80#nanotechnology Government College Of Engineering Tirunelv

NANOTECHNOLOGY ABSTRACT A nanometer is one billionth of a meter. If you blew up a baseball to the size of the earth, the atoms would become visible, about the size of grapes. Some 3- 4 atoms fit lined up inside a nanometer. Nanotechnology is about building things atom by atom, molecule by molecule. The trick is to be able to manipulate atoms individually, and place them where you wish on a structure. Nanotechnology uses well known physical properties of atoms and molecules to make novel devices with extraordinary properties. The anticipated pay off for mastering this technology is beyond any human accomplishment thus far. Nature uses molecular machines to create life.Scientists from several fields including chemistry, biology, physics, and electronics are driving towards the precise manipulation of matter on the atomic scale. How do we get to nanotechnology? Several approaches seem feasible. Ultimately a combination may be the key. The goal of early nanotechnology is to produce the first nano-sized robot arm capable of manipulating atoms and molecules into a useful product or copies of itself. Nanotechnology finds applications as nanotubes, in nanomedicine and so on.Soon you have trillions of assemblers controlled by nano super computers working in parallel assembling objects quickly. Ultimately, with atomic precision, everything could be made. It's all a matter of software.

CONTENTS

* INTRODUCTION * NANOTECHNOLOGY -AN INTERDISCIPLINARY SUBJECT

* BOTTOM-UP TECHNOLOGY * NANOMACHINES * FABRICATION * STEWART PLATFORM * VISUAL IMAGES IN NANO TECNOLOGY * APPLICATIONS * CHALLENGES * ETHICAL ISSUES * CONCLUSION * BIBLIOGRAPHY

INTRODUCTION A nanometer is one billionth of a meter. That's a thousand, million times smaller than a meter. If you blew up a baseball to the size of the earth, the atoms would become visible, about the size of grapes. Some 3- 4 atoms fit lined up inside a nanometer. Nanotechnology is about building things atom-by-atom, molecule-by-molecule. The trick is to be able to manipulate atoms individually, and place them where you wish on a structure. Thus nanotechnology can be defined as: “Thorough, inexpensive control of the structure of matter based on molecule-by-molecule control of products and byproducts; the products and processes of molecular manufacturing. “

LEARNING FROM NATURE Technology-as-we-know-it is a product of industry, of manufacturing and chemical engineering. Industry-as-we-know-it takes things from nature—ore from mountains, trees from forests—and coerces them into forms that someone considers useful. Trees become lumber, then houses. Mountains become rubble, then molten iron, then steel, then cars. Sand becomes a purified gas, then silicon, and then chips. And so it goes. Each process is crude, based on cutting, stirring, baking, spraying, etching, grinding, and the like. Trees, though, are not crude: To make wood and leaves, they neither cut, grind, stir, bake, spray, etch, nor grind. Instead, they gather solar energy using molecular electronic devices, the photosynthetic reaction centers of chloroplasts. They use that energy to drive molecular machines—active devices with moving parts of precise, molecular structure—which process carbon dioxide and water into oxygen and molecular building blocks. They use other molecular machines to join these molecular building blocks to form roots, trunks, branches, twigs, solar collectors, and more molecular machinery. Every tree makes leaves, and each leaf is more sophisticated than a spacecraft, more finely patterned than the latest chip from Silicon Valley. They do all this without noise, heat, toxic fumes, or human labor, and they consume pollutants as they go. Viewed this way, trees are high technology. Chips and rockets aren't. Trees give a hint of what molecular nanotechnology will be like, but nanotechnology won't be biotechnology. Like biotechnology—or ordinary trees—molecular nanotechnology will use molecular machinery, but unlike biotechnology, it will not rely on genetic meddling.

THE SCALE We humans are huge creations with no direct experience of the molecular world, and this can make nanotechnology hard to visualize, hence hard to understand. The nano in

nanotechnology comes from nanos, the Greek word for dwarf. In science, the prefix nanomeans one-billionth of something, as in nanometer and nanosecond, which are typical units of size and time in the world of molecular manufacturing. Lets try to visualize: you say, "Shrink me!", and the world seems to expand.

