Briefing: Nanotechnology

Nanotechnology has great relevance to India today as it has the potential to address the needs of those at the bottom of the economic pyramid through innovative technology solutions.

INDIA AND NANOTECHNOLOGY

Nanotechnology has great relevance to India today as it has the potential to address the needs of those at the bottom of the economic pyramid through innovative technology solutions.

India is in a unique position to excel in the commercialization of nanotechnology. There is a strong market demand for innovative technology solutions that conventional technologies are unable to satisfy. India is richly endowed with natural resources (sunshine, rain, minerals) and nanotechnology offers an opportunity to transform these resources into sustainable and cost-effective solutions that can transform the lives of the masses and the economy of the nation.

Nanoscience is the study of phenomena and manipulation of materials at atomic, molecular, and macromolecular scales, where properties differ significantly (sometimes dramatically) from those at larger scales. Nanotechnology is the application of nanoscience and involves the design, characterization, production, and application of structures, devices, and systems by controlling shape and size on the nanoscale.

Nanotechnology, by virtue of its inherent inter-disciplinary nature, has brought about a paradigm shift in the way research, both in academics and industry, is planned and carried out. Recent innovations in nanotechnology and the successful commercialization of nano-enabled products have cut across the traditional borders of the various disciplines of science and engineering. Prioritization of nanotechnology efforts will help the society solve the most complex problems of energy, water, food, transportation, and shelter in an affordable and a sustainable way.

TECHNOLOGY OVERVIEW: THE NANO AGE

It is customary to trace the evolution of modern man by the materials technology that he mastered (stone age, iron age, bronze age). Now we are witnessing the emergence of the nano age – or more precisely as the age of engineered nanomaterials. Nanomaterials are called so by virtue of having at least one dimension in the order of 1 to 100 nanometers (nm) and unique or novel properties that arise from their small size. It helps the subsequent discussion to take a detour and to get a feel of this small size (2 gm) of spherical nanoparticles of Al (100 nm) which contain sufficient particles to give every human on the planet 300,000 particles each.

The dramatic changes that take place in physical, chemical, and biological properties of materials when they are endowed with nanoscale structure is something fascinating to watch. It is not difficult to understand the causes that drive these dramatic changes. Physical properties of a solid material (like optical transparency, electric conductivity, magnetic permeability, and mechanical strength) are manifestations of the way components of matter interact. If we probe at a more fundamental level, the energy levels in nanostructures, such as nanoclusters, are quantized and deviate well from the predictions of classical condensed-matter physics. For instance, silicon, an indirect semiconductor that shows only very weak luminescence, can be excited purely through nanostructuring to shine in rainbow colors.

Nanostructuring can radically change the chemical properties of materials. In nanostructured materials, the ratio of reactive surface atoms to those in the bulk (hence relatively inert) increases by order of magnitude. Nanoporous materials, whose useful functions are enhanced by the high surface area, find valuable application in catalysis, electrochemistry, materials separation, and more. In the realm of biology and medicine, nanotechnology enables novel approaches in medicine therapy (for example, targeted drug delivery), regenerative medicine (improved implants, self-healing features), and diagnostics (enhanced medical imaging through improved contrast agents). Materials technologists were earlier constrained by the properties of available materials, but nanotechnology is rapidly changing that scenario.

Nanotechnology kindles a materials scientist’s creativity by helping him/her to intelligently design the materials for specific applications.

The spectrum of nanotechnology applications ranges from high tech fields like electronics, optoelectronics, and advanced materials to more traditional branches of mechanical engineering, construction, and textile industry. We also find nanotechnology in products of daily use like cosmetics (nanomaterial UV-blockers in sunscreen creams), sport equipment (nanostructured surface contours on golf balls), and household products (washing machine using nanosilver for antibacterial action, water purifier using nanosilver). Current market forecasts for nano-optimized products expect an economic leverage effect of nanotechnology to a world market volume of up to three trillion dollars by 2015. Let us look at the well established nano-enabled products that are around us today.

Environmental and energy technologies have benefited from the use of nanomaterials – high efficiency nanostructured catalysts, nanomembranes for effective wastewater treatment, anti-reflection layers to enhance the energy conversion of solar cells, and nanostructured coatings for corrosion and wear resistance (see Nanolubricants in the Making). Photocatalytic air and wastewater treatment using nano titanium dioxide, groundwater remediation with iron nanoparticles are ready to enter the market. Health care and medicine routinely use nanomaterials in the form of nano-sized contrast agents for medical imaging, nanoscale drug carriers for targeted drug delivery, nanomembranes for dialysis, and biochips for in- vitro diagnostics. Nano cancer therapy (hyperthermia, that is, localized heating by infrared absorbers like nano gold particles), nanostructured hydroxyapatite as bone substitute, and quantum dot markers for diagnostics will soon be available.

Electronics industry is flooded with examples of advantageous use of nanomaterials. For example, hard disk storage units with giant magnetoresistance (GMR) read heads, compact flash-storage devices, and polymer electronics such as RFID tags. The next-generation electronics will utilize silicon electronics 32 nm structures, carbon nanotube (CNT) field emission displays, nanoparticle heat removers for thermal management, magnetoresistive random access memory, and phase change memory technologies. Optical application of nanomaterials include nanocoatings for scratch proof plastic lenses, ultra precision optics for telescopes, high bright LEDs and anti-reflection coatings on glass. We find numerous nanomaterials applied in our cars too – nanostructured exhaust catalysts, nanocoated diesel injectors, nanofillers in tires, scratchresistant and optically clear lacquers. The next wave of optical applications are based on advances in solid state lighting – inorganic LEDs for illumination, organic LEDs for display, nanophosphors, quantum dot laser and more. Nanomaterials have even permeated the clothes that we wear, for example, dirt-repellant coatings on fabric, antibacterial coating using nano silver, and perfume-impregnated textile using nanocontainers.

The major markets for functional nanomaterials today, the largest by volume, are automotive catalysts, chemical mechanical planarization (CMP), magnetic recording media, and sunscreens with 11, 500, 9, 400, 3,100, and 1, 500 ton respectively. Not all applications use nanomaterials in such large quantities.

For instance, biodetection and labeling materials are used in very minute quantities leading to their sales in much smaller quantities. But the price per kilo of such labeling materials will be higher than CMP materials or UV-blockers for sunscreens.

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The small size of the nanoparticles not only leads to useful properties, but also to concerns about potential health and environmental risks. The primary concerns include: One, at the tiny scale of few nanometers, the ratio of surface area to volume increases by orders of magnitude. With more reactive sites of the molecule thus exposed, the particle may have greater reactive potential and therefore greater potential for toxicity. Second, the small sized nanoparticles can easily permeate biological membranes, making them more readily absorbed and widely dispersed throughout the human body. Ingestion and possibly dermal penetration are likely to become increasingly significant exposure routes as engineered nanomaterials are used in an ever-widening range of products. It is important to the success of nanotechnology industry that health and environmental concerns are addressed early and adequately through systematic scientific investigations.

We need to create sustainable nanotechnological innovations that solve the critical needs of customers. As the first step, the nanomaterials industry needs to focus its efforts to reliably manufacture nanomaterials in an economic and a safe manner. — Shankar MV, principal scientist, R&D, Dow Chemical Company.