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Nanotechnology

Nanotechnology is science, engineering, and technology conducted at the nano-scale, which is about 1 to 100 nanometers. One nanometer (nm) is one-billionth or (10-9) of a metre.
Nano-science and nanotechnology are the study and application of extremely small things and can be used across all the other science fields, such as chemistry, biology, physics, materials science, and engineering. Areas of physics such as nanoelectronics, nanomechanics, nanophotonics, and nanoionics have evolved during the last few decades to provide a basic scientific foundation of nanotechnology.

Two main approaches are used in nanotechnology

• In the “bottom-up” approach, materials and devices are built from molecular components that assemble themselves chemically by principles of molecular recognition.
• In the “top-down” approach, nano-objects are constructed from larger entities without atomic-level control.

The ideas and concepts behind nanoscience and nanotechnology started with a talk entitled “There’s Plenty of Room at the Bottom” by physicist Richard Feynman at an American Physical Society meeting at the California Institute of Technology (CalTech) on December 29, 1959, long before the term nanotechnology was used. Feynman described a process in which scientists would be able to manipulate and control individual atoms and molecules.

Note: Size distribution, specific surface feature, and quantum size effects are the principal factors that cause the properties of nanomaterials to differ significantly from other materials.

The nanomaterials field includes subfields which develop or study materials having unique properties arising from their nanoscale dimensions.

• Interface and colloid science have given rise to many materials that may be useful in nanotechnologies, such as carbon nanotubes and other fullerenes, and various nanoparticles and nanorods.
• Nanomaterials with fast ion transport are related also to nanoionics and nanoelectronics.
• Progress has been made in using these materials for medical applications such as Nanomedicine.
• Nanoscale materials such as nanopillars are sometimes used in solar cells that combat the cost of traditional silicon solar cells.
• Development of applications incorporating semiconductor nanoparticles to be used in the next generation of products, such as display technology, lighting, solar cells, and biological imaging.
• The recent application of nanomaterials includes a range of biomedical applications, such as tissue engineering, drug delivery, and biosensors.

Atomic force microscopy (AFM)

Atomic force microscopy (AFM) or scanning force microscopy (SFM) is a very-high-resolution type of scanning probe microscopy (SPM), with demonstrated resolution on the order of fractions of a nanometer, more than 1000 times better than the optical diffraction limit.

The information is gathered by “feeling” or “touching” the surface with a mechanical probe. Piezoelectric elements that facilitate tiny but accurate and precise movements on (electronic) command enable precise scanning.

The AFM has three major abilities: force measurement, imaging, and manipulation.

• In force measurement, AFMs can be used to measure the forces between the probe and the sample as a function of their mutual separation. This can be applied to perform force spectroscopy, to measure the mechanical properties of the sample, such as the sample’s Young’s modulus, a measure of stiffness.
• For imaging, the reaction of the probe to the forces that the sample imposes on it can be used to form an image of the three-dimensional shape (topography) of a sample surface at a high resolution. This is achieved by raster scanning the position of the sample with respect to the tip and recording the height of the probe that corresponds to a constant probe-sample interaction (see section topographic imaging in AFM for more details). The surface topography is commonly displayed as a pseudocolor plot.
• In manipulation, the forces between tip and sample can also be used to change the properties of the sample in a controlled way. Examples of this include atomic manipulation, scanning probe lithography, and local stimulation of cells.

Tissue Nano-transfection

Nanochip could heal injuries or regrow organs with one touch. A tiny device that sits on the skin and uses an electric field to reprogramme cells could be a breakthrough in the way we treat injured or ageing tissue. A novel device that reprogrammes skin cells could represent a breakthrough in repairing injured or ageing tissue.

The new technique, called tissue nano-transfection, is based on a tiny device that sits on the surface of the skin of a living body.

• An intense, focused electric field is then applied across the device, allowing it to deliver genes to the skin cells beneath it – turning them into different types of cells.
• It offers an exciting development when it comes to repairing damaged tissue, offering the possibility of turning a patient’s own tissue into a “bioreactor” to produce cells to either repair nearby tissues, or for use at another site.
• It avoids an intermediary step where cells are turned into what are known as pluripotent stem cells, instead of turning skin cells directly into functional cells of different types. It is a single-step process in the body.
• The new approach does not rely on applying an electric field across a large area of the cell, or the use of viruses to deliver the genes.