Frame (A) shows a hand holding a computer chip. This is shown magnified 100 times in (B). Another factor of 100 magnification (C) shows a living cell placed on the chip to show scale. Yet another factor of 100 magnification (D) shows two nanocomputers beside the cell. The smaller (shown as block) has roughly the same power as the chip seen in the first view; the larger (with only the corner visible) is as powerful as mid1980s mainframe computer. Another factor of 100 magnification (E) shows an irregular protein from the cell on the lower right, and a cylindrical gear made by molecular manufacturing at top left. Taking a smaller factor of 10 jump, (F) shows two atoms in the protein, with electron clouds represented by stippling. A final factor of 100 magnification (G) reveals the nucleus of the atom as a tiny speck.

NANOTECHNOLOGY-AS AN INTERDISCIPLINARY SUBJECT Another feature of nanotechnology is that it is the one area of research and development that is truly multidisciplinary. Research at the nanoscale is unified by the need to share knowledge on tools and techniques, as well as information on the physics affecting atomic and molecular interactions in this new realm. Materials scientists, mechanical and electronic engineers and medical researchers are now forming teams with biologists, physicists and chemists

BOTTOM-UP TECHNOLOGY The two fundamentally different approaches to nanotechnology are graphically termed 'top down' and 'bottom up'. 'Top-down' refers to making nanoscale structures by machining and etching techniques, whereas 'bottom-up', or molecular nanotechnology, applies to building organic and inorganic structures atom-by-atom, or molecule-by-molecule. Top-down or bottom-up is a measure of the level of advancement of nanotechnology TOP-DOWN

BOTTOM-UP

'Top-down' refers to making nano scale structures by machining and etching techniques.

'Bottom-up', or molecular nanotechnology, applies to building organic and inorganic structures atomby-atom, or molecule-by-molecule.

Microscopic irregularities will always be present.

Atomic scale manufacturing is devoid of all possible irregularities.

Bonds cannot be manipulated. Thus new materials cannot be formed. Eg. Silicon crystal slicedrequired atomic scale silicon wafer obtained.

Manipulation of bonds enables creation of new materials with desired properties. Eg. Silicon atoms assembled by suitable techniques required atomic scale silicon wafer obtained.

NANOMACHINES Manufactured products are made from atoms. The properties of those products depend on how those atoms are arranged. If we rearrange the atoms in coal we can make diamond. If we rearrange the atoms in sand (and add a few other trace elements) we can make computer chips. If we rearrange the atoms in dirt, water and air we can make potatoes. In future we'll be able to snap together the fundamental building blocks of nature easily, inexpensively and in most of the ways permitted by the laws of physics. This will be essential if we are to continue the revolution in computer hardware beyond about the next decade, and will also let us fabricate an entire new generation of products that are cleaner, stronger, lighter, and more precise. Thus molecular nanotechnology should let us :  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.

There are basically two ways to fabricate nanodevices:  Self assembly  Positional control

Self Assembly The ability of chemists to synthesize what they want by stirring things together is truly remarkable. Imagine building a radio by putting all the parts in a bag, shaking, and pulling out the radio -- fully assembled and ready to work! Self assembly -- the art and science of arranging conditions so that the parts themselves spontaneously assemble into the desired structure -- is a well established and powerful method of synthesizing complex molecular structures. A basic principle in self assembly is selective stickiness: if two molecular parts have complementary shapes and charge patterns -- one part has a hollow where the other part has a bump, and one part has a positive charge where the other part has a negative charge -- then they will tend to stick together in one particular way. By shaking these parts around -something which thermal noise does for us quite naturally if the parts are floating in solution -- the parts will eventually, purely by chance, be brought together in just the right way and combine into a bigger part. This bigger part can combine in the same way with other parts, letting us gradually build a complex whole from molecular pieces by stirring them together and shaking. Many viruses use this approach to make more viruses -- if you stir the parts of the T4 bacteriophage together in a test tube, they will self assemble into fully functional viruses. Positional devices and positionally controlled reactions While self assembly is a path to nanotechnology, by itself it would be hard pressed to make the very wide range of products promised by nanotechnology. During self assembly the parts bounce around and bump into each other in all kinds of ways, and if they stick together when we don't want them to stick together, we'll get unwanted globs of random parts. Many types of parts have this problem, so self assembly won't work for them. These parts can't be allowed to randomly bump into each other (or much of anything else, for that matter) because they'd stick together when we didn't want them to stick together and form messy blobs instead of precise molecular machines.

