NANO-TECHNOLOGY AND GMR TECHNOLOGY
INTRODUCTION:
Nanotechnology shortened to “Nanotech” is the study of the control of matter on an atomic and molecular scale. Atoms are the building blocks for all matter in our universe. You and everything around you are made of atoms. Nature has perfected the science of manufacturing matter molecularly. For instance, our bodies are assembled in a specific manner from millions of living cells. Cells are nature’s nanomachines. At the atomic scale, elements are at their most basic level. On the nanosc+-ale, we can potentially put these atoms together to make almost anything.
Nanotechnology is a fundamental, enabling technology, allowing us to do new things in almost every conceivable technological discipline. Nano means small (10A-9 m) but of high potency, and emerging with large applications piercing through all the disciplines of knowledge, leading to industrial and technological growth.
Richard Feynman has been credited with introducing the concept of nanotechnology (creation of devices at the molecular scale) in his book There’s Plenty of Room at the Bottom in 1959.
Nanotechnology deals with materials and machines on an incredibly tiny scale — less than one billionth of a meter. In its original sense, ‘nanotechnology’ refers to the projected ability to construct items from the bottom up, using techniques and tools being developed today to make complete, high-performance products. The potential of this technology to change our world is indeed truly staggering. It will affect every aspect of our lives, from medicine, to the power of our computers, the energy we require, the cars we drive, the building we live in, and even the clothes we wear. It will continuously generate new capabilities, new products, new markets. Its impact in society will be broad.
HOW NANOTECHNOLOGY WORKS
The transition from microparticles to nanoparticles can lead to a number of changes in physical properties. Two of the major factors in this are the increase in the ratio of surface area to volume, and the size of the particle moving into the realm where quantum effects predominate. The increase in the surface-area-to-volume ratio, which is a gradual progression as the particle gets smaller, leads to an increasing dominance of the behaviour of atoms on the surface of a particle over that of those in the interior of the particle.
This affects both the properties of the particle in isolation and its interaction with other materials. High surface area is a critical factor in the performance of catalysis and structures such as electrodes, allowing improvement in performance of such technologies as fuel cells and batteries. It is conceived that this emerging developmental research will allow us to arrange atoms and molecules in most of the ways permitted by physical laws.
Their optical properties, e.g. fluorescence, become a function of the particle diameter. When brought into a bulk material, nanoparticles can strongly influence the mechanical properties of the material, like stiffness or elasticity. For example, traditional polymers can be reinforced by nanoparticles resulting in novel materials which can be used as lightweight replacements for metals. Therefore, an increasing societal benefit of such nanoparticles can be expected. Such nanotechnologically enhanced materials will enable a weight reduction accompanied by an increase in stability and an improved functionality.
Nanotechnology is rapidly becoming an interdisciplinary field. Biologists, chemists, physicists and engineers are all involved in the study of substances at the nanoscale.
Nanotechnology Helps us to:
- Get essentially every atom in the right place.
- Make almost any structure consistent with the laws of physics that we can specify in molecular detail.
- Have manufacturing costs not greatly exceeding the cost of the required raw materials and energy.
Four Phases of Development Visualised
The present phase is that of passive nanostructures, materials designed to perform one task. The second phase, which we are just entering, introduces active nanostructures for multitasking; for example, actuators, drug delivery devices, and sensors. The third generation is expected to begin emerging around 2010 and will feature nanosystems with thousands of interacting components. A few years after that, the first integrated nanosystems, functioning much like a mammalian cell with hierarchical systems within systems, are expected to be developed.
CONCEPTS COMMONLY ASSOCIATED WITH NANOTECHNOLOGY
There are two concepts commonly associated with nanotechnology
Positional Assembly: Clearly, we would be happy with any method that simultaneously achieved the first three objectives. However, this seems difficult without using some form of positional assembly (to get the right molecular parts in the right places) and some form of massive parallelism (to keep the costs down).
The need for positional assembly implies an interest in molecular robotics, e.g., robotic devices that ire molecular both in their size and precision. These molecular scale positional devices are likely to resemble very small versions of their everyday macroscopic counterparts. Positional assembly is frequently used in normal macroscopic manufacturing today, and provides tremendous advantages. Imagine trying to build a bicycle with both hands tied behind your back! The idea of manipulating and positioning individual atoms and molecules is still new and takes some getting used to. However, as Feynman aid in a classic talk in 1959: “The principles of physics, as far as I can see, do not speak against the possibility of maneuvering things atom by atom.” We need to apply at the molecular scale the concept lat has demonstrated its effectiveness at the macroscopic scale: making parts go where we want by putting them where we want.
Massive Parallelism: One robotic arm assembling molecular parts is going to take a long time to assenl the anything large – so we need lots of robotic arms: this is what we mean by massive parallelism. While earlier proposals achieved massive parallelism through self replication, today’s “best guess” is that future molecular manufacturing systems will use some form of convergent assembly. In this process vast numbers of small parts are assembled by vast numbers of small robotic arms into larger parts, those larger parts are assembled by large robotic arms into still larger parts, and so forth. If the size of the parts doubles at each iteration, we can go from one nanometer parts (a few atoms in size) to one meter parts (almost as big as a person) in only 30 steps.
Ø Apocalyptic Goo
Eric Drexler, the man who introduced the word nanotechnology, presented a frightening apocalyptic vision–self-replicating nanorobots malfunctioning, duplicating themselves a trillion times over, rapidly consuming the entire world as they pull carbon from the environment to build more of themselves. It’s called the “grey goo’ scenario, where a synthetic nano-size device replaces all organic material. Another scenario involves nanodevices made of organic material wiping out the Earth – the “green goo” scenario.
