectronics -based cancer diagnostics could lead to tests that can be done in pharmacies . The results promise to be highly accurate and the product promises to be inexpensive. They could take a very small amount of blood and detect cancer anywhere in the body in about five minutes, with a sensitivity that is a thousand times better a conventional laboratory test. These devices are built with nanowires to detect cancer proteins; each nanowire detector is primed to be sensitive to a different cancer marker. [ 34 ] The biggest advantage of the nanowire detectors is that they could test for anywhere from ten to one hundred similar medical conditions without adding cost to the testing device. [ 46 ] Nanotechnology has also helped to personalize oncology for the detection, diagnosis, and treatment of cancer. It is now able to be tailored to each individual's tumor for better performance. They have found ways that they will be able to target a specific part of the body that is being affected by cancer. [ 47 ]
In contrast to dialysis, which works on the principle of the size-related diffusion of solutes and ultrafiltration of fluid across a semi-permeable membrane , the purification using nanoparticles allows specific targeting of substances. [ 48 ] Additionally, larger compounds which are commonly not dialyzable can be removed. [ 49 ]
The purification process is based on functionalized iron oxide or carbon coated metal nanoparticles with ferromagnetic or superparamagnetic properties. [ 50 ] Binding agents such as proteins , [ 48 ] antibiotics , [ 51 ] or synthetic ligands [ 52 ] are covalently linked to the particle surface. These binding agents are able to interact with target species forming an agglomerate. Applying an external magnetic field gradient exerts a force on the nanoparticles, allowing them to be separated from the bulk fluid, thus removing contaminants. [ 53 ] [ 54 ] This can neutralize the toxicity of sepsis, but runs the risk of nephrotoxicity and neurotoxicity. [ 55 ]
The small size (< 100 nm) and large surface area of functionalized nanomagnets offer advantages properties compared to hemoperfusion , which is a clinically used technique for the purification of blood and is based on surface adsorption . These advantages include high loading capacity, high selectivity towards the target compound, fast diffusion, low hydrodynamic resistance, and low dosage requirements. [ 56 ]
Nanotechnology may be used as part of tissue engineering to help reproduce, repair, or reshape damaged tissue using suitable nanomaterial-based scaffolds and growth factors. If successful, tissue engineering may replace conventional treatments like organ transplants or artificial implants. Nanoparticles such as graphene, carbon nanotubes, molybdenum disulfide and tungsten disulfide are being used as reinforcing agents to fabricate mechanically strong biodegradable polymeric nanocomposites for bone tissue engineering applications. The addition of these nanoparticles to the polymer matrix at low concentrations (~0.2 weight %) significantly improves in the compressive and flexural mechanical properties of polymeric nanocomposites. [ 57 ] [ 58 ] These nanocomposites may potentially serve as novel, mechanically strong, lightweight bone implants. [ 59 ]
For example, a flesh welder was demonstrated to fuse two pieces of chicken meat into a single piece using a suspension of gold-coated nanoshells activated by an infrared laser. This could be used to weld arteries during surgery. [ 60 ] Another example is nanonephrology , the use of nanomedicine on the kidney.
The full potential and implications of nanotechnology uses within the tissue engineering are not yet fully understood, despite research spanning the past two decades. [ 59 ]
Today, a significant proportion of vaccines against viral diseases are created using nanotechnology. Solid lipid nanoparticles represent a novel delivery system for some vaccines against SARS-CoV-2 (the virus that causes COVID-19 ). [ 61 ] In recent decades, nanosized adjuvants have been widely used to enhance immune responses to targeted vaccine antigens. Inorganic nanoparticles of aluminum, [ 62 ] silica and clay , as well as organic nanoparticles based on polymers and lipids, are commonly used adjuvants within modern vaccine formulations. [ 63 ] Nanoparticles of natural polymers such as chitosan are commonly used adjuvants in modern vaccine formulations. [ 64 ] Ceria nanoparticles appear very promising for both enhancing vaccine responses and mitigating inflammation, as their adjuvanticity can be adjusted by modifying parameters such as size, crystallinity, surface state, and stoichiometry. [ 65 ]
In addition, virus-like nanoparticles are also being researched. These structures allow vaccines to self-assemble without encapsulating viral RNA, making them non-infectious and incapable of replication. These virus-like nanoparticles are designed to elicit a strong immune response by using a self-assembled layer of virus capsid proteins. [ 66 ] [ 61 ]
Neuro-electronic interfacing is a visionary goal dealing with the construction of nanodevices that will permit computers to connect and interact with the nervous system. This idea requires the building of a molecular structure that will permit control and detection of nerve impulses by an external computer. A refuelable system implies energy is refilled continuously or periodically with external sonic, chemical, tethered, magnetic, or biological electrical sources, while a non-refuelable system implies that all power is drawn from internal energy storage, ceasing operation once the energy is depleted. A nanoscale enzymatic biofuel cell for self-powered nanodevices have been developed, using glucose from biofluids such as human blood or watermelons. [ 67 ] [ 68 ] [ 69 ] One limitation to this innovation is the potential for electrical interference, leakage, or overheating due to power consumption. The wiring of the structure is extremely difficult because they must be positioned precisely in the nervous system. The structures that will provide the interface must also be compatible with the body's immune system. [ 70 ] Current research is developing nanoparticle coatings for the electrodes to allow for improved recording and reduce interference. [ 71 ]
Molecular nanotechnology is a speculative subfield of nanotechnology that explores the potential to engineer molecular assemblers—machines capable of reorganizing matter at a molecular or atomic scale. [ citation needed ] Nanomedicine would make use of these nanorobots , introduced into the body, to repair or detect damages and infections. Molecular nanotechnology is highly theoretical, seeking to anticipate what inventions nanotechnology might yield and to propose an agenda for future inquiry. The proposed elements of molecular nanotechnology, such as molecular assemblers and nanorobots are far beyond current capabilities. [ 1 ] [ 70 ] [ 72 ] Future advances in nanomedicine could give rise to life extension through the repair of many processes thought to be responsible for aging. K. Eric Drexler , one of the founders of nanotechnology, postulated cell repair machines, including ones operating within cells and utilizing as yet hypothetical molecular machines , in his 1986 book Engines of Creation , with the first technical discussion of medical nanorobots by Robert Freitas appearing in 1999. [ 1 ] Raymond Kurzweil , a futurist and transhumanist , stated in his book The Singularity Is Near that he believes that advanced medical nanorobotics could completely remedy the effects of aging by 2030. [ 73 ] According to Richard Feynman , it was his former graduate student and collaborator Albert Hibbs who originally suggested to him ( c. 1959 ) the idea of a medical use for Feynman's theoretical micromachines (see nanotechnology ). Hibbs suggested that certain repair machines might one day be reduced in size to the point that it would, in theory, be possible to (as Feynman put it) " swallow the doctor ". The idea was incorporated into Feynman's 1959 essay There's Plenty of Room at the Bottom . [ 74 ]
As the development of nanomedicine continues to develop and becomes a potential treatments for diseases, regulatory challenges have come to light. This section will highlight some of the regulatory considerations and challenges faced by the Food and Drug Administration (FDA), the European Medicine Agency (EMA), and each manufacturing organization. The major challenges that companies are reproducible manufacturing processes, scalability, availability of appropriate characterization methods, safety issues, and poor understandings of disease heterogeneity and patient preselection strategies. [ 75 ] Despite these challenges, several therapeutic nanomedicine products have been approved by the FDA and EMA. [ 75 ] [ 76 ] In order to be approved for market, these therapies are evaluated for biocompatibility, immunotoxicity, as well as undergo a preclinical assessment. [ 77 ]
The current scope of approved nanomedicine are mainly nano-drugs, but as the field continued to grow and more applications of nanomedicine progress to a marketable scale, more impacts and regulatory oversight will be needed. [ 76 ] [ 78 ] | https://en.wikipedia.org/wiki/Nanomedicine |
The nanomesh is an inorganic nanostructured two-dimensional material, similar to graphene . It was discovered in 2003 at the University of Zurich , Switzerland. [ 1 ]
It consists of a single layer of boron (B) and nitrogen (N) atoms, which forms by self-assembly into a highly regular mesh after high-temperature exposure of a clean rhodium [ 1 ] or ruthenium [ 2 ] surface to borazine under ultra-high vacuum .
The nanomesh looks like an assembly of hexagonal pores [ 3 ] (see right image) at the nanometer (nm) scale. The distance between two pore centers is only 3.2 nm, whereas each pore has a diameter of about 2 nm and is 0.05 nm deep. The lowest regions bind strongly to the underlying metal, while the wires [ 3 ] (highest regions) are only bound to the surface through strong cohesive forces within the layer itself.
The boron nitride nanomesh is not only stable under vacuum, [ 1 ] air [ 4 ] and some liquids, [ 5 ] [ 6 ] but also up to temperatures of 796 °C (1070 K). [ 1 ] In addition it shows the extraordinary ability to trap molecules [ 5 ] and metallic clusters , [ 2 ] which have similar sizes to the nanomesh pores, forming a well-ordered array. These characteristics may provide applications of the material in areas like, surface functionalisation , spintronics , quantum computing and data storage media like hard drives .
h-BN nanomesh is a single sheet of hexagonal boron nitride , which forms on substrates like rhodium Rh (111) or ruthenium Ru (0001) crystals by a self-assembly process.
The unit cell of the h-BN nanomesh consists of 13x13 BN or 12x12 Rh atoms with a lattice constant of 3.2 nm. In a cross-section it means that 13 boron or nitrogen atoms are sitting on 12 rhodium atoms. This implies a modification of the relative positions of each BN towards the substrate atoms within a unit cell, where some bonds are more attractive or repulsive than other (site selective bonding), what induces the corrugation of the nanomesh (see right image with pores and wires).
The nanomesh corrugation amplitude of 0.05 nm causes a strong effect on the electronic structure , where two distinct BN regions are observed. They are easily recognized in the lower right image, which is a scanning tunneling microscopy (STM) measurement, as well as in the lower left image representing a theoretical calculation of the same area. A strongly bounded region assigned to the pores is visible in blue in the left image below (center of bright rings in the right image) and a weakly bound region assigned to the wires appears yellow-red in the left image below (area in-between rings in the right image).
The left image is the theoretical calculation of the same area, where the N height relative to the underlying substrate is given. The exact arrangement of Rh, N and B atoms is given for three different areas (blue: pores, yellow-red: wires).
See [ 1 ] [ 2 ] [ 4 ] [ 5 ] [ 7 ] for more details.
The nanomesh is stable under a wide range of environments like air, water and electrolytes among others. It is also temperature resistant since it does not decompose in temperatures up to 1275K under a vacuum. In addition to these exceptional stabilities, the nanomesh shows the extraordinary ability to act as a scaffold for metallic nano clusters and to trap molecules forming a well-ordered array.
In the case of gold (Au), its evaporation on the nanomesh leads to formation of well-defined round Au nanoparticles, which are centered at the nanomesh pores.
The STM figure on the right shows Naphthalocyanine (Nc) molecules, which were vapor-deposited onto the nanomesh. These planar molecules have a diameter of about 2 nm, whose size is comparable to that of the nanomesh pores (see upper inset). It is spectacularly visible how the molecules form a well-ordered array with the periodicity of the nanomesh (3.22 nm). The lower inset shows a region of this substrate with higher resolution, where individual molecules are trapped inside the pores. In addition, the molecules seem to keep their native conformation , what means that their functionality is kept, which is nowadays a challenge in nanoscience .
Such systems with wide spacing between individual molecules/clusters and negligible intermolecular interactions might be interesting for applications such as molecular electronics and memory elements , in photochemistry or in optical devices.
See [ 2 ] [ 5 ] [ 6 ] for more detailed information.
Well-ordered nanomeshes are grown by thermal decomposition of borazine (HBNH) 3 , a colorless substance that is liquid at room temperature. The nanomesh results after exposing the atomically clean Rh (111) or Ru (0001) surface to borazine by chemical vapor deposition (CVD).
The substrate is kept at a temperature of 796 °C (1070 K) when borazine is introduced in the vacuum chamber at a dose of about 40 L (1 Langmuir = 10 −6 torr sec). A typical borazine vapor pressure inside the ultrahigh vacuum chamber during the exposure is 3x10 −7 mbar .
After cooling down to room temperature, the regular mesh structure is observed using different experimental techniques. Scanning tunneling microscopy (STM) gives a direct look on the local real space structure of the nanomesh, while low energy electron diffraction (LEED) gives information about the surface structures ordered over the whole sample. Ultraviolet photoelectron spectroscopy (UPS) gives information about the electronic states in the outermost atomic layers of a sample, i.e. electronic information of the top substrate layers and the nanomesh.
CVD of borazine on other substrates has not led so far to the formation of a corrugated nanomesh. A flat BN layer is observed on nickel [ 8 ] and palladium , [ 9 ] [ 10 ] whereas stripped structures appear on molybdenum [ 11 ] instead.
http://www.nanomesh.ch
http://www.nanomesh.org | https://en.wikipedia.org/wiki/Nanomesh |
Nanometrology is a subfield of metrology , concerned with the science of measurement at the nanoscale level. Nanometrology has a crucial role in order to produce nanomaterials and devices with a high degree of accuracy and reliability in nanomanufacturing .
A challenge in this field is to develop or create new measurement techniques and standards to meet the needs of next-generation advanced manufacturing, which will rely on nanometer scale materials and technologies. The needs for measurement and characterization of new sample structures and characteristics far exceed the capabilities of current measurement science. Anticipated advances in emerging U.S. nanotechnology industries will require revolutionary metrology with higher resolution and accuracy than has previously been envisioned. [ 1 ]
Control of the critical dimensions are the most important factors in nanotechnology. Nanometrology today, is to a large extent based on the development in semiconductor technology. Nanometrology is the science of measurement at the nanoscale level. Nanometer or nm is equivalent to 10^-9 m. In Nanotechnology accurate control of dimensions of objects is important. Typical dimensions of nanosystems vary from 10 nm to a few hundred nm and while fabricating such systems measurement up to 0.1 nm is required.
At nanoscale due to the small dimensions various new physical phenomena can be observed. For example, when the crystal size is smaller than the electron mean free path the conductivity of the crystal changes. Another example is the discretization of stresses in the system. It becomes important to measure the physical parameters so as to apply these phenomena into engineering of nanosystems and manufacturing them. The measurement of length or size, force, mass, electrical and other properties is included in Nanometrology.
The problem is how to measure these with reliability and accuracy. The measurement techniques used for macro systems cannot be directly used for measurement of parameters in nanosystems. Various techniques based on physical phenomena have been developed which can be used for measure or determine the parameters for nanostructures and nanomaterials. Some of the popular ones are X-Ray diffraction , transmission electron microscopy , High Resolution Transmission Electron Microscopy, atomic force microscopy , scanning electron microscopy , field emission scanning electron microscopy and Brunauer, Emmett, Teller method to determine specific surface.
Nanotechnology is an important field because of the large number of applications it has and it has become necessary to develop more precise techniques of measurement and globally accepted standards. Hence progress is required in the field of Nanometrology.
Nanotechnology can be divided into two branches. The first being molecular nanotechnology which involves bottom up manufacturing and the second is engineering nanotechnology which involve the development and processing of materials and systems at nanoscale. The measurement and manufacturing tools and techniques required for the two branches are slightly different.
Furthermore, Nanometrology requirements are different for the industry and research institutions. Nanometrology of research has progressed faster than that for industry mainly because implementing nanometrology for industry is difficult. In research oriented nanometrology resolution is important whereas in industrial nanometrology accuracy is given precedence over resolution . Further, due to economic reasons it is important to have low time costs in industrial nanometrology, whereas it is not important for research nanometrology. The various measurement techniques available today require a controlled environment like in vacuum , vibration and noise free environment. Also, in industrial nanometrology requires that the measurements be more quantitative with minimum number of parameters.
Metrology standards are objects or ideas that are designated as being authoritative for some accepted reason. Whatever value they possess is useful for comparison to unknowns for the purpose of establishing or confirming an assigned value based on the standard. The execution of measurement comparisons for the purpose of establishing the relationship between a standard and some other measuring device is calibration. The ideal standard is independently reproducible without uncertainty. The worldwide market for products with nanotechnology applications is projected to be at least a couple of hundred billion dollars in the near future. [ citation needed ] Until recently, there almost no established internationally accepted standards for nanotechnology related field. The International Organization for Standardization TC-229 Technical Committee on Nanotechnology recently published few standards for terminology, characterization of nanomaterials and nanoparticles using measurement tools like AFM , SEM , Interferometers , optoacoustic tools, gas adsorption methods etc. Certain standards for standardization of measurements for electrical properties have been published by the International Electrotechnical Commission .
Some important standards which are yet to be established are standards for measuring thickness of thin films or layers, characterization of surface features, standards for force measurement at nanoscale, standards for characterization of critical dimensions of nanoparticles and nanostructures and also Standards for measurement for physical properties like conductivity, elasticity etc.
Because of the importance of nanotechnology in the future, countries around the world have programmes to establish national standards for nanometrology and nanotechnology. These programmes are run by the national standard agencies of the respective countries. In the United States, National Institute of Standards and Technology has been working on developing new techniques for measurement at nanoscale and has also established some national standards for nanotechnology. These standards are for nanoparticle characterization, Roughness Characterization, magnification standard, calibration standards etc.
It is difficult to provide samples using which precision instruments can be calibrated at nanoscale. Reference or calibration standards are important for repeatability to be ensured. But there are no international standards for calibration and the calibration artefacts provided by the company along with their equipment is only good for calibrating that particular equipment. Hence it is difficult to select a universal calibration artefact using which we can achieve repeatability at nanoscale. At nanoscale while calibrating care needs to be taken for influence of external factors like vibration , noise , motions caused by thermal drift and creep , nonlinear behaviour and hysteresis of piezoscanner [ 2 ] and internal factors like the interaction between the artefact and the equipment which can cause significant deviations.
In the last 70 years various techniques for measuring at nanoscale have been developed. Most of them based on some physical phenomena observed on particle interactions or forces at nanoscale. Some of the most commonly used techniques are Atomic Force Microscopy, X-Ray Diffraction, Scanning Electron Microscopy, Transmission Electron Microscopy, High Resolution Transmission Electron Microscopy, and Field Emission Scanning Electron Microscopy.
Atomic force microscopy (AFM) is one of the most common measurement techniques. It can be used to measure topology, grain size, frictional characteristics and different forces. It consists of a silicon cantilever with a sharp tip with a radius of curvature of a few nanometers. The tip is used as a probe on the specimen to be measured. The forces acting at the atomic level between the tip and the surface of the specimen cause the tip to deflect and this deflection is detected using a laser spot which is reflected to an array of photodiodes.
Scanning tunneling microscopy (STM) is another instrument commonly used. It is used to measure 3-D topology of the specimen. The STM is based on the concept of quantum tunneling . When a conducting tip is brought very near to the surface to be examined, a bias (voltage difference) applied between the two can allow electrons to tunnel through the vacuum between them. Measurements are made by monitoring the current as the tip's position scans across the surface, which can then be used to display an image.
Another commonly used instrument is the scanning electron microscopy (SEM) which apart from measuring the shape and size of the particles and topography of the surface can be used to determine the composition of elements and compounds the sample is composed of. In SEM the specimen surface is scanned with a high energy electron beam. The electrons in the beam interact with atoms in the specimen and interactions are detected using detectors. The interactions produced are back scattering of electrons, transmission of electrons, secondary electrons etc. To remove high angle electrons magnetics lenses are used.
The instruments mentioned above produce realistic pictures of the surface are excellent measuring tools for research. Industrial applications of nanotechnology require the measurements to be produced need to be more quantitative. The requirement in industrial nanometrology is for higher accuracy than resolution as compared to research nanometrology.
A coordinate measuring machine (CMM) that works at the nanoscale would have a smaller frame than the CMM used for macroscale objects. This is so because it may provide the necessary stiffness and stability to achieve nanoscale uncertainties in x,y and z directions. The probes for such a machine need to be small to enable a 3-D measurement of nanometre features from the sides and from inside like nanoholes. Also for accuracy laser interferometers need to be used. NIST has developed a surface measuring instrument, called the Molecular Measuring Machine. This instrument is basically an STM. The x- and y-axes are read out by laser interferometers. The molecules on the surface area can be identified individually and at the same time the distance between any two molecules can be determined. For measuring with molecular resolution, the measuring times become very large for even a very small surface area. Ilmenau Machine is another nanomeasuring machine developed by researchers at the Ilmenau University of Technology.
The components of a nano CMM include nanoprobes, control hardware, 3D-nanopositioning platform, and instruments with high resolution and accuracy for linear and angular measurement.
In metrology at macro scale achieving traceability is quite easy and artefacts like scales, laser interferometers, step gauges, and straight edges are used. At nanoscale a crystalline highly oriented pyrolytic graphite ( HOPG ), mica or silicon surface is considered suitable used as calibration artefact for achieving traceability. [ 4 ] [ 5 ] But it is not always possible to ensure traceability. Like what is a straight edge at nanoscale and even if take the same standard as that for macroscale there is no way to calibrate it accurately at nanoscale. This so because the requisite internationally or nationally accepted reference standards are not always there. Also the measurement equipment required to ensure traceability has not been developed. The generally used for traceability are miniaturisation of traditional metrology standards hence there is a need for establishing nanoscale standards. Also there is a need to establish some kind of uncertainty estimation model. Traceability is one of the fundamental requirements for manufacturing and assembly of products when multiple producers are there.
Tolerance is the permissible limit or limits of variation in dimensions, properties, or conditions without significantly affecting functioning of equipment or a process. Tolerances are specified to allow reasonable leeway for imperfections and inherent variability without compromising performance. In nanotechnology the systems have dimensions in the range of nanometers. Defining tolerances at nanoscale with suitable calibration standards for traceability is difficult for different nanomanufacturing methods. There are various integration techniques developed in the semiconductor industry that are used in nanomanufacturing .
There are a variety of nanostructures like nanocomposites, nanowires, nanopowders, nanotubes, fullerenes nanofibers, nanocages, nanocrystallites, nanoneedles , nanofoams, nanomeshes, nanoparticles, nanopillars, thin films, nanorods, nanofabrics, quantumdots etc. The most common way to classify nano structures is by their dimensions.
Nanostructures can be classified on the basis of the grain structure and size there are made up of. This is applicable in the cas of 2-dimensional and 3-Dimensional Nanostructurs.
For nanopowder to determine the specific surface area the B.E.T. method is commonly used. The drop of pressure of nitrogen in a closed container due to adsorption of the nitrogen molecules to the surface of the material inserted in the container is measured. Also, the shape of the nanopowder particles is assumed to be spherical.
Where "D" is the effective diameter, "ρ" is the density and "A" is the surface area found from the B.E.T. method. | https://en.wikipedia.org/wiki/Nanometrology |
The nanomorphic cell [ 1 ] is a conception of an atomic-level, integrated, self-sustaining microsystem with five main functions: internal energy supply, sensing, actuation, computation and communication. Atomic level integration provides the ultimate functionality per unit volume for microsystems. The nanomorphic cell abstraction allows one to analyze the fundamental limits of attainable performance for nanoscale systems in much the same way that the Turing Machine and the Carnot Engine support such limit studies for information processing and heat engines respectively.
The nanomorphic cell concept is inspired by the trend, synergistic with semiconductor device scaling; to use these core technologies for diverse integrated system applications. This trend is called Functional Diversification and is characterized by the integration of non- CMOS devices such as sensors , actuators , energy sources etc. with traditional CMOS and other novel information processing devices. The multifunctional microsystems becomes morphic (literally means in the shape of ) because its architecture are defined by the specific application and the fundamental limits on volumetric system parameters. [ 2 ]
The nanomorphic cell model was applied to analyze the capabilities of an autonomous integrated microsystem on the order of the size of a living cell, i.e. a cube of 10 micrometer on a side [1, 2]. The function of this microsystem is, for example, upon injection into the body, to interact with living cells, e.g. determine the state of the cell and to support certain “therapeutic” action. It must have the capability to collect data on the living cell, analyze the data, and make a decision on the state of the living cell. It must also communicate with an external controlling agent, and possibly, take corrective action. Such a cell would need its own energy sources, sensors, computers, and communication devices, integrated into a complete system whose structure is dictated by the intended nanomorphic cell function. The Nanomorphic Cell can be considered as an extreme example of a class of systems known generically as Autonomous Microsystems, for example WIMS (Wireless Integrated Microsystems), [ 3 ] PicoNode, [ 4 ] Lab-on-a-Pill [ 5 ] and Smartdust . [ 6 ] | https://en.wikipedia.org/wiki/Nanomorphic_cell |
A nanonetwork or nanoscale network is a set of interconnected nanomachines (devices a few hundred nanometers or a few micrometers at most in size) which are able to perform only very simple tasks such as computing , data storing , sensing and actuation. [ 1 ] [ 2 ] Nanonetworks are expected to expand the capabilities of single nanomachines both in terms of complexity and range of operation by allowing them to coordinate, share and fuse information. Nanonetworks enable new applications of nanotechnology in the biomedical field, environmental research, military technology and industrial and consumer goods applications. Nanoscale communication is defined in IEEE P1906.1 .
Classical communication paradigms need to be revised for the nanoscale. The two main alternatives for communication in the nanoscale are based either on electromagnetic communication or on molecular communication.
This is defined as the transmission and reception of electromagnetic radiation from components based on novel nanomaterials . [ 3 ] Recent advancements in carbon and molecular electronics have opened the door to a new generation of electronic nanoscale components such as nanobatteries , [ 4 ] nanoscale energy harvesting systems, [ 5 ] nano-memories, [ 6 ] logical circuitry in the nanoscale and even nano-antennas. [ 7 ] [ 8 ] From a communication perspective, the unique properties observed in nanomaterials will decide on the specific bandwidths for emission of electromagnetic radiation, the time lag of the emission, or the magnitude of the emitted power for a given input energy, amongst others.
For the time being, two main alternatives for electromagnetic communication in the nanoscale have been envisioned. First, it has been experimentally demonstrated that is possible to receive and demodulate an electromagnetic wave by means of a nanoradio , i.e., an electromechanically resonating carbon nanotube which is able to decode an amplitude or frequency modulated wave. [ 9 ] Second, graphene-based nano-antennas have been analyzed as potential electromagnetic radiators in the terahertz band . [ 10 ]
Molecular communication is defined as the transmission and reception of information by means of molecules. [ 11 ] The different molecular communication techniques can be classified according to the type of molecule propagation in walkaway-based, flow-based or diffusion-based communication.
In walkway-based molecular communication, the molecules propagate through pre-defined pathways by using carrier substances, such as molecular motors . [ 12 ] This type of molecular communication can also be achieved by using E. coli bacteria as chemotaxis . [ 13 ]
In flow-based molecular communication, the molecules propagate through diffusion in a fluidic medium whose flow and turbulence are guided and predictable. The hormonal communication through blood streams inside the human body is an example of this type of propagation. The flow-based propagation can also be realized by using carrier entities whose motion can be constrained on the average along specific paths, despite showing a random component. A good example of this case is given by pheromonal long range molecular communications. [ 14 ]
In diffusion-based molecular communication, the molecules propagate through spontaneous diffusion in a fluidic medium. In this case, the molecules can be subject solely to the laws of diffusion or can also be affected by non-predictable turbulence present in the fluidic medium. Pheromonal communication, when pheromones are released into a fluidic medium, such as air or water, is an example of diffusion-based architecture. Other examples of this kind of transport include calcium signaling among cells, [ 15 ] as well as quorum sensing among bacteria. [ 16 ]
Based on the macroscopic theory [ 17 ] of ideal (free) diffusion the impulse response of a unicast molecular communication channel was reported in a paper [ 18 ] that identified that the impulse response of the ideal diffusion based molecular communication channel experiences temporal spreading. Such temporal spreading has a deep impact in the performance of the system, for example in creating the intersymbol interference (ISI) at the receiving nanomachine. [ 19 ] In order to detect the concentration-encoded molecular signal two detection methods named sampling-based detection (SD) and energy-based detection (ED) have been proposed. [ 20 ] While the SD approach is based on the concentration amplitude of only one sample taken at a suitable time instant during the symbol duration, the ED approach is based on the total accumulated number of molecules received during the entire symbol duration. In order to reduce the impact of ISI a controlled pulse-width based molecular communication scheme has been analysed. [ 21 ] The work presented in [ 22 ] showed that it is possible to realize multilevel amplitude modulation based on ideal diffusion. A comprehensive study of pulse-based binary [ 23 ] and sinus-based, [ 24 ] [ 25 ] [ 26 ] [ 27 ] concentration-encoded molecular communication system have also been investigated. | https://en.wikipedia.org/wiki/Nanonetwork |
Nanoneuronics is an emerging discipline involving the application of nanometer-scale methods, materials, science and technology to neurons and neural tissue in order to design and develop advanced medical applications.
Nanoneuronics is a new discipline of engineering that aims to harness the collaborative power and knowledge of nanotechnology , neuroscience , electrical engineering , neural engineering and ethics for the design and development of advanced medical interventions with the nervous system .
Although non-invasive approaches to the nervous system have been effective for diagnosis and therapy in many treatments, an overwhelming number of severe neurological conditions will likely require invasive approaches for effective therapY.
The term “nanoneuronics” was coined in 2006 by Prof. Richard Magin, at the time the head of the Bioengineering Department at the University of Illinois at Chicago .
The National Science Foundation has approved initial funding toward the study of ways in which experts in these fields can work together to promote interdisciplinary research. | https://en.wikipedia.org/wiki/Nanoneuronics |
Nanoneuroscience is an interdisciplinary field that integrates nanotechnology and neuroscience . [ 1 ] One of its main goals is to gain a detailed understanding of how the nervous system operates and, thus, how neurons organize themselves in the brain. Consequently, creating drugs and devices that are able to cross the blood brain barrier (BBB) are essential to allow for detailed imaging and diagnoses. The blood brain barrier functions as a highly specialized semipermeable membrane surrounding the brain, preventing harmful molecules that may be dissolved in the circulation blood from entering the central nervous system.
The main two hurdles for drug-delivering molecules to access the brain are size (must have a molecular weight < 400 Da) and lipid solubility. [ 2 ] Physicians hope to circumvent difficulties in accessing the central nervous system through viral gene therapy . This often involves direct injection into the patient's brain or cerebral spinal fluid. The drawback of this therapy is that it is invasive and carries a high risk factor due to the necessity of surgery for the treatment to be administered. Because of this, only 3.6% of clinical trials in this field have progressed to stage III since the concept of gene therapy was developed in the 1980s. [ 3 ]
Another proposed way to cross the BBB is through temporary intentional disruption of the barrier. This method was first inspired by certain pathological conditions that were discovered to break down this barrier by themselves, such as Alzheimer's disease , Parkinson's disease , stroke , and seizure conditions. [ 2 ]
Nanoparticles are unique from macromolecules because their surface properties are dependent on their size, allowing for strategic manipulation of these properties (or, "programming") by scientists that would not be possible otherwise. Likewise, nanoparticle shape can also be varied to give a different set of characteristics based on the surface area to volume ratio of the particle. [ 4 ]
Nanoparticles have promising therapeutic effects when treating neurodegenerative diseases. Oxygen reactive polymer (ORP) is a nano-platform programmed to react with oxygen and has been shown to detect and reduce the presence of reactive oxygen species (ROS) formed immediately after traumatic brain injuries. [ 5 ] Nanoparticles have also been employed as a "neuroprotective" measure, as is the case with Alzheimer's disease and stroke models. Alzheimer's disease results in toxic aggregates of the amyloid beta protein formed in the brain. In one study, gold nanoparticles were programmed to attach themselves to these aggregates and were successful in breaking them up. [ 6 ] Likewise, with ischemic stroke models, cells in the affected region of the brain undergo apoptosis, dramatically reducing blood flow to important parts of the brain and often resulting in death or severe mental and physical changes. [ 6 ] Platinum nanoparticles have been shown to act as ROS, serving as "biological antioxidants" and significantly reducing oxidation in the brain as a result of stroke . [ 6 ] Nanoparticles can also lead to neurotoxicity and cause permanent BBB damage either from brain oedema or from unrelated molecules crossing the BBB and causing brain damage. [ 5 ] This proves further long term in vivo studies are needed to gain enough understanding to allow for successful clinical trials.
One of the most common nano-based drug delivery platforms is liposome -based delivery. They are both lipid-soluble and nano-scale and thus are permitted through a fully functioning BBB. Additionally, lipids themselves are biological molecules, making them highly biocompatible, which in turn lowers the risk of cell toxicity. The bilayer that is formed allows the molecule to fully encapsulate any drug, protecting it while it is travelling through the body. One drawback to shielding the drug from the outside cells is that it no longer has specificity, and requires coupling to extra antibodies to be able to target a biological site. Due to their low stability, liposome -based nanoparticles for drug delivery have a short shelf life. [ 4 ]
Targeted therapy using magnetic nanoparticles (MNPs) is also a popular topic of research and has led to several stage III clinical trials. [ 7 ] Invasiveness is not an issue here because a magnetic force can be applied from the outside of a patient's body to interact and direct the MNPs. This strategy has been proven successful in delivering brain-derived neurotropic factor , a naturally occurring gene thought to promote neurorehabilitation, across the BBB. [ 5 ]
The visualization of neuronal activity is of key importance in neuroscience. Nano-imaging tools with nanoscale resolution help in these areas. These optical imaging tools are PALM [ 8 ] and STORM [ 9 ] which helps visualize nanoscale objects within cells. So far, these imaging tools revealed the dynamic behavior and organization of the actin cytoskeleton inside the cells, which will assist in understanding how neurons probe their involvement during neuronal outgrowth and in response to injury, and how they differentiate axonal processes and characterization of receptor clustering and stoichiometry at the plasma inside the synapses, which are critical for understanding how synapses respond to changes in neuronal activity. [ 1 ] These past works focused on devices for stimulation or inhibition of neural activity, but the crucial aspect is the ability for the device to simultaneously monitor neural activity. The major aspect that is to be improved in the nano imaging tools is the effective collection of the light as a major problem is that biological tissue are dispersive media that do not allow a straightforward propagation and control of light. These devices use nanoneedle and nanowire for probing and stimulation. [ 8 ]
Nanowires are artificial nano- or micro-sized "needles" that can provide high-fidelity electrophysiological recordings if used as microscopic electrodes for neuronal recordings. Nanowires are an attractive as they are highly functional structures that offer unique electronic properties that are affected by biological/chemical species adsorbed on their surface; mostly the conductivity. [ 10 ] [ 11 ] This conductivity variance depending on chemical species present allows enhanced sensing performances. [ 12 ] Nanowires are also able to act as non-invasive and highly local probes. These versatility of nanowires makes it optimal for interfacing with neurons due to the fact that the contact length along the axon (or the dendrite projection crossing a nanowires) is just about 20 nm. [ 13 ] | https://en.wikipedia.org/wiki/Nanoneuroscience |
Nanoparticle deposition refers to the process of attaching nanoparticles to solid surfaces called substrates to create coatings of nanoparticles. The coatings can have a monolayer or a multilayer and organized or unorganized structure based on the coating method used. Nanoparticles are typically difficult to deposit due to their physical properties.
Nanoparticles can be made from different materials such as metals, ceramics and polymers. The stability of the nanoparticles can be an issue as nanoparticles have a tendency to lower their very high surface energy , which originates from their high surface-to-bulk ratio. Bare nanoparticles tend to stabilize themselves either by sorption of molecules from the surroundings or by lowering the surface area through coagulation and agglomeration. [ 1 ] Usually the formation of these aggregates is unwanted. The tendency of a nanoparticle to coagulate can be controlled by modifying the surface layer. In a liquid medium, suitable ligand molecules are commonly attached to the nanoparticle surface, as they provide solubility in suitable solvents and prevent coagulation.
There are multiple different coating methods available to deposit nanoparticles. The methods differ by their ability to control particle packing density and layer thickness, ability to use different particles and the complexity of the method and the instrumentation needed.
In the Langmuir-Blodgett method, the nanoparticles are injected at air-water interphase in a special Langmuir-Blodgett Trough . The floating particles are compressed closer to each other with motorized barriers which allow to control the packing density of the particles. After compressing the particles to the desired packing density, they are transferred on a solid substrate using vertical (Langmuir-Blodgett) or horizontal (Langmuir-Schaefer) dipping to create a monolayer coating. Controlled multilayer coatings can be made repeating the dipping procedure multiple times. [ 2 ]
The benefits of the Langmuir-Blodgett method include a firm control over the packing density and the layer thickness achieved that have been shown to be better than with other methods, [ 3 ] the ability to use different shapes and materials of substrates and particles and the possibility to characterize the particle layer during deposition for example a Brewster Angle Microscope . As a disadvantage, a successful Langmuir-Blodgett deposition requires optimization of multiple measurement parameters such as dipping speed, temperature and dipping packing density.
The spin and dip coating methods are simple methods for nanoparticle deposition. [ 4 ] They are useful tools especially in creating self-assembled layers and films where the packing density isn't critical. Accurate and vibration-free sample withdrawal speeds can be used to have control over the film thickness. Creating high density monolayers is typically very difficult since the methods are lacking the packing density control. Also, the volume of nanoparticle suspension required for both spin coating and dip coating is rather big which may be an issue when using expensive nanoparticle materials.
Other possible deposition methods include methods utilizing particle self-assembly by solvent evaporation, doctor blade, chemical vapor deposition and transfer printing. Some of these methods like solvent evaporation are extremely simple but produce low-quality films. Other methods such as the chemical vapor deposition are effective for certain types of particles and substrates but are limited in particle types that can be used and require heavier instrumentation investments. Also hybrid methods such as combining self-assembly to Langmuir-Blodgett have been used. [ 5 ]
Coatings and thin films made from nanoparticles are being used in various applications including displays, sensors, medical devices, energy storages and energy harvesting. Examples include | https://en.wikipedia.org/wiki/Nanoparticle_deposition |
A nanoparticle–biomolecule conjugate is a nanoparticle with biomolecules attached to its surface. Nanoparticles are minuscule particles, typically measured in nanometers (nm), that are used in nanobiotechnology to explore the functions of biomolecules. Properties of the ultrafine particles are characterized by the components on their surfaces more so than larger structures, such as cells, due to large surface area-to-volume ratios. Large surface area-to-volume-ratios of nanoparticles optimize the potential for interactions with biomolecules.
Major characteristics of nanoparticles include volume, structure, and visual properties that make them valuable in nanobiotechnology. Depending on specific properties of size, structure, and luminescence, nanoparticles can be used for different applications. Imaging techniques are used to identify such properties and give more information about the tested sample. Techniques used to characterize nanoparticles are also useful in studying how nanoparticles interact with biomolecules, such as amino acids or DNA , and include magnetic resonance imaging (MRI), denoted by the solubility of the nanoparticles in water and fluorescent. MRI can be applied in the medical field to visualize structures; atomic force microscopy (AFM) that gives a topographic view of the sample on a substrate; [ 1 ] transmission electron microscopy (TEM) that gives a top view, but with a different technique then that of atomic force microscopy; [ 2 ] Raman spectroscopy or surface enhanced Raman spectroscopy (SERS) gives information about wavelengths and energy in the sample. [ 3 ] ultraviolet-visible spectroscopy (UV-Vis) measures the wavelengths where light is absorbed; [ 4 ] X-ray diffraction (XRD) generally gives an idea of the chemical composition of the sample. [ 5 ] To quantify protein attachment to nanoparticles, assays such as the Bicinchoninic Acid (BCA) assay and Bradford assay are employed, providing a measure of the average protein labelling per nanoparticle. [ 6 ]
Nanomolecules can be created from virtually any element, but the majority produced in today's industry use carbon as the basis upon which the molecules are built around. Carbon can bond with nearly any element, allowing many possibilities when it comes to creating a specific molecule. Scientists can create thousands upon thousands of individual nanomolecules from a simple carbon basis. Some of the most famous nanomolecules currently in existence are solely carbon; these include carbon nanotubes and buckminsterfullerenes . In contrast with nanomolecules, the chemical components of nanoparticles usually consist of metals, such as iron, gold, silver, and platinum. [ 7 ]
Interactions between nanoparticles and molecules change depending on the nanoparticle's core. Nanoparticle properties depend not only on the composition of the core material, but also on varying thicknesses of material used. Magnetic properties are particularly useful in molecule manipulation, and thus metals are often used as core material. [ 8 ] Metals contain inherent magnetic properties that allow for manipulation of molecular assembly. As nanoparticles interact with molecules via ligand properties, molecular assembly can be controlled by external magnetic fields interacting with magnetic properties in the nanoparticles.
Significant problems with producing nanoparticles initially arise once these nanoparticles are generated in solution. Without the use of a stabilizing agent, nanoparticles tend to stick together once the stirring is stopped. In order to counteract this, a certain collidial stabilizer is generally added. These stabilizers bind to the nanoparticles in a way that prevents other particles from bonding with them. Some effective stabilizers found so far include citrate , cellulose , and sodium borohydride . [ 9 ]
Nanoparticles are desirable in today's industry for their high surface area-to-volume ratio in comparison with larger particles of the same elements. Because chemical reactions occur at a rate directly proportional to the available surface area of reactant compounds, nanoparticles can generate reactions at a much faster rate than larger particles of equal mass. Nanoparticles therefore are among the most efficient means of producing reactions and are inherently valuable in the chemical industry. The same property makes them valuable in interactions with molecules. [ 10 ]
Nanoparticles have the potential to greatly influence biological processes. [ 11 ] [ 12 ] The potency of a nanoparticle increases as its surface area-to-volume-ratio does. Attachments of ligands to the surface of nanoparticles allow them to interact with biomolecules.
Nanoparticles are valuable tools in identification of biomolecules, through the use of bio-tagging or labeling. Attachments of ligands or molecular coatings to the surface of a nanoparticle facilitate nanoparticle-molecule interaction, and make them biocompatible. Conjugation can be achieved through intermolecular attractions between the nanoparticle and biomolecule such as covalent bonding , chemisorption , and noncovalent interactions.
To enhance visualization, nanoparticles can also be made to fluoresce by controlling the size and shape of a nanoparticle probe. Fluorescence increases luminescence by increasing the range of wavelengths the emitted light can reach, allowing for biomarkers with a variety of colors. [ 8 ] This technique is used to track the efficacy of protein transfer both in vivo and in vitro in terms of genetic alternations.
Biological processes can be controlled through transcription regulation , gene regulation , and enzyme inhibition processes that can be regulated using nanoparticles. [ 13 ] Nanoparticles can play a part in gene regulation through ionic bonding between positively charged cationic ligands on the surfaces of nanoparticles and negatively charged anionic nucleic acids present in DNA. In an experiment, a nanoparticle-DNA complex inhibited transcription by T7 RNA polymerase, signifying strong bonding in the complex. [ 14 ] A high affinity of the nanoparticle-DNA complex indicates strong bonding and a favorable use of nanoparticles.
Attaching ionic ligands to nanoparticles allows control over enzyme activity. An example of enzyme inhibition is given by binding of a-chymotrypsin (ChT), an enzyme with a largely cationic active site. When a-chymotrypsin is incubated with anionic (negatively charged) nanoparticles, ChT activity is inhibited as anionic nanoparticles bind to the active site. Enzyme activity can be restored by the addition of cationic surfactants. Alkyl surfactants form a bilayer around ChT, whereas thiol and alcohol surfactants alter the surface of ChT such that interactions with nanoparticles are interrupted. Though formation of a protein-nanoparticle complex can inhibit enzyme activity, studies show that it can also stabilize protein structure, and significantly protect the protein from denaturization. [ 14 ] Experimental and theoretical analyses have also shown that nanoparticles may suppress unfavorable lateral interactions among the adsorbed proteins, thereby leading to significant enhancements in their stability under denaturing conditions. [ 15 ] [ 16 ] Attachments of ligands to segments of nanoparticles selected for functionalization of metallic properties can be used to generate a magnetic nanowire, which generates a magnetic field that allows for the manipulation of cellular assemblies. [ 8 ]
Nanoparticles can also be used in conjunction with DNA to perform genetic alterations. These are frequently monitored through the use of fluorescent materials, allowing scientists to judge if these tagged proteins have successfully been transmitted—for example green fluorescent protein , or GFP. Nanoparticles are significantly less cytotoxic than currently used organic methods, providing a more efficient method of monitoring genetic alternations. They also do not degrade or bleach with time, as organic dyes do. Suspensions of nanoparticles with the same size and shapes (mono-dispersed) with functional groups attached to their surfaces can also electrostatically bind to DNA, protecting them from several types of degradation. Because the fluorescence of these nanoparticles does not degrade, cellular localization can be tracked without the use of additional tagging, with GFPs or other methods. The 'unpacking' of the DNA can be detected in live cells using luminescence resonance energy transfer (LRET) technology. [ 17 ]
Small molecules in vivo have a short retention time, but the use of larger nanoparticles does not. These nanoparticles can be used to avoid immune response, which aids in the treatment of chronic diseases . It has been investigated as a potential cancer therapy and also has the potential to affect the understanding of genetic disorders. [ 18 ] Nanoparticles also have the potential to aid in site-specific drug delivery by improving the amount of unmodified drug that is circulated within the system, which also decreases the necessary dosage frequency. [ 19 ] The targeted nature of nanoparticles also means that non-targeted organs are much less likely to experience side effects of drugs intended for other areas.