We can avoid this problem if we can hold and position the parts. Even though the molecular parts that are used to make diamond are both indiscriminately and very sticky (more technically, the barriers to bond formation are low and the resulting covalent bonds are quite strong), if we can position them we can prevent them from bumping into each other in the wrong way. When two sticky parts do come into contact with each other, they'll do so in the right orientation because we're holding them in the right orientation. In short, positional control at the molecular scale should let us make things which would be difficult or impossible to make without it. If we are to position molecular parts we must develop the molecular equivalent of "arms" and "hands." We'll need to learn what it means to "pick up" such parts and "snap them together.

One of the first questions we'll need to answer is: what does a molecular-scale positional device look like? Current proposals are similar to macroscopic robotic devices but on a much smaller scale. The illustrations show a design for a molecular-scale robotic arm proposed by Eric Drexler, a pioneering researcher in the field. Only 100 nanometers high and 30 nanometers in diameter, this rather squat design has a few million atoms and roughly a hundred moving parts. It uses no lubricants, for at this scale a lubricant molecule is more like a piece of grit.

Stiffness Our molecular arms will be buffeted by something we don't worry about at the macroscopic scale: thermal noise. This makes molecular-scale objects wiggle and jiggle, just as Brownian motion makes small dust particles bounce around at random. The critical property we need here is stiffness. Stiffness is a measure of how far something moves when you push on it. Unfortunately, as we make our positional devices smaller and smaller, they will be more and more subject to thermal noise. To make something that's both small and stiff is more challenging. It helps to get the stiffest material you can find. Diamond, as usual, is stiffer than almost anything else and is an excellent material from which to make a very small, very stiff positional device. Theoretical analysis gives firm support to the idea that positional devices in the 100 nanometer size range able to position their tips to within a small fraction of an atomic diameter in the face of thermal noise at room temperature should be feasible.

STEWART PLATFORM While Drexler's proposal for a small robotic arm is easy to understand and should be adequate to the task, more recent work has focused on the Stewart platform. This positional device has the great advantage that it is stiffer than a robotic arm of similar size.

If we want a full six degrees of freedom (X, Y, Z, roll, pitch and yaw) then we must be able to independently adjust the lengths of six different edges of the polyhedron. If we further want one triangular face of the polyhedron to remain of fixed size and hold a "tool," and a second face of the polyhedron to act as the "base" whose size and position is fixed, then we find that the simplest polyhedron that will suit our purpose is the octahedron. The advantage of the Stewart platform can now be seen: because the six adjustable-length edges are either in pure compression or pure tension and are never subjected to any bending force, this positional device is stiffer than a long robotic arm which can bend and flex. The Stewart platform is also conceptually simpler than a robotic arm, having fewer different types of parts; for this reason, we can reasonably expect that making one will be simpler than making a robotic. Self replication: making things inexpensively Positional control combined with appropriate molecular tools should let us build a truly staggering range of molecular structures -- but a few molecular devices built at great expense would hardly seem to qualify as a revolution in manufacturing. How can we keep the costs down? The requirement for low cost creates an interest in self replicating manufacturing systems. These systems are able both to make copies of themselves and to manufacture useful products. If we can design and build one such system the manufacturing costs for more such systems and the products they make (assuming they can make copies of themselves in some reasonably inexpensive environment) will be very low. Once the product has been assembled by assemblers and time of production quickened using replicators, the assemblers are no more needed in them. The miniature devices used to dissemble these assemblers are known as DISSEMBLERS. They function opposite to the assemblers by breaking bonds between the atoms of assemblers and reducing them to junk atoms.

VISUAL IMAGES IN NANOTECHNOLOGY

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AANANO-PUMP NANO PUMP

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APPLICATIONS

Dip_Pen Nanolithography "One molecule thick letters written using Dip-Pen Nanolithography: Octadecanethiol is the ink and gold is the substrate. Visualized with an atomic force microscope.

NANOTECHNOLOGY AS AN ANALOGY

Nanotechnology is likely to change the way almost everything, including medicine, computers and cars, are designed and constructed. Nanotechnology is anywhere from five to 15 years in the future, and we won't see dramatic changes in our world right away. But let's take a look at the potential effects of nanotechnology:

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The first products made from nanomachines will be stronger fibers. Eventually, we will be able to replicate anything, including diamonds, water and food. Famine could be eradicated by machines that fabricate foods to feed the hungry.

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In the computer industry, the ability to shrink the size of transistors on silicon microprocessors will soon reach its limits. Nanotechnology will be needed to create a new generation of computer components. Molecular computers could contain storage devices capable of storing trillions of bytes of information in a structure the size of a sugar cube.