COMMERCIALISED NANOMATERIALS
Ø Carbon Nanotube
The discovery that carbon could form stable, ordered structures other than graphite and diamond stimulated researchers worldwide to search for other new forms of carbon. The search was given new impetus when it was shown in 1990 that C60 could be produced in a simple arc-evaporation apparatus readily available in all laboratories. It was using such an evaporator that the Japanese scientist Sumio lijima discovered fullerene-related carbon nanotubes in 1991. Carbon nanotubes are molecular-scale tubes of graphitic carbon with outstanding properties. They are among the stiffest and strongest fibres known, and have remarkable electronic properties and many other unique characteristics. Commercial applications have been rather slow to develop, however, primarily because of the high production costs of the best quality nanotubes.
These cylindrical carbon molecules have novel properties that make them potentially useful in many applications in nanotechnology, electronics, optics and other fields of materials science, as well as potential uses in architectural fields. They exhibit extraordinary strength and unique electrical properties, and are efficient conductors of heat.
Ø Nanotube Applications
The properties of carbon nanotubes have caused researchers and companies to consider using them in several fields. For example, because carbon nanotubes have the highest strength to weight ratio of any known material IT researchers at NASA are combining nanotubes with other materials into composites that can be used to build lightweight spacecraft.
Another property of nanotubes is that they can easily penetrate membrances such as cell walls. In (act, nanotubes long, narrow shape make them look like miniature needles, so it makes sense that they can function a like a needle at the cellular level. Medical researchers are using this property by attaching molecules that are c attracted to cancer cells to nanotubes to deliver drugs directly to the diseased cells.
Another interesting property of nanotubes is that their electrical resistance changes significantly when other molecules attach themselves to the carbon atoms. Companies are using this property to develop sensors that can detect chemical vapors such as carbon monoxide or biological molecules.
These are just a few of the potential uses of carbon nanotubes. The following survey of carbon nanotube applications introduces these and many other uses.
A survey of carbon nanotube applications under development:
- Researchers and companies are working to use carbon nanotubes in various fields. The list below introduces many of these uses.
- Strong, lightweight composites of carbon nanotubes and other materials that can be used to build lightweight spacecraft.
- Cables made from carbon nanotubes strong enough to be used for the Space Elevator to drastically reduce the cost of lifting people and materials into orbit.
- Taking advantage of nanotubes ability to enter cancer cells by attaching targeting molecules which have an affinity to cancer cells as well as anti-cancer drugs to the nanotubes which safely transports an anti-cancer drug are tough the bloodstream to the tumor.
- Stronger bicycle components made by adding carbon nanotubes to a matrix of carbon fibers. Improve the healing process for broken bones by providing a carbon nanotube scaffold for new bone material grow on.
- Sensors using carbon nanotube detection elements capable of detecting a range of chemical vapors. These depend upon the fact that the resistance of a carbon nanotube changes in the presence of a chemical
- Static dissipative plastic molding compounds containing nanotubes that can be used to make parts such as automobile fenders that can be electrostatically painted.
- Carbon nanotubes used to direct electrons to illuminate pixels, resulting in a lightweight, millimeter thick “nano emissive” display panel.
- Using carbon nanotubes to improve the efficiency of organic solar cells.
- Portable electronics devices using nanotube “ink” in inkjet printers.
- Transparent, flexible electronics devices using arrays of nanotubes.
Ø Dendrimers
Dendrimers are a new class of polymeric materials. They are highly branched, monodisperse macromolecules. The structure of these materials has a great impact on their physical and chemical properties. As a result of their unique behaviour dendrimers are suitable for a wide range of biomedical and industrial applications. First discovered led in the early 1980s by Donald Tomalia and co-workers [1], these hyperbranched molecules were called dendrimers. The term originates from ‘dendron’ meaning a tree in Greek. Dendritic molecules are repeatedly branched species that are characterized by their structure perfection. The area of dendritic molecules can roughly be divided into the low-molecular-weight and the high-molecular-weight species. The first category includes dendrimers and dendrons whereas the second encompasses dendronized polymers, hyperbranched polymers, and brush polymers. There are attempts to use dendrimers in the targeted delivery of drugs and other therapeutic agents. Drug molecules can be loaded both in the interior of the dendrimers as well as attached to the surface groups.
Ø Quantum Dot
They were discovered by Louis E. Brus. Quantum dots, also known as nanocrystals, are a special class of materials known as semiconductors, which are crystals. Quantum dots are a unique class of semiconductors because they e so small, ranging from 2-10 nanometers (10-50 atoms) in diameter. At these small sizes materials behave differently, giving quantum dots unprecedented tunability and enabling never before seen applications to science and technology. Semiconductors are a cornerstone of the modern electronics industry and make possible applications such as the Light Emitting Diode and personal computer. Being zero dimensional, quantum dots have a harper density of states than higher-dimensional structures. As a result, they have superior transport and optical properties and are being researched for use in diode lasers, amplifiers, and biological sensors. Quantum dots lay be excited within the locally enhanced electromagnetic field produced by the gold nanoparticles. The new generations of quantum dots have far-reaching potential for the study of intracellular processes at the single-molecule level, high-resolution cellular imaging, long-term in vivo observation of cell trafficking, tumor targeting, and diagnostics.
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