Cellular interactions occur at a microscopic level and cannot be easily observed even with the advanced microscopes available today. Due to difficulties observing reactions at the molecular level, indirect methods are used which greatly limits the scope of the understanding that can be gained by studying these processes essential to life. Advances in the material industry has evolved a new field known as nanobiotechnology, that uses nanoparticles to study interactions at the biomolecular level. [ 20 ]
One area of research featuring nanobiotechnology is the extracellular matrices of cells (ECM). The ECM is primarily composed of interwoven fibers of collagen and elastin that have diameters ranging from 10 to 300 nm. [ 20 ] In addition to holding the cell in place, the ECM has a variety of other functions including providing a point of attachment for the ECM of other cells and transmembrane receptors that are essential for life. Until recently it has been nearly impossible to study the physical forces that help cells maintain their functionality, but nanobiotechnology has given us the ability to learn more about these interactions. Using the unique properties of nanoparticles, it is possible to control how the nanoparticles adhere to certain patterns present in the ECM, and as a result can understand how changes in the ECM's shape can affect cell functionality. [ 20 ]
Using nanobiotechnology to study the ECM allows scientists to investigate the binding interactions that occur between the ECM and its supporting environment. Investigators were able to study these interactions by utilizing tools such as optical tweezers , which have the ability to trap nano-scale objects with focused light. The tweezers can affect the binding of a substrate to the ECM by attempting to draw the substrate away from it. The light emitted from the tweezers was used to restrain ECM-coated microbeads , and the changes in the force exerted by the ECM onto the substrate were studied by modulating the effect of the optical tweezers. Experiments showed that the force exerted by the ECM on the substrate positively correlated with the force of the tweezers, which led to the subsequent discovery that the ECM and the transmembrane proteins are able to sense external forces, and can adapt to overcome these forces. [ 20 ]
The blood–brain barrier (BBB) is composed of a system of capillaries that has an especially dense lining of endothelial cells which protects the central nervous system (CNS) against the diffusion of foreign substances into the cerebrospinal fluid . [ 21 ] These harmful objects include microscopic bacteria, large hydrophobic molecules, certain hormones and neurotransmitters , and low- lipid -soluble molecules. The BBB prevents these harmful particles from entering the brain via tight junctions between endothelial cells and metabolic barriers. The thoroughness with which the BBB does its job makes it difficult to treat diseases of the brain such as cancer , Alzheimer's , and autism , because it is very difficult to transport drugs across the BBB. Currently, in order to deliver therapeutic molecules into the brain, doctors must use highly invasive techniques such as drilling directly into the brain, or sabotaging the integrity of the BBB through biochemical means. [ 22 ] Due to their small size and large surface area, nanoparticles offer a promising solution for neurotherapeutics.
Nanotechnology is helpful in delivering drugs and other molecules across the blood–brain barrier (BBB). Nanoparticles allow drugs, or other foreign molecules, to efficiently cross the BBB by camouflaging themselves and tricking the brain into providing them with the ability to cross the BBB in a process called the Trojan Horse Method. [ 22 ] Using nanotechnology is advantageous because only the engineered complex is necessary whereas in ordinary applications the active compound must carry out the reaction. This allows for maximum efficacy of the active drug. Also, the use of nanoparticles results in the attraction of proteins to the surfaces of cells, giving cell membranes a biological identity. They also use endogenous active transport where transferrin , an iron binding protein, is linked to rod-shaped semiconductor nanocrystals , in order to move across the BBB into the brain. [ 23 ] This discovery is a promising development towards designing an efficient nanoparticle-based drug delivery system. | https://en.wikipedia.org/wiki/Nanoparticle–biomolecule_conjugate |
Nanophase ceramics are ceramics that are nanophase materials (that is, materials that have grain sizes under 100 nanometers). [ 1 ] [ 2 ] They have the potential for superplastic deformation . [ 1 ] Because of the small grain size and added grain boundaries properties such as ductility, hardness, and reactivity see drastic changes from ceramics with larger grains.
The structure of nanophase ceramics is not too different than that of ceramics . The main difference is the amount of surface area per mass. Particles of ceramics have small surface areas, but when those particles are shrunk to within a few nanometers, the surface area of the same amount of a mass of a ceramic greatly increases. [ 3 ] So in general, nanophase materials have greater surface areas than that of a similar mass material at a larger scale. [ 3 ] This is important because if the surface area is very large the particles can be in contact with more of their surroundings, which in turn increases the reactivity of the material. [ 3 ] The reactivity of a material changes the material's mechanical properties and chemical properties , among many other things. [ 3 ] This is especially true in nanophase ceramics.
Nanophase ceramics have unique properties than regular ceramics due to their improved reactivity. [ 3 ] Nanophase ceramics exhibit different mechanical properties than their counterpart such as higher hardness , higher fracture toughness , and high ductility . [ 4 ] These properties are far from ceramics which behave as brittle, low ductile materials.
Titanium dioxide ( TiO 2 ), has been shown to have increased hardness and ductility at the nanoscale. In an experiment, grains of titanium dioxide that had an average size of 12 nanometers were compressed at 1.4 GPa and sintered at 200 °C. [ 5 ] The result was a grain hardness of about 2.2 times greater than that of grains of titanium dioxide with an average size of 1.3 micrometers at the same temperature and pressure. [ 5 ] In the same experiment, the ductility of titanium dioxide was measured. The strain rate sensitivity of a 250 nanometer grain of titanium dioxide was about 0.0175, while a grain with size of about 20 nanometers had a strain rate sensitivity of approximately .037; a significant increase. [ 5 ]
Nanophase ceramics can be processed from atomic, molecular, or bulk precursors. [ 6 ] Gas condensation, chemical precipitation , aerosol reactions, biological templating, chemical vapor deposition , and physical vapor deposition are techniques used to synthesis nanophase ceramics from molecular or atomic precursors. [ 6 ] To process nanophase ceramics from bulk precursors, mechanical attrition, crystallization from the amorphous state , and phase separation are used to create nanophase ceramics. [ 6 ] Synthesizing nanophase ceramics from atomic or molecular precursors are desired more because a greater control over microscopic aspects of the nanophase ceramic can occur. [ 6 ]
Gas condensation is one way nanophase ceramics are produced. First, precursor ceramics are evaporated from sources within a gas-condensation chamber. [ 5 ] Then the ceramics are condensed in a gas (dependent on the material being synthesized) and transported via convection to a liquid-nitrogen filled cold finger. [ 5 ] Next, the ceramic powders are scraped off the cold finger and collect in a funnel below the cold finger. [ 5 ] The ceramic powders then become consolidated in a low-pressure compaction device and then in a high-pressure compaction device. [ 5 ] This all occurs in a vacuum, so no impurities can enter the chamber and affect the results of the nanophase ceramics. [ 5 ]
Nanophase ceramics have unique properties that make them optimal for a variety of applications.
Materials used in drug delivery in the past ten years have primarily been polymers . However, nanotechnology has opened the door for the use of ceramics with benefits not previously seen in polymers . The large surface area to volume ratio of nanophase materials makes it possible for large amounts of drugs to be released over long periods of time. Nanoparticles to be filled with drugs can be easily manipulated in size and composition to allow for increased endocytosis of drugs into targeted cells and increased dispersion through fenestrations in capillaries. While these benefits all relate to nanoparticles in general (including polymers ), ceramics have other, unique abilities. Unlike polymers , slow degradation of ceramics allows for longer release of the drug. Polymers also tend to swell in liquid which can cause an unwanted burst of drugs. The lack of swelling shown by most ceramics allows for increased control. Ceramics can also be created to match the chemistry of biological cells in the body increasing bioactivity and biocompatibility . Nanophase ceramic drug carriers are also able to target specific cells. This can be done by manufacturing a material to bond to the specific cell or by applying an external magnetic field, attracting the carrier to a specific location.
Nanophase ceramics have great potential for use in orthopedic medicine . Bone and collagen have structures on the nanoscale. Nanomaterials can be manufactured to simulate these structures which is necessary for grafts and implants to successfully adapt to and handle varying stresses. The surface properties of nanophase ceramics is also very important for bone substitution and regeneration. Nanophase ceramics have much rougher surfaces than larger materials and also have increased surface area. This promotes reactivity and absorption of proteins that assist tissue development. Nano-hydroxyapatite is one nanophase ceramic that is used as a bone substitute. Nano grain size increases the bonding, growth, and differentiation of osteoblasts onto the ceramic. The surfaces of nanophase ceramics can also be modified to be porous allowing osteoblasts to create bone within the structure. The degradation of the ceramic is also important because the rate can be changed by changing the crystallinity. This way as bone grows the substitute can diminish at a similar rate. | https://en.wikipedia.org/wiki/Nanophase_ceramic |
Nanophase materials are materials that have grain sizes under 100 nanometres . They have different mechanical and optical properties compared to the large grained materials of the same chemical composition .
Transparency and different transparent colours can be achieved with nanophase materials by varying the grain size.
This material -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Nanophase_material |
A nanophotonic resonator or nanocavity is an optical cavity which is on the order of tens to hundreds of nanometers in size. Optical cavities are a major component of all lasers , they are responsible for providing amplification of a light source via positive feedback , a process known as amplified spontaneous emission or ASE. Nanophotonic resonators offer inherently higher light energy confinement than ordinary cavities, which means stronger light-material interactions, and therefore lower lasing threshold provided the quality factor of the resonator is high. [ 1 ] Nanophotonic resonators can be made with photonic crystals, silicon, diamond, or metals such as gold.
For a laser in a nanocavity, spontaneous emission (SE) from the gain medium is enhanced by the Purcell effect , [ 2 ] [ 3 ] equal to the quality factor or Q {\displaystyle Q} -factor of the cavity divided by the effective mode field volume, F = Q / V mode {\displaystyle F=Q/V_{\text{mode}}} . Therefore, reducing the volume of an optical cavity can dramatically increase this factor, which can have the effect of decreasing the input power threshold for lasing. [ 4 ] [ 5 ] This also means that the response time of spontaneous emission from a gain medium in a nanocavity also decreases, the result being that the laser may reach lasing steady state picoseconds after it starts being pumped. A laser formed in a nanocavity therefore may be modulated via its pump source at very high speeds. Spontaneous emission rate increases of over 70 times modern semiconductor laser devices have been demonstrated, with theoretical laser modulation speeds exceeding 100 GHz, an order of magnitude higher than modern semiconductor lasers, and higher than most digital oscilloscopes. [ 2 ] Nanophotonic resonators have also been applied to create nanoscale filters [ 6 ] [ 7 ] and photonic chips [ 6 ]
For cavities much larger than the wavelength of the light they contain, cavities with very high Q factors have already been realized (~125,000,000). [ 8 ] However, high Q {\displaystyle Q} cavities on the order of the same size as the optical wavelength have been difficult to produce due to the inverse relationship between radiation losses and cavity size. [ 1 ] When dealing with a cavity much larger than the optical wavelength, it is simple to design interfaces such that light ray paths fulfill total internal reflection conditions or Bragg reflection conditions. For light confined within much smaller cavities near the size of the optical wavelength, deviations from ray optics approximations become severe and it becomes infeasible, if not impossible to design a cavity which fulfills optimum reflection conditions for all three spatial components of the propagating light wave vectors. [ 1 ] [ 9 ]
In a laser, the gain medium emits light randomly in all directions. With a classical cavity, the number of photons which are coupled into a single cavity mode relative to the total number of spontaneously emitted photons is relatively low because of the geometric inefficiency of the cavity, described by the Purcell factor Q / V mode {\displaystyle Q/V_{\text{mode}}} . [ 10 ] The rate at which lasing in such a cavity can be modulated depends on the relaxation frequency of the resonator described by equation 1.
Where τ r 0 {\displaystyle \tau _{r0}} is the intrinsic carrier radiative lifetime of the bulk material, a {\displaystyle a} is the differential gain, v g {\displaystyle v_{g}} is the group velocity, τ p = Q / ω L {\displaystyle \tau _{p}=Q/\omega _{L}} is the photon lifetime, ω L {\displaystyle \omega _{L}} is the lasing frequency, β {\displaystyle \beta } is the spontaneous emission coupling factor which is enhanced by the Purcell effect, and 1 / τ total = F / τ r 0 + 1 / τ n r {\displaystyle 1/\tau _{\text{total}}=F/\tau _{r_{0}}+1/\tau _{nr}} where τ n r {\displaystyle \tau _{nr}} is the non-radiative lifetime. In the case of minimal Purcell effect in a classical cavity with small F = Q / V mode {\displaystyle F=Q/V_{\text{mode}}} , only the first term of equation 1 is considered, and the only way to increase modulation frequency is to increase photon density P 0 {\displaystyle P_{0}} by increasing the pumping power. However, thermal effects practically limit the modulation frequency to around 20 GHz, making this approach is inefficient. [ 2 ] [ 11 ]
In nanoscale photonic resonators with high Q {\displaystyle Q} , the effective mode volume V mode {\displaystyle V_{\text{mode}}} is inherently very small resulting in high F {\displaystyle F} and β {\displaystyle \beta } , and terms 2 and 3 in equation 1 are no longer negligible. Consequently, nanocavities are fundamentally better suited to efficiently produce spontaneous emission and amplified spontaneous emission light modulated at frequencies much higher than 20 GHz without negative thermal effects. [ 2 ] [ 12 ]
Nanocavities made from photonic crystals are typically implemented in a photonic crystal slab structure. Such a slab will generally have a periodic lattice structure of physical holes in the material. For light propagating within the slab, a reflective interface is formed at these holes due to the periodic differences in refractive index in the structure.
A common photonic crystal nanocavity design shown is essentially a photonic crystal with an intentional defect (holes missing). This structure having periodic changes in refractive index on the order of the length of the optical wavelength satisfies Bragg reflection conditions in the y {\displaystyle y} and z {\displaystyle z} directions for a particular wavelength range, and the slab boundaries in the x {\displaystyle x} direction create another reflective boundary due to oblique reflection at dielectric boundaries. This results in theoretically perfect wave confinement in the y {\displaystyle y} and z {\displaystyle z} directions along the axis of a lattice row, and good confinement along the x {\displaystyle x} direction. [ 6 ] [ 7 ] Since this confinement effect along the y {\displaystyle y} and z {\displaystyle z} directions (directions of the crystal lattice) is only for a range of frequencies, it has been referred to as a photonic bandgap , since there is a discrete set of photon energies which cannot propagate in the lattice directions in the material. [ 6 ] However, because of the diffraction of waves propagating inside this structure, radiation energy does escape the cavity within the photonic crystal slab plane. The lattice spacing can be tuned to produce optimal boundary conditions of the standing wave inside the cavity to produce minimal loss and highest Q {\displaystyle Q} . [ 1 ] Beside those conventional resonators, they are some examples of rewritable and/or movable cavities, which are accomplished by a micro infiltration system [ 13 ] and by a manipulation of single nanoparticles inside photonic crystals. [ 14 ] [ 15 ]
Metals can also be an effective way to confine light in structures equal to or smaller than the optical wavelength. This effect is emergent from the confined surface plasmon resonance induced by the resonating light, which, when confined to the surface of a nanostructure such as a gold channel or nanorod, induces electromagnetic resonance . [ 16 ] Surface plasmon effects are strong in the visible range because the permittivity of a metal is very large and negative at visible frequencies. [ 17 ] [ 18 ] At frequencies higher than the visible range, the permittivity of a metal is closer to zero, and the metal stops being useful for focussing electric and magnetic fields. [ 18 ] This effect was originally observed in radio and microwave engineering, where metal antennas and waveguides may be hundreds of times smaller than the free-space wavelength. In the same way, visible light can be constricted to the nano level with metal structures which form channels, tips, gaps, etc. Gold is also a convenient choice for nanofabrication because of its unreactivity and ease of use with chemical vapour deposition. [ 19 ]
A planar nanocavity consists of an absorptive semiconductive film no more than a few nanometers thick over a metal film also a few nanometers thick. [ 7 ] Incident light is absorbed and reflected off of both layers, the absorbed light then resonates between the two interfaces, transmitting some light back at after each cycle. Germanium is commonly used for the absorptive layer, while gold, aluminum, and aluminum oxide are used as alternatives as well. [ 7 ] Planar nanocavities are commonly used for thin film interference, which occurs when incident light waves reflected by the upper and lower boundaries of a thin film interfere with one another forming a new wave. An example of this is the colorful patterns produced by thin layers of oil on a surface. The difference in colors is due to minute differences in the distance reflected light travels whether it reflects from the top or bottom boundary of the oil layer. This difference is called the optical path difference, the difference in distance between the top and bottom reflection paths, which can be calculated with equation 2:
Where n {\displaystyle n} is the refractive index of the absorptive material, d {\displaystyle d} is the thickness of the absorptive film, and θ {\displaystyle \theta } is the angle of reflection. As expressed in the equation 3, the optical path length difference (OPD) can be related to wavelengths which constructively interfere in the thin film. As a result, light which enters the film at different angles interferes with itself varying amounts, produces an intensity gradient for narrowband light, and a spectrum gradient for white light.
Nanophotonic circuit designs are similar in appearance to microwave and radio circuits, minimized by a factor of 100,000 or more. Researchers have made nano-optical antennas which emulate the design and functionality of radio antennas. [ 16 ] There are a number of important differences between nanophotonics and scaled down microwave circuits. At optical frequency, metals behave much less like ideal conductors, and also exhibit plasmon-related effects like kinetic inductance and surface plasmon resonance . [ 20 ] A nantenna is a nanoscopic rectifying antenna, a technology being developed to convert light into electric power. The concept is based on the rectenna which is used in wireless power transmission. A rectenna functions like a specialized radio antenna which is used to convert radio waves into direct current electricity. Light is composed of electromagnetic waves like radio waves, but of a much smaller wavelength. A nantenna, an application of a nanophotonic resonator, is a nanoscale rectenna on the order of the optical wavelength size, which acts as an "antenna" for light, converting light into electricity. Arrays of nantennas could be an efficient means of converting sunlight into electric power, producing solar energy more efficiently than semiconductor bandgap solar cells . [ 20 ]
It has been suggested that nanophotonic resonators be used on multi core chips to both decrease size and boost efficiency. [ 21 ] This is done by creating arrays of nanophotonic optical ring resonators that can transmit specific wavelengths of light between each other. Another use of nanophotonic resonators in computers is in optical RAM (O-RAM). O-Ram uses photonic crystal slab structure with properties such as strong confinement of photons and carriers to replace the functions of electrical circuits. The use of optical signals versus electrical signals is a 66.7% decrease in power consumption. [ 22 ] Researchers have developed planar nanocavities that can reach 90% peak absorption using interference effects. This result is useful in that there are numerous applications that can benefit from these findings, specifically in energy conversion [ 7 ] | https://en.wikipedia.org/wiki/Nanophotonic_resonator |
Nanophotonics is a peer-reviewed open access scientific journal published by De Gruyter and Science Wise Publishing . It covers recent international research results, specific developments, and novel applications in the field of nanophotonics , such as carbon nanotubes, nano metal particles, nanocrystals, semiconductor nanodots, photonic crystals, tissue, and DNA. Its editor-in-chief is Stefan Maier ( LMU München ) and founding editor is Federico Capasso ( Harvard University ). [ 1 ]
In 2010 Nanophotonics was initiated by founding editor Federico Capasso and publishing editor Dennis Couwenberg. The first issue was published in 2012.
The journal is abstracted and indexed in:
According to the Journal Citation Reports , the journal has a 2020 impact factor of 8.449. [ 2 ]
This article about a nanotechnology journal is a stub . You can help Wikipedia by expanding it .
See tips for writing articles about academic journals . Further suggestions might be found on the article's talk page . | https://en.wikipedia.org/wiki/Nanophotonics_(journal) |
Nanophysiology is a field [ 1 ] [ 2 ] that concerns the function of nanodomains, such as the regulation of molecular or ionic flows in cell subcompartments, such as glial protrusions, dendritic spines , dendrites , mitochondria and many more.
Molecular organization in nanocompartments provides the construction required to achieve elementary functions that can sustain higher physiological functions of a cell. This includes calcium homeostatis, protein turn over, plastic changes underlying cell communications. The goal of this field is to determine the function of these nanocompartments based on molecular organization, ionic flow or voltage distribution.
How the voltage is regulated in nanodomains remains an open field. While the classical Goldman-Hodgkin-Huxley-Katz models in biophysics provides a foundation for electrophysiology and has been responsible for many advances in neuroscience , this theory remains insufficient to describe the voltage dynamics in small nano-compartments, such as synaptic terminals or cytoplasm around voltage-gated channels , because they are based on spatial and ionic homogeneity. Instead, electrodiffusion theory [ 1 ] [ 3 ] [ 4 ] should be used to describe electrical current flow in these nanostructures and reveal the structure-function . | https://en.wikipedia.org/wiki/Nanophysiology |
Nanopipettes are pipettes in nanometer scale, [ 1 ] generally made from quartz capillaries with the help of laser-based pipette puller system . [ 2 ] Glass and carbon nanopipettes are most encountered ones in literature. Carbon nanopipettes are nanopipette shaped, hollow carbon layer. The thickness or diameter of nanopipettes can be altered. Glass nanopipettes have a wide range of usage areas like electrophysiological settings, microinjection needles etc. [ 3 ] After glass nanopipettes are fabricated and coated with carbon layer in different ways, wet-etching method is applied to get carbon nanopipettes. [ 4 ] [ 5 ] Wet-etching method is done to get rid of glass nanopipettes. [ 4 ]
Nanopipettes allowed to explore protusions, dendrites and more general the properties of nanostructures, known as nanophysiology . [ 6 ] [ 7 ] | https://en.wikipedia.org/wiki/Nanopipette |
A nanopore is a pore of nanometer size. It may, for example, be created by a pore-forming protein or as a hole in synthetic materials such as silicon or graphene.
When a nanopore is present in an electrically insulating membrane , it can be used as a single- molecule detector. It can be a biological protein channel in a high electrical resistance lipid bilayer , a pore in a solid-state membrane or a hybrid of these – a protein channel set in a synthetic membrane. The detection principle is based on monitoring the ionic current passing through the nanopore as a voltage is applied across the membrane. When the nanopore is of molecular dimensions, passage of molecules (e.g., DNA ) cause interruptions of the "open" current level, leading to a "translocation event" signal. The passage of RNA or single-stranded DNA molecules through the membrane-embedded alpha-hemolysin channel (1.5 nm diameter), for example, causes a ~90% blockage of the current (measured at 1 M KCl solution). [ 1 ]
It may be considered a Coulter counter for much smaller particles. [ 2 ]
The observation that a passing strand of DNA containing different bases corresponds with shifts in current values has led to the development of nanopore sequencing. [ 14 ] Nanopore sequencing can occur with bacterial nanopores as mentioned in the above section as well as with the Nanopore sequencing device(s) created by Oxford Nanopore Technologies .
From a fundamental standpoint, nucleotides from DNA or RNA are identified based on shifts in current as the strand is entering the pore. The approach that Oxford Nanopore Technologies uses for nanopore DNA sequencing labeled DNA sample is loaded to the flow cell within the nanopore. The DNA fragment is guided to the nanopore and commences the unfolding of the helix. As the unwound helix moves through the nanopore, it is correlated with a change in the current value which is measured in thousand times per second. Nanopore analysis software can take this alternating current value for each base detected, and obtain the resulting DNA sequence. [ 15 ] Similarly with the usage of biological nanopores, as a constant voltage is applied to the system, the alternating current can be observed. As DNA, RNA or peptides enter the pore, shifts in the current can be observed through this system that are characteristic of the monomer being identified. [ 16 ] [ 17 ]
Ion current rectification (ICR) is an important phenomenon for nanopore. Ion current rectification can also be used as a drug sensor [ 18 ] [ 19 ] and be employed to investigate charge status in the polymer membrane. [ 20 ]
Apart from rapid DNA sequencing , other applications include separation of single stranded and double stranded DNA in solution, and the determination of length of polymers . At this stage, nanopores are making contributions to the understanding of polymer biophysics, single-molecule analysis of DNA-protein interactions, as well as peptide sequencing. When it comes to peptide sequencing bacterial nanopores like hemolysin , can be applied to both RNA, DNA and most recently protein sequencing. Such as when applied in a study in which peptides with the same Glycine-Proline-Proline repeat were synthesized, and then put through nanopore analysis, an accurate sequence was able to be attained. [ 21 ] This can also be used to identify differences in stereochemistry of peptides based on intermolecular ionic interactions. Some configuration changes of protein could also be observed from the translocation curve. [ 22 ] Understanding this also contributes more data to understanding the sequence of the peptide fully in its environment. [ 23 ] Usage of another bacterial derived nanopore, an aerolysin nanopore, has shown ability having shown similar ability in distinguishing residues within a peptide has also shown the ability to identify toxins present even in proclaimed "very pure" protein samples, while demonstrating stability over varying pH values. [ 16 ] A limitation to the usage of bacterial nanopores would be that peptides as short as six residues were accurately detected, but with larger more negatively charged peptides resulted in more background signal that is not representative of the molecule. [ 24 ]
Since the discovery of track-etched technology in the late 1960s, filter membranes with needed diameter have found application potential in various fields including food safety, environmental pollution, biology, medicine, fuel cell, and chemistry. These track-etched membranes are typically made in polymer membrane through track-etching procedure, during which the polymer membrane is first irradiated by heavy ion beam to form tracks and then cylindrical pores or asymmetric pores are created along the track after wet etching.
As important as fabrication of the filter membranes with proper diameters, characterizations and measurements of these materials are of the same paramount. Until now, a few of methods have been developed, which can be classified into the following categories according to the physical mechanisms they exploited: imaging methods such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM); fluid transport such as bubble point and gas transport; fluid adsorptions such as nitrogen adsorption/desorption (BEH), mercury porosimetry, liquid-vapor equilibrium (BJH), gas-liquid equilibrium (permoporometry) and liquid-solid equilibrium (thermoporometry); electronic conductance; ultrasonic spectroscopy; and molecular transport.
More recently, the use of light transmission technique [ 25 ] as a method for nanopore size measurement has been proposed. | https://en.wikipedia.org/wiki/Nanopore |
Nanopore sequencing is a third generation [ 1 ] approach used in the sequencing of biopolymers — specifically, polynucleotides in the form of DNA or RNA .
Nanopore sequencing allows a single molecule of DNA or RNA be sequenced without PCR amplification or chemical labeling. Nanopore sequencing has the potential to offer relatively low-cost genotyping , high mobility for testing, and rapid processing of samples, including the ability to display real-time results. It has been proposed for rapid identification of viral pathogens, [ 2 ] [ 3 ] [ 4 ] monitoring ebola , [ 5 ] environmental monitoring, [ 6 ] food safety monitoring, human genome sequencing, [ 7 ] plant genome sequencing, [ 8 ] monitoring of antibiotic resistance , [ 9 ] haplotyping [ 10 ] and other applications.
Nanopore sequencing took 25 years to materialize. David Deamer was one of the first to push the idea. In 1989 he sketched out a plan to push single-strands of DNA through a protein nanopore embedded into a thin membrane as part his work to synthesize RNA . Realizing that the approach might allow DNA sequencing , Deamer and his team spent a decade refining the concept. In 1999 they published the first paper using the term 'nanopore sequencing' and two years later produced an image capturing a DNA hairpin passing through a nanopore in real time.
Another foundation for nanopore sequencing was the work of Hagan Bayley 's team, who from the 1990s independently developed stochastic sensing, a technique that measures the change in an ionic current passing through a nanopore to determine the concentration and identity of a substance. By 2005 Bayley had made progress with the DNA sequencing method. He co-founded Oxford Nanopore to push the technology. In 2014 the company released its first portable nanopore sequencing device. This made it possible for DNA sequencing to be carried out almost anywhere, even with limited resources. A quarter of the world's SARS-CoV-2 viral genomes were sequenced with nanopore devices. The technology offers an important tool for combating antimicrobial resistance. [ 11 ] In 2020, China-based Qitan Technology launched its nanopore single-molecule gene sequencer, [ 12 ] while in 2024 MGI Tech launched its own products. [ 13 ]
The biological or solid-state membrane, where the nanopore is found, is surrounded by an electrolyte solution. [ 14 ] The membrane splits the solution into two chambers. [ 15 ] Applying a bias voltage across the membrane induces an electric field that drives charged particles, in this case the ions, into motion. This effect is known as electrophoresis . For a high enough concentrations, the electrolyte solution is well distributed and the voltage drop concentrates near and inside the nanopore. This means charged particles in the solution feel a force only from the electric field when they are near the pore region. [ 16 ] This region is typically referred to as the capture region. Inside the capture region, ions have a directed motion that can be recorded as a steady ionic current by placing electrodes near the membrane. A nano-sized polymer such as DNA or protein placed in one of the chambers has a net charge that feels a force from the electric field in the capture region. [ 16 ] The molecule approaches this capture region aided by Brownian motion . Any attraction it might have to the surface of the membrane. [ 16 ] Once inside the nanopore, the molecule translocates via a combination of electro-phoretic, electro-osmotic and sometimes thermo-phoretic forces. [ 14 ] Inside the pore the molecule occupies a volume that partially restricts the ion flow, observed as an ionic current drop. Based on various factors such as geometry, size and chemical composition, the change in magnitude of the ionic current and the duration of the translocation vary. Different molecules can then be sensed and potentially identified based on this current modulation. [ 17 ]
The magnitude of the electric current density across a nanopore surface depends on the nanopore's dimensions and the composition of DNA or RNA that is occupying the nanopore. Sequencing was made possible because passing through the channel of the nanopore, the samples cause characteristic changes in the density of the electric current. The total charge flowing through a nanopore channel is equal to the surface integral of electric current density flux across the nanopore unit normal surfaces.
Biological nanopore sequencing relies on the use of transmembrane proteins, called protein nanopores, in particular, formed by protein toxins, that are embedded in lipid membranes so as to create size dependent porous surfaces - with nanometer scale "holes" distributed across the membranes. [ 18 ] Sufficiently low translocation velocity can be attained through the incorporation of various proteins that facilitate the movement of DNA or RNA through the pores of the lipid membranes. [ 19 ]
Alpha hemolysin (αHL), a nanopore from bacteria that causes lysis of red blood cells, has been studied for over 15 years. [ 20 ] To this point, studies have shown that all four bases can be identified using ionic current measured across the αHL pore. [ 21 ] [ 22 ] The structure of αHL is advantageous to identify specific bases moving through the pore. The αHL pore is ~10 nm long, with two distinct 5 nm sections. The upper section consists of a larger, vestibule-like structure and the lower section consists of three possible recognition sites (R1, R2, R3), and is able to discriminate between each base. [ 21 ] [ 22 ]
Sequencing using αHL has been developed through basic study and structural mutations, moving towards the sequencing of very long reads. Protein mutation of αHL has improved the detection abilities of the pore. [ 23 ] The next proposed step is to bind an exonuclease onto the αHL pore. The enzyme would periodically cleave single bases, enabling the pore to identify successive bases. Coupling an exonuclease to the biological pore would slow the translocation of the DNA through the pore, and increase the accuracy of data acquisition.
Notably, theorists have shown that sequencing via exonuclease enzymes as described here is not feasible. [ 24 ] This is mainly due to diffusion related effects imposing a limit on the capture probability of each nucleotide as it is cleaved. This results in a significant probability that a nucleotide is either not captured before it diffuses into the bulk or captured out of order, and therefore is not properly sequenced by the nanopore, leading to insertion and deletion errors. Therefore, major changes are needed to this method before it can be considered a viable strategy.
A recent study has pointed to the ability of αHL to detect nucleotides at two separate sites in the lower half of the pore. [ 25 ] The R1 and R2 sites enable each base to be monitored twice as it moves through the pore, creating 16 different measurable ionic current values instead of 4. This method improves upon the single read through the nanopore by doubling the sites that the sequence is read per nanopore.
Mycobacterium smegmatis porin A (MspA) is the second biological nanopore currently being investigated for DNA sequencing. The MspA pore has been identified as a potential improvement over αHL due to a more favorable structure. [ 26 ] The pore is described as a goblet with a thick rim and a diameter of 1.2 nm at the bottom of the pore. [ 27 ] A natural MspA, while favorable for DNA sequencing because of shape and diameter, has a negative core that prohibited single stranded DNA(ssDNA) translocation. The natural nanopore was modified to improve translocation by replacing three negatively charged aspartic acids with neutral asparagines. [ 28 ]
The electric current detection of nucleotides across the membrane has been shown to be tenfold more specific than αHL for identifying bases. [ 26 ] Utilizing this improved specificity, a group at the University of Washington has proposed using double stranded DNA (dsDNA) between each single stranded molecule to hold the base in the reading section of the pore. [ 26 ] [ 28 ] The dsDNA would halt the base in the correct section of the pore and enable identification of the nucleotide. A 2011 grant was awarded to a collaboration from UC Santa Cruz, the University of Washington, and Northeastern University to improve the base recognition of MspA using phi29 polymerase in conjunction with the pore. [ 29 ] MspA with electric current detection can also be used to sequence peptides. [ 30 ] [ 31 ]
Solid state nanopore sequencing approaches, unlike biological nanopore sequencing, do not incorporate proteins into their systems. Instead, solid state nanopore technology uses various metal or metal alloy substrates with nanometer sized pores that allow DNA or RNA to pass through. These substrates most often serve integral roles in the sequence recognition of nucleic acids as they translocate through the channels along the substrates. [ 32 ]
Measurement of electron tunneling through bases as ssDNA translocates through the nanopore is an improved solid state nanopore sequencing method. Most research has focused on proving bases could be determined using electron tunneling. These studies were conducted using a scanning probe microscope as the sensing electrode, and have proved that bases can be identified by specific tunneling currents. [ 33 ] After the proof of principle research, a functional system must be created to couple the solid state pore and sensing devices.
Researchers at the Harvard Nanopore group have engineered solid state pores with single walled carbon nanotubes across the diameter of the pore. [ 34 ] Arrays of pores are created and chemical vapor deposition is used to create nanotubes that grow across the array. Once a nanotube has grown across a pore, the diameter of the pore is adjusted to the desired size. Successful creation of a nanotube coupled with a pore is an important step towards identifying bases as the ssDNA translocates through the solid state pore.
Another method is the use of nanoelectrodes on either side of a pore. [ 35 ] [ 36 ] The electrodes are specifically created to enable a solid state nanopore's formation between the two electrodes. This technology could be used to not only sense the bases but to help control base translocation speed and orientation.
An effective technique to determine a DNA sequence has been developed using solid state nanopores and fluorescence . [ 37 ] This fluorescence sequencing method converts each base into a characteristic representation of multiple nucleotides which bind to a fluorescent probe strand-forming dsDNA. With the two color system proposed, each base is identified by two separate fluorescences, and will therefore be converted into two specific sequences. Probes consist of a fluorophore and quencher at the start and end of each sequence, respectively. Each fluorophore will be extinguished by the quencher at the end of the preceding sequence. When the dsDNA is translocating through a solid state nanopore, the probe strand will be stripped off, and the upstream fluorophore will fluoresce. [ 37 ] [ 38 ]
This sequencing method has a capacity of 50-250 bases per second per pore, and a four color fluorophore system (each base could be converted to one sequence instead of two), will sequence over 500 bases per second. [ 37 ] Advantages of this method are based on the clear sequencing readout—using a camera instead of noisy current methods. However, the method does require sample preparation to convert each base into an expanded binary code before sequencing. Instead of one base being identified as it translocates through the pore, ~12 bases are required to find the sequence of one base. [ 37 ]
Nanopore devices can be used for eDNA analysis in environmental monitoring [ 39 ] [ 40 ] [ 41 ] [ 42 ] and crop epidemiology . [ 40 ] These can be miniaturised more than earlier technologies and so have been made into portable devices, especially the MinION. [ 39 ] [ 40 ] [ 41 ] [ 42 ] The MinION is especially known for the studies of crop viruses by Boykin et al 2018 & Shaffer 2019 [ 40 ] and studies of species prevalence by Menegon et al 2017 [ 40 ] [ 41 ] and Pomerantz et al 2018. [ 39 ] [ 40 ] [ 41 ] [ 42 ] Owing to its high portability, low cost and easiness to use for rapid sequencing applications, it also raised ethical, legal and social concerns [ 43 ] along with other next generation sequencing technologies. [ 44 ] SARS-CoV-2 variants in Prague wastewater were detected by nanopore-based sequencing. Sequencing of sub-sewershed samples benefits epidemiological early warning systems. [ 45 ]
Biological nanopore sequencing systems have several fundamental characteristics that make them advantageous as compared with solid state systems- with each advantageous characteristic of this design approach stemming from the incorporation of proteins into their technology. Uniform pore structure, the precise control of sample translocation through pore channels, and even the detection of individual nucleotides in samples can be facilitated by unique proteins from a variety of organism types.
The use of proteins in biological nanopore sequencing systems, despite the various benefits, also brings with it some negative characteristics. The sensitivity of the proteins in these systems to local environmental stress has a large impact on the longevity of the units, overall. One example is that a motor protein may only unzip samples with sufficient speed at a certain pH range while not operating fast enough outside of the range- this constraint impacts the functionality of the whole sequencing unit. Another example is that a transmembrane porin may only operate reliably for a certain number of runs before it breaks down. Both of these examples would have to be controlled for in the design of any viable biological nanopore system- something that may be difficult to achieve while keeping the costs of such a technology as low and as competitive, to other systems, as possible. [ 19 ]
One challenge for the 'strand sequencing' method was in refining the method to improve its resolution to be able to detect single bases. In the early papers methods, a nucleotide needed to be repeated in a sequence about 100 times successively in order to produce a measurable characteristic change. This low resolution is because the DNA strand moves rapidly at the rate of 1 to 5μs per base through the nanopore. This makes recording difficult and prone to background noise, failing in obtaining single-nucleotide resolution. As of 2006, the problem has been tackled by either improving the recording technology or by controlling the speed of DNA strand by various protein engineering strategies and Oxford Nanopore employs a 'kmer approach', analyzing more than one base at any one time so that stretches of DNA are subject to repeat interrogation as the strand moves through the nanopore one base at a time. [ 46 ] Various techniques including algorithmic have been used to improve the performance of the MinION technology since it was first made available to users. [ 47 ] More recently effects of single bases due to secondary structure or released mononucleotides have been shown. [ 48 ] [ 49 ]
In 2010 Hagan Bayley proposed that creating two recognition sites within an alpha-hemolysin pore may confer advantages in base recognition. [ 25 ]
As of 2009, one challenge for the 'exonuclease approach', [ 50 ] where a processive enzyme feeds individual bases, in the correct order, into the nanopore, has been to integrate the exonuclease and the nanopore detection systems. In particular, [ 51 ] the problem is that when an exonuclease hydrolyzes the phosphodiester bonds between nucleotides in DNA, the subsequently released nucleotide is not necessarily guaranteed to directly move into, say, a nearby alpha-hemolysin nanopore . In 2009, one idea has been to attach the exonuclease to the nanopore, perhaps through biotinylation to the beta barrel hemolysin. [ 51 ]
The central pore of the protein may be lined with charged residues arranged so that the positive and negative charges appear on opposite sides of the pore. However, this mechanism is primarily discriminatory and does not constitute a mechanism to guide nucleotides down some particular path. [ citation needed ] | https://en.wikipedia.org/wiki/Nanopore_sequencing |
Nanoporous materials consist of a regular organic or inorganic bulk phase in which a porous structure is present. Nanoporous materials exhibit pore diameters that are most appropriately quantified using units of nanometers . The diameter of pores in nanoporous materials is thus typically 100 nanometers or smaller. Nanoporous materials include subsets of mesoporous (with typical pores having sizes between 2 and 50 nanometers ) and microporous materials (typical pores with diameters <2nm). [ 1 ] Pores may be open or closed, and pore connectivity and void fraction vary considerably, as with other porous materials. Open pores are pores that connect to the surface of the material whereas closed pores are pockets of void space within a bulk material. Open pores are useful for molecular separation techniques, adsorption, and catalysis studies. Closed pores are mainly used in thermal insulators and for structural applications. [ 2 ]
Most nanoporous materials can be classified as bulk materials or membranes. Activated carbon and zeolites are two examples of bulk nanoporous materials, while cell membranes can be thought of as nanoporous membranes. [ 3 ] A porous medium or a porous material is a material containing pores (voids). The skeletal portion of the material is often called the "matrix" or "frame". The pores are typically filled with a fluid (liquid or gas).
The term nanomaterials covers diverse forms of materials with various applications. According to IUPAC porous materials are subdivided into 3 categories: [ 4 ]
These categories conflict with the classical definition of nanoporous materials, as they have pore diameters between 1 and 100 nm. [ 2 ] This range covers all the classifications listed above. However, for the sake of simplicity, scientists choose to use the term nanomaterials and list its associated diameter instead. [ 2 ]
Microporous and mesoporous materials are distinguished as separate material classes owing to the distinct applications afforded by the pores sizes in these materials. Confusingly, the term microporous is used to describe materials with smaller pores sizes than materials commonly referred to simply as nanoporous. More correctly, microporous materials are better understood as a subset of nanoporous materials, namely materials that exhibit pore diameters smaller than 2 nm. [ 1 ] Having pore diameters with length scales of molecules, such materials enable applications that require molecular selectivity such as filtration and separation membranes . Mesoporous materials, referring generally to materials with average pore diameters in the range 2-50 nm are interesting as catalyst support materials and adsorbents owing to their high surface area to volume ratios.
Sometimes classifying by size becomes difficult as there could be porous materials that have various diameters. For example, microporous materials may have a few pores with 2 to 50 nm diameter due to random grain packing. [ 4 ] These specifics must be taken into consideration when categorizing by pore size.