Top-down and Bottom-up methods

Top-down and bottom-up methods are two types of approaches used in nanofabrication. The bottom-up approach is more advantageous than the top-down approach because the former has a better chance of producing nanostructures with fewer defects, more homogenous chemical composition, and better short- and long-range ordering.
A bottom-up synthesis method implies that the nanostructures are synthesized onto the substrate by stacking atoms onto each other, which gives rise to crystal planes, crystal planes further stack onto each other, resulting in the synthesis of the nanostructures. A bottom-up approach can thus be viewed as a synthesis approach where the building blocks are added onto the substrate to form the nanostructures.
A top-down synthesis method implies that the nanostructures are synthesized by etching out crystals planes (removing crystal planes) which are already present on the substrate. A top-down approach can thus be viewed as an approach where the building blocks are removed from the substrate to form the nanostructure.

• Molecular self-assembly is the process by which molecules adopt a defined arrangement without guidance or management from an outside source. There are two types of self-assembly. These are intramolecular self-assembly and intermolecular self-assembly.
• Molecular Beam Epitaxy is an evaporation process performed in an ultra-high vacuum for the deposition of compounds of extreme regularity of layer thickness and composition from well-controlled deposition rates.
• The agglomeration of metallic nanoparticles can be performed using the well-known inert gas condensation process.

Dip Pen Nanolithography (DPN)

Dip pen nanolithography (DPN) is a scanning probe lithography technique where an atomic force microscope (AFM) tip is used to create patterns directly on a range of substances with a variety of inks.

• DPN is the nanotechnology analog of the dip pen (also called the quill pen), where the tip of an atomic force microscope cantilever acts as a “pen,” which is coated with a chemical compound or mixture acting as an “ink,” and put in contact with a substrate, the “paper.”
• DPN enables the direct deposition of nanoscale materials onto a substrate in a flexible manner. Recent advances have demonstrated massively parallel patterning using two-dimensional arrays of 55,000 tips. Applications of this technology currently range through chemistry, materials science, and the life sciences, and include such work as ultra-high density biological nanoarrays, and additive photomask repair.

Nano Composite

Nano Composite 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.

• The idea behind Nanocomposite is to use building blocks with dimensions in the nanometre range to design and create new materials with unprecedented flexibility and improvement in their physical properties.
• 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.
• 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.
• 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 fibers (e.g. carbon nanotubes or electrospun fibers). 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.
• This large amount of reinforcement surface area means that a relatively small amount of nanoscale reinforcement can have an observable effect on the macro scale properties of the composite. For example, adding carbon nanotubes improves the electrical and thermal conductivity.

Ecophagy

Grey goo (also spelled gray goo) is a hypothetical end-of-the-world scenario involving molecular nanotechnology in which out-of-control self-replicating robots consume all biomass on Earth while building more of themselves, a scenario that has been called ecophagy (“eating the environment”, more literally “eating the habitation”).
The original idea assumed machines were designed to have this capability, while popularizations have assumed that machines might somehow gain this capability by accident.
Self-replicating machines of the macroscopic variety were originally described by mathematician John von Neumann, and are sometimes referred to as von Neumann machines or clanking replicators.

UNNATI Program by ISRO

Unnati or Unispace Nanosatellite Assembly and Training by ISRO is a capacity building program on nano-satellite development.

• ISRO’s U.R Rao Satellite Centre at Bengaluru will be conducting the program for the next 3 years starting from January 2019.
• It also will cooperate and help the participant countries to strengthen their capabilities in assembling, integrating, and testing nanosatellites.