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Nanotechnology may have its biggest impact on the medical industry. Patients will drink fluids containing nanorobots programmed to attack and reconstruct the molecular structure of cancer cells and viruses to make them harmless. There's even speculation that nanorobots could slow or reverse the aging process, and life expectancy could increase significantly. Nanorobots could also be programmed to perform delicate surgeries -- such nanosurgeons could work at a level a thousand times more precise than the sharpest scalpel. By working on such a small scale, a nanorobot could operate without leaving the scars that conventional surgery does. Additionally, nanorobots could change your physical appearance. They could be programmed to perform cosmetic surgery, rearranging your atoms to change your ears, nose, eye color or any other physical feature you wish to alter.

Technology struts, beams, casins cables fasteners, glue solenoids, actuators motors drive shafts bearings clamps tools production lines numerical control systems

Function transmit force, hold positions transmit tension connect parts move things turn shafts transmit torque support moving parts hold workpieces modify workpieces control devices store and read programs

Molecular Examples cell walls, microtubules collagen, silk intermolecular forces muscle actin, myosin flagellar motor bacterial flagella single bonds enzymatic binding sites enzymes, reactive molecules enzyme systems, ribosomes genetic system

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Nanotechnology has the potential to have a positive effect on the environment. For instance, airborne nanorobots could be programmed to rebuild the thinning ozone layer. Contaminants could be automatically removed from water sources, and oil spills could be cleaned up instantly. Manufacturing materials using the bottom-up method of nanotechnology also creates less pollution than conventional manufacturing processes. Our dependence on non-renewable resources would diminish with nanotechnology. Many resources could be constructed by nanomachines. Cutting down trees, mining coal or drilling for oil may no longer be necessary. Resources could simply be constructed by nanomachines. One challenge to effective drug treatment is getting the medication to exactly the right place. To that end, researchers have been investigating myriad new methods to deliver pharmaceuticals. New findings indicate that tiny nanocontainers composed of polymers may one day distribute drugs to specific spots within individual cells

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New findings suggest that artificial leaves comprised of nanocrystals may one day remove carbon dioxide from the atmosphere--even in the dark

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Research suggests that the diminutive tubes can hold twice as much energy as graphite, the form of carbon currently used as an electrode in many rechargeable lithium batteries

CHALLENGES Things behave substantially differently in the micro domain. Forces related to volume, like weight and inertia, tend to decrease in significance. Forces related to surface area, such as friction and electrostatics, tend to become large. And forces like surface tension that depend upon an edge become enormous. It takes awhile to get one's micro intuition sorted out. Some people have come up with obstacles which raise doubts about the question: • •

”Will it work?” “Will Thermal Vibrations Mess Things Up?"

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“Will Quantum Uncertainty Mess Things Up?" "Will Loose Molecules Mess Things Up?" “Will Chemical Instability Mess Things Up?”

ETHICAL ISSUES Some people have recently, publicly (and belatedly) realized that nanotechnology might create new concerns that we should address. Deliberate abuse, the misuse of a technology by some small group or nation to cause great harm, is best prevented by measures based on a clear understanding of that technology. Nanotechnology could, in the future, be used to rapidly identify and block attacks. Distributed surveillance systems could quickly identify arms buildups and offensive weapons deployments, while lighter, stronger, and smarter materials controlled by powerful molecular computers would let us make radically improved versions of existing weapons able to respond to such threats. Replicating manufacturing systems could rapidly churn out the needed defenses in huge quantities. Such systems are best developed by continuing a vigorous R&D program, which provides a clear understanding of the potential threats and countermeasures available. Besides deliberate attacks, the other concern is that a self-replicating molecular machine could replicate unchecked, converting most of the biosphere into copies of itself. Some precautionary measures include such common sense principles as: artificial replicators must not be capable of replication in a natural, uncontrolled environment; they must have an absolute dependence on an artificial fuel source or artificial components not found in nature; they must use appropriate error detection codes and encryption to prevent unintended alterations in their blueprints; and the like.

CONCLUSION The promises of nanotechnology sound great, don't they? Maybe even unbelievable? But researchers say that we will achieve these capabilities within the next century. And if nanotechnology is, in fact, realized, it might be the human race's greatest scientific achievement yet, completely changing every aspect of the way we live. Nanotechnology's potential to improve the human condition is staggering: we would be shirking our duty to future generations if we did not responsibly develop it.

BIBLIOGRAPHY • Electronics for you • www.yahoosearch.com • www.rediffsearch.com • www.howstuffworks.com • Unbounding the future