In addition to classification by size, nanoporous materials can be further classified into organic and inorganic network materials. [ 4 ] A network material is the structure 'hosts' the pores and is where the medium (gas or liquid) interacts with the substrate. [ 4 ] While there are plenty of inorganic nanoporous membranes, there are few organic ones due to issues with stability. [ 7 ]
Organic nanoporous materials are polymers made from elements such as boron, carbon, nitrogen, and oxygen. [ 8 ] These materials are usually microporous although mesoporous/microporous structures do exist. [ 8 ] These include covalent organic frameworks (COFs), covalent triazine frameworks, polymers of intrinsic microporosity (PIMs), hyper cross-linked polymers (HCPs), and conjugated microporous polymers (CMPs). [ 8 ] Each of these has different structures and manufacturing steps. In general, to create organic nanoporous materials, a monomer with greater than 2 branches (i.e. covalent bonds ) is dissolved in a solvent . After additional monomers are added and polymerization occurs, the solvent is removed and the remaining structure is considered a nanoporous material. [ 8 ]
Organic nanoporous materials can be further classified into crystalline and amorphous networks. [ 8 ] Crystalline networks are materials that have a well-defined pore sizes. The pore sizes are so well defined that simply by changing the monomer, one can obtain different pore sizes. [ 8 ] COFs are an example of such crystalline structure. In contrast, amorphous nanoporous materials have a distribution of pore sizes and are usually disordered. An example is PIMs. Both categories have various uses in gas sorption and catalysis reactions. [ 8 ]
Inorganic nanoporous materials are porous materials that include the use of oxide-type, carbon, binary, and pure metal materials. Examples include zeolites , nanoporous alumina , and titania nanotubes. [ 4 ] Zeolites are crystalline hydrated tectoaluminosilicates. This material is a combination of alkali/alkali earth metals, alumina, and silica hydrates. These are used for ion-exchange beds [ 9 ] and for water purification. [ 10 ] Nanoporous alumina is a biocompatible material widely used in various dental and orthopedic implants. [ 11 ] Titania nanotubes are also used in orthopedics but are special as they can form a titanium oxide layer upon exposure to oxygen. [ 12 ] Because the surface of the material is oxide-protected, this material has excellent biocompatibility with incredible mechanical strength. [ 12 ]
Gas storage is crucial for energy, medical, and environmental applications. Nanoporous materials enable a unique method of gas storage through adsorption . [ 13 ] When the substrate and gas interact with each other, the gas molecules can physio-adsorb or covalently bond with the nanoporous material, which is known as physical storage and chemical storage, respectively. [ 14 ] While one may store gases in the bulk phase, such as in a bottle, nanoporous materials enable higher storage density, which is attractive for energy applications. [ 13 ]
One example of this application is hydrogen storage . With the onset of climate change, there is an increased interest in zero-emission vehicles, especially in fuel cell electric vehicles. [ 15 ] By storing hydrogen at high densities using porous materials, one can increase electric car mileage range. [ 13 ]
Another use case for nanoporous materials is as a substrate for gas sensors. For example, measuring the electrical resistivity of a porous metal can yield the exact concentration of an analyte species in gaseous form. [ 2 ] Since the resistivity of the substrate is proportional to the surface area of the porous media, using nanoporous materials will yield higher sensitivity in detecting trace gaseous species than their bulk counterparts. This is especially useful as nanoporous materials have a higher effective surface area normalized to the top-view surface area
Nanoporous materials are used in biological applications as well. Enzyme catalyzed reactions in biological applications are highly utilized for metabolism and processing large molecules. Nanoporous materials offer the opportunity to embed enzymes onto the porous substrate which enhances the lifetime of the reactions for long-term implants. [ 2 ] Another application is found in DNA sequencing. By coating an inorganic nanoporous membrane on an insulating material, nanopores can be utilized for single-molecule analysis. By threading DNA through these nanopores, one can read out the ionic current through the pore which can be correlated to one of four nucleotides . [ 16 ] | https://en.wikipedia.org/wiki/Nanoporous_materials |
A nanoprobe is an optical device developed by tapering an optical fiber to a tip measuring 100 nm = 1000 angstroms wide.
Nanoprobes can be used in bioimaging to provide improved contrast and spatial resolution of cells and tissues . [ 1 ] Types of nanoprobes used for bioimaging include fluorescence , chemiluminescence , and photoacoustic imaging . [ 1 ]
When light interacts with matter, a phenomenon known as Raman scattering [ 2 ] occurs, which provides important information about the vibrational frequencies of the sample. This phenomenon happens when a sample's molecules interact with incident light, scattering it. Every material has a different Raman spectrum because of the information the scattered light has about the vibrational modes of the constituent molecules.
A very thin coating of silver nanoparticles helps to enhance the Raman scattering effect of the light. (The phenomenon of light reflection from an object when illuminated by a laser light is referred to as Raman scattering.) The reflected light demonstrates vibration energies unique to each object (samples in this case), which can be characterized and identified.
The term nanoprobe also refers more generically to any chemical or biological technique that deals with nanoquantitles, that is, introducing or extracting substances measured in nanoliters or nanograms rather than microliters or micrograms. For example:
In semiconductor manufacturing, nanoprobing is showing potential for conventional IC failure analysis and debugging, as well as for transistor design, circuit, and process development, and even for yield engineering. [ 7 ]
Nanotechnology solutions can be used in the diagnosis and early treatment of diabetes. There are two types of diabetes: type 1 [ 8 ] and type 2. [ 8 ] Regular checking of blood glucose involves a painful mechanism by piercing the finger. Still, New nanotechnology innovations have made it possible to check blood sugar non-invasively, leading to the early detection of diabetes. [ 9 ] Nanoprobe devices have improved the insulin monitoring system, which is necessary for diabetes management, gene therapy and Islet cell screening, pre-transplantation. [ 9 ]
This nanotechnology-related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Nanoprobe_(device) |
Nanoprobing is method of extracting device electrical parameters through the use of nanoscale tungsten wires, used primarily in the semiconductor industry. The characterization of individual devices is instrumental to engineers and integrated circuit designers during initial product development and debug. It is commonly utilized in device failure analysis laboratories to aid with yield enhancement, quality and reliability issues and customer returns. Commercially available nanoprobing systems are integrated into either a vacuum-based scanning electron microscope (SEM) or atomic force microscope (AFM). Nanoprobing systems that are based on AFM technology are referred to as Atomic Force nanoProbers (AFP).
AFM based nanoprobers, enable up to eight probe tips to be scanned to generate high resolution AFM topography images, as well as Conductive AFM, Scanning Capacitance, and Electrostatic Force Microscopy images. Conductive AFM provides pico-amp resolution to identify and localize electrical failures such as shorts, opens, resistive contacts and leakage paths, enabling accurate probe positioning for current-voltage measurements. [ 1 ] AFM based nanoprobers enable nanometer scale device defect localization and accurate transistor device characterization without the physical damage and electrical bias induced by high energy electron beam exposure.
For SEM based nanoprobers, the ultra-high resolution of the microscopes that house the nanoprobing system allow the operator to navigate the probe tips with precise movement, allowing the user to see exactly where the tips will be landed, in real time. Existing nanoprobe needles or “probe tips” have a typical end-point radius ranging from 5 to 35 nm. [ 2 ] The fine tips enable access to individual contacts nodes of modern IC transistors. Navigation of the probe tips in SEM based nanoprobers are typically controlled by precision piezoelectric manipulators. Typical systems have anywhere from 2 to 8 probe manipulators with high end tools having better than 5 nm of placement resolution in the X, Y & Z axes and a high accuracy sample stage for navigation of the sample under test.
Common nanoprobing techniques include, but are not limited to:
Common issues that arise: | https://en.wikipedia.org/wiki/Nanoprobing |
A nanoradio (also called carbon nanotube radio) is a nanotechnology acting as a radio transmitter and receiver by using carbon nanotubes . One of the first nanoradios was constructed in 2007 by researchers under Alex Zettl at the University of California, Berkeley where they successfully transmitted an audio signal. [ 1 ] Due to the small size, nanoradios can have several possible applications such as radio function in the bloodstream. [ 2 ]
The first observation of a nanoradio can be accredited to a Japanese physicist Sumio Iijima in 1991 who saw a "a luminous discharge of electricity" coming from a carbon nanotube on a graphite electrode. [ 2 ] On October 31, 2007, a team of researchers under Alex Zettl at the University of California, Berkeley created one of the first nanoradios. [ 1 ] Their experiment consisted of placing a multilayered nanotube placed on a silicon electrode and connecting it to a counter electrode through a wire and a DC battery. Both the electrode and nanotube were also put in a vacuum of about 10 −7 Torr . [ 3 ] They then placed the apparatus into a high-resolution transmission electron microscope to document the movement of the nanotube. They observed the nanoradio vibrating and transmitted a song called "Layla" by Eric Clapton. [ 4 ] After some minor adjustments, the team was able to transmit and receive signals from a couple meters across the laboratory; [ 2 ] however, the initial audio receptions from the radio were scratchy which Zettl believed was due to the lack of a better vacuum. [ 1 ]
The small size, roughly 10 nanometers wide and hundreds of nanometers long, and composition of nanoradios provide several distinct properties. The small size of nanoradios enables electrons to pass through without much friction, making nanoradios efficient conductors. Nanoradios can also come in different sizes; they can be double-walled, tripled-walled and multi-walled. Aside from the different sizes, nanoradios can also take different shapes such as bent, straight or toroidal . Common among all nanoradios is how relatively strong they are. The resistance can be attributed to the strength of the bonds between carbon atoms. [ 2 ]
The fundamental parts of a radio are the antenna, tuner, demodulator and amplifier. Carbon nanotubes are special in that they can function as these parts without the need of extra circuitry.
The nanoradio is small enough for electromagnetic signals to mechanically vibrate the nanoradio. The nanoradio essentially acts as an antenna by vibrating with the same frequency as the signal from incoming electromagnetic waves; this is in contrast with traditional radio antennas, which are generally stationary. [ 3 ] The nanotube can vibrate in high frequencies, from "thousands to millions of times per second." [ 1 ]
The nanoradio can also function as a tuner by extending or reducing the length of the nanotube; doing so changes the resonance frequency at which it vibrates, enabling the radio to tune into specific frequencies. The length of the nanotube can be extended by pulling the tip with a positive electrode and can be shortened by removing atoms off the tip. [ 1 ] Consequently, changing the length is permanent and can't be reversed; however, the method of varying the electric field can also affect the frequency that the nanoradio responds without being permanent. [ 2 ]
As a benefit of the microscopic size and needle-like shape, the nanoradio functions naturally as an amplifier . The nanoradio exhibits field emission , in which a small voltage emits a flow of electrons; due to this, a small electromagnetic wave would produce a large flow of electrons, amplifying the signal. [ 2 ]
Demodulation is essentially the separation of the information signal from the carrier wave. When the nanoradio vibrates in sync with the carrier wave, the nanoradio responds only to the information signal and ignores the carrier wave ; and so, the nanoradio can act as a demodulator without the need of circuitry. [ 2 ]
Currently, chemotherapy uses chemicals that harm not only cancerous cells, but also healthy ones since they are put into the blood stream. Nanoradios can be used to prevent damage to healthy cells by remotely communicating with the radio to release drugs and specifically target cancerous cells. Nanoradios can also be injected into individual cells to release certain chemicals, enabling repair of specific cells. [ 2 ] Nanoradios can also be used to monitor insulin levels of diabetes patients and use that information to release a drug or chemical. [ 5 ]
The implanting of nanoradios in the body is now feasible with manipulation of directed energy. The nanoradio radiates about 4.5 x 10 −27 W of electromagnetic power; however, much of this power is lost when passing through the body. The amount of energy input can be increased, which would generate much heat in the body, which can pose a safety risk. [ 6 ] | https://en.wikipedia.org/wiki/Nanoradio |
Nanoreactors are a form of chemical reactor that are particularly in the disciplines of nanotechnology and nanobiotechnology . These special reactors are crucial in maintaining a working nanofoundry ; which is essentially a foundry that manufactures products on a nanotechnological scale.
The term nanoreactor refers to an isolated system on the nanometer scale that is used to run chemical reactions in an environment that differs drastically from a reaction in bulk solution. The synthesis and analysis of these nanoreactors is a highly interdisciplinary subject, spanning from chemistry and physics to biology and materials science. These systems can be synthetic, such as nanopores and hollow nanoparticles, or they can be biological systems, including protein pores and channels. [ 1 ] Generally, the effect of confinement provided by these nanoreactors results in novel chemistry. This field has only begun to receive significant attention in the last two decades, and more work is constantly being published as nanoreactors become more sophisticated and begin to show promise for industrial applications.
Researchers in the Netherlands have succeeded in building nanoreactors that can perform one-pot multistep reactions - the next step towards artificial cell -like devices in addition for applications involving the screening and diagnosis of a disease or illness. [ 2 ] A biochemical nanoreactor is created simply by unwrapping a biological virus through scientific methods, eliminating its harmful contents, and re-assembling its protein coat around a single molecule of enzyme. [ 3 ] The kinetic isotope effect is trapped in a single molecule within a membrane-based nanoreactor. [ 4 ] This is a phenomenon that has been found by researchers in the United Kingdom during experiments done in September 2010. [ 4 ] The kinetic isotope effect, where the rate of a reaction is influenced by the presence of an isotopic atom in solution, is an important principle for elucidating reaction mechanisms. [ 4 ] This recent finding could open up new methods to study chemical reactions. [ 4 ] They may even aid in the process of creating new (and even more powerful) nanoreactors. [ 4 ]
Using nanocrystals, a scalable and inexpensive process can ultimately create nanoreactors. [ 5 ] Researchers at the Lawrence Berkeley National Laboratory in Berkeley have the ability to take advantage of the large difference in select components to create these nanocrystals and nanoreactors. [ 5 ] Nanocrystals are easier to use and less expensive than methods that employ sacrificial templates in the creation process of hollow particles . [ 5 ] Catalyst particles are separated into shells in order to prevent particle aggregation . [ 5 ] Selective entry into the catalysis chamber reduces the likelihood of desired products undergoing secondary reactions . [ 5 ]
Nanoreactors can also be built by controlling the positioning of two different enzymes in the central water reservoir or the plastic membrane of synthetic nanoscopic bubbles. [ 6 ] Once the third enzyme is added into the surrounding solution, it becomes possible for three different enzymatic reactions to occur at once without interfering with each other (resulting in a "one-pot" reaction). [ 6 ] The potential for nanoreactors can be demonstrated by binding the enzyme horseradish peroxidase into the membrane itself; trapping the enzyme glucose oxidase . [ 6 ] The surrounding solution would end up containing the enzyme lipase B with the glucose molecules containing four acetyl groups as the substrate. [ 6 ] The resulting glucose would cross the membrane, become oxidized, and the horseradish peroxidase would convert the sample substrate ABTS (2,2’-azinobis(3-ethylbenzthiazoline-6-sulfonic acid)) into its radical cation. [ 6 ]
Nanoreactors can also be used to emulsify water, create hydrofuels (which essentially blends 15% water into the refined diesel product), play a helpful role in the chemical industry by allowing multiple streams of raw materials to exists in a single nanoreactor, manufacture personal care products (i.e., lotions , pharmaceutical creams , shampoos , conditioners , shower gels , deodorants ), and improve the food and beverage industries (by processing sauces , purées , cooking bases for soup, emulsifying non-alcoholic beverages , and salad dressings ). [ 7 ]
Personal care goods can be enhanced by companies feeding multiple phases of material, using a mixing device with water, and creating instant emulsions . [ 7 ] These emulsions would come with smaller particles, are expected to have a longer shelf life and an give off an enhanced appearance when sold at retailers. [ 7 ] The needs of the food and beverage industry can result in lower processing costs, more space, better efficiency, and lower equipment costs. [ 7 ] This may bring down the cost of food and beverages for consumers; even alcoholic beverages that are subject to hidden sin taxes .
Hydrofuel can be used to move heavy duty transports , trains , earth-moving equipment (including bulldozers ), in addition to providing fuel to most boats and ships . [ 7 ] Reduced pollution and increased fuel efficiency may come out of nanoreactor-produced hydrofuel. [ 7 ] The increased usage of renewable energy may also help to improve the world's environment thanks to nanoreactors. [ 7 ]
Roy, Skinner, et al. studied the dynamics of water in self-assembled gemini surfactants in 2014. [ 8 ] This work illustrates not only the utility of nano-scale materials for chemical reactions, but also the complexity that is required to study the effects. The team utilized spectroscopic techniques and molecular dynamics simulations to determine that within the nanoporous structures, the dynamics of water in the gyroid phase is an order of magnitude slower than in the bulk water. This result arises from the difference in curvature at the interfaces of the normal gyroid. When compared with water confined in a reverse spherical micelle of a sulfonate surfactant, the water exhibited faster dynamics. This complex behavior was postulated to have implications for future work in ion transport.
Carbon nanotubes have been a popular area of research, and specifically, single-walled carbon nanotubes provide unique surfaces for chemistry. Li, G and Fu, C et al. report on large changes to the Raman spectra by encapsulating sulfur in these single-walled carbon nanotubes. In an example of how confinement to such small spaces influences chemistry, the authors theorize that the changes to the Raman spectra can be attributed to van der Waals interactions of the sulfur with the walls of the nanotubes. These effects are highly sensitive to the size of the confinement chamber, as the van der Waals interactions were not significant for larger diameter single-walled nanotubes. The authors suggest that confinement within the single-walled nanotubes allows S 2 molecules to undergo polymerization to linear diradicals. [ 9 ]
Nanoreactors are also being applied to biological spaces. In a study by Tagliazucchi and Szleifer, they study the binding of proteins to ligands inside of both long nanochannels and short nanopores. Inside these confined spaces, the ligands are attached to the walls by polymeric tethers. This technology has already seen applications as sensors that measure concentrations of proteins in solution. This study developed a theory to model how the proteins bind under these highly confined conditions to inform the design of these sensors. [ 10 ] | https://en.wikipedia.org/wiki/Nanoreactor |
Nanoid robotics , or for short, nanorobotics or nanobotics , is an emerging technology field creating machines or robots , which are called nanorobots or simply nanobots , whose components are at or near the scale of a nanometer (10 −9 meters). [ 1 ] [ 2 ] [ 3 ] More specifically, nanorobotics (as opposed to microrobotics ) refers to the nanotechnology engineering discipline of designing and building nanorobots with devices ranging in size from 0.1 to 10 micrometres and constructed of nanoscale or molecular components. [ 4 ] [ 5 ] The terms nanobot , nanoid , nanite , nanomachine and nanomite have also been used to describe such devices currently under research and development. [ 6 ] [ 7 ]
Nanomachines are largely in the research and development phase, [ 8 ] but some primitive molecular machines and nanomotors have been tested. An example is a sensor having a switch approximately 1.5 nanometers across, able to count specific molecules in the chemical sample. The first useful applications of nanomachines may be in nanomedicine . For example, [ 9 ] biological machines could be used to identify and destroy cancer cells. [ 10 ] [ 11 ] Another potential application is the detection of toxic chemicals, and the measurement of their concentrations, in the environment. Rice University has demonstrated a single-molecule car developed by a chemical process and including Buckminsterfullerenes (buckyballs) for wheels. It is actuated by controlling the environmental temperature and by positioning a scanning tunneling microscope tip.
Another definition [ 12 ] [ 13 ] [ 14 ] is a robot that allows precise interactions with nanoscale objects, or can manipulate with nanoscale resolution. Such devices are more related to microscopy or scanning probe microscopy , instead of the description of nanorobots as molecular machines . Using the microscopy definition, even a large apparatus such as an atomic force microscope can be considered a nanorobotic instrument when configured to perform nanomanipulation. For this viewpoint, macroscale robots or microrobots that can move with nanoscale precision can also be considered nanorobots.
According to Richard Feynman , it was his former graduate student and collaborator Albert Hibbs who originally suggested to him (circa 1959) the idea of a medical use for Feynman's theoretical micro-machines (see biological machine ). Hibbs suggested that certain repair machines might one day be reduced in size to the point that it would, in theory, be possible to (as Feynman put it) " swallow the surgeon ". The idea was incorporated into Feynman's case study 1959 essay There's Plenty of Room at the Bottom . [ 15 ]
Since nano-robots would be microscopic in size, it would probably be necessary for very large numbers of them to work together to perform microscopic and macroscopic tasks. [ citation needed ] These nano-robot swarms, both those unable to replicate (as in utility fog ) and those able to replicate unconstrained in the natural environment (as in grey goo and synthetic biology ), are found in many science fiction stories, such as the Borg nano-probes in Star Trek and The Outer Limits episode " The New Breed ".
Some proponents of nano-robotics, in reaction to the grey goo scenarios that they earlier helped to propagate, hold the view that nano-robots able to replicate outside of a restricted factory environment do not form a necessary part of a purported productive nanotechnology, and that the process of self-replication, were it ever to be developed, could be made inherently safe. They further assert that their current plans for developing and using molecular manufacturing do not in fact include free-foraging replicators. [ 16 ] [ 17 ]
A detailed theoretical discussion of nanorobotics, including specific design issues such as sensing, power communication, navigation , manipulation, locomotion, and onboard computation, has been presented in the medical context of nanomedicine by Robert Freitas . [ 18 ] [ 19 ] Some of these discussions [ which? ] remain at the level of unbuildable generality and do not approach the level of detailed engineering.
A document with a proposal on nanobiotech development using open design technology methods, as in open-source hardware and open-source software , has been addressed to the United Nations General Assembly . [ 20 ] According to the document sent to the United Nations , in the same way that open source has in recent years accelerated the development of computer systems, a similar approach should benefit the society at large and accelerate nanorobotics development. The use of nanobiotechnology should be established as a human heritage for the coming generations, and developed as an open technology based on ethical practices for peaceful purposes. Open technology is stated as a fundamental key for such an aim.
In the same ways that technology research and development drove the space race and nuclear arms race , a race for nanorobots is occurring. [ 21 ] [ 22 ] [ 23 ] [ 24 ] [ 25 ] There is plenty of ground allowing nanorobots to be included among the emerging technologies . [ 26 ] Some of the reasons are that large corporations, such as General Electric , Hewlett-Packard , Synopsys , Northrop Grumman and Siemens have been recently working in the development and research of nanorobots; [ 27 ] [ 28 ] [ 29 ] [ 30 ] [ 31 ] surgeons are getting involved and starting to propose ways to apply nanorobots for common medical procedures; [ 32 ] universities and research institutes were granted funds by government agencies exceeding $2 billion towards research developing nanodevices for medicine; [ 33 ] [ 34 ] bankers are also strategically investing with the intent to acquire beforehand rights and royalties on future nanorobots commercialisation. [ 35 ] Some aspects of nanorobot litigation and related issues linked to monopoly have already arisen. [ 36 ] [ 37 ] [ 38 ] A large number of patents have been granted recently on nanorobots, mostly by patent agents, companies specializing solely on building patent portfolios, and lawyers. After a long series of patents and eventually litigations, see for example the invention of radio , or the war of currents , emerging fields of technology tend to become a monopoly , which normally is dominated by large corporations. [ 39 ]
Manufacturing nanomachines assembled from molecular components is a very challenging task. Because of the level of difficulty, many engineers and scientists continue working cooperatively across multidisciplinary approaches to achieve breakthroughs in this new area of development. Thus, it is quite understandable the importance of the following distinct techniques currently applied towards manufacturing nanorobots:
The joint use of nanoelectronics , photolithography , and new biomaterials provides a possible approach to manufacturing nanorobots for common medical uses, such as surgical instrumentation, diagnosis, and drug delivery. [ 40 ] [ 41 ] [ 42 ] This method for manufacturing on nanotechnology scale is in use in the electronics industry since 2008. [ 43 ] So, practical nanorobots should be integrated as nanoelectronics devices, which will allow tele-operation and advanced capabilities for medical instrumentation. [ 44 ] [ 45 ]
A nucleic acid robot (nubot) is an organic molecular machine at the nanoscale. [ 46 ] DNA structure can provide means to assemble 2D and 3D nanomechanical devices. DNA based machines can be activated using small molecules, proteins and other molecules of DNA. [ 47 ] [ 48 ] [ 49 ] Biological circuit gates based on DNA materials have been engineered as molecular machines to allow in-vitro drug delivery for targeted health problems. [ 50 ] Such material based systems would work most closely to smart biomaterial drug system delivery, [ 51 ] while not allowing precise in vivo teleoperation of such engineered prototypes.
Several reports have demonstrated the attachment of synthetic molecular motors to surfaces. [ 52 ] [ 53 ] These primitive nanomachines have been shown to undergo machine-like motions when confined to the surface of a macroscopic material. The surface anchored motors could potentially be used to move and position nanoscale materials on a surface in the manner of a conveyor belt.
Nanofactory Collaboration, [ 54 ] founded by Robert Freitas and Ralph Merkle in 2000 and involving 23 researchers from 10 organizations and 4 countries, focuses on developing a practical research agenda [ 55 ] specifically aimed at developing positionally-controlled diamond mechanosynthesis and a diamondoid nanofactory that would have the capability of building diamondoid medical nanorobots.
The emerging field of bio-hybrid systems combines biological and synthetic structural elements for biomedical or robotic applications. The constituting elements of bio-nanoelectromechanical systems (BioNEMS) are of nanoscale size, for example DNA, proteins or nanostructured mechanical parts. Thiol-ene e-beams resist allow the direct writing of nanoscale features, followed by the functionalization of the natively reactive resist surface with biomolecules. [ 56 ] Other approaches use a biodegradable material attached to magnetic particles that allow them to be guided around the body. [ 57 ]
This approach proposes the use of biological microorganisms, like the bacterium Escherichia coli [ 58 ] and Salmonella typhimurium . [ 59 ] Thus the model uses a flagellum for propulsion purposes. Electromagnetic fields normally control the motion of this kind of biological integrated device. [ 60 ] Chemists at the University of Nebraska have created a humidity gauge by fusing a bacterium to a silicon computer chip. [ 61 ]
Retroviruses can be retrained to attach to cells and replace DNA . They go through a process called reverse transcription to deliver genetic packaging in a vector . [ 62 ] Usually, these devices are Pol – Gag genes of the virus for the Capsid and Delivery system. This process is called retroviral gene therapy , having the ability to re-engineer cellular DNA by usage of viral vectors . [ 63 ] This approach has appeared in the form of retroviral , adenoviral , and lentiviral gene delivery systems. [ 64 ] [ 65 ] These gene therapy vectors have been used in cats to send genes into the genetically modified organism (GMO), causing it to display the trait. [ 66 ]
Research has led to the creation of helical silica particles coated with magnetic materials that can be maneuvered using a rotating magnetic field. [ 67 ]
Such nanorobots are not dependent on chemical reactions to fuel the propulsion. A triaxial Helmholtz coil can provide directed rotating field in space. It was shown how such nanomotors can be used to measure viscosity of non-newtonian fluids at a resolution of a few microns. [ 68 ] This technology promises creation of viscosity map inside cells and the extracellular milieu. Such nanorobots have been demonstrated to move in blood. [ 69 ] Researchers have managed to controllably move such nanorobots inside cancer cells allowing them to trace out patterns inside a cell. [ 68 ] Nanorobots moving through the tumor microenvironment have demonstrated the presence of sialic acid in the cancer-secreted extracellular matrix . [ 70 ]
A magnetic helical nanorobot consists of at least two components - one being a helical body, and the other being a magnetic material. The helical body provides a structure to the nanorobot capable of translation along the helical axis. The magnetic material, on the other hand, allows the structure to rotate by following an externally applied rotating magnetic field. Not only do magnetic helical nanorobots take advantage of magnetic actuation, but they also take advantage of helical propulsion methods.
In short, magnetic helical nanorobots translate a rotational motion into translational movement through a fluid in low Reynolds number environments. These nanorobots have been inspired by naturally occurring microorganisms such as flagella, cilia, and Escheric coli (otherwise known as E. coli) which rotate in a helical wave. [ 71 ]
One approach to the wireless manipulation of helical swimmers is through externally applied gradient rotation magnetic field. This can be done through Helmholtz coil as the helical swimmers are actuated by a rotating magnetic field. All magnetized objects within an externally imposed magnetic field will have both forces and torques exerted on them. The helical swimmers can rotate due the magnetic field received by the magnetic head and the forces acting upon it. Once the whole structure feels the field then the helical shape of its body converts this rotational movement into a propulsive force. Magnetic forces (fm) are proportional to the gradient of the magnetic field (∇B) on the magnetized object, and act to move the object to local maxima. Also, magnetic torques (τ) are proportional to the magnetic field (B) and act to align the internal magnetization of an object (M) with the field. The equations that express the interactions are as follows where V is the volume of the magnetized object. [ 72 ]
F = V ⋅ ( M ⋅ ∇ B ) {\displaystyle {\boldsymbol {F}}=V\cdot ({\boldsymbol {M}}\cdot \nabla {\boldsymbol {B}})} (Equation 1)
τ = V ⋅ ( M × B ) {\displaystyle {\boldsymbol {\tau }}=V\cdot ({\boldsymbol {M}}{\boldsymbol {\times }}{\boldsymbol {B}})} (Equation 2)
Equation one indicates that, increasing the volume of the magnetic material will increase the force experienced by the material proportionally. If the volume is doubled, the force will also double, assuming the magnetization (M) and the gradient of the magnetic field (∇B) remain constant. This would be the same for the torque of the magnetic material too since it is proportional to the volume.
This increase in magnetic dipoles enhances the overall magnetic response of the material to an external magnetic field, resulting in greater force and torque. Hence when the magnetic material gets bigger than the helical swimmer it can move faster.
To use the rotation magnetic field, a permanent magnet can be planted in the helical swimmer’s head, whose magnetization direction would be perpendicular to the swimmer body. When a rotating magnetic field is applied, the swimmer’s head experiences a magnetic torque, causing it to rotate. The helical shape converts this rotational movement into a propulsive force. As the swimmer’s head rotates, its helical tail generates a force against the surrounding fluid, propelling it forward. [ 73 ] According to equation 2, the magnetic torque around the x -axis is zero
( M × B ) ∗ u x = 0 {\displaystyle ({\boldsymbol {M}}{\boldsymbol {\times }}{\boldsymbol {B}})*{\boldsymbol {ux}}=0}
at the initial position. After the magnet manipulator turns 45°, the magnetic field near the head position of the square magnet turns at an angle around the x -axis, as shown in
the figure below. If the square magnet stays in its initial position, it will be subject to a magnetic torque around the x -axis
( M × B ) ∗ u x ≠ 0 {\displaystyle ({\boldsymbol {M}}{\boldsymbol {\times }}{\boldsymbol {B}})*{\boldsymbol {ux}}\neq 0}
Thus, the helical swimmer will follow the magnetic field. If the magnet manipulator rotates one turn, the magnetic field near the head position of the swimmer projected on the plane yoz rotates a whole turn around the x-axis. [ 74 ] This results in the helical shape to move, resulting in propulsion as follows:
i p u s h = sin φ i n sin θ i n cos φ i n cos θ i n cos φ i n {\displaystyle i_{push}=\sin {\varphi _{in}}\sin {\theta _{in}}\cos {\varphi _{in}}\cos {\theta _{in}}\cos {\varphi _{in}}}
This propulsion helps the helical structure to rotate with the angle of the force. As a result, the magnetic robot rotates around the x -axis by the action of the rotating magnetic field.
Due to its small scale and helical shape providing propulsion, helical swimmers can be used in some biomedical applications such as; targeted drug delivery and targeted cell delivery. In 2018, there was a proposed biocompatible and biodegradable chistosan-based helical micro/nanoswimmer loaded with doxorubicin (DOX), a common anticancer drug that was designed to deliver its payload to a desired location. Using 3.4 × 10 –1 W/cm 2 intensity UV light radiation, when the swimmer approached the target location, a dose of 60% of the total DOX was released within 5 minutes. However, it was seen that the dosage release rate slowed down after the initial 5 minutes that were reported. This was theorized to be caused by a decreasing diffusion rate of DOX molecules coming from the center of the swimmer. [ 75 ] Another group’s spirulina-based helical micro/nanoswimmer also carrying DOX used a different method for controlled drug release. Once the swimmer had reached its destination, near-infrared (NIR) laser irradiation was used to heat up the location to dissolve the swimmer into individual particles, releasing the drug in the process. Through multiple tests, it was found that weak acidic external environments led to an increase in the dosage release rate. [ 76 ]
Using magnetic helical micro/nanorobots for cell transport can also lead to opportunities in solving male infertility, repairing damaged tissue, and cell assembly. In 2015, a helical micro-/nanomotor with a holding ring on the head was used to successfully capture and transport sperm cells with motion deficiencies. The helix device would approach the sperm cell’s tail and confine it with the body of the micro-/nanomotor. It would then use the holding ring to loosely capture the head of the sperm cell to prevent escape. After reaching the target location, the sperm cell would be released into the membrane of the oocyte by reversing the rotation of the helix device. This strategy was considered to be an efficient strategy while also reducing risk of damage to the sperm cells. [ 77 ]
3D printing is the process by which a three-dimensional structure is built through the various processes of additive manufacturing. Nanoscale 3D printing involves many of the same process, incorporated at a much smaller scale. To print a structure in the 5-400 μm scale, the precision of the 3D printing machine needs to be improved greatly. A two-step process of 3D printing, using a 3D printing and laser etched plates method was incorporated as an improvement technique. [ 78 ] To be more precise at a nanoscale, the 3D printing process uses a laser etching machine, which etches the details needed for the segments of nanorobots into each plate. The plate is then transferred to the 3D printer, which fills the etched regions with the desired nanoparticle . The 3D printing process is repeated until the nanorobot is built from the bottom up.
This 3D printing process has many benefits. First, it increases the overall accuracy of the printing process. [ citation needed ] Second, it has the potential to create functional segments of a nanorobot. [ 78 ] The 3D printer uses a liquid resin, which is hardened at precisely the correct spots by a focused laser beam. The focal point of the laser beam is guided through the resin by movable mirrors and leaves behind a hardened line of solid polymer, just a few hundred nanometers wide. This fine resolution enables the creation of intricately structured sculptures as tiny as a grain of sand. This process takes place by using photoactive resins, which are hardened by the laser at an extremely small scale to create the structure. This process is quick by nanoscale 3D printing standards. Ultra-small features can be made with the 3D micro-fabrication technique used in multiphoton photopolymerisation. This approach uses a focused laser to trace the desired 3D object into a block of gel. Due to the nonlinear nature of photo excitation, the gel is cured to a solid only in the places where the laser was focused while the remaining gel is then washed away. Feature sizes of under 100 nm are easily produced, as well as complex structures with moving and interlocked parts. [ 79 ]
There are number of challenges and problems that should be addressed when designing and building nanoscale machines with movable parts. The most obvious one is the need of developing very fine tools and manipulation techniques capable of assembling individual nanostructures with high precision into operational device. Less evident challenge is related to peculiarities of adhesion and friction on nanoscale. It is impossible to take existing design of macroscopic device with movable parts and just reduce it to the nanoscale. Such approach will not work due to high surface energy of nanostructures, which means that all contacting parts will stick together following the energy minimization principle. The adhesion and static friction between parts can easily exceed the strength of materials, so the parts will break before they start to move relative to each other. This leads to the need to design movable structures with minimal contact area [ [ 80 ] ].
In spite of the fast development of nanorobots, most of the nanorobots designed for drug delivery purposes, there is "still a long way to go before their commercialization and clinical applications can be achieved." [ 81 ] [ 82 ]
Potential uses for nanorobotics in medicine include early diagnosis and targeted drug-delivery for cancer , [ 83 ] [ 84 ] [ 85 ] biomedical instrumentation, [ 86 ] surgery , [ 87 ] [ 88 ] pharmacokinetics , [ 10 ] monitoring of diabetes , [ 89 ] [ 90 ] [ 91 ] and health care.
In such plans, future medical nanotechnology is expected to employ nanorobots injected into the patient to perform work at a cellular level. Such nanorobots intended for use in medicine should be non-replicating, as replication would needlessly increase device complexity, reduce reliability, and interfere with the medical mission.
Nanotechnology provides a wide range of new technologies for developing customized means to optimize the delivery of pharmaceutical drugs . Today, harmful side effects of treatments such as chemotherapy are commonly a result of drug delivery methods that don't pinpoint their intended target cells accurately. [ 92 ] Researchers at Harvard and MIT , however, have been able to attach special RNA strands, measuring nearly 10 nm in diameter, to nanoparticles, filling them with a chemotherapy drug. These RNA strands are attracted to cancer cells . When the nanoparticle encounters a cancer cell, it adheres to it, and releases the drug into the cancer cell. [ 93 ] This directed method of drug delivery has great potential for treating cancer patients while avoiding negative effects (commonly associated with improper drug delivery). [ 92 ] [ 94 ] The first demonstration of nanomotors operating in living organisms was carried out in 2014 at University of California, San Diego. [ 95 ] MRI-guided nanocapsules are one potential precursor to nanorobots. [ 96 ]
Another useful application of nanorobots is assisting in the repair of tissue cells alongside white blood cells . [ 97 ] Recruiting inflammatory cells or white blood cells (which include neutrophil granulocytes , lymphocytes , monocytes , and mast cells ) to the affected area is the first response of tissues to injury. [ 98 ] Because of their small size, nanorobots could attach themselves to the surface of recruited white cells, to squeeze their way out through the walls of blood vessels and arrive at the injury site, where they can assist in the tissue repair process. Certain substances could possibly be used to accelerate the recovery.
The science behind this mechanism is quite complex. Passage of cells across the blood endothelium , a process known as transmigration, is a mechanism involving engagement of cell surface receptors to adhesion molecules, active force exertion and dilation of the vessel walls and physical deformation of the migrating cells. By attaching themselves to migrating inflammatory cells, the robots can in effect "hitch a ride" across the blood vessels, bypassing the need for a complex transmigration mechanism of their own. [ 97 ]
As of 2016 [update] , in the United States, Food and Drug Administration (FDA) regulates nanotechnology on the basis of size. [ 99 ]
Nanocomposite particles that are controlled remotely by an electromagnetic field was also developed. [ 100 ] This series of nanorobots that are now enlisted in the Guinness World Records , [ 100 ] can be used to interact with the biological cells . [ 101 ] Scientists suggest that this technology can be used for the treatment of cancer . [ 102 ] [ 70 ] [ 103 ]
Magnetic nanorobots have demonstrated capabilities to prevent and treat antimicrobial resistant bacteria. Application of nanomotor implants have been proposed to achieve thorough disinfection of the dentine. [ 104 ] [ 105 ]
The Nanites are characters on the TV show Mystery Science Theater 3000 . They're self-replicating, bio-engineered organisms that work on the ship and reside in the SOL's computer systems. They made their first appearance in Season 8.
Nanites are used in a number of episodes in the television series Travelers . They be programmed and injected into injured people to perform repairs, and first appear in season 1.
Nanites also feature in the Rise of Iron 2016 expansion for the video game Destiny in which SIVA, a self-replicating nanotechnology is used as a weapon.
Nanites (referred to more often as nanomachines) are often referenced in Konami 's Metal Gear series, being used to enhance and regulate abilities and body functions.
In the Star Trek franchise TV shows nanites play an important plot device. Starting with " Evolution " in the third season of The Next Generation , Borg Nanoprobes perform the function of maintaining the Borg cybernetic systems, as well as repairing damage to the organic parts of a Borg. They generate new technology inside a Borg when needed, as well as protecting them from many forms of disease.
Nanites play a role in the Deus Ex video game series, being the basis of the nano-augmentation technology which gives augmented people superhuman abilities.
Nanites are also mentioned in the Arc of a Scythe book series by Neal Shusterman and are used to heal all nonfatal injuries, regulate bodily functions, and considerably lessen pain.
Nanites are also an integral part of Stargate SG1 and Stargate Atlantis , where grey goo scenarios are portrayed.
Nanomachines are central to the plot of the Silo book series , in which they are used as a weapon of mass destruction propagated via the air, and enter undetected into the human body where, when receiving a signal, they kill the recipient. They are then used to wipe out the majority of the human race. | https://en.wikipedia.org/wiki/Nanorobotics |
A nanoruler is a tool or a method used within the subfield of " nanometrology " to achieve precise control and measurements at the nanoscale (i.e. nanometer, a billion times smaller than a meter). Measurements of extremely tiny proportions require more complicated procedures, such as manipulating the properties of light ( plasmonic ) or DNA to determine distances. At the nanoscale, materials and devices exhibit unique properties that can significantly influence their behavior. In fields like electronics, medicine, and biotechnology, where advancements come from manipulating matter at the atomic and molecular levels, nanoscale measurements become essential.
The nanoruler is also a tool developed by the Massachusetts Institute of Technology with extreme precision, achieved through the technique of scanning beam interference lithography (SBIL). The director of the project, Mark L. Schattenburg, began it with the intention of helping the semiconductor industry, which is required in devices such as computer chips that have components nanometers in size, hence the importance of having a tool capable of nanoscale precision. The Nanoruler was developed in the Space Nanotechnology Laboratory of the Kavli Institute for Astrophysics and Space Research at the Massachusetts Institute of Technology. [ 1 ]
Surface plasmon resonance (SPR) is a phenomenon where free electrons in metals oscillate when illuminated by light at a specific wavelength(color) at a particular angle. This oscillation is similar to the ripples created when a rock is thrown into a pond. Localized surface plasmon resonance (LSPR) refers to a concentrated region of SPR found on metallic nanoparticles , or metals at the nanoscale, enabling more precise analysis. Each nanoparticle will have its unique LSPR depending on the particle's size and geometry. When multiple nanoparticles are brought together within nanometer distances, their LSPRs interact, leading to optical changes. LSPRs are highly sensitive and can be influenced by various factors, including plasmonic coupling, the surrounding dielectric medium, or distances. [ 2 ] Scientists observe these effects and analyze the data, typically in the form of refractive index and shifts in wavelength, to determine measurements. [ 3 ]
Some nanorulers utilize Fano resonances , which are asymmetric line curves resulting from the interference of multiple electromagnetic waves. These resonances are typically observed at specific distances of separation, such as those between gold (Au) nanostructures. Analogous to LSPRs, Fano resonances are used for measurement because of their strong sensitivity to change, such as distances. This allows for precise measurements in very tiny separations for analysis. In certain applications, second harmonic generation (SHG), a nonlinear optical process where two photons of the same frequency combine to generate a single photon at twice the frequency, is utilized in support with Fano resonances for nonlinear measurements. Certain nanostructures (e.g. a gold nanodolmen using three gold nanorods) can exhibit strong SHG responses and lead to specific emission patterns. This method has been used to accurately determine complex 3-dimensional macromolecular entities. [ 4 ]
In 2006, Paul Rothemund made a breakthrough in DNA nanotechnology, developing the DNA origami. His DNA origami took a long, single-stranded DNA molecule (referred to as the "scaffold") and folded it into short, single-stranded DNA oligonucleotides (referred to as "staples"). This revolution allowed for the creation of nanostructures with highly controlled dimensions by designing the DNA scaffold strand and selecting the appropriate staple strands that can serve as nanorulers by itself. DNA origami structures can be designed with specific attachment sites for other nanoscale components, such as nanoparticles, fluorophores , or proteins. By measuring the distances between these components on the origami structures, researchers can perform precise distance measurements at the nanoscale through atomic force microscopy (AFM) and the use of RNA. In the design process, DNA origami structures are equipped with predetermined binding sites for RNA molecules, strategically positioned to facilitate hybridization . Upon introducing RNA molecules, these hybridization events are measured using AFM, providing both visualization and precise nanoscale measurements. [ 5 ]
In 2004, MIT developed the Nanoruler, a machine that was more precise and faster at grating than any other methods at the time. To achieve this, MIT combined two conventional methods of grating, mechanical ruling and interference lithography , into a new technique: scanning beam interference lithography (SBIL). In "traditional" interference lithography, two beams of light interfere with each other producing fringes, similar to how two ripples in the water will create a standing wave where the two ripples meet. The standing wave is the fringe, which gets recorded onto a photoresist on top of a substrate, eventually becoming grating lines. The difference between the "traditional" interference lithography method and the SBIL method is the final gratings they produce. Interference lithography struggles to produce linear gratings and the end results are often nonlinear. It's not ideal, since gratings should be linear and uniform. With SBIL, the approach is similar to that of interference lithography but utilizes two, narrow UV laser beams that interfere and create fringes. The narrowness creates smaller distortions, thereby more linear fringes than interference lithography. The substrate is also attached to a stage, enabling the photoresist to move in a "scanning" motion. This motion creates the grating pattern with near 1 nm precision across a 300 nm substrate in around 20 minutes. [ 6 ] [ 7 ]
Nanotechnology is a modern field that has yet to be fully understood. Nanorulers allow scientists to investigate the fundamental building blocks of matter, including atoms and molecules, which is essential for advancing our knowledge of the physical and chemical properties of materials. As research on nanomaterials is being done, it is important for manufacturing of these nanomaterials to be scalable and efficient.
Life sciences have particularly benefited from nanotechnology. Nanoscale measurements are used for characterizing nanoparticles for drug delivery, studying biological molecules, and exploring cell structures at the nanoscale. Additionally, SPR has been well-established and widely used for biosensing . [ 8 ]
In MIT's case, they developed the Nanoruler machine in order to manufacture semiconductors with higher precision and at faster speeds. Reducing size is important in this industry because the smaller a semiconductor is, the more semiconductors can be placed within a device such as a microchip, which makes the microchip more powerful. [ 1 ] | https://en.wikipedia.org/wiki/Nanoruler |
Nanosensors are nanoscale devices that measure physical quantities and convert these to signals that can be detected and analyzed. There are several ways proposed today to make nanosensors; these include top-down lithography, bottom-up assembly , and molecular self-assembly . [ 1 ] There are different types of nanosensors in the market and in development for various applications, most notably in defense, environmental, and healthcare industries. These sensors share the same basic workflow: a selective binding of an analyte, signal generation from the interaction of the nanosensor with the bio-element, and processing of the signal into useful metrics.