Graphene

• Graphene has been touted in the global electronics industry as a “miracle material” given its strength, electrical conductivity, and elasticity, and has been seen as an alternative to lithium-ion batteries since its discovery in 2004.
• It is a form of carbon that can be used to develop smaller, slimmer batteries but with higher capacity.
• Graphene is an allotrope (form) of carbon consisting of a single layer of carbon atoms arranged in a hexagonal lattice. 
• It is nearly transparent.
• It is the basic structural element of many other allotropes of carbon, such as graphite, charcoal, carbon nanotubes, and fullerenes.
• Its thin composition and high conductivity means it is used in applications ranging from miniaturized electronics to biomedical devices.
• These properties also enable thinner wire connections; providing extensive benefits for computers, solar panels, batteries, sensors, and other devices.
• The one-atom-thick sheets of carbon conduct electrons better than silicon and have been made into fast, low-power transistors. Researchers have measured the intrinsic strength of graphene, and they’ve confirmed it to be the strongest material ever tested.
• Applications
  (i) Graphene is widely used in making solar cells, light-emitting diodes, touch panels, and smart windows. Graphene supercapacitors serve as energy storage devices with a capacity for faster charging and a longer life span than traditional electrolytic batteries.
  (ii) Other potential applications of graphene include water filtration and purification, renewable energy, sensors, personalized healthcare, and medicine, to name a few.

Nanomaterials

Carbon Nanotubes

Carbon nanotubes (CNTs) are an allotrope (Not isotope) of carbon.

• They take the form of cylindrical carbon molecules and have novel properties that make them potentially useful in a wide variety of applications in nanotechnology, electronics, optics, and other fields of materials science.
• They exhibit extraordinary strength and unique electrical properties and are efficient conductors of heat.
• Inorganic nanotubes have also been synthesized.
• Nanotubes are members of the fullerene structural family, which also includes buckyballs.
• Whereas buckyballs are spherical in shape, a nanotube is cylindrical, with at least one end typically capped with a hemisphere of the buckyball structure.
• Their name is derived from their size, since the diameter of a nanotube is on the order of a few nanometers (approximately 50,000 times smaller than the width of a human hair), while they can be up to several millimeters in length.
• There are two main types of nanotubes: single-walled nanotubes (SWNTs) and multiwalled nanotubes (MWNTs).

Fullerenes

Buckminsterfullerene C60, also known as the buckyball, is a representative member of the carbon structures known as fullerenes. Members of the fullerene family are a major subject of research falling under the nanotechnology umbrella.
Fullerenes are also called Buckyballs due to their shape.

• Buckyballs may be used to trap free radicals generated during an allergic reaction and block the inflammation that results from an allergic reaction.
• The antioxidant properties of buckyballs may be able to fight the deterioration of motor function due to multiple sclerosis.
• Combining buckyballs, nanotubes, and polymers to produce inexpensive solar cells that can be formed by simply painting a surface.
• Buckyballs may be used to store hydrogen, possibly as a fuel tank for fuel cell-powered cars.
• Buckyballs may be able to reduce the growth of bacteria in pipes and membranes in water systems.
• Researchers are attempting to modify buckyballs to fit the section of the HIV molecule that binds to proteins, possibly inhibiting the spread of the virus.
• Making bulletproof vests with inorganic (tungsten disulfide) buckyballs.

Steps by Government

• Department of Science and Tech-Nanomission (nano-biotechnology activities) through DBT, ICMR, and CoE in Nanoelectronics by MeitY support nanoscience, nanotechnology, nanobiotechnology, and nanoelectronics activities.
• Eighteen sophisticated analytical instruments facilities (SAIFs) established by DST across India play a major role in the advanced characterization and synthesis of nanomaterials for various applications.
• The Center of Excellence in Nanoscience and Nanotechnology established by DSTNanomission helps research and PG students in various thrust areas.
• Thematic Units of Excellence (TUEs) for various areas of nanoscience and nanotechnology play a major role in product-based research to support nanotechnology.
• Visveswaraya Ph.D. fellowships offered by MeitY supports various nanotechnology activities in the country.
• INSPIRE scheme supports research fellows to work in interdisciplinary nanotechnology, nanoscience, and nano-biotechnology areas.
• DST-Nanomission supports more than 20 PG teaching programs to create a baseline for nanoscience and nanotechnology in India, out of about 70 PG programs currently running in India.