Nanomaterials -based sensors have several benefits in sensitivity and specificity over sensors made from traditional materials, due to nanomaterial features not present in bulk material that arise at the nanoscale. [ 2 ] [ 3 ] Nanosensors can have increased specificity because they operate at a similar scale as natural biological processes, allowing functionalization with chemical and biological molecules, with recognition events that cause detectable physical changes. Enhancements in sensitivity stem from the high surface-to-volume ratio of nanomaterials, as well as novel physical properties of nanomaterials that can be used as the basis for detection, including nanophotonics . Nanosensors can also potentially be integrated with nanoelectronics to add native processing capability to the nanosensor. [ 4 ] : 4–10
In addition to their sensitivity and specificity, nanosensors offer significant advantages in cost and response times, making them suitable for high-throughput applications. Nanosensors provide real-time monitoring compared to traditional detection methods such as chromatography and spectroscopy. These traditional methods may take days to weeks to obtain results and often require investment in capital costs as well as time for sample preparation. [ 5 ] [ 6 ] [ 7 ] [ 8 ]
One-dimensional nanomaterials such as nanowires and nanotubes are well suited for use in nanosensors, as compared to bulk or thin-film planar devices. They can function both as transducers and wires to transmit the signal. Their high surface area can cause large signal changes upon binding of an analyte. Their small size can enable extensive multiplexing of individually addressable sensor units in a small device. Their operation is also "label free" in the sense of not requiring fluorescent or radioactive labels on the analytes. [ 4 ] : 12–26 Zinc oxide nanowire is used for gas sensing applications, given that it exhibits high sensitivity toward low concentration of gas under ambient conditions and can be fabricated easily with low cost. [ 9 ]
There are several challenges for nanosensors, including avoiding drift and fouling , developing reproducible calibration methods, applying preconcentration and separation methods to attain a proper analyte concentration that avoids saturation, and integrating the nanosensor with other elements of a sensor package in a reliable manufacturable manner. [ 4 ] : 4–10 Because nanosensors are a relatively new technology, there are many unanswered questions regarding nanotoxicology, which currently limits their application in biological systems.
Potential applications for nanosensors include medicine, detection of contaminants and pathogens, and monitoring manufacturing processes and transportation systems. [ 4 ] : 4–10 By measuring changes in physical properties ( volume , concentration , displacement and velocity , gravitational , electrical , and magnetic forces, pressure , or temperature ) nanosensors may be able to distinguish between and recognize certain cells at the molecular level in order to deliver medicine or monitor development to specific places in the body. [ 10 ] The type of signal transduction defines the major classification system for nanosensors. Some of the main types of nanosensor readouts include optical, mechanical, vibrational, or electromagnetic. [ 11 ]
As an example of classification, nanosensors that use molecularly imprinted polymers (MIP) can be divided into three categories, which are electrochemical , piezoelectric , or spectroscopic sensors. Electrochemical sensors induce a change in the electrochemical properties of the sensing material, which includes charge , conductivity , and electric potential . Piezoelectric sensors either convert mechanical force into electric force or vice versa. This force is then transduced into a signal. MIP spectroscopic sensors can be divided into three subcategories, which are chemiluminescent sensors, surface plasmon resonance sensors, and fluorescence sensors. As the name suggests, these sensors produce light based signals in forms of chemiluminescence, resonance, and fluorescence. As described by the examples, the type of change that the sensor detects and type of signal it induces depend on the type of sensor [ 12 ]
There are multiple mechanisms by which a recognition event can be transduced into a measurable signal; generally, these take advantage of the nanomaterial sensitivity and other unique properties to detect a selectively bound analyte.
Electrochemical nanosensors are based on detecting a resistance change in the nanomaterial upon binding of an analyte, due to changes in scattering or to the depletion or accumulation of charge carriers . One possibility is to use nanowires such as carbon nanotubes , conductive polymers , or metal oxide nanowires as gates in field-effect transistors , although as of 2009 they had not yet been demonstrated in real-world conditions. [ 4 ] : 12–26 Chemical nanosensors contain a chemical recognition system (receptor) and a physiochemical transducer, in which the receptor interacts with analyte to produce electrical signals. [ 13 ] In one case, [ 14 ] upon interaction of the analyte with the receptor, the nanoporous transducer had a change in impedance which was determined as the sensor signal. Other examples include electromagnetic or plasmonic nanosensors, spectroscopic nanosensors such as surface-enhanced Raman spectroscopy , magnetoelectronic or spintronic nanosensors, and mechanical nanosensors. [ 4 ] : 12–26
Biological nanosensors consist of a bio-receptor and a transducer. The transduction method of choice is currently fluorescence because of the high sensitivity and relative ease of measurement. [ 15 ] [ 16 ] The measurement can be achieved by using the following methods: binding active nanoparticles to active proteins within the cell, using site-directed mutagenesis to produce indicator proteins, allowing for real-time measurements, or by creating a nanomaterial (e.g. nanofibers) with attachment sites for the bio-receptors. [ 15 ] Even though electrochemical nanosensors can be used to measure intracellular properties, they are typically less selective for biological measurements, as they lack the high specificity of bio-receptors (e.g. antibody, DNA). [ 17 ] [ 15 ]
Photonic devices can also be used as nanosensors to quantify concentrations of clinically relevant samples. A principle of operation of these sensors is based on the chemical modulation of a hydrogel film volume that incorporates a Bragg grating . As the hydrogel swells or shrinks upon chemical stimulation, the Bragg grating changes color and diffracts light at different wavelengths. The diffracted light can be correlated with the concentration of a target analyte. [ 18 ]
Another type of nanosensor is one that works through a colorimetric basis. Here, the presence of the analyte causes a chemical reaction or morphological alteration for a visible color change to occur. One such application, is that gold nanoparticles can be used for the detection of heavy metals. [ 19 ] Many harmful gases can also be detected by a colorimetric change, such as through the commercially available Dräger Tube . These provide an alternative to bulky, lab-scale systems, as these can be miniaturized to be used for point-of-sample devices. For example, many chemicals are regulated by the Environmental Protection Agency and require extensive testing to ensure contaminant levels are within the appropriate limits. Colorimetric nanosensors provide a method for on-site determination of many contaminants. [ 20 ] [ 21 ] [ 22 ]
The production method plays a central role in determining the characteristics of the manufactured nanosensor in that the function of nanosensor can be made through controlling the surface of nanoparticles. There are two main approaches in the manufacturing of nanosensors: top-down methods, which begin with a pattern generated at a larger scale, and then reduced to microscale. Bottom-up methods start with atoms or molecules that build up to nanostructures.
It involves starting out with a larger block of some material and carving out the desired form. These carved out devices, notably put to use in specific microelectromechanical systems used as microsensors, generally only reach the micro size, but the most recent of these have begun to incorporate nanosized components. [ 1 ] One of the most common method is called electron beam lithography. Although very costly, this technique effectively forms a distribution of circular or ellipsoidal plots on the two dimensional surface. Another method is electrodeposition, which requires conductive elements to produce miniaturized devices. [ 23 ]
This method consists in using a tension device to stretch the major axis of a fiber while it is heated, to achieve nano-sized scales. This method is specially used in optical fiber to develop optical-fiber-based nanosensors. [ 17 ]
Two different types of chemical etching have been reported. In the Turner method , a fiber is etched to a point while placed in the meniscus between hydrofluoric acid and an organic overlayer . This technique has been shown to produce fibers with large taper angles (thus increasing the light reaching the tip of the fiber) and tip diameters comparable to the pulling method. The second method is tube etching, which involves etching an optical fiber with a single-component solution of hydrogen fluoride . A silica fiber, surrounded with an organic cladding , is polished and one end is placed in a container of hydrofluoric acid. The acid then begins to etch away the tip of the fiber without destroying the cladding. As the silica fiber is etched away, the polymer cladding acts as a wall, creating microcurrents in the hydrofluoric acid that, coupled with capillary action , cause the fiber to be etched into the shape of a cone with large, smooth tapers. This method shows much less susceptibility to environmental parameters than the Turner method. [ 17 ]
This type of methods involve assembling the sensors out of smaller components, usually individual atoms or molecules. This is done by arranging atoms in specific patterns, which has been achieved in laboratory tests through use of atomic force microscopy , but is still difficult to achieve en masse and is not economically viable.
Also known as “growing”, this method most often entails an already complete set of components that would automatically assemble themselves into a finished product. Accurately being able to reproduce this effect for a desired sensor in a laboratory would imply that scientists could manufacture nanosensors much more quickly and potentially far more cheaply by letting numerous molecules assemble themselves with little or no outside influence, rather than having to manually assemble each sensor.
Although the conventional fabrication techniques have proven to be efficient, further improvements in the production method can lead to minimization of cost and enhancement in performance. Challenges with current production methods include uneven distribution, size, and shape of nanoparticles, which all lead to limitation in performance. In 2006, researchers in Berlin patented their invention of a novel diagnostic nanosensor fabricated with nanosphere lithography (NSL), which allows precise control oversize and shape of nanoparticles and creates nanoislands. The metallic nanoislands produced an increase in signal transduction and thus increased sensitivity of the sensor. The results also showed that the sensitivity and specification of the diagnostic nanosensor depend on the size of the nanoparticles, that decreasing the nanoparticle size increases the sensitivity. [ 23 ]
Current density is influenced by distribution, size, or shape of nanoparticles. These properties can be improved by exploitation of capillary forces . In recent research, capillary forces were induced by applying five microliters of ethanol and, as result, individual nanoparticles have been merged in a larger islands (i.e. 20 micrometer-sized) particles separated by 10 micrometers on average, while the smaller ones were dissolved and absorbed. On the other hand, applying twice as much (i.e. 10 microliters) of ethanol has damaged the nanolayers, while applying too small (i.e. two microliters) of ethanol has failed to spread across them. [ 24 ]
One of the first working examples of a synthetic nanosensor was built by researchers at the Georgia Institute of Technology in 1999. [ 25 ] It involved attaching a single particle onto the end of a carbon nanotube and measuring the vibrational frequency of the nanotube both with and without the particle. The discrepancy between the two frequencies allowed the researchers to measure the mass of the attached particle. [ 1 ]
Since then, increasing amounts of research have gone into nanosensors, whereby modern nanosensors have been developed for many applications. Currently, the applications of nanosensors in the market include: healthcare, defense and military, and others such as food, environment, and agriculture. [ 26 ]
Nanoscience as a whole has many potential applications in the defense and military sector- including chemical detection, decontamination, and forensics. Some nanosensors in development for defense applications include nanosensors for the detection of explosives or toxic gases. Such nanosensors work on the principle that gas molecules can be distinguished based on their mass using, for example, piezoelectric sensors. If a gas molecule is adsorbed at the surface of the detector, the resonance frequency of the crystal changes and this can be measured as a change in electrical properties. In addition, field effect transistors, used as potentiometers , can detect toxic gases if their gate is made sensitive to them. [ 27 ]
In a similar application, nanosensors can be utilized in military and law enforcement clothing and gear. The Navy Research Laboratory's Institute for Nanoscience has studied quantum dots for application in nanophotonics and identifying biological materials. Nanoparticles layered with polymers and other receptor molecules will change color when contacted by analytes such as toxic gases. [ 27 ] This alerts the user that they are in danger. Other projects involve embedding clothing with biometric sensors to relay information regarding the user's health and vitals, [ 27 ] which would be useful for monitoring soldiers in combat.
Surprisingly, some of the most challenging aspects in creating nanosensors for defense and military use are political in nature, rather than technical. Many different government agencies must work together to allocate budgets and share information and progress in testing; this can be difficult with such large and complex institutions. In addition, visas and immigration status can become an issue for foreign researchers - as the subject matter is very sensitive, government clearance can sometimes be required. [ 28 ] Finally, there are currently not well defined or clear regulations on nanosensor testing or applications in the sensor industry, which contributes to the difficulty of implementation.
Nanosensors can improve various sub-areas within food and environment sectors including food processing, agriculture, air and water quality monitoring, and packaging and transport. Due to their sensitivity, as well as their tunability and resulting binding selectivity, nanosensors are very effective and can be designed for a wide variety of environmental applications. Such applications of nanosensors help in a convenient, rapid, and ultrasensitive assessment of many types of environmental pollutants. [ 29 ]
Chemical sensors are useful for analyzing odors from food samples and detecting atmospheric gases. [ 30 ] The "electronic nose" was developed in 1988 to determine the quality and freshness of food samples using traditional sensors, but more recently the sensing film has been improved with nanomaterials. A sample is placed in a chamber where volatile compounds become concentrated in the gas phase, whereby the gas is then pumped through the chamber to carry the aroma to the sensor that measures its unique fingerprint. The high surface area to volume ratio of the nanomaterials allows for greater interaction with analytes and the nanosensor's fast response time enables the separation of interfering responses. [ 31 ] Chemical sensors, too, have been built using nanotubes to detect various properties of gaseous molecules. Many carbon nanotube based sensors are designed as field effect transistors, taking advantage of their sensitivity. The electrical conductivity of these nanotubes will change due to charge transfer and chemical doping by other molecules, enabling their detection. To enhance their selectivity, many of these involve a system by which nanosensors are built to have a specific pocket for another molecule. Carbon nanotubes have been used to sense ionization of gaseous molecules while nanotubes made out of titanium have been employed to detect atmospheric concentrations of hydrogen at the molecular level. [ 32 ] [ 33 ] Some of these have been designed as field effect transistors, while others take advantage of optical sensing capabilities. Selective analyte binding is detected through spectral shift or fluorescence modulation. [ 34 ] In a similar fashion, Flood et al. have shown that supramolecular host–guest chemistry offers quantitative sensing using Raman scattered light [ 35 ] as well as SERS . [ 36 ]
Other types of nanosensors, including quantum dots and gold nanoparticles , are currently being developed to detect pollutants and toxins in the environment. These take advantage of the localized surface plasmon resonance (LSPR) that arises at the nanoscale, which results in wavelength specific absorption. [ 37 ] This LSPR spectrum is particularly sensitive, and its dependence on nanoparticle size and environment can be used in various ways to design optical sensors. To take advantage of the LSPR spectrum shift that occurs when molecules bind to the nanoparticle, their surfaces can be functionalized to dictate which molecules will bind and trigger a response. [ 38 ] For environmental applications, quantum dot surfaces can be modified with antibodies that bind specifically to microorganisms or other pollutants. Spectroscopy can then be used to observe and quantify this spectrum shift, enabling precise detection, potentially on the order of molecules. [ 38 ] Similarly, fluorescent semiconducting nanosensors may take advantage of fluorescence resonance energy transfer (FRET) to achieve optical detection. Quantum dots can be used as donors, and will transfer electronic excitation energy when positioned near acceptor molecules, thus losing their fluorescence. These quantum dots can be functionalized to determine which molecules will bind, upon which fluorescence will be restored. Gold nanoparticle-based optical sensors can be used to detect heavy metals very precisely; for example, mercury levels as low as 0.49 nanometers. This sensing modality takes advantage of FRET, in which the presence of metals inhibits the interaction between quantum dots and gold nanoparticles, and quenches the FRET response. [ 39 ] Another potential implementation takes advantage of the size dependence of the LSPR spectrum to achieve ion sensing. In one study, Liu et al. functionalized gold nanoparticles with a Pb 2+ sensitive enzyme to produce a lead sensor. Generally, the gold nanoparticles would aggregate as they approached each other, and the change in size would result in a color change. Interactions between the enzyme and Pb 2+ ions would inhibit this aggregation, and thus the presence of ions could be detected.
The main challenge associated with using nanosensors in food and the environment is determining their associated toxicity and overall effect on the environment. Currently, there is insufficient knowledge on how the implementation of nanosensors will affect the soil, plants, and humans in the long-term. This is difficult to fully address because nanoparticle toxicity depends heavily on the type, size, and dosage of the particle as well as environmental variables including pH, temperature, and humidity. To mitigate potential risk, research is being done to manufacture safe, nontoxic nanomaterials, as part of an overall effort towards green nanotechnology. [ 40 ]
Nanosensors possess great potential for diagnostic medicine, enabling early identification of disease without reliance on observable symptoms. [ 41 ] Ideal nanosensor implementations look to emulate the response of immune cells in the body, incorporating both diagnostic and immune response functionalities, while transmitting data to allow for monitoring of the sensor input and response. However, this model remains a long-term goal, and research is currently focused on the immediate diagnostic capabilities of nanosensors. The intracellular implementation of nanosensor synthesized with biodegradable polymers induces signals that enable real-time monitoring and thus paves way for advancement in drug delivery and treatment. [ 42 ]
One example of these nanosensors involves using the fluorescence properties of cadmium selenide quantum dots as sensors to uncover tumors within the body. A downside to the cadmium selenide dots, however, is that they are highly toxic to the body. As a result, researchers are working on developing alternate dots made out of a different, less toxic material while still retaining some of the fluorescence properties. In particular, they have been investigating the particular benefits of zinc sulfide quantum dots which, though they are not quite as fluorescent as cadmium selenide, can be augmented with other metals including manganese and various lanthanide elements. In addition, these newer quantum dots become more fluorescent when they bond to their target cells. [ 34 ]
Another application of nanosensors involves using silicon nanowires in IV lines to monitor organ health. The nanowires are sensitive to detect trace biomarkers that diffuse into the IV line through blood which can monitor kidney or organ failure. These nanowires would allow for continuous biomarker measurement, which provides some benefits in terms of temporal sensitivity over traditional biomarker quantification assays such as ELISA. [ 43 ]
Nanosensors can also be used to detect contamination in organ implants. The nanosensor is embedded into the implant and detects contamination in the cells surrounding the implant through an electric signal sent to a clinician or healthcare provider. The nanosensor can detect whether the cells are healthy, inflammatory, or contaminated with bacteria. [ 44 ] However, a main drawback is found within the long term use of the implant, where tissue grows on top of the sensors, limiting their ability to compress. This impedes the production of electrical charges, thus shortening the lifetime of these nanosensors, as they use the piezoelectric effect to self-power.
Similarly to those used to measure atmospheric pollutants, gold-particle based nanosensors are used to give an early diagnosis to several types of cancer by detecting volatile organic compounds (VOCs) in breath, as tumor growth is associated with peroxidation of the cell membrane. [ 45 ] Another cancer related application, though still in mice probing stage, is the use of peptide-coated nanoparticles as activity-based sensors to detect lung cancer. The two main advantages of the use of nanoparticles to detect diseases is that it allows early stage detection, as it can detect tumors the size in the order of millimeters. It also provides a cost-effective, easy-to-use, portable, and non-invasive diagnostic tool. [ 45 ] [ 46 ]
A recent effort towards advancement in nanosensor technology has employed molecular imprinting , which is a technique used to synthesize polymer matrices that act as a receptor in molecular recognition. Analogous to the enzyme-substrate lock and key model , molecular imprinting uses template molecules with functional monomers to form polymer matrices with specific shape corresponding to its target template molecules, thus increasing the selectivity and affinity of the matrices. This technique has enabled nanosensors to detect chemical species. In the field of biotechnology, molecularly imprinted polymers (MIP) are synthesized receptors that have shown promising, cost-effective alternatives to natural antibodies in that they are engineered to have high selectivity and affinity. For example, an experiment with MI sensor containing nanotips with non-conductive polyphenol nano-coating (PPn coating) showed selective detection of E7 protein and thus demonstrated potential use of these nanosensors in detection and diagnosis of human papillomavirus, other human pathogens, and toxins. [ 12 ] As shown above, nanosensors with molecular imprinting technique are capable of selectively detecting ultrasensitive chemical species in that by artificially modifying the polymer matrices, molecular imprinting increases the affinity and selectivity. [ 12 ] Although molecularly imprinted polymers provide advantages in selective molecular recognition of nanosensors, the technique itself is relatively recent and there still remains challenges such as attenuation signals, detection systems lacking effective transducers, and surfaces lacking efficient detection. Further investigation and research on the field of molecularly imprinted polymers is crucial for development of highly effective nanosensors. [ 47 ]
In order to develop smart health care with nanosensors, a network of nanosensors, often called nanonetwork, need to be established to overcome the size and power limitations of individual nanosensors. [ 48 ] Nanonetworks not only mitigates the existing challenges but also provides numerous improvements. Cell-level resolution of nanosensors will enable treatments to eliminate side effects, enable continuous monitoring and reporting of patients’ conditions.
Nanonetworks require further study in that nanosensors are different from traditional sensors. The most common mechanism of sensor networks are through electromagnetic communications. However, the current paradigm is not applicable to nanodevices due to their low range and power. Optical signal transduction has been suggested as an alternative to the classical electromagnetic telemetry and has monitoring applications in human bodies. Other suggested mechanisms include bioinspired molecular communications, wired and wireless active transport in molecular communications, Forster energy transfer, and more. It is crucial to build an efficient nanonetwork so that it can be applied in fields such as medical implants, body area networks (BAN), internet of nano things (IoNT), drug delivery and more. [ 49 ] With an adept nanonetwork, bio implantable nanodevices can provide higher accuracy, resolution, and safety compared to macroscale implants. Body area networks (BAN) enable sensors and actuators to collect physical and physiological data from the human body to better anticipate any diseases, which will thus facilitate the treatment. Potential applications of BAN include cardiovascular disease monitoring, insulin management, artificial vision and hearing, and hormonal therapy management. The Internet of Bio-Nano Things refers to networks of nanodevices that can be accessed by the internet. Development of IoBNT has paved the way to new treatments and diagnostic techniques. [ 50 ] Nanonetworks may also help drug delivery by increasing localization and circulation time of drugs. [ 48 ]
Existing challenges with the aforementioned applications include biocompatibility of the nano implants, physical limitations leading to lack of power and memory storage, and bio compatibility of the transmitter and receiver design of IoBNT. The nanonetwork concept has numerous areas for improvements: these include developing nanomachines , protocol stack issues, power provisioning techniques, and more. [ 48 ]
There are still stringent regulations in place for the development of standards for nanosensors to be used in the medical industry, due to insufficient knowledge of the adverse effects of nanosensors as well as potential cytotoxic effects of nanosensors. [ 51 ] Additionally, there can be a high cost of raw materials such as silicon, nanowires, and carbon nanotubes, which prevent commercialization and manufacturing of nanosensors requiring scale-up for implementation. To mitigate the drawback of cost, researchers are looking into manufacturing nanosensors made of more cost-effective materials. [ 26 ] There is also a high degree of precision needed to reproducibly manufacture nanosensors, due to their small size and sensitivity to different synthesis techniques, which creates additional technical challenges to be overcome. | https://en.wikipedia.org/wiki/Nanosensor |
Nanospheres are a type or class of nanostructure consisting of a solid core and matrix made from a polymeric material—both organic and inorganic are common. They are not necessarily spherical in shape. [ 1 ] In a nanoengineering context, they are generally divided into two categories: magnetic nanospherers and immune nanospheres, and can range from 10 to 200 nm in size. [ 2 ]
Magnetic nanospheres are mostly inorganic and can be manipulated easily using a magnetic field . For their mass, they have very high surface area and saturation magnetisation . This means they have the potential to be used in a variety of ways, including: ion exchange separation, drug delivery, targeted gene therapy , and magnetic resonance imaging . [ 3 ] They may be hollow and filled with molecules—such as anti- cancer drugs—for delivery, through a needle or otherwise, into the body. [ 4 ] This delivery method can avoid much more invasive surgery and pores in the nanospheres allow them to effectively deliver cells or act as a microreactor . [ 5 ]
Immune nanospheres are designed to induce an immune response —both adaptive and innate—by delivering specific nucleotides, such as CpG oligodeoxynucleotide , to the body. They may be designed to have enhanced dispersity and solubility . [ 6 ]
Nanospheres are found in the natural world, such as in the amelogenin proteins found in enamel in teeth and in photonic crystals found in some plants— edelweiss , for example. [ 7 ] [ 8 ] | https://en.wikipedia.org/wiki/Nanosphere |
Nanosubmarines , or nanosubs , are synthetic microscopic devices that can navigate and perform specific tasks within the human body. Most of the self-propelled devices will be used to detect substances, decontaminate the environment, perform targeted drug delivery , conduct microsurgery and destroy malicious cells. Nanosubmarines use a variety of methods to navigate through the body; currently the preferred method uses the electrochemical properties of molecules. There have been multiple successful tests using this technology to heal mice with inflammatory bowel diseases . The general goal of nanosubmarines is to be able to produce a machine which can sense and respond autonomously, all while being fueled by its environment. [ 1 ]
The main purpose of a nanosubmarine is to navigate the body and perform a specific task. The most speculated task is the treatment and diagnosis of diseases from within the body. [ 2 ] This is supported by the task of detecting substances, as most diseases cause a specific type of protein or other molecule to be made in abundance within the bloodstream . Another speculated task is microsurgery . With this technology, doctors will be able to perform surgery on specific locations from within the body. [ 1 ] One example of this could be a treatment for cancer . A nanosubmarine could be built to detect specific cancer cells within the body; after locating the cells, the nanosub would be able to kill only the mutated cells and ignore healthy cells. [ 3 ]
Navigation is one of the most difficult aspects to develop in nanosubmarines. The goal is to be able to travel throughout the bloodstream without getting stuck in even the smallest of capillaries . However, this is difficult because the smallest capillaries are 2 μm across (2.0 x 10 −6 m); blood cells are about 7μm but they are easily pliable and can squeeze through the capillaries. Another challenge with navigation is the fact that physics restricts the amount of propulsion such a small device can output. The blood flow is simply too strong for any device even compete with the flow, therefore the nanosubmarine would have to be carried by the blood. [ 4 ]
One form of propulsion nanosubmarines could use is electrochemical. One example of a motor is a nanorod which is platinum on one side and gold on the other. When submerged in hydrogen peroxide the platinum oxidizes the H 2 O 2 into 2H + and O 2 . This process occurs because platinum takes two electrons from the molecule. On the other side of the rod, the gold reduces hydrogen peroxide into water, in doing so an electron is pulled from the gold. This causes a steady electron flow from the platinum side of the rod towards the gold side. Since the rod is so small, Newton's third law of physics applies. For any action there is a reaction, when the electrons are pulled across the surface of the rod, so too is the rod pulled in the opposite direction. [ 1 ]
The first recorded success of a nanosubmarine was performed by a team of students led by Dan Peer from Tel Aviv University in Israel. This was a continuation to Peer's work at Harvard on nanosubmarines and targeted drug delivery. Tests have proven successful in delivering drugs to heal mice with ulcerative colitis . Tests will continue and the team plans to experiment on the human body soon. [ 5 ] | https://en.wikipedia.org/wiki/Nanosubmarine |
Nanotechnology education involves a multidisciplinary natural science education with courses such as physics , chemistry , mathematics , and molecular biology . [ 1 ] It is being offered by many universities around the world. The first program involving nanotechnology was offered by the University of Toronto 's Engineering Science program, where nanotechnology could be taken as an option.
Here is a partial list of universities offering nanotechnology education, and the degrees offered ( Bachelor of Science , Master of Science , or PhD in Nanotechnology).
Important:
A list of the master's programs is kept by the UK-based Institute of Nanotechnology in their Nano, Enabling, and Advanced Technologies (NEAT) Post-graduate Course Directory. [ 18 ]
In recent years, there has been a growing interest in introducing nanoscience and nanotechnology in grade schools, especially at the high school level. In the United States , although very few high schools officially offer a two-semester course in nanotechnology, “nano” concepts are bootstrapped and taught during traditional science classes using a number of educational resources and hands-on activities developed by dedicated non-profit organizations, such as:
In Egypt, in2nano is a high school outreach program aiming to increase scientific literacy and prepare students for the sweeping changes of nanotechnology. [ 96 ] | https://en.wikipedia.org/wiki/Nanotechnology_education |
Research has shown nanoparticles to be a groundbreaking tool for tackling many arising global issues, the agricultural industry being no exception. In general, a nanoparticle is defined as any particle where one characteristic dimension is 100 nm or less. [ 1 ] Because of their unique size, these particles begin to exhibit properties that their larger counterparts may not. Due to their scale, quantum mechanical interactions become more important than classic mechanical forces, allowing for the prevalence of unique physical and chemical properties due to their extremely high surface-to-body ratio. Properties such as cation exchange capacity , enhanced diffusion, ion adsorption , and complexation are enhanced when operating at nanoscale. [ 2 ]
This is primarily the consequence of a high proportion of atoms being present on the surface, with an increased proportion of sites operating at higher reactivities with respect to processes such as adsorption processes and electrochemical interactions. Nanoparticles are promising candidates for implementation in agriculture. Because many organic functions such as ion exchange and plant gene expression operate on small scales, nanomaterials offer a toolset that works at just the right scale to provide efficient, targeted delivery to living cells. [ 3 ] Current areas of focus of nanotechnology development in the agricultural industry include development of environmentally conscious nano fertilizers to provide efficient ion, and nutrient delivery into plant cells, and plant gene transformations to produce plants with desirable genes such as drought resistance and accelerated growth cycles. [ 2 ]
Nanotechnology in agriculture has been gaining traction due to the limitations that traditional farming methods impose at both the scientific and policy level. Nanotechnology aims to address productivity and mitigate damage on local ecosystems. [ 4 ] With the global population on the rise, it is necessary to make advancements in sustainable farming methods that generate higher yields in order to meet the rising food demand. Although there are seemingly numerous advantages in using nanotechnology in this sector, certain sustainability and ethical concerns around the topic cannot be ignored. The extent of their transport and interaction within their surrounding environments, as well as potential phytotoxicity and bioaccumulation of nanoparticles in food systems are not fully known. [ 5 ] Ethical considerations also arise when we consider public discourse and regulatory challenges. The accessibility and affordability of nanotechnology-based agricultural solutions could disproportionately benefit large-scale industrial farms, potentially widening socioeconomic disparities with smallholder and Indigenous farmers. Experts emphasize the need for low-cost, scalable innovations that make these technologies accessible to diverse farming communities. [ 5 ]
There are multiple properties of nanoparticles that make them effective and sought after for agricultural applications. Their small size, high surface area, and tunable surface chemistry allow for improved efficiency in nutrient delivery, pest control, and environmental remediation. A high surface-to-volume ratio allows for enhanced reactivity, solubility, and absorption, which are key to a thriving agricultural industry. These properties specifically allow for increased nutrient uptake & enhanced plant cell penetration. [ 6 ]
These nanomaterials can be made from a variety of chemical structures, with the most prominent being various metal oxides, carbon-based nanomaterials, and organic nanoparticles. Iron is an essential micronutrient, playing a role in chlorophyll synthesis, electron transport, and enzyme activation, and a deficiency can lead to reduced growth and crop yields. [ 7 ] Iron oxide (Fe 3 O 4 ) nanoparticles have been shown to improve seed germination, enhancing shoot and root development more than traditional iron supplements do. [ 8 ] One example shows these particles increasing rice plant growth by enhancing iron bioavailability, as these nanoparticles are soil stable and penetrate root epidermal cells, ensuring sufficient nutrient transport to other parts of the plant. [ 9 ] Other elements, such as silver (Ag) and Copper (Cu), are becoming popular because of their antifungal and antimicrobial properties, making them useful in terms of disease and pest prevention. [ 10 ] Specifically, the release of silver ions disrupts bacterial and fungal cell membranes that prevents diseases like powdery mildew , bacterial blight , and leaf spot . [ 11 ] Nanoparticles can also be chemically modified to control properties like solubility. Chitosan or other polymer coatings have been shown to improve biodegradability and nutrient release, [ 12 ] and one study shows Chitosan-coated zinc nanoparticles extend the release of zinc, reducing soil toxicity and preventing its over-accumulation in plants. [ 13 ]
At the nanoscale, quantum confinement effects alter electronic, optical, and chemical properties, which allow nanomaterials to be tailored to specific agricultural applications, particularly in crop protection, light absorption, and antimicrobial activity. For example, silver nanoparticles are known to absorb UV light , a useful property for antimicrobial crop coatings. [ 11 ] They can also scatter and reflect excess UV radiation, which has been shown to reduce sunburn damage to crops like tomatoes and grapes. [ 5 ] Studies have also shown that silver nanoparticle sprays have reduced fungal infections in wheat crops while maintaining low toxicity to beneficial soil microbes. [ 8 ] Zinc oxide nanoparticles have a wide bandgap of 3.37 eV, which allows them to regulate photosynthetic activity by enhancing light absorption and electron transport, as well as increasing chlorophyll content. [ 9 ]
The environmental stability and degradability of these materials is a key component of what makes them so desirable for these applications. These properties are influenced by a variety of factors, including chemical composition, surface modification, and interactions with soil pH and organic matter. Understanding these interactions is crucial for noting pollution control and long-term environmental impact. As for chemical composition and solubility, metal-based particles can dissolve, releasing ions influencing soil and microbial activity, [ 5 ] while carbon-based nanomaterials have been shown to absorb heavy metals from contaminated environments and resist degradation for much longer. [ 10 ] Polymers such as chitosan or polyethylene glycol are used in coatings to increase water dispersion and prevent particle aggregation, [ 12 ] while being selective with functional groups can enhance contaminant absorption. [ 14 ] Nanoparticles can interact with substances like clay minerals, organic matter, and soil microbes, influencing their mobility and availability for plant uptake, while higher organic matter content enhances stability by reducing aggregation and sedimentation [ 8 ] [ 9 ] .
Soil remediation is one of the biggest sought-after benefits of utilizing nanoparticles in agriculture. The most promising materials include carbon-based nanomaterials and nano-clay materials, all of which exhibit high reactivity and selective adsorption capabilities. The molecular structure of graphene oxide and carbon nanotubes allows capture of metal ions due to high surface areas and strong absorption capacities. Activated carbon-based nanocomposites have been shown to remove up to 90% of heavy metal cadmium ions from water in a short time span of a few hours. [ 6 ] [ 15 ]
Nano-clay materials, such as montmorillonite -based nanoclays, trap pesticide residues, preventing them from leaching into water sources and maintaining soil fertility. By modifying their surface chemistry, nanoclays retain other harmful chemicals, mitigating impact on surrounding ecosystems. One practical application involves clay-polymer nanocomposites , which have been deployed in farmland runoff control to reduce pesticide and herbicide contamination, protecting nearby water bodies from exposure. [ 16 ] [ 17 ] These aforementioned properties are essential for agricultural applications—nanotechnology has been applied to create nanofertilizers, nanopesticides, and nanosensors, reducing excess waste, remediating soil conditions, and providing targeted nutrient uptake, reducing toxic conditions.
One area of active research in this field is the use of nanofertilizers. Because of the aforementioned special properties of nanoparticles, nanofertilizers can be tuned to have specialized delivery to plants. Conventional fertilizers can be dangerous to the environment because of the sheer amount of runoff that stems from their use. [ 18 ] Having a detrimental effect on everything from water quality to air particulate matter, being able to negate runoff from agriculture is extremely important for improving quality of life around the world for millions. For example, runoff from sugar plantations in Florida has spawned the infamous algae bloom called "red tide" in water tributaries across the state, creating respiratory issues in humans and killing vital ecosystems for years. [ 19 ]
Nanofertilizers deliver nutrients more efficiently than conventional fertilizers by increasing plant bioavailability and reducing leaching into water systems, [ 20 ] and their small-scale size allows them to pass through plant cell walls for nutrient transport. [ 21 ] For example, silica (SiO 2 ) nanoparticles bind to soil, allowing retention of essential root macronutrients and water retention such as Nitrogen (N), Phosphorus (P), and Potassium (K) for longer periods of time. [ 22 ]
Studies have shown that, in most cases, greater than 50% of the amount of fertilizer applied to soil is lost to the environment, in some cases up to 90%. [ 23 ] As mentioned before, this poses extremely negative environmental implications, while also demonstrating the high waste associated with conventional fertilizers. On the other hand, nanofertilizers are able to amend this issue because of their high absorption efficiency into the targeted plant- which is owed to their remarkably high surface area to volume ratios. In a study done on the use of phosphorus nano-fertilizers, absorption efficiencies of up to 90.6% were achieved, making them a highly desirable fertilizer material. [ 24 ] Another beneficial aspect of using nanofertilizers is the ability to provide slow release of nutrients into the plant over a 40-50 day time period, rather than the 4-10 day period of conventional fertilizers. [ 23 ] This again proves to be beneficial economically, requiring less resources to be devoted to fertilizer transport, and less amount of total fertilizer needed.
As expected with greater ability for nutrient uptake, crops have been found to exhibit greater health when using nanofertilizers over conventional ones. One study analyzed the effect of a potato-specific nano fertilizer composed of a variety of elements including K , P , N , and Mg , in comparison to a control group using their conventional counterparts. The study found that the potato crop which used the nano-fertilizer had an increased crop yield in comparison to the control, as well as more efficient water use and agronomic efficiency, defined as units of yield increased per unit of nutrient applied. In addition, the study found that the nano fertilized potatoes had a higher nutrient content, such as increased starch and ascorbic acid content. [ 25 ] Another study analyzed the use of iron-based nanofertilizers in black eyed peas , and determined that root stability increased dramatically in the use of nano fertilizer, as well as chlorophyll content in leaves, thus improving photosynthesis. [ 26 ] A different study found that zinc nanofertilizers enhanced photosynthesis rate in maize crops, measured through soluble carbohydrate concentration, likely as a result of the role of zinc in the photosynthesis process. [ 27 ]
Much work needs to be done in the future to make nanofertilizers a consistent, viable alternative to conventional fertilizers. Effective legislation needs to be drafted regulating the use of nanofertilizers, drafting standards for consistent quality and targeted release of nutrients. [ 28 ] Further, more studies need to be done to understand the full benefits and potential downsides of nanofertilizers, to gain the full picture in approach of using nanotechnology to benefit agriculture in an ever-changing world.
Nanopesticides are viewed as being more effective than conventional pesticides, aiming for targeted pest control and chemical delivery while reducing the threat of environmental toxicity. Some nanopesticides utilize a controlled gradual release mechanism through nano-encapsulation, which means pesticides are delivered through a variety of nanocarriers. [ 29 ] This extends their effectiveness and reduces the amount of pesticide applications needed. One chitosan-based nano-encapsulated pesticide was able to be stabilized for several weeks, while maintaining efficacy against aphid infestation. [ 30 ] Traditional pesticides can often have adverse effects on wildlife, harming insects, birds, and other beneficial pollinators. [ 5 ] One solution has been to create pH-sensitive nanocarriers that remain inert in neutral environments, but activate in the alkaline bodies of pests. [ 31 ] Nanopesticides also aim to address the problem of chemical adhesion to plant surfaces. Hydrophobicity and degradation from sun and rain can cause runoff into soil and waterways. [ 32 ] Research has made advances in electrostatic attraction to plant cuticles, [ 22 ] deeper plant tissue penetration, [ 21 ] and hydrophilic formulations. [ 13 ]
Nanopesticides take on a variety of classifications based on chemical composition and their mode of action. Nano-encapsulated pesticides use nanocarriers such as polymers , liposomes , or metal-organic frameworks to carry active pesticides to plants, aiming for a slow and controlled release of these chemicals. [ 22 ] One neem oil chitosan-based formulation has increased bioactivity of botanical pesticides. [ 21 ] Nano-emulsions are classified as oil-in-water emulsions meant to improve solubility and stability, [ 6 ] with a highlight being a nano-emulsified azadirachtin defending against insecticidal activity more than traditional pesticide formulations. [ 9 ] Inorganic pesticides are known to show antimicrobial properties, with Zinc oxide nanoparticles showing promise in fungicidal activity against mainstream plant pathogens. [ 6 ]
Despite all the apparent benefits, there are no clear regulations set for nanopesticides, [ 33 ] and there is debate as to how silver and copper nanoparticle accumulation in soil and water can affect insect, aquatic, and microbial communities. [ 34 ] [ 22 ]
Nanosensors are new devices in precision agriculture , designed to monitor soil health, detect pathogens, optimize irrigation, and assess overall soil and plant conditions. They utilize nanomaterials to respond to environmental changes by detecting changes in nutrient levels, pH, and soil contaminants. Graphene-based nanosenors have been created to monitor nitrate and phosphate concentrations, [ 35 ] electrochemical sensors can measure heavy metal contamination, aiding in land remediation, [ 14 ] and Zinc oxide sensors track nitrogen deficiency in soil. [ 12 ] Other sensors have detected plant viruses and bacteria, such as Tobacco Mosaic Virus , Citrus Tristeza Virus , and Xylella fastidiosa , before symptoms appear. [ 36 ] [ 11 ]
A major concern in agricultural practices is water scarcity, and nanosensors hope to alleviate this by analyzing moisture levels in real-time. For example, Silicon-based nanosensors track water retention in soil, ensuring efficient irrigation and reducing water waste. [ 10 ] Silver-based systems have detected nitrates and heavy metals in irrigation water, [ 5 ] and hydrogel-embedded nanosensors are able to save water by adjusting release based on soil hydration levels. [ 37 ] They have also been used to detect ethylene, allowing for precision harvesting, [ 38 ] monitor photosynthesis rates, [ 39 ] and track plant stress signals in droughts or nutrient deficiencies. [ 40 ]
Nanosensors represent a significant advancement in the field of precision agriculture, and as the technology continues to evolve, they will play a vital role in enhancing productivity, although further research is needed to know the extent of long-term impacts on the ecosystem and farming practices. [ 8 ] Recent work also highlights how nanosensors can assist in real-time monitoring of crops by tracking environmental and biological changes as they occur. These insights support timely responses during cultivation, helping farmers protect yields and manage resources more efficiently. [ 41 ]
Nanotechnology has played a pivotal role in the field of genetic engineering and plant transformations, making it a desirable candidate in the optimization and manipulation of cultivated plants. In the past, most genetic modifications to plants have been done with Agrobacterium , or utilising tools such as the gene gun (biolistics); however, these older methods of gene implementation face roadblocks due to low species compatibility lack of versatility/compatibility with Chloroplastial/Mitochondrial gene transformations, and potential for cell or organelle damage (due to impact of biolistics). While biolistics and Agrobacterium are useful in specific species of plants- more refined approaches are being explored through the utilisation of nanomaterials- allowing for a less invasive and forced delivery approach. These methods utilise Carbon Nanotube (CNT) and various porous nanoparticle (NP) enabled delivery methods, which may allow for higher-throughput plant transformation- while also circumventing legal GMO restrictions. [ 42 ] The research of non-incorporative/DNA-Free genetic modifications has become a very important field of study, since traditional methods of plant transformation (agrobacterium and biolistics) risk DNA incorporation in the plant genome, thus making them transgenic and qualifying them as a GMO. [ 43 ]
A novel strategy utilizes highly-tailorable diffusion based nanocarriers for the delivery of genetic material, allowing for non-transgenic, non-destructive plant transformation. The method specificity is highly dependent on the properties of the material utilized, with key factors including size, polarity, and surface chemistry. Some approaches to diffusion based delivery have used Nano-Structured-DNA, [ 44 ] carbon nanotubes , [ 43 ] and other nanoparticles [ 45 ] as vesicles for the delivery of genetic information. . These methods typically rely on functionalization of the surface or manipulation of porosity of a nanocarrier in order to optimize the loading and delivery of genetic information. DNA nanostructures have been shown to be a highly programmable modality in terms of delivery of small interfering RNA (siRNA), exploring the optimal design parameters necessary for plant cell internalization. [ 44 ] A recent study utilizing DNA loaded CNTs was able to successfully express desired traits in various mature model plant systems- and even isolated Eruca sativa protoplasts while managing to protect and maintain the fidelity of the transferred genetic material. [ 43 ] Lastly, porous nanoparticles have been shown to be an effective DNA delivering agent for plant transformations- with efficiency depending on pore size and strand length. [ 45 ] All in all, these diffusion based gene transformation methodologies offer a cheaper mode of plant gene transformation with lower impact to plant tissue, lower transformation efficiencies, and little to no risk of DNA incorporation.
Biolistics is the primary approach to plant transformation. The biolistic process involves launching microprojectiles (usually gold microparticles) carrying genetic information through the cell walls and membranes of cells to impart genetic transformation. [ 42 ] As previously mentioned, biolistics may result in damaging the targeted cells or organelles- thus in order to minimize potential cell damage, nano-biolistic methods have been developed. Due to the significantly reduced size of the particle being launched into the cell, the impact can be minimized, while offering a similar efficiency of genetic transformation as traditional biolistics. However, most studies utilizing nanoscale biolistic approaches are done with animal cells, so implementation in plant transformation is still fairly novel and may encounter roadblocks unseen in animal cell studies. [ 46 ]
Overall, nanotechnology provides a novel and competitive approach to genetic transformation of plants. Going forward, future research into the applications of these approaches will span a greater variety of crops, aim to utilize cheaper, more scalable methods, and explore potential environmental effects. Ultimately, once these design criteria will determine whether nanomaterial plant transformations will become a widespread practice in the future of agriculture.
Some case studies celebrate the success of nanotechnology with its transformative potential to enhance farming practices, boost yields, reduce costs, and improve sustainability in certain regions of the world. In recent years, as applications of nanotechnology have exhibited promise in many fields of study, an increasing number of government, scientific, and independent institutional bodies have seen the potential of nanotechnology in making significant contributions to alleviating the burden of the global food supply . Current public views on nanotechnology development in the agricultural industry are mixed. [ 2 ] With consideration of the potential hazards in conjunction with the potential benefits, the current public opinion appears to be relatively neutral as critics see the technology as less risky, and more beneficial than a number of other technologies such as pesticides and chemical disinfectants; however, it is perceived as riskier and less beneficial than solar technologies and vaccinations. [ 47 ]
Despite potential publicized advantages for sustainability, the use of nanotechnology in agriculture raises concerns about environmental toxicity and bioaccumulation of particles in ecosystems. Among the general public, there still exists negative connotations related to fertilizers and genetic modification of living organisms. Concerns that despite the benefit of higher yields and shorter growing cycles, fertilizers are associated with toxic runoff that contaminate sources of water and can lead to the generation of acid rain. [ 48 ] Additionally, there exists the unfounded fear that consumption of genetically modified foods is 'unnatural' and dangerous , which has led to numerous legislative efforts- limiting the field to non-transgenic transformations. [ 2 ] While the majority of public fears and concerns are unfounded, it is more the result of poor communication and lack of public awareness related to the issue of introducing novel technology to a traditional industry such as agriculture. Ultimately the production of clean and healthy food is considered by many to be of high importance, simply due to the high frequency of consumption and intimate relation people have with the food they consume.
Concerns have also been raised about equitable access, cultural compatibility, and socioeconomic disparities, particularly in developing regions and in places still utilizing traditional and Indigenous farming practices. Arguments have been made that nanotechnology disproportionately favors large businesses over smaller farmers, widening the gap between industrial and traditional farming communities. [ 49 ] Accessibility concerns from the cost of nanotechnology products that could impact lower-income regions have also been raised. [ 50 ] Skepticism has been raised from Indigenous and traditional farming communities, due to the uncertainties about long-term effects on soil, water, and the ecosystem. [ 51 ] Addressing ethical considerations requires inclusive policymaking, transparent risk assessment, and equitable benefit distribution, preventing marginalization of certain agricultural communities. [ 52 ] | https://en.wikipedia.org/wiki/Nanotechnology_in_agriculture |
Nanomaterials are materials with a size ranging from 1 to 100 nm in at least one dimension. At the nanoscale , material properties become different. These unique properties can be exploited for a variety of applications, including the use of nanoparticles in skincare and cosmetics products .
Cosmeceuticals is one of the fastest growing industries in terms of personal care , accompanied by an increase in nano cosmeceuticals research and applications.
Sunscreens are utilized to secure the skin from the destructive impacts of ultraviolet radiation from the sun. UVB (290-320 nm) together with UVA-2 (320–340 nm) and UVA-1 (340–400 nm) cause organic and metabolic reactions in the skin. [ 1 ] [ 2 ] Titanium dioxide (TiO 2 ) and zinc oxide (ZnO) minerals are often utilized in sunscreens as inorganic physical sun blockers owing to their absorption of light in the UV range. As TiO 2 is proven to be more effective for blocking UVB and ZnO in the UVA range, the mix of these particles guarantees a broad-band UV shield. [ 3 ]
To solve the cosmetic disadvantage of these opaque sunscreens, TiO 2 and ZnO nanoparticles have been used as a replacement for TiO 2 and ZnO microparticles . Since the surface area to volume proportion of particles increases as the particle measurement diminishes, nanoparticles (NPs), ie, nano objects with all dimensions in the nanoscale, [ 4 ] might be increasingly (bio)reactive than typical mass materials. When particles become smaller than 100 nm, novel optical attributes develop, owing to discrete nature of nanoparticle optical energy levels. Pat et al., for instance, measured a 0.15 eV blue shift for 4.7 nm TiO 2 nanoparticles relative to the bulk material counterpart. [ 5 ]
When particles become smaller than the ideal light dispersing size (roughly half of the wavelength ) visible light is transmitted and the particles appear transparent. This phenomenon explains the cosmetically undesired opaqueness of inorganic sunscreens and makes the utilization of NPs monetarily appealing. ZnO particles of 200 nm or smaller are transparent to the human eye. [ 6 ]
TiO 2 NPs become more effective sunblocking materials due to their larger surface area to volume ratio. The purpose behind this is in direct-illegal gap semiconductors , for example, TiO 2 , direct electron transmissions are not allowed due to crystal symmetry . Absorption is subsequently small. However, it might be significantly upgraded when it happens at the precious crystal surface. This absorption upgrade gets significant for particles of 20 nm or smaller. [ 7 ] Similarly, TiO 2 becomes visibly transmissive when particle sizes are reduced to 10-20 nm in size.
The International Agency for Research on Cancer (IARC) has categorized TiO 2 as an IARC group 2B carcinogen . [ 8 ] [ 9 ] The IARC made these decisions based on studies where rats are exposed to high concentrations of pigment-grade and ultrafine TiO 2 dust. [ 10 ] The lung cancers in rats appear similar pathology to those seen in people who are working in a dusty environment, thus the IARC concluded that the same impacts from high concentrations of pigment-grade and ultrafine TiO 2 dust are relevant to human health.
However, ZnO is generally considered as safe a substance by the FDA when utilized as an UV filter as indicated by beauty care products directives. [ 10 ] Although both the US Environmental Protection Agency and the European Community (inside the Registration, Evaluation, Authorization and Restriction of Chemical Substances law) have taken preventative steps to reduce nanoparticle risk, there are still no standardized rule for nanoparticles specifically.
Liposomes are sphere-shaped vesicular structures self-assembled in a solvent composed of a broad type of lipids or other amphiphilic molecules. [ 11 ] [ 12 ] The vesicle structure of liposomes improves the effects on drug penetration through biological membranes, which enhance transdermal drug delivery. [ 13 ]
Source: [ 12 ]
The skin is the largest organ of the human body that restricts the movement of drug to the systemic circulation. The topical drug delivery system is a system where the drug reaches the systemic circulation through the protective skin layer. The main disadvantage of this route is the low diffusion rate of the drugs across the layer of skin which is the stratum corneum . To overcome this problem to a certain extent, ethosomes are used to enhance transdermal drug delivery systems. [ 15 ]
The utilization of gold in skin care and cosmetics dates back at least to the 1st century B.C in Egypt, where Queen Cleopatra is said to have used masks made from gold to maintain her skin complexion. [ 16 ] It was said that she used it every night to enhance her complexion and improve the suppleness of her skin. Nowadays, gold has made its way into various skincare products such as lotion and cream, as well as skincare treatments such as facial masks. Gold in skincare products are usually in the form of colloidal gold , or more commonly called nanogold. [ 17 ] These nanoparticles ranges in size from 5 nm to 400 nm. [ 18 ] This section will discuss about the effect of gold nanoparticle in wound healing application together with the effect of gold in lotion and cream products.
Gold nanoparticles usually have colors ranging from red to purple to blue and black depending on the size and aggregation state. [ 19 ] They also come in various shapes and sizes: nanosphere, nanoshell, nanocluster, nanorod, nanostar, nanocube, branched, and nanotriangle. [ 18 ] The shape of the gold nanoparticles is the main determinant for uptake into cells and for optical properties. Gold nanoparticles are stable and chemically inert. Moreover, they are also biocompatible, which is the main reason why nanogold is commonly integrated in skincare and cosmetics. [ 18 ] Furthermore, gold nanoparticles have been investigated for antifungal and antibacterial properties, which are very valuable properties in cosmeceutical industries and in wound healing applications. [ 20 ]
In 2016, a paper published in the Journal of Biomaterials Application , titled "Collagen/gold nanoparticle composites: A potential skin wound healing biomaterial," discussed that in vivo studies of gold nanoparticle and collagen composites demonstrated high wound closure percentage, reduced inflammatory response, increased neovascularization , and granulation tissue formation. [ 20 ] It was also shown that these improvements in healing effects increase proportionally with the amount of gold nanoparticles worked into the collagen scaffold.
In another study, the effect of spherical gold nanoparticles as a wound healing agent was tested in rat model by coupling gold nanoparticles with photobiomodulation therapy (PBMT). PBMT is a light stimulated therapy that is used for wound healing treatment without any significant temperature changes. [ 21 ] The coupling of gold nanoparticles and PBMT increase the wound contraction rate by approximately 1.25 times than the control group that received no gold. nanoparticle treatment. [ 21 ]
Gold has been widely used in facial masks. Aside from its antifungal and antibacterial properties, gold is also known to have anti-ageing benefits, anti-inflammatory properties as well as radiance-boosting qualities. [ 22 ] Gold nanoparticles can help repair skin damage and improve skin texture which improves skin elasticity and suppleness. Its anti-inflammatory properties makes it an excellent agent for treating acne , sun-damaged, and or sensitive skin .
Furthermore, due to gold's natural light-reflecting color, gold nanoparticle can also create a brightening effect by making skin radiant and luminous. Over the course of the treatment, gold nanoparticle can make the skin appear smoother and even in color. [ 22 ] A study in 2010 titled, "Novel Vitamin and Gold-Loaded Nanofiber Facial Mask for Topical Delivery" investigated how gold nanoparticle can be incorporated to facial mask along with Vitamin C (L-ascorbic acid), retinoic acid , and collagen using electrospinning . [ 23 ] All of these properties and studies have suggested that gold nanoparticles can be beneficial when included in cream, lotion, or mask formulations for topical applications. | https://en.wikipedia.org/wiki/Nanotechnology_in_cosmetics |
The use of nanotechnology in fiction has attracted scholarly attention. [ 1 ] [ 2 ] [ 3 ] [ 4 ] The first use of the distinguishing concepts of nanotechnology was " There's Plenty of Room at the Bottom ", a talk given by physicist Richard Feynman in 1959. K. Eric Drexler 's 1986 book Engines of Creation introduced the general public to the concept of nanotechnology. Since then, nanotechnology has been used frequently in a diverse range of fiction, often as a justification for unusual or far-fetched occurrences featured in speculative fiction . [ 5 ]
In 1931, Boris Zhitkov wrote a short story titled "Microhands" ( Микроруки ), where the narrator builds for himself a pair of microscopic remote manipulators and uses them for fine tasks like eye surgery . When he attempts to build even smaller manipulators operated by the first pair, the story goes into detail about the problem of regular materials behaving differently on a microscopic scale.
In his 1956 short story titled " The Next Tenants " , Arthur C. Clarke describes tiny machines that operate at the micrometer scale – although not strictly nanoscale ("billionth of a meter"), they are perhaps the first fictional example of the concepts now associated with nanotechnology.
A concept similar to nanotechnology, called "micromechanical devices," was described in Stanislaw Lem 's 1959 novel Eden . These devices were used by the aliens as "seeds" to grow a wall around the human spaceship. [ 6 ] Lem's 1964 novel The Invincible involves the discovery of an artificial ecosystem of minuscule robots, although like in Clarke's story they are larger than what is strictly meant by the term 'nanotechnology'.
Robert Silverberg 's 1969 short story How It Was when the Past Went Away describes nanotechnology [ clarification needed ] being used in the construction of stereo loudspeakers, with a thousand speakers per inch. [ 5 ]
The 1984 novel Peace on Earth by Stanislaw Lem tells about small bacteria-sized nanorobots that look like normal dust (developed by artificial intelligence placed by humans on the Moon in the era of cold warfare) that later come to Earth and are begin replicating, destroying all weapons, modern technology and software, while leaving living organisms (as there were no living organisms on the Moon) intact.
The 1985 novel Blood Music by Greg Bear (originally a 1983 short story) features genetically engineered white blood cells that eventually learn to manipulate matter on an atomic scale.
The 1991 novelization of Terminator 2: Judgment Day , authored by Randall Frakes , expands the origin story of the T-1000 Terminator through the inclusion of a prologue set in the future. It is explained that the T-1000 is a 'Nanomorph', created by Skynet , through the use of programmable nanotechnology. This was only implied in the film itself.
The 1992 novel Assemblers of Infinity is a science-fiction novel authored by Kevin J. Anderson and Doug Beason. The plot line makes specific mention of nano-assembly and nano-disassembly robots, along with admonitions regarding the dangers that these bacteria-sized machines might pose.
In Kim Stanley Robinson 's Red Mars (1992), the extraordinary tensile strength of carbon nanotubes is used to create a tether for a space elevator , which connects Mars to an asteroid that has been led into orbit around the planet. The space elevator speeds travel of people and materials between Earth and Mars, but also creates tension between factions — and is later destroyed.
Neal Stephenson 's 1995 novel The Diamond Age is set in a world where nanotechnology is commonplace. Nanoscale warfare, fabrication at the molecular scale, and self-assembling islands all exist.
The morphing technology in Animorphs is described as a form of nanotechnology that allows its users to transform into other animal and alien species, as well as members of their own species.
The Trinity Blood series published 2001-2004features an alien nanomachine found on Mars that is present in the body of the protagonist, Abel Nightroad. These nanomachines are known as Krusnik nanomachines, and feed on the cells of vampires.
Nanobots (called Nanoes) are central to Stel Pavlou 's novel Decipher (2001).
Michael Crichton 's novel Prey (2002) is a cautionary tale about the possible risks of developing nanotechnology. [ 7 ] In Prey , a swarm of molecule-sized nanorobots develops intelligence and becomes a large scale threat.
The 2003 Dean Koontz novel By the Light of the Moon features characters injected with nanotechology against their will by an unscrupulous research scientist.
Robert Ludlum 's 2005 novel The Lazarus Vendetta also focuses on nanotechnology, particularly its ability to cure cancer.
The 2006 children's novel The Doomsday Dust (book 4 in the Spy Gear Adventures series by Rick Barba) features a nanite swarm as the villain.
A nanomorph, a term first coined by science fiction writer David Pulver in 1986's GURPS Robots , is a fictional robot entirely made of nanomachines . Its brain is distributed throughout its whole body, which also acts as an all-around sensor, making it impossible to surprise as long as the target is in line of sight. A nanomorph is arguably the robotic ultimate in versatility, maybe even in power. [ citation needed ] Further uses of the concept could include using parts of its body as a tracking to perform several tasks, or merging with another nanomorphs to form a greater one, or gliding/flying like an ornithopter (by molding itself into a giant, articulated kite ). A common improvement is the ability to cover itself with specific colors and textures in a realistic manner (the ultimate being to look like a human, à la doppelgänger ).
In the Expanse series, the protomolecule was created by a race of ancient aliens and sent to star systems across the galaxy to terraform planets into habitable worlds and develop a gateway network to facilitate interstellar travel. The protomolecule could consume biomass and technology and use them to serve various functions. Numerous violent conflicts occurred between factions of humanity, notably the United Nations, Martian Congressional Republic, Outer Planets Alliance, and Laconian Empire, for control of this technology.
Rudy Rucker 's 2007 novel Postsingular depicts the protagonists' experiences with three generations of swarm nanorobots: "nants", initially tasked with consuming the Earth and Moon (including organic life) to create a virtual Earth before being reversed; "orphids", tasked with a more ubiquitous and assistive role in augmenting reality , interfacing with human thought and even enabling interdimensional travel; and "silps", which accomplish the Singularity by replacing the previous generations of nanorobots and enable organic beings and inorganic material on Earth to express sentient, intelligible thought to each other. Rucker's 2009 sequel Hylozoic continues the protagonists' experiences with silps after the Singularity as they enable interstellar and interdimensional travel and communication with Earth by extraterrestrial beings who have already experienced similar Singularities themselves.
One of the first mentions on a television show was an announcement to students over the school loudspeakers in the 1987 Max Headroom episode, " Academy " that, "Nanotechnology pod test results are posted in the Submicron Lab for your viewing."
The anime series Ghost in the Shell: Stand Alone Complex employs a plotline heavily involved in the use of "micromachines" as a form of treatment against complex diseases after a subject undergoing cyberisation.
In the Star Trek universe, from Star Trek: The Next Generation onward, the Borg use nanomachines, referred to as nanoprobes , to assimilate individuals into their collective. In another episode, an experiment by Wesley Crusher gone awry led to nanites developing a collective intelligence and interfering with ship systems, eventually being deposited on a planet to establish their own civilization.
On the television show Red Dwarf , nanobots played a notable role in series VII to IX. Nanobots are nanotechnology created to be a self-repair system for androids like Kryten as they can also change anything into anything else. Kryten's nanobots grow bored of their duties and take over the ship Red Dwarf , leaving the crew to try and recapture it aboard the smaller Starbug . In the end the ship they are chasing is actually a smaller Red Dwarf built by the nanobots (which evaded their scanners in the end by coming aboard Starbug ), with the rest being changed into a planet. Once the crew discover this and find the nanobots, they force them to rebuild Red Dwarf (as well as Dave Lister 's then-missing arm). In the end the nanobots build an enhanced Red Dwarf based on the original design plans. They also resurrect the original full crew killed in the first episode .
The episode The New Breed of the show Outer Limits featured nanobots.
Nanobots were also featured during the Sci-Fi Channel era of Mystery Science Theater 3000 , where they were known as "nanites". They were depicted on the show as microscopic, bug-like, freestanding robots with distinct personalities.
Nanotechnology appeared several times in the TV series Stargate SG-1 and Stargate Atlantis , in the form of the replicators and the Asurans , respectively. A "nanovirus" is also seen in Stargate Atlantis .
In Cowboy Bebop: The Movie (2001), a criminal blows up a tanker trunk containing a nanobot virus that instantly kills thousands.
In the 2003 film Agent Cody Banks , a scientist creates nanobots programmed to clean up oil spills.
In the 2004 film I, Robot , nanites are used to wipe out artificial intelligence in the event of a malfunction and are depicted as a liquid containing tiny silver objects.
In the 2005 Doctor Who television episode " The Empty Child / The Doctor Dances " a metal cylinder falls from space and lands in World War II -era London , releasing nanobots which transform every human they come into contact with into gas mask -wearing zombies, like the first human they encountered, a gas mask-wearing child.
In the 2008 film The Day the Earth Stood Still , the alien robot "GORT" disintegrates into a swarm of self-replicating nanobots shaped like bugs that cover Earth and destroy all humans and artificial structures by seemingly devouring them within seconds.
The revamped Knight Rider television series and TV movie incorporate nanotechnology into the Knight Industries Three Thousand (KITT), allowing it to change color and shape, as well as providing abilities such as self-regeneration.
In the 2009 film G.I. Joe: The Rise of Cobra , the main plot is to save the world from a warhead containing deadly nanobots called the "Nanomites", which if detonated over a city could destroy it in hours.
The popular NBC science fiction show, Revolution , is based on a worldwide blackout due to the manipulation of nanotechnology.
In 2010 Generator Rex was shown on Cartoon Network. It was based on a laboratory experiment going wrong and infecting the world with bad "Nanites" which turned people into monsters known as E.V.Os.
In the Ben 10 series, there is a nanotechnology-based alien species called Nanochips, who first appeared in the live-action movie Ben 10: Alien Swarm .
Nanotechnology is featured heavily within the Terminator film series. The 1991 film Terminator 2: Judgment Day and 2015 film Terminator: Genisys feature the T-1000 terminator. The T-1000 is composed of Mimetic Polyalloy, a liquid metal that utilizes nanites for shapeshifting abilities; Giving the T-1000 the ability to mimic anyone it samples through physical contact. It can also form its arms into blades and stabbing weapons and instantly recover from any damage. In the 2003 film Terminator 3: Rise of the Machines a new terminator, the T-X , also utilities Mimetic Polyalloy for shapeshifting abilities; like the T-1000 it can mimic anyone it touches. The T-X is also equipped with nanotechnological transjectors, and can infect and control other machines using nanites.
In Terminator Genisys , human resistance leader John Connor is infected with "machine phase matter" by a T-5000 terminator, transforming John into a " T-3000 ". The T-3000, like the T-1000 and T-X units, has shapeshifting and replication abilities. This unit's deadly structure gives the T-3000 the unique ability to instantly scatter into particles and then quickly reform to avoid harmful impact as well as instantly recovering from damage.
In the 2014 film Transcendence , the uploaded consciousness of Will Caster (Johnny Depp) uses nanotechnology to turn himself, and the local townsfolk, into a self-healing defense force with superhuman strength.
In Venture Brothers Season 6 Episode 3 " Faking Miracles " a laboratory accident leads nanobots to enter Dean Venture's body. Billy Quizboy and Peter White take remote control of the nanobots, inadvertently torturing Dean to showcase the power of the nanobots to Dr. Venture. Eventually they are used, unbeknownst to Dean, to improve his intelligence so that he can pass an entrance examination for college. In the post-credit scene Dean painfully urinates them out like a set of kidney stones.
Nanotechnology is featured in the Marvel Cinematic Universe (MCU):
In PlanetSide and PlanetSide 2 , nanites are used to fabricate weapons, vehicles, structures, equipment, and even resurrect human bodies. The development of rebirthing technology has allowed soldiers achieve immortality by downloading their consciousness into a new body composed entirely of nanites.
In Rise of the Robots and Rise 2: Resurrection , A nanomorth features a gynoid known as the Supervisor which composed of Chromium element, a liquid metal that utilizes nanites for shapeshifting abilities and a hive mind constructed from trillions of nanobots in a sealed central chamber within Metropolis 4 . Due to the corruption of the EGO virus which infect the Supervisor, she now controls the Electrocorp and all other machines in Metropolis 4.
In Total Annihilation nanobots are used to build structures and units.
In some games of the Mortal Kombat series, the character Smoke is a cloud of nanobots.
In System Shock 2 (1999), "nanites" are used as currency as well as a type of weapon ammo.
In Deus Ex (2000), nanotechnology is an important part of both the plot and game mechanics. A very dangerous technology in the wrong hands, it provides a number of superhuman abilities to the protagonist along with novel approaches to weaponry such as the coveted Dragon's Tooth Sword.
The MMORPG Anarchy Online (launched 2001) is set on a planet with well-developed nanotechnology, which generally is used as magic in fantasy-themed games.
In Metal Gear Solid (1998) the protagonist got nanomachines to supply and administer adrenalin, nutrients, sugar, nootropics, and benzedrine and to recharge a Codec's battery. The protagonist of Metal Gear Solid 2 (2001) had artificial blood infused with nanomachine that served functions such as healing. Metal Gear Solid 4 (2008) featured a great deal of nanotechnology, such as the Sons of the Patriots, an artificial intelligence/nanomachine network that regulated and enhanced the actions of every lawful combatant in the world. In Metal Gear Rising Revengeance (2013) the main antagonist Senator Armstrong also augments himself with nanotechnology.
In Red Faction (2001), nanotechnology is used on Mars to control miners, and Red Faction Guerilla (2009) features nanotechnology, in particular a device called the Nano Forge, as a major plot point.
The computer game Hostile Waters features a narrative involving nanotech assemblers.
In the Ratchet & Clank series, the health system involves nanotechnology. The nanotech can be upgraded by purchase in the first game, or by defeating enemies in other games of the series.
Nanotechnology is also found in Crysis (2007), Crysis 2 (2011), and Crysis 3 (2013). The protagonists of these games are equipped with a "Nano Suit", which enables them to become stronger, invisible, heavily armored, etc.
In Marvel: Ultimate Alliance 2 (2009), Reed Richards creates nanites that are meant to control the minds of supervillains. However, the nanites evolve into a group mind called the Fold which serves as the primary antagonist for the game.
In SpaceChem the player has to build molecular assembler/disassemblers using nanomachines called "Waldos" controlled by a visual programming language .
The Distant Stars expansion for Stellaris heavily features nanotechnology in many aspects.
In the 2022 third-person shooter action role-playing video game for mobile Goddess of Victory: Nikke features the titular character's biological brains in game are flooded with nanomachines referred to as NIMPH ( N euro- I mplanted M achine for the P rotection of H umans), which manipulate the synaptic connections of neurons to control the Nikke's memories. These are employed to erase familial memories to ensure they are made into ideal obedient humanoid weapons, not bound by human attachments. [ 8 ] The NIMPHs are also utilized as a fetter to have codes that prevent them from disobeying humans as well as attacking them. [ 9 ]
In the manga series Battle Angel Alita: Last Order , nanotechnology is referenced numerously and its use is heavily restricted, owing to the loss of Mercury as a potential planetary colony due to a grey goo catastrophe. Its danger and control has become one of the main driving narratives in the story.
In Dx13: Nano A Mano [ 10 ] - a manga series by Kirupagaren Kanni - the protagonist uses nanobots to create a giant mecha , which is remotely controlled by custom-built equipment such as electronic glove, microphones, cameras, etc.
Nanomites appear in the G.I. Joe Reinstated series published by Devil's Due.
In the anime and manga series Black Cat , Eve has the ability to manipulate nanomachines. Nanobots are later used for a variety of purposes, from turning victims into berserk warriors to granting Creed Diskenth immortality.
In the anime and manga series To Love-Ru , the Transformation Weapons Golden Darkness and Mea Kurosaki have nanomachines within them, in the same manner as Eve from Black Cat.
In the anime and manga series Project ARMS , the ARMS are weapons made from many nanomachines imbued into compatible biological beings, granting them a great variety of combative abilities and regeneration. The four protagonists each have an ARMS that have artificial intelligence, but the Keith series and the modulated ARMS do not.
In the LEGO franchise BIONICLE , it is eventually revealed that all characters from the 2001–2008 storyline are biomechanical nanobots (though roughly human-sized, given the size of the gigantic robot they inhabit (12,192 km tall)).
One of the earliest appearances of nanotech in comics was the Technovore from Iron Man 294 (July 1993).
In several X-Men storylines, nano- sentinels appear, either used to modify human beings into Prime Sentinels (including the character Fantomex ), or to infect mutants and attack their cells. | https://en.wikipedia.org/wiki/Nanotechnology_in_fiction |
Nanotechnology in warfare is a branch of nano-science in which molecular systems are designed, produced and created to fit a nano-scale (1-100 nm). [ 1 ] The application of such technology, specifically in the area of warfare and defence, has paved the way for future research in the context of weaponisation. Nanotechnology unites a variety of scientific fields including material science, chemistry, physics, biology and engineering. [ 2 ] [ 3 ]
Advancements in this area, have led to categorized development of such nano-weapons with classifications varying from; small robotic machines, hyper-reactive explosives, and electromagnetic super-materials. [ 4 ] With this technological growth, has emerged implications of associated risks and repercussions, as well as regulation to combat these effects. These impacts give rise to issues concerning global security, the safety of society, and the environment. Nanotechnology has the ability to dramatically escalate the destructive capacity of preexisting weaponry. Legislation may need to be constantly monitored to keep up with the dynamic growth and development of nano-science, due to the potential benefits or dangers of its use. Anticipation of such impacts through regulation, would 'prevent irreversible damages' of implementing defence related nanotechnology in warfare. [ 5 ]
Historical use of nanotechnology in the area of warfare and defence has been rapid and expansive. Over the past two decades, numerous countries have funded military applications of this technology including; China, United Kingdom, Russia, and most notably the United States. The US government has been considered a national leader of research and development in this area, however now rivalled by international competition as appreciation of nanotechnology's eminence increases. [ 6 ] Therefore, the growth of this area in the use of its power has a dominant platform in the front line of military interests.
In 2000, the United States government developed a National Nanotechnology Initiative to focus funding towards the development of nano-science and its technology, with a heavy focus on utilizing the potential of nano-weapons . This initial US proposal has now grown to coordinate application of nanotechnology in numerous defence programs, as well as all military factions including Air Force, Army and Navy. From the financial year 2001 through to 2014, the US government contributed around $19.4 billion to nano-science, moreover the development and manufacturing of nano-weapons for military defence. [ 7 ] The 21st Century Nanotechnology Research and Development Act (2003), envisions the United States continuing its leadership in the field of nanotechnology through national collaboration, productivity and competitiveness, to maintain this dominance. [ 8 ]
Successful transitions of nanotechnology into defence products: [ 9 ]
The United States government has had military purposed development of nanotechnology at the forefront of its national budget and policy throughout the Clinton and Bush administrations, with the Department of Defense planning to continue with this priority throughout the 21st century. [ 10 ] In response to America's assertive public funding of defence purposed nanotechnology, numerous global actors have since created similar programmes.
In the sub-category of nano materials, China secures second place behind the United States in the amount of research publications they have released. [ 11 ] Conjecture stands over the purpose of China's quick development to rival the U.S., with 1/5 of their government budget spent on research (US$337million). [ 12 ] In 2018, Tsinghua University, Beijing, released their findings where they have enhanced carbon nanotubes to now withstand the weight of over 800 tonnes, requiring just 1 c m 3 {\displaystyle cm^{3}} of material. [ 13 ] The scientific nanotechnology team hinted at aerospace, and armour boosting applications, showing promise for defence related nano-weapons. [ 14 ] The Chinese Academy of Science 's Vice President Chunli Bai, has stated the need to focus on closing the gap between "basic research and application," [ 15 ] in order for China to advance its global competitiveness in nanotechnology.
Between 2001 and 2004, approximately 60 countries globally implemented national nanotechnology programmes. According to R.D Shelton, an international technology assessor, research and development in this area "has now become a socio-economic target...an area of intense international collaboration and competition." [ 16 ] As of 2017, data showed 4725 patents published in USPTO by the USA alone, maintaining their position as a leader in nanotechnology for over 20 years. [ 17 ]
Most recent research into military nanotechnological weapons includes production of defensive military apparatus, with objectives of enhancing existing designs of lightweight, flexible and durable materials. These innovative designs are equipped with features to also enhance offensive strategy through sensing devices and manipulation of electromechanical properties.
The Institute for Soldier Nanotechnologies (ISN), deriving from a partnership between the United States Army and MIT , provided an opportunity to focus funding and research activities purely on developing armour to increase soldier survival. Each of seven teams produces innovative enhancements for different aspects of a future U.S. soldier bodysuit. These additional characteristics include energy-absorbing material protecting from blasts or ammunition shocks, engineered sensors to detect chemicals and toxins, as well as built in nano devices to identify personal medical issues such as haemorrhages and fractures. [ 18 ] This suit would be made possible with advanced nano-materials such as carbon nanotubes woven into fibres, allowing strengthened structural capacities and flexibility, however preparation becomes an issue due to inability to use automated manufacturing. [ 19 ]
With the use of nanoparticles, it is evidently possibly to procure "invisible" suits for soldiers that will act as the ultimate camouflage. This possibility is rooted from the fact that objects are only visible due to how light reflects off of them. Therefore, if the particle is smaller than the wavelength of the light, it is not visible. Visible light wavelengths fall within the range of 300-700 nanometers. In order to achieve this invisible cloak, the particles that make up the suit should be varying in size. Another approach for concealment includes cloaks that act as a chameleon. Instead of being completely invisible, this nanoparticle coated cloak adapts to any colors surrounding it in order to blend in. [ 20 ]
Creation of sol-gel ceramic coatings has protected metals from; wear, fractures and moisture, allowing adjustability to numerous shapes and sizes, as well as aiding "materials that cannot withstand high temperature". [ 21 ] Current research focuses on resolving durability issues, where stress cracks between the coating and material set limitations on its use and longevity. The drive for this research is finding more efficient and cost effective uses in application of nanotechnology for Airforce and Navy military groups. Integration of fibre-reinforced nano-materials in structural features, such as missile casings, can limit overheating, increase reliability, strength and ductility of the materials used for such nanotechnology. [ 22 ]
Nanotechnology designed for advanced communication is expected to equip soldiers and vehicles with micro antenna rays, tags for remote identification, acoustic arrays, micro GPS receivers and wireless communication. [ 23 ] Nanotech facilitates easier defence related communications due to lower energy consumption, light weight, efficiency of power, as well as smaller and cheaper to manufacture. [ 24 ] Specific military uses of this technology include aerospace applications such as; solid oxide fuel cells to provide three times the energy, surveillance cameras on microchips, performance monitors, and cameras as light as 18g. [ 25 ]
The United States, along with countries such as Russia and Germany, are sing the convenience of small nanotechnologies, adhering it to nuclear "mini-nuke" explosive devices. [ 26 ] This weapon would weigh 5 lbs, with the force of 100 tonnes of TNT, [ 27 ] [ better source needed ] giving it the possibility to annihilate and threaten humanity. The structural integrity would remain the same as nuclear bombs , however manufactured with nano-materials to allow production to a smaller scale. [ 28 ]
Engineers and scientists alike, realise some of these proposed developments may not be feasible within the next two decades as more research needs to be undertaken, improving models to be quicker and more efficient. Particularly molecular nanotechnology , requires further understanding of manipulation and reaction, in order to adapt it to a military arena. [ 29 ]
Nanotechnology and its use in warfare promises economic growth however comes with the increased threat to international security and peacekeeping. The rapid emergence of new nanotechnologies have sparked discussion surrounding the impacts such developments will have on geo-politics, ethics, and the environment.
Difficulty in categorisation of nano-weapons, and their intended purposes (defensive or offensive) compromises the balance of stability and trust in the global environment. "A lack of transparency about an emerging technology not only negatively effects public perception but also negatively impacts the perceived balance of powers in the existing security environment." [ 30 ] The peace and cohesion of the international structure may possibly be negatively affected with a continuing military-focused development of nanotechnology in warfare. Ambiguity and a lack of transparency in research increases difficulty of regulation in this area. Similarly, arguments put forward from a scientific standpoint, highlight the limited information known, concerning the implications of creating such powerful technology, in regards to reaction of the nano-particles themselves. "Although great scientific and technological progress has been made, many questions about the behaviour of matter at the nanoscale level remain, and considerable scientific knowledge has yet to be learned." [ 9 ]
The introduction of nanotechnology into everyday life enables potential benefits of use, yet carries the possibility of unknown consequences for the environment and safety. Possible positive developments include creation of nano-devices to decrease remaining radio-activity in areas, as well as sensors to detect pollutants and adjust fuel-air mixtures. [ 31 ] Associated risks may involve; military personnel inhaling nanoparticles added to fuel, possible absorption of nanoparticles from sensors into the skin, water, air or soil, dispersion of particles from blasts through the environment (via wind), alongside disposal of nano-tech batteries potentially affecting ecosystems. [ 32 ] Applications for materials or explosive devices, allow a greater volume of nano-powders to be packed into a smaller weapon, resulting in a stronger and possibly lethal toxic effect. [ 33 ]
It is unknown the full extent of consequences that may arise in social and ethical areas. Estimates can be made on the associated impacts as they may mirror similar progression of technological developments and affect all areas. [ 34 ] The main ethical uncertainties entail the degree to which modern nanotechnology will threaten privacy, global equity and fairness, while giving rise to patent and property right disputes. [ 35 ] An overarching social and humanitarian issue, branches from the creative intention of these developments. 'The power to kill or capture debate', highlights the unethical purpose and function of destruction these nanotechnological weapons supply to the user. [ 36 ]
Controversy surrounding the innovation and application of nanotechnology in warfare highlights dangers of not pre-determining risks, or accounting for possible impacts of such technology. "The threat of nuclear weapons led to the cold war. The same trend is foreseen with nanotechnology, which may lead to the so-called nanowars, a new age of destruction", stated by the U.S. Department of Defense. [ 22 ] Similarly a report released by Oxford University, warns of the pre-eminent extinction of the human race with a 5% risk of this occurring due to development of 'molecular nanotech weapons'. [ 37 ]
International regulation for such concerns surrounding issues of nanotechnology and its military application, are non existent. There is currently no framework to enforce or support international cooperation to limit production or monitor research and development of nanotechnology for defensive use. [ 38 ] "Even if a transnational regulatory framework is established, it is impossible to determine if a nation is non-compliant if one is unable to determine the entire scope of research, development, or manufacturing." [ 30 ]
Producing legislation to keep-up with the rapid development of products and new materials in the scientific spheres, would pose as a hindrance to constructing working and relevant regulation. Productive regulation should assure public health and safety, account for environmental and international concerns, yet not restrict innovation of emerging ideas and applications for nanotechnology. [ 39 ]
Approaches to development of legislation, possibly include progression towards classified non-disclosive information pertaining to military use of nanotechnology. A paper written by Harvard Journal of Law and Technology , discusses laws that would revolve around specific export controls and discourage civilian or private research into nano-materials. [ 40 ] This proposal suggests mimicking the U.S. Atomic Energy Act of 1954 , restricting any distribution of information regarding the properties and features of the nanotechnology at creation. [ 41 ]
A United States National Registry for Nanotechnology has enabled a public sphere where reports are available for curated data on physico-chemical characteristics and interactions of nanomaterials . [ 42 ] Requiring further development and more frequent voluntary additions, the register could initiate global regulation and cooperation regarding nanotechnology in warfare.
The registry was developed to assist in the standardisation, formatting, and sharing of data. With more compliance and cooperation this data sharing model may "simplify the community level of effort in assessing nanomaterial data from environmental and biological interaction studies." [ 43 ] Analysis of such a registry would be carried out with expertise by professional nano-scientists, creating a filtering mechanism for any potentially newly developed or dangerous materials.
However, this idea of a specific nonmaterial registry is not original, as several databases have been developed previously including the caNanoLab and InterNano which are both engaging and accessible to the public, informatively curated by experts, and detail tools of nano manufacturing . [ 44 ] [ 45 ] The National Nanomaterial Registry, is a more updated version in which information is collated from a range of these sources and multiple additional data resources. It translates a greater range of content regarding; comparison tools with other materials, encouraging standard methods, alongside compliance rating features. [ 43 ] | https://en.wikipedia.org/wiki/Nanotechnology_in_warfare |
A nanotextured surface ( NTS ) is a surface which is covered with nano -sized structures. Such surfaces have one dimension on the nanoscale , i.e., only the thickness of the surface of an object is between 0.1 and 100 nm. They are currently gaining popularity because of their special applications due to their unique physical properties. Nanotextured surfaces are in various forms like cones, columns, or fibers. These are water, ice, oil, and microorganism repellent that is superamphiphobic, anti-icing , and antifouling respectively and thus self-cleaning. They are simultaneously anti-reflective and transparent, hence they are termed smart surfaces. [ 1 ]
In research published online October 21, 2013, in Advanced Materials , of a group of scientists at the U.S. Department of Energy 's Brookhaven National Laboratory (BNL), led by BNL physicist and lead author Antonio Checco, proposed that nanotexturing surfaces in the form of cones produces highly water-repellent surfaces. These nano-cone textures are super hydrophobic or super-water-hating. [ 2 ] [ 3 ]
Cyril R. A. John Chelliah, Cyril R. A. John Chelliah, Rajesh Swaminathan, Rajesh Swaminathan, "Pulsed laser deposited hexagonal wurzite ZnO thin-film nanostructures/nanotextures for nanophotonics applications," Journal of Nanophotonics 12(1), 016013 (13 February 2018). https://doi.org/10.1117/1.JNP.12.016013 [ 1 ] | https://en.wikipedia.org/wiki/Nanotextured_surface |
Nanothermometry is a branch of physics and engineering exploring the use of non-invasive precise thermometers working at the nanoscale . These devices have high spatial resolution (below one micrometer ), where conventional methods are ineffective.
The sensitivity is a parameter that characterizes a thermometer giving information about the relative change on the output of the thermometer per degree of temperature change. Numerically, it can be computed using the calibration curve (temperature dependence of the thermometric parameter, Q)
As S r have small values, usually it is expressed as a percentage, like 1.0%· K −1 , meaning that a degree change in temperature will be measured in the thermometric parameter as a change of 1.0%. This quantity is telling to determine the appropriate detector to be used in order to measure the temperature from the thermometric parameter change. [ 1 ]
The well-known limitations of contact thermometers to work at submicron scale lead to the development of non-contact thermometry techniques, such as, IR thermography, thermoreflectance, optical interferometry, Raman spectroscopy, and luminescence. Luminescence nanothermometry exploits the relationship between temperature and luminescence properties to achieve thermal sensing from the spatial and spectral analysis of the light generated from the object to be thermally imaged. [ 2 ] | https://en.wikipedia.org/wiki/Nanothermometry |
Nanotopography refers to specific surface features which form or are generated at the nanoscopic scale . While the term can be used to describe a broad range of applications ranging from integrated circuits to microfluidics , in practice it typically applied to sub-micron textured surfaces as used in biomaterials research.
Several functional nanotopographies have been identified in nature. Certain surfaces like that of the lotus leaf have been understood to apply nanoscale textures for abiotic processes such as self-cleaning. [ 1 ] Bio-mimetic applications of this discovery have since arrived in consumer products. In 2012, it was recognized that nanotopographies in nature are also used for antibiotic purposes. The wing of the cicada , the surface of which is covered in nanoscale pillars, induces lysis of bacteria. While the nano-pillars were not observed to prevent cell adhesion, they acted mechanistically to stretch microbial membranes to breakage. In vitro testing of the cicada wing demonstrated its efficacy against a variety of bacterial strains. [ 2 ]
Numerous technologies are available for the production of nanotopography. High-throughput techniques include plasma functionalization , abrasive blasting , and etching . Though low cost, these processes are limited in the control and replicability of feature size and geometry. [ 3 ] Techniques enabling greater feature precision exist, among them electron beam lithography and particle deposition , but are slower and more resource intensive by comparison. Alternatively, processes such as molecular self-assembly can be utilized which provide an enhanced level of production speed and feature control.
Though the effects of nanotopography on cell behavior have only been recognized since 1964, some of the first practical applications of the technology are being realized in the field of medicine. [ 4 ] Among the few clinical applications is the functionalization of titanium implant surfaces with nanotopography, generated with submersion etching and sand blasting. This technology has been the focal point of a diverse body of research aimed at improving post-operative integration of certain implant components. The determinant of integration varies, but as most titanium implants are orthopedics-oriented, osseointegration is the dominant aim of the field.
Nanotopography is readily applied to cell culture and has been shown to have a significant impact on cell behavior across different lineages . [ 4 ] Substrate features in the nanoscale regime down to the order of 9 nm are able to retain some effect. Subjected solely to topographical cues, a wide variety of cells demonstrate responses including changes in cell growth and gene expression . [ 5 ] Certain patterns are able to induce stem cells to differentiate down specific pathways. [ 6 ] Notable results include osteogenic induction in the absence of media components [ 7 ] as well as near-total cell alignment as seen in smooth muscle . [ 8 ] The potential of topographical cues to fulfill roles otherwise requiring xeno-based media components offers high translatability to clinical applications, as regulation and cost related to animal-derived products constitutes a major roadblock in a number of cell-related technologies. | https://en.wikipedia.org/wiki/Nanotopography |
Nanotoxicology is the study of the toxicity of nanomaterials . [ 1 ] Because of quantum size effects and large surface area to volume ratio, nanomaterials have unique properties compared with their larger counterparts that affect their toxicity. Of the possible hazards, inhalation exposure appears to present the most concern, with animal studies showing pulmonary effects such as inflammation , fibrosis , and carcinogenicity for some nanomaterials. [ 2 ] Skin contact and ingestion exposure are also a concern.
Nanomaterials have at least one primary dimension of less than 100 nanometers , and often have properties different from those of their bulk components that are technologically useful. Because nanotechnology is a recent development, the health and safety effects of exposures to nanomaterials, and what levels of exposure may be acceptable, is not yet fully understood. [ 3 ] Nanoparticles can be divided into combustion-derived nanoparticles (like diesel soot), manufactured nanoparticles like carbon nanotubes and naturally occurring nanoparticles from volcanic eruptions, atmospheric chemistry etc. Typical nanoparticles that have been studied are titanium dioxide , alumina, zinc oxide, carbon black , carbon nanotubes , and buckminsterfullerene .
Nanotoxicology is a sub-specialty of particle toxicology. Nanomaterials appear to have toxicity effects that are unusual and not seen with larger particles, and these smaller particles can pose more of a threat to the human body due to their ability to move with a much higher level of freedom while the body is designed to attack larger particles rather than those of the nanoscale. [ 4 ] For example, even inert elements like gold become highly active at nanometer dimensions. Nanotoxicological studies are intended to determine whether and to what extent these properties may pose a threat to the environment and to human beings. [ 5 ] Nanoparticles have much larger surface area to unit mass ratios which in some cases may lead to greater pro-inflammatory effects in, for example, lung tissue. In addition, some nanoparticles seem to be able to translocate from their site of deposition to distant sites such as the blood and the brain.
Nanoparticles can be inhaled, swallowed, absorbed through skin and deliberately or accidentally injected during medical procedures. They might be accidentally or inadvertently released from materials implanted into living tissue. [ 6 ] [ 7 ] [ 8 ] One study considers release of airborne engineered nanoparticles at workplaces, and associated worker exposure from various production and handling activities, to be very probable. [ 9 ]
Size is a key factor in determining the potential toxicity of a particle. [ 10 ] However it is not the only important factor. Other properties of nanomaterials that influence toxicity include: chemical composition, shape, surface structure, surface charge, aggregation and solubility, [ 11 ] and the presence or absence of functional groups of other chemicals.
The large number of variables influencing toxicity means that it is difficult to generalise about health risks associated with exposure to nanomaterials – each new nanomaterial must be assessed individually and all material properties must be taken into account.
Metal based nanoparticles (NPs) are a prominent class of NPs synthesized for their functions as semiconductors , electroluminescents , and thermoelectric materials . [ 12 ] Biomedically, these antibacterial NPs have been utilized in drug delivery systems to access areas previously inaccessible to conventional medicine. With the recent increase in interest and development of nanotechnology , many studies have been performed to assess whether the unique characteristics of these NPs, namely their large surface area to volume ratio, might negatively impact the environment upon which they were introduced. [ 13 ] Researchers have found that some metal and metal oxide NPs may affect cells inducing DNA breakage and oxidation, mutations, reduced cell viability, warped morphology , induced apoptosis and necrosis , and decreased proliferation. [ 12 ] Moreover, metal nanoparticles may persist in the organisms after administration if not carefully engineered. [ 14 ]
The latest toxicology studies on mice as of 2013 involving exposure to carbon nanotubes (CNT) showed a limited pulmonary inflammatory potential of MWCNT at levels corresponding to the average inhalable elemental carbon concentrations observed in U.S.-based CNT facilities. The study estimated that considerable years of exposure are necessary for significant pathology to occur. [ 15 ]
One review concludes that the evidence gathered since the discovery of fullerenes overwhelmingly points to C 60 being non-toxic. As is the case for toxicity profile with any chemical modification of a structural moiety, the authors suggest that individual molecules be assessed individually. [ 16 ]
Other classes of nanomaterials include polymers such as nanocellulose , and dendrimers .
There are many ways that size can affect the toxicity of a nanoparticle. For example, particles of different sizes can deposit in different places in the lungs, and are cleared from the lungs at different rates. Size can also affect the particles' reactivity and the specific mechanism by which they are toxic. [ 17 ]
Many nanoparticles agglomerate or aggregate when they are placed in environmental or biological fluids. The terms agglomeration and aggregation have distinct definitions according to the standards organizations ISO and ASTM, where agglomeration signifies more loosely bound particles and aggregation signifies very tightly bound or fused particles (typically occurring during synthesis or drying). Nanoparticles frequently agglomerate due to the high ionic strength of environmental and biological fluids, which shields the repulsion due to charges on the nanoparticles. Unfortunately, agglomeration has frequently been ignored in nanotoxicity studies, even though agglomeration would be expected to affect nanotoxicity since it changes the size, surface area, and sedimentation properties of the nanoparticles. In addition, many nanoparticles will agglomerate to some extent in the environment or in the body before they reach their target, so it is desirable to study how toxicity is affected by agglomeration.
The agglomeration/deagglomeration (mechanical stability) potentials of airborne engineered nanoparticle clusters also have significant influences on their size distribution profiles at the end-point of their environmental transport routes. Different aerosolization and deagglomeration systems have been established to test stability of nanoparticle agglomerates.
NPs , in their implementation, are covered with coatings and sometimes given positive or negative charges depending upon the intended function. Studies have found that these external factors affect the degree of toxicity of NPs.
Inhalation exposure is the most common route of exposure to airborne particles in the workplace. The deposition of nanoparticles in the respiratory tract is determined by the shape and size of particles or their agglomerates, and they are deposited in the lungs to a greater extent than larger respirable particles. Based on animal studies , nanoparticles may enter the bloodstream from the lungs and translocate to other organs, including the brain. [ 18 ] The inhalation risk is affected by the dustiness of the material, the tendency of particles to become airborne in response to a stimulus. Dust generation is affected by the particle shape, size, bulk density, and inherent electrostatic forces, and whether the nanomaterial is a dry powder or incorporated into a slurry or liquid suspension . [ 19 ]
Animal studies indicate that carbon nanotubes and carbon nanofibers can cause pulmonary effects including inflammation , granulomas , and pulmonary fibrosis , which were of similar or greater potency when compared with other known fibrogenic materials such as silica , asbestos , and ultrafine carbon black . Some studies in cells or animals have shown genotoxic or carcinogenic effects, or systemic cardiovascular effects from pulmonary exposure. Although the extent to which animal data may predict clinically significant lung effects in workers is not known, the toxicity seen in the short-term animal studies indicate a need for protective action for workers exposed to these nanomaterials. As of 2013, further research was needed in long-term animal studies and epidemiologic studies in workers. No reports of actual adverse health effects in workers using or producing these nanomaterials were known as of 2013. [ 20 ] Titanium dioxide (TiO 2 ) dust is considered a lung tumor risk, with ultrafine (nanoscale) particles having an increased mass-based potency relative to fine TiO 2 , through a secondary genotoxicity mechanism that is not specific to TiO 2 but primarily related to particle size and surface area. [ 21 ]
Some studies suggest that nanomaterials could potentially enter the body through intact skin during occupational exposure. Studies have shown that particles smaller than 1 μm in diameter may penetrate into mechanically flexed skin samples, and that nanoparticles with varying physicochemical properties were able to penetrate the intact skin of pigs. Factors such as size, shape, water solubility, and surface coating directly affect a nanoparticle's potential to penetrate the skin. At this time, it is not fully known whether skin penetration of nanoparticles would result in adverse effects in animal models, although topical application of raw SWCNT to nude mice has been shown to cause dermal irritation, and in vitro studies using primary or cultured human skin cells have shown that carbon nanotubes can enter cells and cause release of pro-inflammatory cytokines , oxidative stress , and decreased viability. It remains unclear, however, how these findings may be extrapolated to a potential occupational risk. [ 18 ] [ 20 ] In addition, nanoparticles may enter the body through wounds, with particles migrating into the blood and lymph nodes. [ 22 ]
Ingestion can occur from unintentional hand-to-mouth transfer of materials; this has been found to happen with traditional materials, and it is scientifically reasonable to assume that it also could happen during handling of nanomaterials. Ingestion may also accompany inhalation exposure because particles that are cleared from the respiratory tract via the mucociliary escalator may be swallowed. [ 18 ]
The extremely small size of nanomaterials also means that they much more readily gain entry into the human body than larger sized particles. How these nanoparticles behave inside the body is still a major question that needs to be resolved. The behavior of nanoparticles is a function of their size, shape and surface reactivity with the surrounding tissue. In principle, a large number of particles could overload the body's phagocytes , cells that ingest and destroy foreign matter, thereby triggering stress reactions that lead to inflammation and weaken the body's defense against other pathogens . In addition to questions about what happens if non-degradable or slowly degradable nanoparticles accumulate in bodily organs, another concern is their potential interaction or interference with biological processes inside the body. Because of their large surface area , nanoparticles will, on exposure to tissue and fluids, immediately adsorb onto their surface some of the macromolecules they encounter. This may, for instance, affect the regulatory mechanisms of enzymes and other proteins.
Nanomaterials are able to cross biological membranes and access cells , tissues and organs that larger-sized particles normally cannot. [ 23 ] Nanomaterials can gain access to the blood stream via inhalation [ 6 ] or ingestion. [ 7 ] Broken skin is an ineffective particle barrier , suggesting that acne, eczema, shaving wounds or severe sunburn may accelerate skin uptake of nanomaterials . Then, once in the blood stream, nanomaterials can be transported around the body and be taken up by organs and tissues, including the brain , heart, liver, kidneys, spleen , bone marrow and nervous system . [ 8 ] Nanomaterials can be toxic to human tissue and cell cultures (resulting in increased oxidative stress , inflammatory cytokine production and cell death ) depending on their composition and concentration. [ 6 ]
For some types of particles , the smaller they are, the greater their surface area to volume ratio and the higher their chemical reactivity and biological activity. The greater chemical reactivity of nanomaterials can result in increased production of reactive oxygen species (ROS), including free radicals .
ROS production has been found in a diverse range of nanomaterials including carbon fullerenes , carbon nanotubes and nanoparticle metal oxides. ROS and free radical production is one of the primary mechanisms of nanoparticle toxicity; it may result in oxidative stress, inflammation, and consequent damage to proteins, membranes and DNA. [ 11 ] For example, the application of nanoparticle metal oxide with magnetic fields that modulate ROS leading to enhanced tumor growth. [ 2 ]
A primary marker for the damaging effects of NPs has been cell viability as determined by state and exposed surface area of the cell membrane. Cells exposed to metallic NPs have, in the case of copper oxide, had up to 60% of their cells rendered unviable. When diluted, the positively charged metal ions often experience an electrostatic attraction to the cell membrane of nearby cells, covering the membrane and preventing it from permeating the necessary fuels and wastes. [ 12 ] With less exposed membrane for transportation and communication, the cells are often rendered inactive.
NPs have been found to induce apoptosis in certain cells primarily due to the mitochondrial damage and oxidative stress brought on by the foreign NPs electrostatic reactions. [ 12 ]
Metal and metal oxide NPs such as silver, zinc, copper oxide, uraninite , and cobalt oxide have also been found to cause DNA damage. [ 12 ] The damage done to the DNA will often result in mutated cells and colonies as found with the HPRT gene test.
Characterization of a nanomaterial's physical and chemical properties is important for ensuring the reproducibility of toxicology studies, and is also vital for studying how the properties of nanomaterials determine their biological effects. [ 24 ] The properties of a nanomaterial such as size distribution and agglomeration state can change as a material is prepared and used in toxicology studies, making it important to measure them at different points in the experiment. [ 17 ]
With comparison to more conventional toxicology studies, in nanotoxicology, characterisation of the potential contaminants is challenging. The biological systems are themselves still not completely known at this scale. Visualisation methods such as electron microscopy (SEM and TEM) and atomic force microscopy (AFM) analysis allow visualisation of the nano world. Further nanotoxicology studies will require precise characterisation of the specificities of a given nano-element: size, chemical composition, detailed shape, level of aggregation, combination with other vectors, etc. Above all, these properties would have to be determined not only on the nanocomponent before its introduction in the living environment but also in the (mostly aqueous) biological environment.
There is a need for new methodologies to quickly assess the presence and reactivity of nanoparticles in commercial, environmental, and biological samples since current detection techniques require expensive and complex analytical instrumentation.
Toxicology studies of nanomaterials are a key input into determining occupational exposure limits .
The Royal Society identifies the potential for nanoparticles to penetrate the skin, and recommends that the use of nanoparticles in cosmetics be conditional upon a favorable assessment by the relevant European Commission safety advisory committee.
The Woodrow Wilson Centre's Project on Emerging Technologies conclude that there is insufficient funding for human health and safety research, and as a result there is currently limited understanding of the human health and safety risks associated with nanotechnology. While the US National Nanotechnology Initiative reports that around four percent (about $40 million) is dedicated to risk related research and development, the Woodrow Wilson Centre estimate that only around $11 million is actually directed towards risk related research. They argued in 2007 that it would be necessary to increase funding to a minimum of $50 million in the following two years so as to fill the gaps in knowledge in these areas. [ 25 ]
The potential for workplace exposure was highlighted by the 2004 Royal Society report which recommended a review of existing regulations to assess and control workplace exposure to nanoparticles and nanotubes. The report expressed particular concern for the inhalation of large quantities of nanoparticles by workers involved in the manufacturing process. [ 26 ]
Stakeholders concerned by the lack of a regulatory framework to assess and control risks associated with the release of nanoparticles and nanotubes have drawn parallels with bovine spongiform encephalopathy (‘mad cow's disease'), thalidomide , genetically modified food , nuclear energy, reproductive technologies, biotechnology, and asbestosis . In light of such concerns, the Canadian-based ETC Group have called for a moratorium on nano-related research until comprehensive regulatory frameworks are developed that will ensure workplace safety. [ 27 ] | https://en.wikipedia.org/wiki/Nanotoxicology |
Nanotribology is the branch of tribology that studies friction , wear , adhesion and lubrication phenomena at the nanoscale , where atomic interactions and quantum effects are not negligible. The aim of this discipline is characterizing and modifying surfaces for both scientific and technological purposes.
Nanotribological research has historically involved both direct and indirect methodologies. [ 1 ] [ 2 ] [ 3 ] Microscopy techniques, including Scanning Tunneling Microscope (STM), Atomic-Force Microscope (AFM) and Surface Forces Apparatus , (SFA) have been used to analyze surfaces with extremely high resolution, while indirect methods such as computational methods [ 4 ] and Quartz crystal microbalance (QCM) have also been extensively employed. [ 5 ] [ 6 ]
Changing the topology of surfaces at the nanoscale, friction can be either reduced or enhanced more intensively than macroscopic lubrication and adhesion; in this way, superlubrication and superadhesion can be achieved. In micro- and nano-mechanical devices problems of friction and wear, that are critical due to the extremely high surface volume ratio, can be solved covering moving parts with super lubricant coatings . On the other hand, where adhesion is an issue, nanotribological techniques offer a possibility to overcome such difficulties.
Friction and wear have been technological issues since ancient periods. On the one hand, the scientific approach of the last centuries towards the comprehension of the underlying mechanisms was focused on macroscopic aspects of tribology. On the other hand, in nanotribology, the systems studied are composed of nanometric structures , where volume forces (such as those related to mass and gravity ) can often be considered negligible compared to surface forces . Scientific equipment to study such systems have been developed only in the second half of the 20th century. In 1969 the very first method to study the behavior of a molecularly thin liquid film sandwiched between two smooth surfaces through the SFA was developed. [ 7 ] From this starting point, in 1980s researchers would employ other techniques to investigate solid state surfaces at the atomic scale.
Direct observation of friction and wear at the nanoscale started with the first Scanning Tunneling Microscope (STM), which can obtain three-dimensional images of surfaces with atomic resolution; this instrument was developed by Gerd Binnig and Henrich Rohrer in 1981. [ 8 ] STM can study only conductive materials, but in 1985 with the invention of the Atomic Force Microscope (AFM) by Binning and his colleagues, also non conductive surfaces can be observed. [ 9 ] Afterwards, AFMs were modified to obtain data on normal and frictional forces: these modified microscopes are called Friction Force Microscopes (FFM) or Lateral Force Microscopes (LFM). The term "Nanotribology" was first used in the title of a 1990 publication [ 10 ] and in a 1991 publication . [ 11 ] in a title of a major review paper published in Nature in 1995 [ 6 ] and in a title of a major Nanotribology Handbook in 1995. [ 1 ]
From the beginning of the 21st century, computer-based atomic simulation methods have been employed to study the behaviour of single asperities, even those composed by few atoms. Thanks to these techniques, the nature of bonds and interactions in materials can be understood with a high spatial and time resolution.
The SFA ( Surface Forces Apparatus ) is an instrument used for measuring physical forces between surfaces, such as adhesion and capillary forces in liquids and vapors , and van der Waals interactions . [ 12 ] Since 1969, the year in which the first apparatus of this kind was described, numerous versions of this tool have been developed.
SFA 2000, which has fewer components and is easier to use and clean than previous versions of the apparatus, is one of the currently most advanced equipment utilized for nanotribological purposes on thin films , polymers , nanoparticles and polysaccharides . SFA 2000 has one single cantilever which is able to generate mechanically coarse and electrically fine movements in seven orders of magnitude, respectively with coils and with piezoelectric materials. The extra-fine control enables the user to have a positional accuracy lesser than 1 Å . The sample is trapped by two molecularly smooth surfaces of mica in which it perfectly adheres epitaxially . [ 12 ]
Normal forces can be measured by a simple relation:
where Δ D a p p l i e d {\displaystyle \Delta D_{applied}} is the applied displacement by using one of the control methods mentioned before, k {\displaystyle k} is the spring constant and Δ D m e a s u r e d {\displaystyle \Delta D_{measured}} is the actual deformation of the sample measured by MBI . Moreover, if ∂ F ( D ) ∂ D > k {\displaystyle {\partial F(D) \over \partial D}>k} then there is a mechanical instability and therefore the lower surface will jump to a more stable region of the upper surface. And so, the adhesion force is measured with the following formula:
Using the DMT model , the interaction energy per unit area can be calculated:
where R {\displaystyle R} is the curvature radius and F c u r v e d ( D ) {\displaystyle F_{curved}(D)} is the force between cylyndrically curved surfaces. [ 12 ] [ 13 ]
SPM techniques such as AFM and STM are widely used in nanotribology studies. [ 14 ] [ 15 ] [ 2 ] The Scanning Tunneling Microscope is used mostly for morphological topological investigation of a clean conductive sample, because it is able to give an image of its surface with atomic resolution.
The Atomic Force Microscope is a powerful tool in order to study tribology at a fundamental level. It provides an ultra-fine surface-tip contact with a high refined control over motion and atomic-level precision of measure . The microscope consists, basically, in a high flexible cantilever with a sharp tip, which is the part in contact with the sample and therefore the crossing section must be ideally atomic-size, but actually nanometric (radius of the section varies from 10 to 100 nm). In nanotribology AFM is commonly used for measuring normal and friction forces with a resolution of pico-Newtons . [ 16 ]
The tip is brought close to the sample's surface, consequently forces between the last atoms of the tip and the sample's deflect the cantilever proportionally to the intensity of this interactions. Normal forces bend the cantilever vertically up or down of the equilibrium position, depending on the sign of the force. The normal force can be calculated by means of the following equation:
where k {\displaystyle k} is the spring constant of the cantilever, Δ V {\displaystyle \Delta V} is the output of the photodetector , which is an electric signal, directly with the displacement of the cantilever and σ {\displaystyle \sigma } is the optical-lever sensitivity of the AFM. [ 17 ] [ 18 ]
On the other hand, lateral forces can be measured with the FFM, which is fundamentally very similar to the AFM. The main difference resides in the tip motion, that slides perpendicularly to its axis. These lateral forces, i.e. friction forces in this case, result in twisting the cantilever, which is controlled to ensure that only the tip touches the surface and not other parts of the probe. At every step the twist is measured and related with the frictional force with this formula:
where Δ V {\displaystyle \Delta V} is the output voltage , k ϕ {\displaystyle k_{\phi }} is the torsional constant of the cantilever, h e f f {\displaystyle h_{eff}} is the height of the tip plus the cantilever thickness and δ {\displaystyle \delta } is the lateral deflection sensitivity. [ 17 ]
Since the tip is part of a compliant apparatus, the cantilever, the load can be specified and so the measurement is made in load-control mode; but in this way the cantilever has snap-in and snap-out instabilities and so in some regions measurements cannot be completed stably. These instabilities can be avoided with displacement-controlled techniques, one of this is the interfacial force microscopy. [ 13 ] [ 19 ] [ 20 ]
The tap can be at contact with the sample in the whole measurement process, and this is called contact mode (or static mode), otherwise it can be oscillated and this is called tapping mode (or dynamic mode). Contact mode is commonly applied on hard sample, on which the tip cannot leave any sign of wear, such as scars and debris. For softer materials tapping mode is used to minimize the effects of friction. In this case the tip is vibrated by a piezo and taps the surface at the resonant frequency of the cantilever, i.e. 70-400 kHz , and with an amplitude of 20-100 nm, high enough to allow the tip to not get stuck to the sample because of the adhesion force. [ 21 ]
The atomic force microscope can be used as a nanoindenter in order to measure hardness and Young's modulus of the sample. For this application, the tip is made of diamond and it is pressed against the surface for about two seconds, then the procedure is repeated with different loads. The hardness is obtained dividing the maximum load by the residual imprint of the indenter, which can be different from the indenter section because of sink-in or pile-up phenomena. [ 22 ] The Young's modulus can be calculated using the Oliver and Pharr method, which allows to obtain a relation between the stiffness of the sample, function of the indentation area, and its Young's and Poisson's moduli. [ 23 ]
Computational methods are particularly useful in nanotribology for studying various phenomena, such as nanoindentation, friction, wear or lubrication. [ 13 ] In an atomistic simulation, every single atom's motion and trajectory can be tracked with a very high precision and so this information can be related to experimental results, in order to interpret them, to confirm a theory or to have access to phenomena, that are invisible to a direct study. Moreover, many experimental difficulties do not exist in an atomistic simulation, such as sample preparation and instrument calibration . Theoretically every surface can be created from a flawless one to the most disordered. As well as in the other fields where atomistic simulations are used, the main limitations of these techniques relies on the lack of accurate interatomic potentials and the limited computing power . For this reason, simulation time is very often small ( femtoseconds ) and the time step is limited to 1 fs for fundamental simulations up to 5 fs for coarse-grained models. [ 13 ]
It has been demonstrated with an atomistic simulation that the attraction force between the tip and sample's surface in a SPM measurement produces a jump-to-contact effect. [ 24 ] This phenomenon has a completely different origin from the snap-in that occurs in load-controlled AFM, because this latter is originated from the finite compliance of the cantilever. [ 13 ] The origin of the atomic resolution of an AFM was discovered and it has been shown that covalent bonds form between the tip and the sample which dominate van der Waals interactions and they are responsible for a such high resolution. [ 25 ] Simulating an AFM scansion in contact mode, It has been found that a vacancy or an adatom can be detected only by an atomically sharp tip. Whether in non-contact mode vacancies and adatoms can be distinguished with the so-called frequency modulation technique with a non-atomically sharp tip. In conclusion only in non-contact mode can be achieved atomic resolution with an AFM. [ 26 ]
Friction, the force opposing to the relative motion, is usually idealized by means of some empirical laws such as Amonton ’s First and Second laws and Coulomb's law . At the nanoscale, however, such laws may lose their validity. For instance, Amonton's second law states that friction coefficient is independent from the area of contact. Surfaces, in general, have asperities, that reduce the real area of contact and therefore, minimizing such area can minimize friction. [ 21 ] [ 27 ] [ 28 ]
During the scanning process with an AFM or FFM, the tip, sliding on the sample's surface, passes through both low (stable) and high potential energy points, determined, for instance, by atomic positions or, on a larger scale, by surface roughness. [ 21 ] Without considering thermal effects, the only force that makes the tip overcome these potential barriers is the spring force given by the support: this causes the stick-slip motion.
At the nanoscale, friction coefficient depends on several conditions. For example, with light loading conditions, tend to be lower than those at the macroscale. With higher loading conditions, such coefficient tends to be similar to the macroscopic one. Temperature and relative motion speed can also affect friction.
Lubrication is the technique used to reduce friction between two surfaces in mutual contact. Generally, lubricants are fluids introduced between these surfaces in order to reduce friction. [ 21 ] [ 27 ]
However, in micro- or nano-devices, lubrication is often required and traditional lubricants become too viscous when confined in layers of molecular thickness. A more effective technique is based on thin films, commonly produced by Langmuir–Blodgett deposition, or self-assembled monolayers [ 29 ]
Thin films and self-assembled monolayers are also used to increase adhesion phenomena.
Two thin films made of perfluorinated lubricants (PFPE) with different chemical composition were found to have opposite behaviors in humid environment: hydrophobicity increases the adhesive force and decreases lubrication of films with nonpolar end groups; instead, hydrophilicity has the opposite effects with polar end groups.
“ Superlubricity is a frictionless tribological state sometimes occurring in nanoscale material junctions”. [ 30 ]
At the nanoscale, friction tends to be non isotropic: if two surfaces sliding against each other have incommensurate surface lattice structures, each atom is subject to different amount of force from different directions . Forces, in this situation, can offset each other, resulting in almost zero friction.
The very first proof of this was obtained using a UHV-STM to measure. If lattices are incommensurable, friction was not observed, however, if the surfaces are commensurable, friction force is present. [ 31 ] At the atomic level, these tribological properties are directly connected with superlubricity. [ 32 ]
An example of this is given by solid lubricants , such as graphite , MoS2 and Ti3SiC2: this can be explained with the low resistance to shear between layers due to the stratified structure of these solids. [ 33 ]
Even if at the macroscopic scale friction involves multiple microcontacts with different size and orientation, basing on these experiments one can speculate that a large fraction of contacts will be in superlubric regime. This leads to a great reduction in average friction force, explaining why such solids have a lubricant effect.
Other experiments carried out with the LFM shows that the stick-slip regime is not visible if the applied normal load is negative: the sliding of the tip is smooth and the average friction force seems to be zero. [ 34 ]
Other mechanisms of superlubricity may include: [ 35 ] (a) Thermodynamic repulsion due to a layer of free or grafted macromolecules between the bodies so that the entropy of the intermediate layer decreases at small distances due to stronger confinement; (b) Electrical repulsion due to external electrical voltage; (c) Repulsion due to electrical double layer; (d) Repulsion due to thermal fluctuations. [ 36 ]
With the introduction of AFM and FFM, thermal effects on lubricity at the atomic scale could not be considered negligible any more. [ 37 ] Thermal excitation can result in multiple jumps of the tip in the direction of the slide and backward. When the sliding velocity is low, the tip takes a long time to move between low potential energy points and thermal motion can cause it to make a lot of spontaneous forward and reverse jumps: therefore, the required lateral force to make the tip follow the slow support motion is small, so the friction force becomes very low.
For this situation was introduced the term thermolubricity.
Adhesion is the tendency of two surfaces to stay attached together. [ 21 ] [ 27 ]
The attention in studying adhesion at the micro- and nanoscale increased with the development of AFM: it can be used in nanoindentation experiments, in order to quantify adhesion forces [ 2 ] [ 38 ] [ 39 ]
According to these studies, hardness was found to be constant with film thickness, and it's given by: [ 40 ]
where A c {\textstyle A_{c}} is the indentation's area and P c {\textstyle P_{c}} is the load applied to the indenter.
Stiffness, defined as S = d P d h {\textstyle S={\frac {dP}{dh}}} , where h {\displaystyle h} is the indentation's depth, can be obtained from r c {\textstyle r_{c}} , the radius of the indenter-contact line.
E ′ {\textstyle E'} is the reduced Young's modulus, E i {\textstyle E_{i}} and ν i {\displaystyle \nu _{i}} are the indenter's Young's modulus and Poisson's ratio and E s {\displaystyle E_{s}} , ν s {\displaystyle \nu _{s}} are the same parameters for the sample.
However, r c {\textstyle r_{c}} can't always be determined from direct observation; it could be deduced from the value of h c {\textstyle h_{c}} (depth of indentation), but it's possible only if there is no sink-in or pile-up (perfect Sneddon's surface conditions). [ 41 ]
If there is sink in, for example, and the indenter is conical the situation is described below.
From the image, we can see that:
From Oliver and Pharr's study [ 38 ]
where ε depends on the geometry of the indenter; ϵ = 1 − 2 π {\textstyle \epsilon =1-{\frac {2}{\pi }}} if it's conical, ϵ = 1 2 {\textstyle \epsilon ={\frac {1}{2}}} if it's spherical and ϵ = 1 {\textstyle \epsilon =1} if it's a flat cylinder.
Oliver and Pharr, therefore, did not consider adhesive force, but only elastic force, so they concluded:
Considering adhesive force [ 41 ]
Introducing W a {\textstyle W_{a}} as the adhesion energy and γ a {\displaystyle \gamma _{a}} as the work of adhesion:
obtaining
In conclusion:
The consequences of the additional term of adhesion is visible in the following graph:
During loading, indentation depth is higher when adhesion is not negligible: adhesion forces contributes to the work of indentation; on the other hand, during unloading process, adhesion forces opposes indentation process.
Adhesion is also related to capillary forces acting between two surfaces when in presence of humidity. [ 42 ]
This phenomenon is very important in thin films, because a mismatch between the film and the surface can cause internal stresses and, consequently interface debonding.
When a normal load is applied with an indenter, the film deforms plastically, until the load reaches a critical value: an interfacial fracture starts to develop. The crack propagates radially, until the film is buckled. [ 40 ]
On the other hand, adhesion was also investigated for its biomimetic applications: several creatures including insects, spiders, lizards and geckos have developed a unique climbing ability that are trying to be replicated in synthetic materials .
It was shown that a multi-level hierarchical structure produces adhesion enhancement: a synthetic adhesive replicating gecko feet organization was created using nanofabrication techniques and self-assembly . [ 43 ]
Wear is related to the removal and the deformation of a material caused by the mechanical actions. At the nanoscale, wear is not uniform. The mechanism of wear generally begins on the surface of material. The relative motion of two surfaces can cause indentations obtained by the removal and deformation of surface material. Continued motion can eventually grow in both width and depth these indentations. [ 21 ] [ 27 ]
At the macro scale wear is measured by quantifying the volume (or mass) of material loss or by measuring the ratio of wear volume per energy dissipated. At the nanoscale, however, measuring such volume can be difficult and therefore, it is possible to use evaluate wear by analyzing modifications in surface topology, generally by means of AFM scanning. [ 44 ] [ 2 ] | https://en.wikipedia.org/wiki/Nanotribology |
Nanovid microscopy , from "nanometer video-enhanced microscopy", is a microscopic technique aimed at visualizing colloidal gold particles of 20–40 nm diameter (nanogold, immunogold ) as dynamic markers at the light-microscopic level. The nanogold particles as such are smaller than the diffraction limit of light , but can be visualized by using video-enhanced differential interference contrast (VEDIC). The technique is based on the use of contrast enhancement by video techniques and digital image processing . Nanovid microscopy, by combining small colloidal gold probes with video-enhanced quantitative microscopy, allows studying the intracellular dynamics of specific proteins in living cells . | https://en.wikipedia.org/wiki/Nanovid_microscopy |
Second Sino-Japanese War
Asia-Pacific
Mediterranean and Middle East
Other campaigns
Coups
Resistance movements
The Nashitou massacre ( simplified Chinese : 南石头大屠杀 ; traditional Chinese : 南石頭大屠殺 ) was large-scale unnatural deaths among the refugees detained by the Imperial Japanese Army and Wang Jingwei regime at the Nanshitou Refugee Camp in Guangzhou , China , between 1942 and 1945. The event was triggered by the Japanese expulsion of Chinese residents from Japanese-occupied Hong Kong in 1942, which resulted in refugees crowding into the city of Guangzhou by ferry along the Pearl River . [ 1 ] They were stopped at Nanshitou for physical examinations. [ 2 ] [ 3 ] A former soldier of Unit 8604 stated that the unit was instructed to poison Chinese refugees with the pathogens of typhoid and paratyphoid , which they put into the thin porridge and drinking water prepared for the refugees, causing a large number of deaths. [ 4 ] Additionally, survivors claimed that the Japanese used detainees for human experimentation . [ 5 ] In the 1950s and 1980s, Guangzhou Paper Mill found a massive amount of human skeletons and bones during construction projects, which were believed to be victims of the refugee camp. [ 6 ] [ 2 ] Chinese scholar Tan Yuanheng asserts that at least 100,000 died in the refugee camp . [ 4 ]
In October 1938, following the Japanese occupation of Guangzhou, 100,000 to 200,000 Guangzhou residents fled Hong Kong due to the historical ties between the two cities. [ 7 ] : 84 The Japanese took British Hong Kong in December 1941, following its attack on the Pearl Harbor . The Japanese military authorities considered the massive Chinese population in Hong Kong could be a burden to the city and soon began expelling Chinese from the city. [ 7 ] : 85
By 19 February 1942, 554,000 individuals had been repatriated. Subsequently, a governor's office was established in Hong Kong, overseeing the expulsion of another 419,000 people by the end of September 1943. [ 8 ] : 48 It is estimated that a significant portion of refugees returning to Guangzhou by sea numbered at least 150,000 or more. [ 7 ] : 89 In April 1944, the Hong Kong Occupied Territories Government halted rice distribution to the general population. The surge in repatriates prompted the cessation of encouraged evacuation in July. By the time of Japan's surrender , Hong Kong's population had dwindled to 600,000. [ 4 ]
The refugee camp at Nanshitou was a prison in the south suburb of Guangzhou, which had a dock upon the Pearl River . [ 8 ] : 73–74 It was turned into a refugee camp, with the surge of refugees arriving from Hong Kong until the Japanese surrender in 1945. [ 7 ] : 90 As the number of refugees was far above the capacity of the camp, ferries carrying refugees were anchored on the Pearl River near Nanshitou. The refugees were prohibited from leaving Nanshitou and forced them to work for the Japanese or Wang Jingwei authorities. [ 7 ] : 93–94
By the end of 1939, the Imperial Japanese Army in Guangzhou had organised Unit 8604 , purportedly tasked with providing epidemic prevention water supply for the Japanese army. However, its actual activities involved bacteriological research and bacteriological warfare. [ 8 ] : 72 While the refugee camp was run by the Guangdong Provincial Government under the Wang Jingwei regime , Unit 8604 took control of the epidemic prevention in the camp, where the unit secretly murdered refugees with bacteriological weapons and experimentations. [ 7 ] : 108–109
According to eyewitness accounts, the quarantine process roughly proceeded as follows: Upon anchoring the ships, quarantine procedures were conducted, whereby individuals suspected of being infected were isolated and taken away, while the rest were driven back onto the ships. Quarantine inspections sometimes took place on board, at other times at the Yuehai Customs Harbor Quarantine Office, and occasionally on the riverbanks or flat ground ashore. The so-called quarantine procedure involved "men, women, old, and young being forced to strip naked, exposing their buttocks upwards," followed by rectal examinations using glass rods. However, in Japanese military records, there is no detailed documentation regarding the specific quarantine procedures for refugees in the so-called "refugee camps on board ships." Furthermore, if thermometers were used, this step alone would not accurately detect infectious diseases. If sampling probes were used, questions arose regarding whether there were registration numbers, and how large quantities of samples were stored and tested, among other issues. It is unlikely that standard quarantine procedures would lead to the destruction of relevant documentation. Due to the limited capacity of the Nanshitou Refugee Camp, which could accommodate only about 5,000 people at most, many refugees were initially placed on refugee ships awaiting processing. Once the camp reached full capacity, refugees were transferred to the camp, and this cycle repeated as needed. [ 7 ] : 97–98
Survivors typically described that there was a significant decrease in the number of people aboard the ships. Some refugees couldn't endure the waiting period and died on the ships, mostly due to starvation or disease, with some potentially being caused by the spread of pathogens. While fleas were typically absent on board, some refugees recalled sudden infestations of fleas, followed by a succession of deaths, with "people dying every day," and the deceased being thrown into the river. Refugees believed this was the result of the deliberate dissemination of fleas carrying pathogens by the Japanese. Others attempted to escape secretly. [ 7 ] : 99
After the establishment of the Guangdong Provincial Infectious Diseases Hospital by the Japanese following the Customs Quarantine Station at Nanshitou, it was purported to be for the centralized treatment of cholera among Cantonese-Hong Kong refugees, with the cholera outbreak in Guangzhou attributed to the refugees. Locals referred to this hospital as the "Japanese Hospital." According to records from the Japanese hospital, Hong Kong refugees were generally in a state of starvation, with 90.1% suffering from malnutrition, which was the leading cause of death. Among those afflicted with cholera , the highest mortality rates were observed in individuals aged 1 to 10 and 61 to 70, reaching 60-70%. After the age of 40, mortality rates increased significantly. Mortality rates for other age groups ranged from 40 to 70%. Deaths were concentrated in July, during the warmer months, and mortality rates sometimes reached 90% between July and September. Therefore, research suggests that the mortality of cholera is most strongly correlated with temperature rather than gender. When patients experienced severe diarrhoea, mortality rates could reach 40%; with vomiting, mortality rates rose to 57.1%. The mortality rate for patients who vomited five times a day reached 24.7%. Additionally, 52.2% of patients experienced spasms: 31.8% in the upper limbs, 47.8% in the lower limbs, and 20.4% in both upper and lower limbs. [ 8 ] : 99–102
Trapped bird, dreams of skies so vast,
Struggles to soar, held fast,
Rejects bland gruel, hunger gnaws within,
Pains in belly, no remedy to win,
Inevitably to perish, in bone's abyss.
Japanese records show that Unit 8604 allegedly contacted the Army Military School in Tokyo for the disposal of the refugees. The School requested information regarding the infection rates and death tolls of the bacteria they provided. The unit then decided to experiment on refugees and visualised their results in figures and tables. The infected Chinese people were also sent north to the Chinese-controlled area to infect the Chinese army , [ 7 ] : 104–105 in order to alleviate the pressure faced by the refugee camp. [ 7 ] : 93
According to a former soldier of the unit, they brought a strain of intestinal salmonella from the Army Medical School in Tokyo and chose to delay the soup supply during breakfast time when provincial government officials were not yet on duty. They took advantage of the refugees' unfamiliarity with the routine and chaotic conditions to secretly release the bacteria while avoiding the destruction of salmonella due to high temperatures. [ 7 ] : 107
The use of salmonella, such as typhoid-like strains, in bacteriological warfare is related to their pathological characteristics. These bacteria, when ingested through contaminated water sources, dust, etc., enter the human body via the digestive tract and can rapidly cause severe infection. Even those who are asymptomatic or have mild infections can continue to carry the bacteria, some for several years, thereby spreading the infection widely among both military personnel and civilians during acute outbreaks. Moreover, the ability of asymptomatic carriers to harbour the bacteria for extended periods and over broader geographical areas contributes to greater harm to more individuals over a longer period of time. [ 7 ] : 107
The Customs Quarantine Station located in the west of Nanshitou served as a live testing ground for the Japanese bacteriological weapons. Witnesses reported that the Japanese selected young people and sent them into the quarantine station to be fed on by mosquitoes. [ 3 ] [ 1 ] Tai Wei, a villager from Nanshitou, identified that the Japanese captured mosquito larvae in the rice fields, had people feed the mosquitoes, and then extracted the mosquito blood for experimentation. His brother-in-law was seized and fed to mosquitoes in the quarantine station, only to succumb to illness afterward. [ 8 ] : 32 According to survivor Feng Qi's account, refugees in the camp were forcibly administered vaccination shots. Many developed high fevers and convulsions shortly after receiving the injection, and within days, they died. [ 5 ]
The provincial government of the Wang Jingwei regime was responsible for burying the deceased, employing the method of on-site burial where bodies were stacked together. Even the soil used for burying the bodies became increasingly scarce. [ 7 ] : 104–105
Japanese records only mentioned the deaths of over 300 people and revealed that the outbreak of cholera led to a significant reduction in population, necessitating the commencement of cremation and the use of two large pools to allow natural decay of the bodies. Each pool could accommodate 50–60 bodies at a time, alternating between the two pools. Therefore, the number of deaths far exceeded 300 people. [ 7 ] : 102
Zhong Ruirong, an elderly resident of Nanshitou, pointed out that there were two huge pools in the refugee camp at that time to handle the bodies. After each layer of bodies was laid down in the pits, an unknown liquid was poured in, followed by a layer of lime. Within just two or three days, the two pools were filled with bodies. [ 5 ] Feng Qi, a survivor of the refugee camp, noted that after the pools were filled with bodies, they were sealed with additional liquid, emitting a foul smell. [ 5 ]
According to Xiao Zheng, a retired worker from the Guangzhou Paper Group and a victim of bacteriological warfare, his father witnessed both pools in the refugee camp being filled with skeletal remains, and it took six grave diggers several months to clear them. After the refugees died, they would be transported to the area around Nanji Road for burial. [ 2 ]
The present location of the Nanshitou Refugee Camp Quarantine Station is situated opposite 44 Xinglong Street, West Nanshitou Road, Nanshitou Subdistrict, Guangzhou. [ 8 ] : 73–74 Originally, it served as the office space for the Guangzhou Public Security Bureau's Water Division. The refugee camp was located in the vicinity of the former motorcycle factory and surrounding enterprises. [ 9 ]
In 1995, a memorial monument for the Cantonese-Hong Kong refugees was established in the Guangzhou Paper Mill Dormitory Area. [ 3 ] In 2002, the Quarantine Station was registered as a protected cultural site in Guangzhou under the name "Former Site of Guangdong Customs Quarantine Station." In 2012, the Haizhu District Government named the unit the "Former Site of the South China Epidemic Prevention and Water Supply Department of the Invading Japanese Army." In 2016, the Haizhu District Government and the Guangzhou Paper Group funded the construction of the area into a green square. In 2018, the Guangzhou Municipal Government announced plans to establish the Cantonese-Hong Kong Refugee Park. [ 8 ] : 17–18
In October 1947, the Guangzhou municipal government relocated the remains from Nanshitou to the outskirts of Qixing Hill. [ 8 ] : 22–23
In 1953, during the construction of worker housing projects in Nanshitou by the Guangzhou Paper Mill, numerous uncoffined bones were discovered along both sides of Nanji Road, buried less than 0.5 meters deep. The bones were stacked in layers, separated by yellow soil, with a thickness of about 20 to 40 centimetres and visible from 2 meters underground. Local residents mentioned that these remains were transported from nearby punitive fields for burial. Due to the lack of other hills nearby and the overwhelming number of corpses, it was likely impractical to dig individual graves. Instead, a thin layer of soil was simply placed over the bodies each year. Construction workers treated the remains as ordinary soil and used them to fill road sections needing soil. [ 7 ] : 122 According to witness and retired Guangzhou Paper Mill worker Cao Xiuying, at least three to four hundred bodies were observed in the area. [ 7 ] : 124
In the 1980s, during the construction of worker dormitories on Nanji Road by the Guangzhou Paper Mill, another three to four hundred bodies were discovered. Local residents identified them as the deceased from the Nanshitou Refugee Camp. Shen Shisheng, the former head of the Guangzhou Paper Mill's construction office, mentioned that besides the foundation pits, the exact number of bodies beneath the dormitory building was unknown. The bodies were placed in ossuaries, with each ossuary containing the remains of 2–3 individuals. There were over a hundred ossuaries in total, eventually relocated to Mashihu, Xiaolou Town, Zengcheng County. [ 7 ] : 124–125
According to Assistant Professor Chi Man Kwong from the History Department of Hong Kong Baptist University , the notion of Japanese conducting bacteriological experiments in Nanshitou is not surprising, given historical instances of extreme actions by the Japanese military. While some individuals have provided eyewitness testimonies and identified locations, along with some relevant documentation, there is currently a lack of sufficiently clear evidence to fully depict this event, particularly concerning the specific individuals responsible for this water supply unit and detailed information related to it. [ 10 ] | https://en.wikipedia.org/wiki/Nanshitou_massacre |
Naomi Chayen is a biochemist and structural biologist. She is a professor of Biomedical Sciences at Imperial College London , where she leads the Crystallization Group in Computational and Systems Medicine. She is best known for developing the microbatch method and inventing novel nucleants for protein crystallization which have been applied to high-throughput screening for rational drug design .
Chayen earned her first degree in pharmacy at the Hebrew University of Jerusalem . During her undergraduate studies, she visited the Kennedy Institute of Rheumatology to learn histochemistry . She subsequently pursued MSc and PhD research at the Kennedy Institute. [ 1 ] In 1983, Chayen submitted her thesis on stimulus-response coupling in smooth muscle cells and received a PhD from Brunel University London . [ 2 ]
Chayen began her first postdoctoral fellowship at Imperial College London , where she studied the biophysics of muscle proteins. When her grant was not renewed, she joined the lab of David Mervyn Blow to develop novel protein crystallization techniques. There, she began her influential work of utilizing phase diagrams to optimize conditions for crystal growth. [ 1 ]
Currently, Chayen is a professor of Biomedical Sciences and head of the Crystallization Group in Computational and Systems Medicine at Imperial College London. [ 3 ]
Chayen is best known for her invention of novel protein crystallization methods. In 1990, she first published a method of suspending droplets of protein solution and precipitant solutions in low-density paraffin oil to prevent evaporation during the microbatch crystallization process. The microbatch process can be suitable for membrane proteins , which are ordinarily difficult to crystallize. [ 1 ] Chayen's method has since been applied towards the analysis of many biomolecules that are relevant to human diseases such as cancer , HIV , diabetes , and heart disease . [ 4 ]
In addition to her work on microbatch methods, Chayen invented a novel gel-glass nucleant now known as "Naomi's Nucleant." [ 5 ] Naomi's Nucleant has been used to crystallize more than 20 proteins, the most of any single nucleant. [ 1 ] In 2015, she collaborated with Subrayal Reddy at University of Central Lancashire to develop the first non-protein nucleant, a semi-liquid molecularly imprinted polymer designed for high-throughput screening . The nucleant was commercialized as "Chayen Reddy MIP." [ 6 ]
Chayen's current research interests include protein crystallization , structural biology , and structural genomics and proteomics . [ 3 ]
Chayen holds nine patents and has launched several commercial products for protein crystallization, such as "Chayen Reddy MIP" and "Naomi's nucleant." [ 3 ] In addition, she has won the following awards:
Chayen was the Sterling Drug Visiting Professor of Pharmacology at Yale School of Medicine in 2009. [ 10 ] She was formerly [ when? ] the president of the International Organization for Biological Crystallization . [ 3 ] | https://en.wikipedia.org/wiki/Naomi_Chayen |
Naphtha ( / ˈ n æ f θ ə / , recorded as less common or nonstandard [ 1 ] in all dictionaries: / ˈ n æ p θ ə / ) is a flammable liquid hydrocarbon mixture. Generally, it is a fraction of crude oil, but it can also be produced from natural-gas condensates , petroleum distillates , and the fractional distillation of coal tar and peat . In some industries and regions, the name naphtha refers to crude oil or refined petroleum products such as kerosene or diesel fuel .
Naphtha is also known as Shellite in Australia. [ 2 ]
The word naphtha comes from Latin through Ancient Greek ( νάφθα ), derived from Middle Persian naft ("wet", "naphtha"), [ 3 ] [ 4 ] the latter meaning of which was an assimilation from the Akkadian 𒉌𒆳𒊏 napṭu (see Semitic relatives such as Arabic نَفْط nafṭ ["petroleum"], Syriac ܢܰܦܬܳܐ naftā , and Hebrew נֵפְט neft , meaning petroleum). [ 5 ]
The book of II Maccabees (2nd cent. BC) tells how a "thick water" was put on a sacrifice at the time of Nehemiah and when the sun shone it caught fire. It adds that "those around Nehemiah termed this 'Nephthar', which means Purification, but it is called Nephthaei by the many." [ 6 ] This same substance is mentioned in the Mishnah as one of the generally permitted oils for lamps on Shabbat , although Rabbi Tarfon permits only olive oil (Mishnah Shabbat 2).
In Ancient Greek, it was used to refer to any sort of petroleum or pitch . The Greek word νάφθα designates one of the materials used to stoke the fiery furnace in the Song of the Three Children (possibly 1st or 2nd cent. BC). The translation of Charles Brenton renders this as " rosin ".
The naphtha of antiquity is explained to be a "highly flammable light fraction of petroleum, an extremely volatile, strong-smelling, gaseous liquid, common in oil deposits of the Near East"; it was a chief ingredient in incendiary devices described by Latin authors of the Roman period. [ 7 ]
Since the 19th century, solvent naphtha has denoted a product ( xylene or trimethylbenzenes ) derived by fractional distillation from petroleum; [ 8 ] these mineral spirits , also known as "Stoddard Solvent", were originally the main active ingredient in Fels Naptha laundry soap. [ 9 ] The naphtha in Fels Naptha was later removed as a cancer risk. [ 10 ]
The usage of the term "naphtha" during this time typically implies petroleum naphtha, a colorless liquid with a similar odor to gasoline. However, "coal tar naphtha", a reddish brown liquid that is a mixture of hydrocarbons (toluene, xylene, and cumene , etc.), could also be intended in some contexts. [ 11 ]
In older usage, [ when? ] "naphtha" simply meant crude oil , but this usage is now obsolete in English. There are a number of cognates to the word in different modern languages, typically signifying "petroleum" or "crude oil".
The Ukrainian and Belarusian word нафта ( nafta ), Lithuanian , Latvian and Estonian "nafta" and the Persian naft ( نفت ) mean "crude oil". The Russian word нефть ( neft' ) means "crude oil", but нафта ( nafta ) is a synonym of ligroin . Also, in Albania , Bosnia and Herzegovina , Bulgaria , Croatia , Finland , Italy , Serbia , Slovenia , Macedonia nafta (нафта in Cyrillic) is colloquially used to indicate diesel fuel and crude oil . In the Czech Republic and Slovakia , nafta was historically used for both diesel fuel and crude oil, but its use for crude oil is now obsolete [ 12 ] and it generally indicates diesel fuel. In Bulgarian , nafta means diesel fuel, while neft , as well as petrol (петрол in Cyrillic), means crude oil. Nafta is also used in everyday parlance in Argentina, Paraguay and Uruguay to refer to gasoline/petrol. [ 13 ] In Poland, the word nafta means kerosene , [ 14 ] and colloquially crude oil (technical name for crude oil is ropa naftowa , also colloquially used for diesel fuel as ropa ). In Flemish , the word naft(e) is used colloquially for gasoline. [ 15 ]
Various qualifiers have been added to the term "naphtha" by different sources in an effort to make it more specific:
One source [ 16 ] distinguishes by boiling point:
Light naphtha is the fraction boiling between 30 °C and 90 °C and consists of molecules with 5–6 carbon atoms. Heavy naphtha boils between 90 °C and 200 °C and consists of molecules with 6–12 carbon atoms.
Another source [ 17 ] which differentiates light and heavy comments on the hydrocarbon structure, but offers a less precise dividing line:
Light [is] a mixture consisting mainly of straight-chained and cyclic aliphatic hydrocarbons having from five to six carbon atoms per molecule. Heavy [is] a mixture consisting mainly of straight-chained and cyclic aliphatic hydrocarbons having from seven to nine carbon atoms per molecule.
Both of these are useful definitions, but they are incompatible with one another and the latter does not provide for mixes containing both six and seven carbon atoms per molecule. These terms are also sufficiently broad that they are not widely useful.
"Petroleum naphtha", which contains both heavy and light naphtha, typically constitutes 15-30% of crude oil by weight. [ 18 ]
Naphtha is used to dilute heavy crude oil to reduce its viscosity and enable/facilitate transport; undiluted heavy crude cannot normally be transported by pipeline, and may also be difficult to pump onto oil tankers . Other common dilutants include natural-gas condensate and light crude . However, naphtha is a particularly efficient dilutant and can be recycled from diluted heavy crude after transport and processing. [ 19 ] [ 20 ] [ 21 ] The importance of oil dilutants has increased as global production of lighter crude oils has fallen and shifted to exploitation of heavier reserves. [ 20 ]
Light naphtha is used as a fuel in some commercial applications. One notable example is wick-based cigarette lighters, such as the Zippo , which draw "lighter fluid"—naphtha—into a wick from a reservoir to be ignited using the flint and wheel.
It is also a fuel for camping stoves and oil lanterns, known as "white gas", where naphtha's low boiling point makes it easy to ignite. Naphtha is sometimes preferred over kerosene because it clogs fuel lines less. The outdoor equipment manufacturer MSR published a list of trade names and translations to help outdoor enthusiasts obtain the correct products in various countries. [ 22 ]
Naphtha was also historically used as a fuel in some small launch boats where steam technology was impractical; most were built to circumvent safety laws relating to traditional steam launches. [ 23 ]
As an internal combustion engine fuel, petroleum naphtha has seen very little use and suffers from lower efficiency and low octane ratings , typically 40 to 70 RON . It can be used to run unmodified diesel engines, though it has a longer ignition-delay than diesel. Naphtha tends to be noisy in combustion due to the high pressure rise rate. There is a possibility of using naphtha as a low-octane base fuel in an octane-on-demand concept, with the engine drawing a high-octane mix only when needed. Naptha benefits from lesser emissions in refinement: fuel energy losses from "well-to-tank" are 13%; lower than the 22% losses for petroleum. [ 18 ]
Naphtha is a crucial component in the production of plastics . [ 24 ]
The safety data sheets (SDSs) from various naphtha vendors indicate various hazards such as flammable mixture of hydrocarbons : flammability , carcinogenicity , skin and airway irritation, etc. [ 25 ] [ 2 ] [ 26 ] [ 27 ]
Humans can be exposed to naphtha in the workplace by inhalation, ingestion, dermal contact, and eye contact. The US Occupational Safety and Health Administration (OSHA) has set the permissible exposure limit for naphtha in the workplace as 100 ppm (400 mg/m 3 ) over an 8-hour workday. The US National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit (REL) of 100 ppm (400 mg/m 3 ) over an 8-hour workday. At levels of 1000 ppm, which equates to 10 times the lower exposure limit, naphtha is immediately dangerous to life and health . [ 28 ] | https://en.wikipedia.org/wiki/Naphtha |
1 2,4 .0 5,13 ]tetradeca-1(12),5,7,9(13),10-
7-4-2-6-9(10(7)8)12(14,15-11)
NpP 2 S 4 is a compound related to Lawesson's reagent formed by the reaction of 1- bromonaphthalene with P 4 S 10 , [ 1 ] this is a 1,3,2,4-dithiadiphosphetane 2,4-disulfide which has a naphth-1,8-diyl group holding the two phosphorus atoms together. The mechanism by which the NpP 2 S 4 forms is not yet elucidated, but it is thought to occur by a process involving free radicals , and naphthalene has been detected as a side product in its synthesis. In general, NpP 2 S 4 has been found to be less reactive than Lawesson's reagent, in agreement with the hypothesis that the dithiophosphine ylides are responsible for the majority of the chemical reactions of the 1,3,2,4-dithiadiphosphetane 2,4-disulfides.
NpP 2 S 4 has been found to react with many hydroxyl compounds, such as methanol , ethylene glycol and a catechol to form species with oxygen atoms bonded to the phosphorus atoms.
NpP 2 S 4 when refluxed in methanol reacts to form a heterocycle C 12 H 12 OP 2 S with one O-methyl and one S-methyl bonded to the two phosphorus atoms. [ 1 ] | https://en.wikipedia.org/wiki/Naphthalen-1,8-diyl_1,3,2,4-dithiadiphosphetane_2,4-disulfide |
Naphthalene poisoning (or mothball poisoning) is a form of poisoning that occurs when naphthalene is ingested. Severe poisoning can result in haemolytic anaemia. [ citation needed ] Naphthalene was introduced in 1841 by Rossbach as an antiseptic to counteract typhoid fever . Although naphthalene was widely used industrially, only nine cases of poisoning have been reported since 1947 as of 1956, suggesting underdiagnosis of the condition. As a result, the condition has limited coverage within medical journals. [ 1 ]
Until the late 1950s coal tar was the principal source of naphthalene. From 1981 to 1983 the U.S. National Institute for Occupational Safety and Health found over 100,000 workers were potentially exposed to toxic levels of naphthalene, working primarily for major industrial and agricultural businesses. Exposure may often be a result of oral ingestion, inhalation, or through prolonged skin exposure.
Naphthalene is a precursor in the production of phthalic anhydride . [ 2 ] This application has been displaced by alternative technologies.
Naphthalene is a major component of some mothballs . It repels moths as well as some animals. [ citation needed ]
Since mothballs that contain naphthalene are considered hazards, safer alternatives have been developed, such as the use of 1,4-dichlorobenzene , however, 1,4-dichlorobenzene has been declared as a potential neurotoxin . 1,4-dichlorobenzene has been linked to potentially causing depression as a form of encephalopathy. [ 3 ] This complication resulted with an increased use of Camphor as a moth repellent. Camphor is frequently used in place of naphthalene in Asia.
The European Union enforced a ban on the distribution and production of mothballs containing naphthalene in 2008, as a part of the new regulations of the Registration, Evaluation and Authorisation of Chemicals (REACH), regulating chemical use within its representative countries. [ 4 ]
In 2014, New Zealand banned the distribution of mothballs. [ 5 ] Mothballs are restricted within Australia, only being distributed in forms that prevent them from being ingested. [ 5 ] [ 6 ]
Tobacco is also a source of exposure, creating an estimated range of 0.3 to 4 micrograms of naphthalene inhalation per cigarette that is consumed. A regular pack a day smoker on average would be inhaling amounts of 6-80 micrograms of naphthalene daily, which is a small and negligible amount of naphthalene, and is similar in magnitude to normal exposure near highways and areas where car exhaust is frequently inhaled or consumed. [ 7 ] The naphthalene within cigarettes is different to other sources of naphthalene. The naphthalene that is produced in cigarette smoke is bound to other particles and is not presented as a free vapour, meaning the exposure is small. Naphthalene exposure is usually insignificant unless exposed to large amounts of naphthalene within production or being near proximity of a product that contains naphthalene. Naphthalene levels within an area are very unstable and frequently change over time and space. Due to this variance, sampling protocols must be conducted carefully and are usually analysed using different analytical methods. [ 7 ]
Naphthalene has also been found to be secreted by termites in order to protect their nests. [ 8 ] The termites use naphthalene to repel ants and any intruders who try to invade their nests. This naphthalene produced is not only toxic for the insects but can also affect humans in the same way [ dubious – discuss ] . [ 9 ] Naphthalene poisoning via termite nest was featured in the eleventh episode of the first season of the American television medical drama House , "Detox" , where the final diagnosis ended up as acute naphthalene poisoning as a result of a termite nest being contained within the walls of the patient's bedroom, leading him to inhale naphthalene in his sleep and become sick. [ 10 ]
Treatment of naphthalene toxicity usually follows the same treatments involved for haemolytic anaemia, which involves a series of blood transfusions, in order to restore healthy levels of haemoglobin. This may include intravenous methylene blue and ascorbic acid . The methylene blue allows the methaemoglobin to be converted to haemoglobin. Supportive treatment is also usually provided, depending on the severity of the toxicity, that resulted in the anaemia. [ 11 ]
Ascorbic acid is used to treat methemoglobinemia , a symptom of naphthalene poisoning and is used when methylene blue is not available, or in conjunction with methylene blue in order to restore haemoglobin count. [ 12 ]
According to the International Agency for Research on Cancer , naphthalene is possibly carcinogenic to humans ( Group 2B ), [ 13 ] [ 14 ] as there is inadequate evidence in humans for the carcinogenicity of naphthalene, however there is sufficient evidence in experimental animals for the carcinogenicity of naphthalene. The carcinogenicity was tested on rats in mice, via intraperitoneal administration and subcutaneous administration, of newborns and adult rats, providing evidence of tumours. The IARC also discovered that naphthalene toxicity also had potential to cause cataracts in humans, rats, rabbits and mice, however the tests were considered inefficient to substantiate a diagnosis resulting in naphthalene as a potential carcinogen classification. Likewise, the European Chemical agency classified naphthalene as Group C, a possible human carcinogen. This was classified due to lack of evidence of naphthalene alone causing carcinogenic properties in rats, and limited human contact with naphthalene within industrial environments. [ 15 ]
Haemolysis occurs either through haemoglobin defects, such as formation of Heinz bodies , or cell membrane defects, especially those with glucose-6-phosphate dehydrogenase deficiency and a low tolerance to oxidative stress. This haemolysis is usually accompanied by neurological effects such as vertigo, lethargy and convulsions, usually caused by cerebral edema. Gastrointestinal bleeding may also appear as a symptom after ingestion of mothballs, especially for those who are younger. [ 16 ]
Acute exposure to naphthalene is unlikely to cause toxicity and must be ingested unless prolonged contact is provided along the skin or eyes. After ingestion of mothballs containing naphthalene, symptoms of haemolytic anaemia are presented and treated normally through the use of methylene blue and regular blood transfusions, and patients are usually released after 6–10 days depending on their haemoglobin levels.
Repeated naphthalene exposure has also been found to potentially cause airway epithelial damage, aberrant repair, and inflammation. Greater numbers of peribronchial Mac-3-positive macrophages and CD3-positive T-cells were observed throughout the airways which displays acute inflammation within the airways. [ 17 ]
Naphthalene metabolites of 1,2-hydroxynaphthalene has also been found to be a mechanism of oxidative DNA damage within humans. In the presence of the reduced form of nicotinamide adenine dinucleotide (NADH). [ 18 ] The damaging activity of the DNA of the activity of 1,2-hydroxynaphthalene was observed at much larger levels. 1,2-hydroxynaphthalene is reduced by NADH to be formed as a part of the redox cycle, resulting in the speeding up of DNA damage, however, this is only presented within larger prolonged exposure to naphthalene, values that are unrealistic for any individual not working near a place where naphthalene production occurs. [ 18 ]
1,2-Dihydroxynaphthalene has been used as a potential biomarker of excessive exposure to naphthalene levels and was tested on smokers and those exposed to naphthalene among the working population. After collecting the urine samples of multiple workers, Median 1,2-Dihydroxynaphthalene values were 1012 micrograms per litre for those exposed to naphthalene and 8 micrograms per litre for those who were in the control group indicating that it is useful as a biomarker for exposure within humans. The median results for the concentrations of 1,2-Dihydroxynaphthalene were about ten times the amount of the standard markers of 1-naphthol and 2-naphthol within human urine. [ 19 ] [ 20 ] | https://en.wikipedia.org/wiki/Naphthalene_poisoning |
Naphthalocyanine is a cross-shaped organic molecule consisting of 48 carbon , 8 nitrogen and 26 hydrogen atoms. It is a derivative of phthalocyanine , differing by having 4 extra carbon rings, one on each "arm." IBM Research labs used it for developing single-molecule logic switches [ 1 ] and visualizing charge distribution in a single molecule. [ 2 ] [ 3 ]
Naphthalocyanine derivatives have a potential use in photodynamic cancer treatment . [ 4 ]
This article about a heterocyclic compound is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Naphthalocyanine |
Naphthenic acids ( NAs ) are mixtures of several cyclopentyl and cyclohexyl carboxylic acids with molecular weights of 120 to well over 700 atomic mass units . The main fractions are carboxylic acids with a carbon backbone of 9 to 20 carbons. McKee et al. claim that "naphthenic acids (NAs) are primarily cycloaliphatic carboxylic acids with 10 to 16 carbons", [ 1 ] although acids containing up to 50 carbons have been identified in heavy petroleum. [ 2 ]
Naphthenic acid can refer to derivatives and isomers of naphthalene carboxylic acids . In the petrochemical industry, NA's refer to alkyl carboxylic acids found in petroleum. [ 3 ] The term naphthenic acid has roots in the somewhat archaic term "naphthene" (cycloaliphatic but non-aromatic) used to classify hydrocarbons. It was originally used to describe the complex mixture of petroleum-based acids when the analytical methods available in the early 1900s could identify only a few naphthene-type components with accuracy. Today "naphthenic" acid is used in a more generic sense to refer to all of the carboxylic acids present in petroleum, [ 1 ] whether cyclic, acyclic, or aromatic compounds, and carboxylic acids containing heteroatoms such as N and S. Although commercial naphthenic acids often contain a majority of cycloaliphatic acids, multiple studies [ 4 ] [ 5 ] have shown they also contain straight chain and branched aliphatic acids and aromatic acids; some naphthenic acids contain >50% combined aliphatic and aromatic acids.
Salts of naphthenic acids, called naphthenates , are widely used as hydrophobic sources of metal ions in diverse applications. [ 6 ]
Naphthenic acids are represented by a general formula C n H 2n-z O 2 , where n indicates the carbon number and z specifies a homologous series. The z is equal to 0 for saturated, acyclic acids and increases to 2 in monocyclic naphthenic acids, to 4 in bicyclic naphthenic acids, to 6 in tricyclic acids, and to 8 in tetracyclic acids. [ 5 ] Crude oils with total acid number (TAN) as little as 0.5 mg KOH/g acid or petroleum fractions greater than about 1.0 mg KOH/g oil usually qualify as a high acid crude or oil. At the 1.0 mg/g TAN level, acidic crude oils begin to be heavily discounted in value and so are referred to as opportunity crudes. [ 7 ] Commercial grades of naphthenic acid are most often recovered from kerosene/jet fuel and diesel fractions, where their corrosivity [ 6 ] and negative impact on burning qualities require their removal. Naphthenic acids are also a major contaminant in water produced during the extraction of oil from Athabasca oil sands . [ 8 ] [ 9 ]
Naphthenic acids are extracted from petroleum distillates by extraction with aqueous base. Acidification of this extract acidic neutralization returns the acids free from hydrocarbons. Naphthenic acid is removed from petroleum fractions not only to minimize corrosion but also to recover commercially useful products. [ 10 ] Some crude oils are high in acidic compounds (up to 4%). [ 11 ]
The composition varies with the crude oil composition and the conditions during refining and oxidation. [ 3 ] [ 12 ] Fractions that are rich in naphthenic acids can cause corrosion damage to oil refinery equipment; the phenomenon of naphthenic acid corrosion (NAC). [ 13 ] [ 14 ] Crude oils with a high content of naphthenic acids are often referred to as high total acid number (TAN) crude oils or high acid crude oil (HAC).
Naphthenic acid was first discovered as a method for yttrium extraction from lanthanide elements by the Bureau of Mines in the USA in 1964. [ 15 ] The application of naphthenic acid in rare earth separation was identified by the Changchun Institute of Applied Chemistry in 1974. Between 1974 and 1975, the Nanchang 603 Factory collaborated with the Changchun Institute and other units to successfully develop a third-generation extraction process for yttrium oxide. This process, which utilized naphthenic acid for one-step extraction of high-purity yttrium oxide, was put into operation in 1976. [ 16 ]
Naphthenic acid has been successfully used in industrial rare earth separation due to its advantages of low cost and abundant availability. [ 17 ] In solvent extraction , the H + released from naphthenic acid decrease the aqueous acidity, thereby limiting the positive extraction reaction and leading to an unsatisfied extraction efficient. To address this issue, alkaline substances ( bases ) are used to saponify naphthenic acid before extraction. This step helps avoid the generation of H + , effectively controlling the equilibrium acidity and improving extraction efficiency. [ 18 ] However, this process produces a significant amount of ammonium nitrogen wastewater, which necessitates additional wastewater treatment after extraction. [ 19 ] Currently, research is ongoing to minimize the use of bases and maximize separation efficiency, including adding additives and/or ionic liquids. [ 18 ] [ 20 ]
As the greatest current and historical usage, naphthenic acid are used to produce metal naphthenates . [ 10 ] Metal naphthenates are referred often to as "salts" of naphthenic acids, but metal naphthenates are not ionic. They are covalent, hydrophobic coordination complexes . More specifically they are metal carboxylate complexes with the formula M(naphthenate) 2 , or M 3 O(naphthenate) 6 for basic oxides. Metal naphthenates are not well defined in conventional chemical sense because they are a complex mixture rather than a specific single component, structure or formula. They have diverse applications. [ 6 ] [ 21 ]
The naphthenates have industrial applications including synthetic detergents , lubricants , corrosion inhibitors, fuel and lubricating oil additives, wood preservatives , insecticides , fungicides , acaricides , wetting agents , thickening agent of napalm and oil drying agents used in painting and wood surface treatment. Industrially useful naphthenates include those of aluminium, magnesium, calcium, barium, cobalt, copper, lead, manganese, nickel, vanadium, and zinc. [ 6 ] Illustrative is the use of cobalt naphthenate for the oxidation of tetrahydronaphthalene to the hydroperoxide. [ 22 ]
The complex mixture and hydrophobic nature of naphthenic acid allows metal naphthenates to be highly soluble in organic media such as petroleum-based hydrocarbons, oftentimes much more so than single isomer carboxylates such as metal acetates and stearates. Their industrial applications exploits this property, where they are used as oil-borne detergents , lubricants , corrosion inhibitors, fuel and lubricating oil additives, wood preservatives , insecticides , fungicides , acaricides , wetting agents , oil drying agents (driers) used in oil-based paint and wood surface treatment including varnish . Industrially useful metal naphthenates include those of aluminum, barium, calcium, cobalt, copper, iron, lead, magnesium manganese, nickel, potassium, vanadium, zinc, and zirconium. [ 5 ]
Naphthenic acid are used in extraction process for yttrium oxide and other rare earth elements . [ 23 ] [ 24 ] This process produces a significant amount of ammonium nitrogen wastewater, which necessitates additional wastewater treatment after extraction. [ 25 ] Currently, research is ongoing to minimize the use of bases and maximize separation efficiency, including adding additives and/or ionic liquids. [ 24 ]
Naphthenic acids are the major contaminant in water produced from the extraction of oil from Athabasca oil sands (AOS). [ 26 ]
It has been stated that "naphthenic acids are the most significant environmental contaminants resulting from petroleum extraction from oil sands deposits." Nonetheless, the same authors suggest that "under worst-case exposure conditions, acute toxicity is unlikely in wild mammals exposed to naphthenic acids in AOS tailings pond water, but repeated exposure may have adverse health effects." [ 27 ] Naphthenic acids are present in Athabasca oil sands and tailings pond water at an estimated concentration of 81 mg/L [ 28 ]
Using Organisation for Economic Co-operation and Development [OECD] protocols for testing toxicity, refined NAs are not acutely genotoxic to mammals. [ 1 ] Damage, however, induced by NAs while transient in acute or discontinuous exposure, may be cumulative in repeated exposure. [ 27 ]
Naphthenic acids have both acute and chronic toxicity to fish and other organisms. [ 29 ] | https://en.wikipedia.org/wiki/Naphthenic_acid |
Crude oil is extracted from the bedrock before being processed in several stages, removing natural contaminants and undesirable hydrocarbons. This separation process produces mineral oil , which can in turn be denoted as paraffinic , naphthenic or aromatic . The differences between these different types of oils are not clear-cut, but mainly depend on the predominant hydrocarbon types in the oil. Paraffinic oil, for example, contains primarily higher alkanes, whereas naphthenic oils have a high share of cyclic alkanes in the mixture.
Crude oil appears in a host of different forms, which in turn determine how it should be refined. Classification of the crude oil can vary, because different actors have different starting points. For refineries, the interest has been primarily focused on the distribution between the distillation fractions: petrol, paraffin, gas oil, lubricant distillate, etc. Refiners look at the density of the crude oil – whether it is light, medium or heavy – or the sulfur content, i.e. whether the crude oil is “ sweet ” or “ sour ”. The general classification of different kinds of crude oil is based on the guidelines drawn up by American Petroleum Institute (API), in which the properties can vary depending on, for example, hydrocarbon composition and sulfur content.
Crude oil classification provides refiners with a rough guide to appropriate processing condition to reach desired products. Terminology like paraffinic, asphaltic, aromatic and naphthenic have been in use for a long time. With the progress of the science of the petroleum, addition of physical and chemical properties has been utilized to further enhance classification of crude oils. [ 1 ]
Density has always been an important criterion of oils, generally an oil with low density is considered to be more valuable than an oil with higher density due to the fact that if contains more light fractions (i.e. gasoline). Thus, the API gravity or specific gravity is widely used for the classification of crude oils, based on a scheme proposed by the American Petroleum Institute (Table 1). A high API value >30 means a light crude with paraffinic character; a low API value means a heavy crude with increasing aromatic character.
Table 1. Classifications of crude oil according to API gravity
Low specific gravity ⇒ High °API value = paraffinic High specific gravity ⇒ Low °API value = naphthenic
The UOP characterisation factor (K w ) (UOP 375-07 [ 2 ] ), is based on the observation that the specific gravities of the hydrocarbons are related to their H/C ratio (and thus to their chemical character) and that their boiling points are linked to their number of carbon atoms in their molecules.
High values of Kw (13-12.5) indicate a predominately paraffinic character of its components; naphthenic hydrocarbons vary between 12-11 and values near 10 indicate aromatic character.
The major types of hydrocarbons present in crude oils consist of 1) normal paraffins , 2) branched paraffins (iso-paraffins) , 3) cycloparaffins (naphthenes) and 4) aromatics .
According to API guidelines base stocks (the lubricant component, which are obtained after the crude oil is refined ) are divided into five general categories.
Table 2. API base stock classifications [ 3 ] .* Viscosity Index (section 4.1) .
Besides the above-mentioned properties, there are other methods that can be used to check if an oil is naphthenic or paraffinic. Among those:
The viscosity gravity constant is a mathematical relationship between the viscosity and specific gravity (ASTM D2501 [ 4 ] ) Paraffinic cuts have lower densities (and specific gravities) than naphthenic ones of about the same distillation range. VGC is of particular value in indicating a predominately paraffinic or cyclic composition. VGC is low for paraffinic crudes and high for naphthenic. [ 5 ] VGC is reported for base stocks and ranges from approximately 0.78 (paraffinic base stocks) to 1.0 (highly aromatic base stocks) and its value provides some guidance for the solvency properties of the oil. Like the results of the n-d-M method, VGC is usually reported for naphthenic products, but not for paraffinic ones.
One way of obtaining compositional information on lubricating base oil is the n-d-M method (ASTM D3238 [ 6 ] ), an empirical method for determining the carbon type distribution by indicating the percentage of carbons in aromatic structure (%CA), the percentage of carbon in naphthenic structure (%CN) and the percentage of carbon in paraffinic structure (%CP). Development of the n-d-M method was the consequence of much preceding work relating composition refractive index (n), density (d), and molecular weight (M). [ 1 ]
If the viscosity, density, relative density (specific gravity) and refractive index [ 7 ] for a mineral oil is determined, the viscosity-gravity constant (VGC) and refractivity intercept (ri) can be calculated. Using the given values, the percent carbons (%CA, %CN, %CP) can be derived from a correlation chart, the ASTM D2140 method. [ 8 ] As with the n-d-M method, the results are normally reported for naphthenic oils.
Although several systems have been developed with the purpose for the classification of crude oils, they are usually mentioned as (1) paraffin base, (2) naphthene base (3) mixed base or (4) asphalt base. However, there appears to be no specific definition for these classifications. [ 9 ] Base oil specifications, as defined by the producer or the purchaser, largely encompass the physical properties required for the fluid; density, viscosity, viscosity index (VI), pour point and flash point, and solubility information from aniline point or viscosity-gravity constant (VGC). [ 10 ] Naphthenic base oils generally have intermediate VI's and very low pour points which make them useful in the manufacture of specialty lubricants. Dewaxing is normally not required due to the low quantities of linear paraffins (n-paraffins).
Viscosity index (ASTM D2270 [ 11 ] ) is a measure of the extent of viscosity change with temperature; the higher the VI, the less the change. VI is calculated from viscosity measurements at 40°C and 100°C. The viscosities of paraffinic and naphthenic base oils have very different behavior with temperature change. Normally, paraffinic base oils have less viscosity variation (higher VI) than naphthenic base oil which display larger variation with temperature (lower VI). The low to intermediate VI make naphthenic base oils particularly suitable for specialty applications. [ 10 ]
The pour point (ASTM D97 [ 12 ] ) measures the temperature at which a base oil no longer flows. For paraffinic base oils, pour points are usually between −12 °C and −15 °C, and are determined by operation of the dewaxing unit. The pour points of naphthenic base oils, generally devoid of wax content, may be much lower (down to <−70 °C). [ 10 ]
The aniline point (ASTM D611 [ 13 ] ) is of considerable value in the characterization of petroleum products. The aniline point measure of the ability of the base oil to act as a solvent and is determined from the temperature at which equal volumes of aniline and the base stock are soluble High aniline points (approximately 100°C or greater) imply a paraffinic base stock, while low aniline points (less than 100°C) imply a naphthenic or aromatic stock. [ 10 ]
VGC [ 4 ] is an indicator of base oil composition and solvency that is calculated from the density and viscosity. High values indicate higher solvency and therefore greater naphthenic or aromatic content. [ 10 ]
The refractive index can provide information of the composition of the base oil. Low RI values indicate paraffinic materials and high RI values indicate aromatic components. The RI value also increases with molecular weight. [ 14 ]
Naphthenic oils have extraordinary low-temperature properties, high compatibility with many polymers and good solvent power. These are properties that make naphthenic oils particularly useful for the speciality oil market:
1. Transformer oils. Naphthenic oils have excellent cooling and insulating properties because of a low viscosity index. The good solubility of the oils is also important for enhanced compatibility with seals and gaskets, for example.
2. Process oils. Naphthenic oils are used in a large number of chemical processes due to their good solvent power. These include, for example, plasticizers in polymer-based formulations, rheology modifier in printing inks and carrier oil in anti-foaming agents. Naphthenic oils have been proven to be suitable in the tyre oils segment because of their low content of polycyclic aromatic hydrocarbons (PAHs), which are hazardous to health and the environment.
3. Lubricating oils. Base oils are needed to manufacture products such as greases and industrial lubricants. Naphthenic base oils are particularly suited as metalworking fluids. The main functions of the naphthenic oil in this case are cooling and lubrication, providing a balance between the two. | https://en.wikipedia.org/wiki/Naphthenic_oil |
α-Naphtholphthalein (C 28 H 18 O 4 ) is a phthalein dye used as a pH indicator with a visual transition from colorless/reddish to greenish blue at pH 7.3–8.7.
This article about an organic compound is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Naphtholphthalein |
In geometry , the napkin-ring problem involves finding the volume of a "band" of specified height around a sphere , i.e. the part that remains after a hole in the shape of a circular cylinder is drilled through the center of the sphere. It is a counterintuitive fact that this volume does not depend on the original sphere's radius but only on the resulting band's height.
The problem is so called because after removing a cylinder from the sphere, the remaining band resembles the shape of a napkin ring .
Suppose that the axis of a right circular cylinder passes through the center of a sphere of radius R {\displaystyle R} and that h {\displaystyle h} represents the height (defined as the distance in a direction parallel to the axis) of the part of the cylinder that is inside the sphere. The "band" is the part of the sphere that is outside the cylinder. The volume of the band depends on h {\displaystyle h} but not on R {\displaystyle R} : V = π h 3 6 . {\displaystyle V={\frac {\pi h^{3}}{6}}.}
As the radius R {\displaystyle R} of the sphere shrinks, the diameter of the cylinder must also shrink in order that h {\displaystyle h} can remain the same. The band gets thicker, and this would increase its volume. But it also gets shorter in circumference, and this would decrease its volume. The two effects exactly cancel each other out. In the extreme case of the smallest possible sphere, the cylinder vanishes (its radius becomes zero) and the height h {\displaystyle h} equals the diameter of the sphere. In this case the volume of the band is the volume of the whole sphere , which matches the formula given above.
An early study of this problem was written by 17th-century Japanese mathematician Seki Kōwa . According to Smith & Mikami (1914) , Seki called this solid an arc-ring, or in Japanese kokan or kokwan . [ 1 ]
Suppose the radius of the sphere is R {\displaystyle R} and the length of the cylinder (or the tunnel) is h {\displaystyle h} .
By the Pythagorean theorem , the radius of the cylinder is
R 2 − ( h 2 ) 2 , ( 1 ) {\displaystyle {\sqrt {R^{2}-\left({\frac {h}{2}}\right)^{2}}},\qquad \qquad (1)} and the radius of the horizontal cross-section of the sphere at height y {\displaystyle y} above the "equator" is R 2 − y 2 . ( 2 ) {\displaystyle {\sqrt {R^{2}-y^{2}}}.\qquad \qquad (2)}
The cross-section of the band with the plane at height y {\displaystyle y} is the region inside the larger circle of radius given by (2) and outside the smaller circle of radius given by (1). The cross-section's area is therefore the area of the larger circle minus the area of the smaller circle: π ( larger radius ) 2 − π ( smaller radius ) 2 = π ( R 2 − y 2 ) 2 − π ( R 2 − ( h 2 ) 2 ) 2 = π ( ( h 2 ) 2 − y 2 ) . {\displaystyle {\begin{aligned}&{}\quad \pi ({\text{larger radius}})^{2}-\pi ({\text{smaller radius}})^{2}\\&=\pi \left({\sqrt {R^{2}-y^{2}}}\right)^{2}-\pi \left({\sqrt {R^{2}-\left({\frac {h}{2}}\right)^{2}\,{}}}\,\right)^{2}=\pi \left(\left({\frac {h}{2}}\right)^{2}-y^{2}\right).\end{aligned}}}
The radius R does not appear in the last quantity. Therefore, the area of the horizontal cross-section at height y {\displaystyle y} does not depend on R {\displaystyle R} , as long as y ≤ h 2 ≤ R {\displaystyle y\leq {\tfrac {h}{2}}\leq R} . The volume of the band is
and that does not depend on R {\displaystyle R} .
This is an application of Cavalieri's principle : volumes with equal-sized corresponding cross-sections are equal. Indeed, the area of the cross-section is the same as that of the corresponding cross-section of a sphere of radius h / 2 {\displaystyle h/2} , which has volume 4 3 π ( h 2 ) 3 = π h 3 6 . {\displaystyle {\frac {4}{3}}\pi \left({\frac {h}{2}}\right)^{3}={\frac {\pi h^{3}}{6}}.}
We can also find the napkin ring's volume V n {\displaystyle V_{n}} using previous results. [ 2 ] Specifically, volume V n {\displaystyle V_{n}} must equal the original sphere's volume 4 π R 3 / 3 {\displaystyle 4\pi R^{3}/3} minus the cylinder's volume minus the volume of two spherical caps
V n ( R , h , r c , h s ) = { 4 3 π R 3 } − { π ( r c ) 2 h } − 2 { π 3 ( h s ) 2 ( 3 R − h s ) } {\displaystyle V_{n}(R,h,r_{c},h_{s})=\left\{{\frac {4}{3}}\pi R^{3}\right\}-\left\{\pi (r_{c})^{2}\,h\right\}-2\left\{{\frac {\pi }{3}}(h_{s})^{2}(3R-h_{s})\right\}}
In the above, the cylinder volume uses its radius r c {\displaystyle r_{c}} which can be written in terms of R {\displaystyle R} and h {\displaystyle h} as shown in (1)
r c = R 2 − ( h 2 ) 2 {\displaystyle r_{c}={\sqrt {R^{2}-\left({\frac {h}{2}}\right)^{2}}}}
The spherical cap volume used in V n {\displaystyle V_{n}} uses the cap's height h s {\displaystyle h_{s}} . This is found by knowing the height of the sphere 2 R {\displaystyle 2R} also equals the cylinder's height h {\displaystyle h} plus two spherical cap heights
2 R = h + 2 h s ⟹ h s = R − h 2 {\displaystyle 2R=h+2h_{s}\qquad \implies \qquad h_{s}=R-{\frac {h}{2}}}
Substituting r c {\displaystyle r_{c}} and h s {\displaystyle h_{s}} into the expression above for V n {\displaystyle V_{n}} one finds all terms containing R {\displaystyle R} cancel and one gets
V n = π 6 h 3 {\displaystyle V_{n}={\frac {\pi }{6}}h^{3}} | https://en.wikipedia.org/wiki/Napkin_ring_problem |
Napoleon's problem is a compass construction problem. In it, a circle and its center are given. The challenge is to divide the circle into four equal arcs using only a compass . [ 1 ] [ 2 ] Napoleon was known to be an amateur mathematician, but it is not known if he either created or solved the problem. Napoleon's friend the Italian mathematician Lorenzo Mascheroni introduced the limitation of using only a compass (no straight edge) into geometric constructions . But actually, the challenge above is easier than the real Napoleon's problem , consisting in finding the center of a given circle with compass alone. The following sections will describe solutions to three problems and proofs that they work.
Georg Mohr 's 1672 book " Euclides Danicus " anticipated Mascheroni's idea, though the book was only rediscovered in 1928.
Centred on any point X on circle C , draw an arc through O (the centre of C ) which intersects C at points V and Y. Do the same centred on Y through O, intersecting C at X and Z. Note that the line segments OV, OX, OY, OZ, VX, XY, YZ have the same length, all distances being equal to the radius of the circle C .
Now draw an arc centred on V which goes through Y and an arc centred on Z which goes through X; call where these two arcs intersect T. Note that the distances VY and XZ are 3 {\displaystyle {\sqrt {3}}} times the radius of the circle C .
Put the compass radius equal to the distance OT ( 2 {\displaystyle {\sqrt {2}}} times the radius of the circle C ) and draw an arc centred on Z which intersects the circle C at U and W. UVWZ is a square and the arcs of C UV, VW, WZ, and ZU are each equal to a quarter of the circumference of C .
Let (C) be the circle, whose centre is to be found. [ 3 ]
Let A be a point on (C).
A circle (C1) centered at A meets (C) at B and B'.
Two circles (C2) centered at B and B', with radius AB, cross again at point C.
A circle (C3) centered at C with radius AC meets (C1) at D and D'.
Two circles (C4) centered at D and D' with radius AD meet at A, and at O, the sought center of (C).
Note: for this to work the radius of circle (C1) must be neither too small nor too large. More precisely, this radius must be between half and double of the radius of (C): if the radius is greater than the diameter of (C), (C1) will not intersect (C); if the radius is shorter than half the radius of (C), point C will be between A and O and (C3) will not intersect (C1).
The idea behind the proof is to construct, with compass alone, the length b²/a when lengths a and b are known, and a/2 ≤ b ≤ 2a.
In the figure on the right, a circle of radius a is drawn, centred at O; on it a point A is chosen, from which points B and B' can be determined such that AB and AB' have a length of b . Point A' lies opposite A, but does not need to be constructed (it would require a straightedge); similarly point H is the (virtual) intersection of AA' and BB'. Point C can be determined from B and B', using circles of radius b .
Triangle ABA' has a right angle at B and BH is perpendicular to AA', so :
Therefore, A H = b 2 2 a {\displaystyle AH={\frac {b^{2}}{2a}}} and AC = b²/a.
In the above construction of the center, such a configuration appears twice :
Therefore, O is the centre of circle (C).
Let |AD| be the distance , whose centre is to be found. [ 4 ]
Two circles (C 1 ) centered at A and (C 2 ) centered at D with radius |AD| meet at B and B'.
A circle (C 3 ) centered at B' with radius |B'B| meets the circle (C 2 ) at A'.
A circle (C 4 ) centered at A' with radius |A'A| meets the circle (C 1 ) at E and E'.
Two circles (C 5 ) centered at E and (C 6 ) centered at E' with radius |EA| meet at A and O. O is the sought center of |AD|. | https://en.wikipedia.org/wiki/Napoleon's_problem |
In hydraulic engineering , a nappe is a sheet or curtain of water that flows over a weir or dam . The upper and lower water surface have well-defined characteristics that are created by the crest of a dam or weir. [ 1 ] Both structures have different features that characterize how a nappe might flow through or over impervious concrete structures. [ 2 ] Hydraulic engineers distinguish these two water structures in characterizing and calculating the formation of a nappe. [ 3 ] Engineers account for the bathymetry of standing bodies (like lakes) or moving bodies of water (like rivers or streams). An appropriate crest is built for the dam or weir so that dam failure is not caused by nappe vibration [ 4 ] or air cavitation from free-overall structures. [ 5 ]
There are three types of nappe that form over the crest of a weir, depending on the air ventilation structure of a weir: free nappes, depressed nappes, and clinging nappes. [ 6 ] A free nappe, which is ventilated to maintain atmospheric pressure below, does not come into contact with the underside of the weir. [ 7 ] A depressed nappe is partially ventilated, which creates negative pressure beneath the nappe. The negative pressure leads to a 6% to 7% increase in discharged water compared to a free nappe. [ 8 ] Clinging nappes have no air beneath, and the stream flows along the face of the weir. The shape that fills in this area is called an ogee . Discharge for these weirs is approximately 25% to 30% more than free nappes. The geometry of a weir dictates the coefficient of discharge that passes through the crest, which is proportional to the nappe formation. [ 9 ] Engineers solve for the amount of discharge and the cross sectional area of a river to calculate the adequate shape of the weir that should be implemented.
Many pathways of water can enter through a dam structure to produce a well-defined nappe. However, engineers classify dams as either overflow dams, where water consistently flows over or is blocked through a gate on top of crest, or non-overflow dams, which channel water through or around the dam with emergency floodgates. They both range in size. [ 10 ] An overflow dam has a similar nappe typology to weirs (free, depressed, and clinging nappes). [ 11 ] Engineers usually construct an ogee crest, which forms a clinging nappe. This increases discharge, reduces atmospheric pressure, and decreases the chances of air cavitation occurring. [ 12 ] [ 13 ]
Nappe vibration is classified in hydraulic literature as fluid dynamic excitation; vibrations are generated by the fluid, and the flow characteristics at the point of detachment and impact are critical. [ 14 ] This well-known phenomenon occurs on free-overall structures (i.e. weirs, fountains, or dams) and produces excessive noise on concrete structures. [ 15 ] These are undesirable and dangerous on gates and further characterized by oscillations in the thin-flow nappe cascading downstream of the crest. The vibrations send out a constant noise as water flows over structure, and may lead to cracks or air cavitation, which cause catastrophic failure. The phenomenon results from Kelvin–Helmholtz instability , the shear forces that occur between two fluids of different velocities. [ 16 ]
Cavitation is defined as the explosive growth of vapor bubbles within a liquid. [ 17 ] These bubbles are formed in, and may be carried into, areas of higher local pressures, which disappear before by collapse. Surface irregularities on hydraulic structures are prone to experiencing cavitation. Damage on this type of surface will start at the downstream end of the cloud of collapsing cavitation bubbles. [ 18 ] Damage from cavitation has been reported in several hydraulic structures, including open-channel spillways, bottom outlets in dams, high-head gates and gate slots, and energy dissipators with hydraulic-jump stilling basins. The velocity of water that impinges at the surface point is one of the causes of cavitation. Also, the increased height of spillways on high dams leads to an increase of cavitation caused by nappe flow. [ 19 ] | https://en.wikipedia.org/wiki/Nappe_(water) |
V H , V L : variable (antigen binding) domains of antibody fragment C H 1 , C L : constant domains of antibody fragment
Naptumomab estafenatox (ABR-217620) is a drug being developed for the treatment of various types of cancer like non-small cell lung carcinoma [ 1 ] and renal cell carcinoma . [ 2 ]
Chemically, it is a fusion protein consisting of the antigen-binding fragment (Fab) of a monoclonal antibody with the superantigen staphylococcal enterotoxin A (SEA/E-120, "estafenatox"). [ 3 ] The Fab binds to 5T4 , an antigen expressed by various tumor cells, and the superantigen induces an immune response by activating T lymphocytes . [ 4 ]
This monoclonal antibody –related article is a stub . You can help Wikipedia by expanding it .
This antineoplastic or immunomodulatory drug article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Naptumomab_estafenatox |
The Naranjo algorithm , Naranjo Scale , or Naranjo Nomogram is a questionnaire designed by Naranjo et al. for determining the likelihood of whether an adverse drug reaction (ADR) is actually due to the drug rather than the result of other factors. Probability is assigned via a score termed definite, probable, possible or doubtful. Values obtained from this algorithm are often used in peer reviews to verify the validity of author's conclusions regarding ADRs.
It is often compared to the WHO - UMC system for standardized causality assessment for suspected ADRs.
Empirical approaches to identifying ADRs have fallen short because of the complexity of the set of variables involved in their detection. Computer decision programs have helped in this analysis. Electronic medical record systems can be programmed to fire alerts when a potential adverse drug event is about to occur or has already occurred.[3,4] Automated adverse drug event monitors can search for keywords or phrases throughout the patient's medical record to identify drug therapies , laboratory results , or problem lists that may indicate that a patient has already been treated for an ADR. This detection method uncovers significantly more adverse events, including medication errors , than relying only on empirical methods or incident reports.[1,2]
Empirical methods to assess the likelihood that an ADR has taken place have been lacking. More formal, logical analysis can help differentiate between events that are attributable to a drug from those associated with underlying diseases or other factors, underlying the complexity of detection.[5]
Several investigators, among them researchers at the FDA , have developed such logical evaluation methods, or algorithms, for evaluating the probability of an ADR.[2, 20-24] Almost all of these methods employ critical causation variables identified by Sir Austin Bradford Hill in 1965.[6] The most widely accepted of these instruments is the Naranjo algorithm[22] (Table). This method has been tested for internal validity with between-rater reliability testing, and its probability scale has consensual, content, and concurrent validity as well as ease of use in clinical settings and controlled studies .
1. Are there previous conclusive reports on this reaction?
Yes (+1) No (0) Do not know or not done (0)
2. Did the adverse events appear after the suspected drug was given?
Yes (+2) No (-1) Do not know or not done (0)
3. Did the adverse reaction improve when the drug was discontinued or a specific antagonist was given?
Yes (+1) No (0) Do not know or not done (0)
4. Did the adverse reaction appear when the drug was re administered?
Yes (+2) No (-1) Do not know or not done (0)
5. Are there alternative causes that could have caused the reaction?
Yes (-1) No (+2) Do not know or not done (0)
6. Did the reaction reappear when a placebo was given?
Yes (-1) No (+1) Do not know or not done (0)
7. Was the drug detected in any body fluid in toxic concentrations?
Yes (+1) No (0) Do not know or not done (0)
8. Was the reaction more severe when the dose was increased, or less severe when the dose was decreased?
Yes (+1) No (0) Do not know or not done (0)
9. Did the patient have a similar reaction to the same or similar drugs in any previous exposure?
Yes (+1) No (0) Do not know or not done (0)
10. Was the adverse event confirmed by any objective evidence?
Yes (+1) No (0) Do not know or not done (0)
Scoring
A*l-Tajir GK, Kelly WN. Epidemiology, comparative methods of detection, and preventability of adverse drug events. Ann Pharmacother. 2005;39:1169-1174. Abstract | https://en.wikipedia.org/wiki/Naranjo_algorithm |
The Narasaka–Prasad reduction , sometimes simply called Narasaka reduction , is a diastereoselective reduction of β-hydroxy ketones to the corresponding syn - dialcohols . The reaction employs a boron chelating agent , such as BBu 2 OMe, and a reducing agent , commonly sodium borohydride . This protocol was first discovered by Narasaka in 1984. [ 1 ]
The reaction proceeds through the 6-membered transition state shown below. Chelation by the boron agent favors hydride delivery from the top face because it leads directly to the more stable chair-like conformation of the product ( Fürst-Plattner Rule ). The intermolecular hydride delivery from NaBH 4 therefore proceeds via an axial attack from the opposite face with respect to the existing alcohol . [ 1 ]
This reaction can be contrasted with the similar Evans–Saksena reduction that employs a different boron reagent in order to achieve intramolecular hydride delivery from the same face of the alcohol, thus producing the anti -diol.
The Narasaka–Prasad reduction has been employed in many total syntheses in the literature, [ 2 ] such as discodermolide [ 3 ] | https://en.wikipedia.org/wiki/Narasaka–Prasad_reduction |
In mathematics , the Narasimhan–Seshadri theorem , proved by Narasimhan and Seshadri ( 1965 ), says that a holomorphic vector bundle over a Riemann surface is stable if and only if it comes from an irreducible projective unitary representation of the fundamental group .
The main case to understand is that of topologically trivial bundles, i.e. those of degree zero (and the other cases are a minor
technical extension of this case). This case of the Narasimhan–Seshadri theorem says that a degree zero holomorphic vector bundle over a Riemann surface is stable if and only if it comes from an irreducible unitary representation of the fundamental group of the Riemann surface.
Donaldson ( 1983 ) gave another proof using differential geometry , and showed that the stable vector bundles have an essentially unique unitary connection of constant ( scalar ) curvature . In the degree zero case, Donaldson's version of the theorem says that a degree zero holomorphic vector bundle over a Riemann surface is stable if and only if it admits a flat unitary connection compatible with its holomorphic structure. Then the fundamental group representation appearing in the original statement is just the monodromy representation of this flat unitary connection.
This Riemannian geometry -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Narasimhan–Seshadri_theorem |
Narasinh Narayan Godbole (28 December 1887 – 4 December 1984) [ 1 ] was an Indian food chemist and the first Director of Industries & Supplies of Government of Rajasthan . [ 2 ]
Godbole was born at Dharwad . [ 1 ] He was educated at Bombay University and qualified BSc and MA . [ 1 ] He was a professor at D. J. Sindh Government Science College and Government Dayal Singh College, Lahore (1911–1919). [ 1 ] In 1919, Godbole was invited by Madan Mohan Malaviya to join the Banaras Hindu University (BHU) to establish for the first time in India, the Department of Industrial Chemistry. [ 1 ] The BHU later expanded into a College of Technology of which Godbole was appointed the first principal. [ 1 ] He visited Japan to study industrial development. [ 1 ]
Godbole spent two years in Germany specialising in the study of fats, oils and soaps. [ 1 ] He obtained his PhD from Berlin University in 1925. [ 3 ] Godbole was a lecturer on modern industrial development in Japan at the Universities of Banaras, Delhi , Calcutta & Mysore . [ 4 ] After retiring from BHU in 1948 he was Director of Industries of Rajasthan (1949–1959). [ 1 ] [ 3 ]
He was known for his research on milk products and Sarasvati River . [ 5 ] [ 6 ] He was awarded the Padma Bhushan , third highest civilian honour of India by the President of India, in 1965. [ 7 ] Godbole invented a new "Home Pasteurizer" for domestic use. [ 3 ] He was a member of the Indian Chemical Society . [ 3 ]
Godbole was an advocate of lacto-vegetarianism . [ 8 ] He authored Milk: The Most Perfect Food , in 1936. A review of the book in the Current Science journal, noted that "this is an excellent treatise, worthy to be in every household. Prof. Godbole has approached his task in a scientific spirit and in the performance of it he displays the commendable zeal of the convinced advocate of the principles he wishes to propagate." [ 9 ] A review in the Journal of Dairy Science , commented that Godbole "presents the dairy industry of India with special reference to improvement of the Hindu diet through increased consumption of dairy products... The promotion of the vegetarian diet is uppermost in the thoughts of the author which is essential in India for both religious and health reasons." [ 8 ] Godbole corresponded with Mahatma Gandhi . In a 1937 letter, Gandhi wrote that the book "is good so far as it goes" but was disappointed that it did not examine the methods of using milk. [ 10 ]
Godbole died in Pune on 4 December 1984. [ 1 ] | https://en.wikipedia.org/wiki/Narasinh_Narayan_Godbole |
Narayana polynomials are a class of polynomials whose coefficients are the Narayana numbers . The Narayana numbers and Narayana polynomials are named after the Canadian mathematician T. V. Narayana (1930–1987). They appear in several combinatorial problems. [ 1 ] [ 2 ] [ 3 ]
For a positive integer n {\displaystyle n} and for an integer k ≥ 0 {\displaystyle k\geq 0} , the Narayana number N ( n , k ) {\displaystyle N(n,k)} is defined by
The number N ( 0 , k ) {\displaystyle N(0,k)} is defined as 1 {\displaystyle 1} for k = 0 {\displaystyle k=0} and as 0 {\displaystyle 0} for k ≠ 0 {\displaystyle k\neq 0} .
For a nonnegative integer n {\displaystyle n} , the n {\displaystyle n} -th Narayana polynomial N n ( z ) {\displaystyle N_{n}(z)} is defined by
The associated Narayana polynomial N n ( z ) {\displaystyle {\mathcal {N}}_{n}(z)} is defined as the reciprocal polynomial of N n ( z ) {\displaystyle N_{n}(z)} :
The first few Narayana polynomials are
A few of the properties of the Narayana polynomials and the associated Narayana polynomials are collected below. Further information on the properties of these polynomials are available in the references cited.
The Narayana polynomials can be expressed in the following alternative form: [ 4 ]
The ordinary generating function the Narayana polynomials is given by
The n {\displaystyle n} -th degree Legendre polynomial P n ( x ) {\displaystyle P_{n}(x)} is given by
Then, for n > 0, the Narayana polynomial N n ( z ) {\displaystyle N_{n}(z)} can be expressed in the following form: | https://en.wikipedia.org/wiki/Narayana_polynomials |
Narcissa Niblack Thorne (May 2, 1882 – June 25, 1966) was an American artist known for her extremely detailed miniature rooms. Her works depict historical interiors from Europe, Asia and North America from the late 13th to the early 20th century. The Thorne rooms are honored with dedicated exhibits in the Phoenix Art Museum , the Knoxville Museum of Art , and the Art Institute of Chicago , where a special wing was built to house them.
Thorne was born in Vincennes, Indiana , in 1882; her parents moved to Chicago when she was a child. [ 1 ] She was educated partially at home and partially in public school, finishing at the Kenwood Institute . [ 1 ] She married James Ward Thorne, an heir to the Montgomery Ward department store fortune, on May 29, 1901; they had been childhood sweethearts . [ 1 ] They had two sons, named Ward and Niblack. [ 1 ]
There are various stories of how Thorne was initially prompted to construct the miniature rooms. [ 2 ] Her interest in miniatures began early, and was encouraged by trinkets sent to her by her uncle, a Rear Admiral in the US Navy. [ 1 ]
The first known exhibit of her work occurred in 1932. [ 1 ] The high unemployment of the Great Depression made it possible for her to hire workers with highly specialized skills. [ 1 ] Most of her exhibitions were private, held to raise funds for local charitable causes, but at the Century of Progress Exposition in 1933, Thorne's works were publicly exhibited in a dedicated building. [ 3 ] Subsequent public exhibits included the Art Institute of Chicago and the New York World's Fair of 1940. In 1936, she received a request to make a miniature library depicting a room at Windsor Castle , to mark the planned coronation of Edward VIII ; although the coronation never occurred, she delivered the room and it was displayed at the Victoria and Albert Museum . [ 4 ]
Thorne's best-known works show the interiors of upper-class homes from England, the United States, and France. [ 1 ] The rooms are generally built on a scale of approximately 1:12, or one inch to one foot. [ 5 ] They are painstakingly precise, and when maintenance is required, it has to be done with delicate tweezers and cotton swabs, the furnishings being carefully restored to their original position with reference to a detailed layout plan. [ 4 ]
Although her rooms were extremely time-consuming and expensive to produce, Thorne never sought or received payment for any of them. [ 4 ] The death of her husband in 1946 left Thorne with an estate worth upwards of 2 million dollars, enabling her to continue focusing on her work. [ 4 ] However, eventually a shortage of sufficiently skilled workers forced her to focus on dioramas and shadow boxes . [ 4 ]
When a permanent gallery was established for the Thorne rooms at the Art Institute in 1954, Thorne set up a fund to cover the costs of caring for the works. [ 4 ]
Due to poor health, Thorne closed her studio in March 1966, donating her remaining works to charity. [ 4 ] She died in Chicago in June of that year, and was buried in Rosehill Cemetery . [ 4 ]
Most of Thorne's works were donated to museums and remain there, although some were auctioned off in 1985. [ 6 ] Thorne herself arranged for thirty of the rooms to be auctioned off for charity in 1963. [ 4 ]
Approximately one hundred Thorne rooms are known to exist. The Art Institute of Chicago holds 68 Thorne rooms, which originally occupied a dedicated wing but are now housed in a large room in the building's lower level. [ 7 ] An additional 20 are held by the Phoenix Art Museum , [ 8 ] and nine by the Knoxville Museum of Art . The remaining two are at The Children's Museum of Indianapolis , and the Kaye Miniature Museum in Los Angeles. In addition to these, a bar that Thorne auctioned off for charity in the 1950s is at the Museum of Miniature Houses in Carmel, Indiana. [ 9 ] | https://en.wikipedia.org/wiki/Narcissa_Niblack_Thorne |
Narendra Nayak (born 5 February 1951) is a rationalist , sceptic , and godman debunker from Mangalore , Karnataka , India. [ 1 ] Nayak is the current president of the Federation of Indian Rationalist Associations (FIRA), he got re-elected for a fresh term recently. [ 2 ] He founded the Dakshina Kannada Rationalist Association in 1976 and has been its secretary since then. [ 1 ] He also founded an NGO called Aid Without Religion in July 2011. [ 3 ]
He tours the country conducting workshops to promote scientific temper and showing people how to debunk godmen and frauds. He has conducted over 3500 such demonstrations in India, including some in Australia , Greece , England , Norway , Denmark , Sri Lanka and Nepal . [ 4 ] He is also a polyglot who speaks 9 languages fluently, which helps him when he is giving talks in various parts of the country. [ 5 ]
Nayak was named after Swami Vivekananda (born Narendra Nath Datta). He has stated that seeing his father's business premises being repossessed by the bank and his father buying a lottery ticket on the advice of an astrologer to pay off the loan with the total confidence that it would get the first prize made him turn to rationalism . [ 6 ] He married Asha Nayak, a lawyer in Mangaluru in a non-religious ceremony. Nayak started out working as a lecturer in the Department of biochemistry in the Kasturba Medical College in Mangalore in 1978. [ 7 ] [ 8 ] In 1982, he met Basava Premanand , a notable rationalist from Kerala , and was influenced by him. [ 6 ]
Karnataka State Police withdrew his security wherein Nayak was quoted to say that it was an open invitation by forces to finish him. [ 9 ]
Nayak decided to take on full-time anti-superstition activism in 2004 when he heard that a girl had been sacrificed in Gulbarga in Karnataka . [ 4 ] He was an assistant professor of biochemistry when he took voluntary retirement on 25 November 2006, [ 1 ] after working there for 28 years. [ 7 ] [ 8 ]
Before the general election in 2009 , Nayak laid an open challenge to any soothsayer to answer 25 questions correctly about the forthcoming elections. The prize was set at ₹ 1,000,000 [ 10 ] (about US$ 15,000). About 450 responses were mailed to him, but none were found to be correct. [ 11 ] [ 12 ] The Federation of Indian Rationalist Associations has been conducting such challenges since 1991. [ 13 ] During May 2013 Karnataka state assembly election, disappointed at the challenge being one-sided, Nayak had decided against the idea of challenging astrologers this time. But when a Bengaluru-based astrologer Shankar Hegde made claims to predict the election results accurately, he received the challenge. Nayak offered to hand over a cheque of Rs.10 lakh (after deducting taxes as applicable under income Tax Act), if 19 out of the 20 results were proven right. [ 14 ] However, later on astrologer Hegde did not turn up.
Through the organisation named Aid Without Religion which was registered in July 2011, he has been helping people and institutions where there are no religious rituals, superstitious practices, unscientific systems of medicine and such supernatural beliefs. The registration was done at Rahu Kalam, a time of the day which is the most inauspicious – so it was a double rather a triple whammy, a Saturday, new moon day that too in the month of Ati which is considered to be the most unlucky time and at Rahu Kalam! [ 3 ]
He has been featured on National Geographic 's television show Is it real? . [ 15 ] He has also appeared on the Discovery Channel . [ 6 ] He has been a regular columnist at the newspaper Mangalore Today since its inception. [ 8 ] He also serves on the editorial board of the Folks Magazine. [ 16 ]
He has admitted to have been attacked for his activism a few times. [ 17 ] He also has stated that his scooter 's brake wires were once found severed, after an astrologer predicted his death or injury. [ 11 ] He was a close associate to Gauri Lankesh , M. M. Kalburgi , and Narendra Dabholkar ; all three like-minded and were assassinated in a more-or-less similar fashion. [ 18 ]
He was also involved in fighting against Midbrain activation , an alleged modern technique that enables students to see objects despite being blindfolded. [ 19 ] In March 2017, there was an attempt on Narendra Nayak's life. During the early morning hours, while on his way to the Mangala swimming pool in his car, he was approached by two unidentified men in a bike wearing helmets and hinted that his tyres were punctured. An unfazed Nayak suspected foul play and with a great presence of mind drove all the way to a nearby gas station and saw that everything was in order. He immediately filed a Police Complain. Nayak suspected that this attempt on his life could possibly be the repercussions to his fight for the justice of the slain RTI activist Vinayak Baliga , who was murdered exactly a year previous to this episode. Nayak's personal gunman was on holidays. Nayak continues to have personal gunman handed over by Mangalore Police till date. [ 20 ]
Narendra presented at the first Global Congress on Scientific Thinking and Action which was held on March 17–20, 2021. During Session III on Alternative Medicine, he talked about the wide use of alternative medicines in India, including homeopathy, and said that various alternative treatments are often claimed to be Indian in origin. In addition, he states that the relatively low death rate from COVID in India has been falsely attributed to the use of homeopathic medicines as preventative. When asked what should be done about the use of alternative medicines in India, he said, flatly, “They should be banned.” [ 21 ] [ 22 ]
Nayak advocates that more people should be taught to perform the so-called miracles of godmen . [ citation needed ] He also advocates that people should be trained to recognize pseudoscience and demand scientific evidence . He holds the opinion that well-known scientists should be convinced to join the cause and form pressure groups against pseudoscience. [ 23 ]
He is also lobbying for a bill for the separation of state and religion to be introduced in the Indian parliament . [ 24 ] [ 25 ] After the murder of anti-superstition activist Narendra Dabholkar and enactment of the anti-superstition ordinance in Maharashtra state, Nayak expressed the need of a similar law in Karnataka . [ 26 ]
Regarding fellow Mangalorean George Fernandes , Nayak said the "You can hate George Fernandes, You can love Fernandes, but you cannot ignore him". [ 27 ] Nayak was the guest of honour during the launch event of the book Bandh Samrat - Tales of Eternal Rebel written on George Fernandes's early trade union activities in Mangalore and Bombay [ 28 ] | https://en.wikipedia.org/wiki/Narendra_Nayak |
Narrativity has previously been applied as a method of research and form of therapy. Narrative gerontology applies narratives to explore the metaphor of “life as story” and is intended as a “heuristic for the study of aging”. [ 1 ] Thus, narrative gerontology can be understood as a method to view ageing and what it entails and it encompasses the view that people can add value to their lives by creating and maintaining a personal narrative. [ 2 ]
Constructing narratives can be thought to be primarily motivated by the desire to make sense of experiences. Narratives may be combined with interpersonal manipulation such as teaching or impressing listeners. [ 3 ]
Possible needs to gain meaning from experiences include:
Gerontological narratives are organized around a number of themes, such as time, story and wisdom. [ 4 ]
The narrative perspective takes the stance that time is human, not real and felt, not measured. In this respect, human time is considered ‘narrative’ or ‘story time’. Storytime embodies the subjective time of an individual’s life and may vary with flow and focus.
Storytime is considered open with humans being unable to foreshadow events because there are no set endings available to send signals to the past. However, it has been argued that in later reminiscing about life, an individual may “backshadow” where “the past is treated as if it had inevitability lead to the present”. [ 5 ] A further proposed possibility called “sideshadowing” refers to a middle realm of possibility where actual events in addition to potential events are made visible. [ 5 ]
Instead of equal attention, humans have a varied focus on each occurrence in life. For example, multiple years can be summarised under titles like “good times” or short events can take much longer to recall. Discourse time refers to the inequities between experiences and recollections and can be broken down into three overarching features – order, duration and frequency.
Self-storying takes the viewpoint of a novel analogy whereby there is a focus on the narrativity of life in addition to the way it is a “story-world”. It involves stages, levels, genres and contexts.
Three phases of narrative development have been outlined. The pre-mythic phase occurs during childhood, whereby material is being gathered for what later becomes part of the narrative. The mythic phase occurs between adolescence to adulthood and narratives are engaged with greater awareness. The post-mythic phase occurs in later adulthood, during which people edit and retell their life stories.
Narratives are typically constructed to reach a particular goal and may take three forms:
Combinations of these forms can result in the formation of genres within narratives. For example, progressive to regressive could be considered a tragedy.
Narratives can be culturally shaped, involving societies within which humans live. Narrative environments refer to stories of immediate communities such as families, along with broader communities such as gender and any ideological or religious master narratives that the individual believes in.
The subjective understanding of wisdom development includes patterns in narrative structure, self-reflective processes and life-event characteristics. [ 6 ] Narrative coherence, meaning-making and personal growth have been positively correlated with wisdom in addition to the reconstructive and analytical components of self-reflection. Life events tend to be relatively fundamental, culturally non-normative and emotionally negative. Other frequently reported events include those concerning relationships (such as divorce) and those that are life-threatening (such as serious illness).
Research suggests that the richer the story the more resilient the person. [ 7 ]
Using guided autobiographies, research has found that as individuals aged, their narratives suggested they were self-attributing traits of the opposite genders, albeit to different extents. As such, on an individual level, narratives of men and women and how they interpret their lives is not explained by gender role stereotypes. [ 8 ]
Research suggests narratives can differ depending on the mode of narration. [ 9 ] Overall, autobiographical writing groups express more self-refining moments or those related to individual turning points. Conversely, oral reminiscence groups express more group-defining or generally shared historical moments.
Traumatic events challenge the ability to create narratives that provide meaning to events due to the desire to avoid the reflection of associated memories. However, the perception of social support may aid the creation or maintenance of a coherent narrative identity. [ 10 ] Analysis of narratives of male veterans found that those with coherent narratives reported positive interactions with family and friends in earlier and later life while those with incoherent narratives reported negative interactions.
Common motivations for sharing life narratives through reminiscence involve the maintenance of a sense of self and the intergenerational transfer of knowledge. Further purposes include reinforcing claims to dignity and acting as a means of revisiting positive experiences. [ 11 ] However, the nearness of death can create feelings of potential ‘social erasure’. Recording memories using digital tools have been explored, including the possibility of intergenerational digital storytelling. The ability to preserve memories thus provide a semblance of ‘life after death’ and a method of allowing the elderly to feel that they continue to play a role in their loved ones’ lives once they pass. [ 11 ] | https://en.wikipedia.org/wiki/Narrative_gerontology |
Narrowband Internet of things ( NB-IoT ) is a low-power wide-area network (LPWAN) radio technology standard developed by 3GPP for cellular network devices and services. [ 1 ] [ 2 ] The specification was frozen in 3GPP Release 13 ( LTE Advanced Pro ), in June 2016. [ 3 ] Other 3GPP IoT technologies include eMTC (enhanced Machine-Type Communication) and EC-GSM-IoT. [ 4 ]
NB-IoT focuses specifically on indoor coverage, long battery life, and high connection density. NB-IoT uses a subset of the LTE standard, but limits the bandwidth to a single narrow-band of 200kHz. It uses OFDM modulation for downlink communication and SC-FDMA for uplink communications. [ 5 ] [ 6 ] [ 7 ] [ 8 ] [ 9 ] IoT applications which require more frequent communications will be better served by LTE-M , which has no duty cycle limitations operating on the licensed spectrum.
In March 2019, the Global Mobile Suppliers Association (GSA) announced that over 100 operators had either NB-IoT or LTE-M networks. [ 10 ] This number had risen to 142 deployed/launched networks by September 2019. [ 11 ]
2 Mbit/s (EGPRS2B)
16.9 kbit/s (single-tone)
2 Mbit/s (EGPRS2B)
As of March 2019 GSA identified: [ 14 ]
The 3GPP -compliant LPWA device ecosystem continues to grow. In April 2019, GSA identified 210 devices supporting either Cat-NB1/NB-2 or Cat-M1 – more than double the number in its GAMBoD database at the end of March 2018. [ 16 ] This figure had risen a further 50% by September 2019, with a total of 303 devices identified as supporting either Cat-M1, Cat-NB1 (NB-IoT) or Cat-NB2. Of these, 230 devices support Cat-NB1 (including known variants) and 198 devices support Cat-M1 (including known variants). The split of devices (as of September 2019) was 60.4% modules, 25.4% asset trackers, and 5.6% routers, with data loggers, femtocells, smart-home devices, and smart watches, USB modems, and vehicle on-board units (OBUs), making up the balance. [ 17 ]
In 2018 first NB-IoT data loggers and other certified devices started to appear. For example ThingsLog released their first CE certified single channel NB-IoT data logger on Tindie in late 2018.
To integrate NB-IoT into a maker board for IoT developments, SODAQ, a Dutch IoT hardware and software engineering company, crowdfunded an NB-IoT shield on Kickstarter . [ 18 ] They then went on to partner with module manufacturer u-blox to create maker boards with NB-IoT and LTE-M integrated. [ 19 ]
Since 2021, there also is a cheap all-in-one NB-IoT solution available to the general public developed by the Chinese manufacturer Ai-Thinker. [ 20 ]
At the beginning of 2023 the Belgian company DPTechnics released the Walter IoT board which combines an ESP32-S3 together with a Sequans Monarch 2 NB-IoT/LTE-M platform. The board is focused on long-term availability and includes a GNSS receiver. | https://en.wikipedia.org/wiki/Narrowband_IoT |
In mathematics, the Narumi polynomials s n ( x ) are polynomials introduced by Narumi (1929) given by the generating function
( Roman 1984 , 4.4), ( Boas & Buck 1958 , p.37)
This polynomial -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Narumi_polynomials |
The nasal mucosa lines the nasal cavity . It is part of the respiratory mucosa , the mucous membrane lining the respiratory tract . [ 1 ] [ 2 ] The nasal mucosa is intimately adherent to the periosteum or perichondrium of the nasal conchae . It is continuous with the skin through the nostrils , and with the mucous membrane of the nasal part of the pharynx through the choanae . From the nasal cavity its continuity with the conjunctiva may be traced, through the nasolacrimal and lacrimal ducts ; and with the frontal , ethmoidal , sphenoidal , and maxillary sinuses , through the several openings in the nasal meatuses . The mucous membrane is thickest, and most vascular, over the nasal conchae . It is also thick over the nasal septum where increased numbers of goblet cells produce a greater amount of nasal mucus . It is very thin in the meatuses on the floor of the nasal cavities, and in the various sinuses . It is one of the most commonly infected tissues in adults and children. Inflammation of this tissue may cause significant impairment of daily activities, with symptoms such as stuffy nose, headache, mouth breathing, etc.
Owing to the thickness of the greater part of this membrane , the nasal cavities are much narrower, and the middle and inferior nasal conchæ appear larger and more prominent than in the skeleton ; also the various apertures communicating with the meatuses are considerably narrowed.
The epithelium of the nasal mucosa is of two types – respiratory epithelium , and olfactory epithelium differing according to its functions. In the respiratory region it is columnar and ciliated. [ 3 ] [ 4 ] Interspersed among the columnar cells are goblet or mucin cells, while between their bases are found smaller pyramidal cells . Beneath the epithelium and its basement membrane is a fibrous layer infiltrated with lymph corpuscles, so as to form in many parts a diffuse adenoid tissue, and under this a nearly continuous layer of small and larger glands , some mucous and some serous, the ducts of which open upon the surface. In the olfactory region the mucous membrane is yellowish in color and the epithelial cells are columnar and non-ciliated; they are of two kinds, supporting cells and olfactory cells . The supporting cells contain oval nuclei, which are situated in the deeper parts of the cells and constitute the zone of oval nuclei; the superficial part of each cell is columnar, and contains granules of yellow pigment , while its deep part is prolonged as a delicate process which ramifies and communicates with similar processes from neighboring cells, so as to form a net-work in the mucous membrane. Lying between the deep processes of the supporting cells are a number of bipolar nerve cells , the olfactory cells, each consisting of a small amount of granular protoplasm with a large spherical nucleus , and possessing two processes—a superficial one which runs between the columnar epithelial cells, and projects on the surface of the mucous membrane as a fine, hair-like process, the olfactory hair; the other or deep process runs inward, is frequently beaded, and is continued as the axon of an olfactory nerve fiber. Beneath the epithelium, and extending through the thickness of the mucous membrane, is a layer of tubular, often branched, glands, the glands of Bowman , identical in structure with serous glands . The epithelial cells of the nose , fauces and respiratory passages play an important role in the maintenance of an equable temperature, by the moisture with which they keep the surface always slightly lubricated. [ 4 ] | https://en.wikipedia.org/wiki/Nasal_mucosa |
The Nasal Provocation Test (NPT or nasal challenge test) is a medical procedure indicated for help the diagnosis of allergic rhinitis and nonallergic rhinitis. [ 1 ] NPT may be monitored by clinical scores, rhinomanometry , acoustic rhinometry , nasal smear cytology and/or spirometry . | https://en.wikipedia.org/wiki/Nasal_provocation_test |
A nasal vaccine is a vaccine administered through the nose that stimulates an immune response without an injection. It induces immunity through the inner surface of the nose , a surface that naturally comes in contact with many airborne microbes . [ 1 ] Nasal vaccines are emerging as an alternative to injectable vaccines because they do not use needles and can be introduced through the mucosal route. Nasal vaccines can be delivered through nasal sprays to prevent respiratory infections, such as influenza .
Nasal inoculation dates as far back as the 17th century in China during the Kangxi Emperor ’s reign. Documentation during this period indicates that the Kangxi Emperor vaccinated his family, army, and others for mild smallpox. Manuals detailing vaccination techniques at the time all focused on sending smallpox up the nose of the individual being vaccinated. Although other vaccination techniques were developed using an infected individual’s scabs, a common method was to place a cotton swab with the fluid from an infected person’s pustule up the nose. [ 2 ]
Following smallpox, influenza became a prominent focus for nasal vaccine development. The first live attenuated influenza vaccine (LAIV) in the form of a nasal spray was created in Russia by the Institute of Experimental Medicine in 1987. This nasal vaccine development was based on the Russian backbone of LAIV while nasal vaccines since then have been based on other LAIV backbones. [ 3 ] The first nasal influenza vaccine was released in the United States in 2001 but was taken off the market due to toxicity concerns. FluMist , one of the most prominent nasal LAIVs, was released in 2003 as nasal LAIVs continued developing. [ 4 ]
Anthrax attacks at the beginning of the 21st century caused a demand for nasal vaccine development. As anthrax is an airborne substance that can be inhaled, a nasal vaccine has the potential to be used to protect individuals from the effects it can have on the respiratory system. [ 5 ] Following the September 11, 2001 terrorist attacks in the United States, several individuals at news stations and U.S. senators died after being sent letters with anthrax as an act of bioterrorism. [ 6 ] Nasal vaccine research and development against anthrax was encouraged by the U.S. government in an effort to vaccinate troops. [ 5 ] [ 7 ] BioThrax , the current anthrax vaccine that is licensed and administered in the United States, requires up to five intramuscular injections and annual boosters; research within the past decade has developed an alternative nasal vaccine that follows the path of infection for anthrax and induces both humoral and cellular immune responses. [ 5 ]
The global COVID-19 pandemic led to a rise in nasal vaccines against coronavirus. International efforts for vaccine development occurred as countries such as India , Iran , Russia , and China created nasal COVID-19 vaccines. [ citation needed ]
Nasal vaccines are a subsection of mucosal immunization as they use a mucosal route for vaccine delivery. As many pathogens can enter the body through the nose, nasal vaccines take advantage of this mechanism to deliver the vaccine. The nose has multiple lines of defense to prevent pathogens from entering further into the body. Nasal hairs are the first defense as they are at the entrance of the nose and prevent large particles from entering. The mucus layer in the nasal cavity can trap smaller particles that get past the nose hairs. [ 8 ] The nasal cavity has a large vascularization network so particles can go through the epithelial layer and directly enter the bloodstream. [ 9 ] Intruding particles will interact with the mucosal immune system if they reach the nasal mucosa. The mucosal immune system is composed of lymphoid tissue, B cells, T cells, and antigen-presenting cells. These different types of cells work together to identify intruding particles and trigger an immune response. [ 8 ] Nasal vaccines must overcome these barriers and get clearance to deliver the viral antigen to patients. [ 4 ] [ 10 ]
Nasal vaccines can come in different forms such as solutions (liquids), powders, gels, and solid inserts. The most prevalent type of nasal vaccine in research and clinical application is solutions due to its ease of use. Although solutions are usually pipetted into test subjects’ nostrils when conducting animal trials for nasal vaccines, nasal sprays are considered the most practical approach for mass human vaccination using nasal vaccines. [ 8 ] A nasal spray is able to bypass the initial layers of the nasal mucosa and deliver the vaccine particles directly to the mucoadhesive layer. [ 11 ] The antigen in the nasal vaccine can then trigger an immune response and prevent infection due to nasal vaccines’ accessibility to the immune system. [ 12 ] [ 13 ]
Nasal sprays are commonly used for delivering drugs in addition to vaccines. Decongestant drugs are often directly delivered to the nose through nasal sprays. Cold and allergy medication can be administered using nasal sprays for local delivery by bypassing nasal hairs and being introduced to the nasal cavity. Intranasal administration can have less drug degradation compared to oral administration because of direct particle delivery. Peptide drugs used for hormone treatments can be delivered nasally through nasal sprays instead of orally to retain particle integrity. Nasal sprays can also be used to deliver diabetes treatment, steroids, and intranasal oxytocin to induce labor. Nasal administration is also used to deliver anesthetics and sedatives due to direct access to the mucosal immune system and bloodstream. [ 14 ]
The olfactory epithelium makes up approximately 7% of the surface area of the nasal cavity and is connected to the olfactory bulb in the brain. Drugs and vaccines can be delivered to the brain past the blood-brain barrier through olfactory nerve cells. [ 14 ]
Compared to injectable vaccines, nasal vaccines can be advantageous because they are safe, painless, and easy to use. Nasal vaccines do not require a needle, which eliminates pain from needlestick injuries and safety concerns due to cross-contamination and needle disposal. Some studies also show that intranasal vaccines can generate cross-reactive antibodies that could lead to cross-protection. [ 8 ]
The live attenuated influenza vaccine (LAIV) in the form of a nasal spray was one of the first nasal vaccines released on the market. Nasal spray LAIVs have been used since the late 1980s as an alternative to the injectable influenza vaccine. [ 3 ] Nasal influenza vaccines have become popular as they reduce the risk of intramuscular injuries from administration and are painless. They can also be given more easily to patients because they do not require a needle.
The most prominent nasal LAIV is FluMist, which was released in 2003. [ 4 ] FluMist, officially known as FluMist Quadrivalent in the United States and Fluenz in Europe, is known to be the only flu vaccine on the market that does not use a needle. [ 15 ] All nasal LAIVs for recent flu seasons (2022-2023) are considered quadrivalents because “they are designed to protect against four types of flu viruses: an influenza A(H1N1) virus, an influenza A(H3N2) virus and two influenza B viruses.” [ 16 ] Although injectable and nasal LAIVs are presented as options for yearly vaccination against influenza, FluMist was pulled off of the United States market from 2016 to 2018 due to its inefficiency against a common influenza strain in children. Since then, FluMist has been reformulated and has re-entered the market. [ 17 ]
The active ingredients in nasal LAIVs are grown in fertilized chicken eggs. The practice of growing viruses in chicken eggs is common in vaccine production because these viruses need to be grown inside cells. [ 18 ] Virus fluid from the incubated chicken eggs is extracted and killed for the viral antigen to be purified for LAIV production. [ 19 ] Similar to other vaccines, nasal LAIVs contain ingredients in addition to the viral antigen. Stabilizers such as gelatine, arginine hydrochloride, monosodium glutamate, and sucrose are commonly used in vaccines to assure the vaccines are still effective during and after production, transportation, and storage as well as delivery. [ 20 ] [ 21 ] Stabilizers are especially important for nasal vaccines as proteases and amino-peptidase in the mucosal membrane can degrade proteins and peptides in vaccines. [ 4 ] Research continues to improve nasal LAIVs as influenza affects nearly 9 million people. [ 22 ] As influenza changes slightly each year, continuous research on new strains can improve vaccine efficiency. Research on nasal vaccine development for nontypeable Haemophilus influenzae shows that the vaccine binding to surface proteins prevented biofilm formation. As a result, this vaccine can have the potential to treat ear infections caused by biofilm from influenza infection. [ 23 ] New components like α-galactosylceramide (α-GalCer) are also being researched to be used as nasal vaccines against influenza. Since α-GalCer induced immune responses when immunized with a replication-deficient live adenovirus, there is evidence that nasal LAIVs can be co-immunized with other treatments against influenza. [ 24 ]
Prior to the 2020 global COVID-19 pandemic, animal studies in 2004 on African green monkeys tested a SARS-associated coronavirus (SARS-CoV) vaccine and showed that these monkeys did not emit the virus from their upper respiratory tract after being infected. [ 25 ] Since then, several intranasal COVID-19 vaccines have been developed with the onset of the COVID-19 pandemic. inCOVACC , Razi Cov Pars , Sputnik , and Convidicia are nasal COVID-19 vaccines that were developed throughout the world to improve vaccine availability and reduce the spread of COVID-19. [ citation needed ]
In August 2020, during the COVID-19 pandemic , studies in mice and monkeys demonstrated that protection from the new coronavirus might be obtained through the nasal route. Another study postulated that if a COVID-19 vaccine could be given by a spray in the nose, people might be able to vaccinate themselves. [ 26 ] Research about the main characteristics of nasal spray vaccines that can affect the efficiency of vaccine delivery for COVID-19 indicates that the spray cone angle can impact the delivery efficiency; droplet initial velocity and composition did not have as much of an impact on nasal vaccine efficiency as the spray cone angle. [ 27 ]
India and China approved inCOVACC and Convidecia , respectively, to be used as boosters for those who have already received at least two COVID-19 vaccine doses. [ 28 ] Although nasal COVID-19 vaccine research continues in the United States, lack of government funding could prevent this research from moving on to human trials to get approval for public administration. [ 29 ] Privately funded research for nasal COVID-19 vaccines is starting to reach clinical trials; a nasal COVID-19 vaccine by Blue Lake Biotechnology has started its Phase 1 clinical trials as of late February 2023. Scientists speculate that nasal vaccines might have an advantage over other types of vaccines because they provide immune defense at the site of administration. [ 30 ]
Species other than humans use nasal vaccines to prevent diseases. Intranasal vaccines are used on dogs for Bordetella bronchiseptica to prevent infectious tracheobronchitis (ITB). ITB, commonly known as kennel cough, typically spreads in highly populated environments such as kennels and dog shelters. Consistent vaccination against ITB using an intranasal vaccine can create an immune response to protect the vaccinated dog. Consistent vaccination against ITB using an intranasal vaccine can create an immune response to protect the vaccinated dog. [ 31 ]
Cattle receive nasal vaccines against diseases such as bovine herpesvirus 1 , parainfluenza type 3, and bovine rhinotracheitis virus. [ 32 ] [ 33 ] As all three of these viruses are related to respiratory infection, using an intranasal route can bring the vaccine directly to the respiratory system.
Recent discoveries indicate that rainbow trout have a previously unknown lymphoid structure in their nasal cavity. This structure allows them to have fast innate and adaptive responses to nasal vaccines. [ 34 ]
Current research is exploring new technologies and developments to improve nasal vaccine delivery methods. Particle size and characteristics have become a focus of research as smaller particles can travel more easily to reach the epithelial layer of the nasal cavity compared to larger particles. Nanoparticles and nanosystems are being researched to optimize nasal delivery. Coated nanoparticles are an area of focus due to their properties to induce immune effects. Glycol chitosan-coated nanoparticles induced more of an immune response compared to the other types of nanoparticles. [ 35 ] Nanocarriers designed based on the characteristics of the nasal epithelium can be used to deliver nasal vaccines and can therefore make nasal vaccination more accessible. [ 36 ] Polymeric nanosystems are also being developed to deliver vaccines to target sites while preventing them from degrading; current research is focused on understanding the material and physical properties of biodegradable materials to be used in nanosystems to improve vaccine efficacy. [ 37 ] Research on the movement of nasal vaccine particles is focused on developing more effective ways for these vaccines to enter the body. An animal study on mice tested how a nasal vaccine can bypass issues with entry into the nasal epithelium by taking advantage of ciliary movement. The results indicated that tubulin tyrosine ligase-like family member 1 (Ttll1) knockout mice had higher levels of the vaccine antigen compared to the hetero mice. [ 38 ] | https://en.wikipedia.org/wiki/Nasal_vaccine |
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