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80 nanotechnology 80 nanotechnology Document Transcript

  • 101seminartopics.com 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.
  • 101seminartopics.com * CHALLENGES * ETHICAL ISSUES * CONCLUSION * BIBLIOGRAPHYINTRODUCTION A nanometer is one billionth of a meter. Thats a thousand, million times smaller than a meter. Ifyou blew up a baseball to the size of the earth, the atoms would become visible, about the size ofgrapes. Some 3- 4 atoms fit lined up inside a nanometer. Nanotechnology is about building thingsatom-by-atom, molecule-by-molecule. The trick is to be able to manipulate atoms individually, andplace 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-moleculecontrol of products and byproducts; the products and processes of molecular manufacturing. “LEARNING FROM NATURETechnology-as-we-know-it is a product of industry, of manufacturing and chemicalengineering. Industry-as-we-know-it takes things from nature—ore from mountains, treesfrom forests—and coerces them into forms that someone considers useful. Trees becomelumber, then houses. Mountains become rubble, then molten iron, then steel, then cars. Sandbecomes 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 molecularmachines—active devices with moving parts of precise, molecular structure—which processcarbon dioxide and water into oxygen and molecular building blocks. They use other
  • 101seminartopics.commolecular machines to join these molecular building blocks to form roots, trunks, branches,twigs, solar collectors, and more molecular machinery. Every tree makes leaves, and eachleaf is more sophisticated than a spacecraft, more finely patterned than the latest chip fromSilicon Valley. They do all this without noise, heat, toxic fumes, or human labor, and theyconsume pollutants as they go. Viewed this way, trees are high technology. Chips androckets arent.Trees give a hint of what molecular nanotechnology will be like, but nanotechnology wontbe biotechnology. Like biotechnology—or ordinary trees—molecular nanotechnology willuse molecular machinery, but unlike biotechnology, it will not rely on genetic meddling.THE SCALEWe humans are huge creations with no direct experience of the molecular world, and this canmake nanotechnology hard to visualize, hence hard to understand. The nano innanotechnology comes from nanos, the Greek word for dwarf. In science, the prefix nano-means one-billionth of something, as in nanometer and nanosecond, which are typical unitsof 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 mid-1980s 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.
  • 101seminartopics.comNANOTECHNOLOGY-AS AN INTERDISCIPLINARY SUBJECTAnother feature of nanotechnology is that it is the one area of research and development thatis truly multidisciplinary. Research at the nanoscale is unified by the need to shareknowledge on tools and techniques, as well as information on the physics affecting atomicand molecular interactions in this new realm. Materials scientists, mechanical and electronicengineers and medical researchers are now forming teams with biologists, physicists andchemistsTOP-DOWN BOTTOM-UPTop-down refers to making nano scale structures Bottom-up, or molecular nanotechnology,by machining and etching techniques. applies to building organic and inorganic structures atom-by-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 materialscannot be formed. Manipulation of bonds enables creation of newEg. Silicon crystal slicedrequired atomic materials with desired properties.scale silicon wafer obtained. Eg. Silicon atoms assembled by suitable techniques required atomic scale silicon wafer obtained.BOTTOM-UP TECHNOLOGYThe two fundamentally different approaches to nanotechnology are graphically termed topdown and bottom up. Top-down refers to making nanoscale structures by machining andetching techniques, whereas bottom-up, or molecular nanotechnology, applies to buildingorganic and inorganic structures atom-by-atom, or molecule-by-molecule. Top-down orbottom-up is a measure of the level of advancement of nanotechnologyNANOMACHINESManufactured products are made from atoms. The properties of those products depend onhow those atoms are arranged. If we rearrange the atoms in coal we can make diamond. If werearrange the atoms in sand (and add a few other trace elements) we can make computerchips. If we rearrange the atoms in dirt, water and air we can make potatoes.In future well 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 beessential if we are to continue the revolution in computer hardware beyond about the nextdecade, and will also let us fabricate an entire new generation of products that are cleaner,stronger, lighter, and more precise.
  • 101seminartopics.comThus 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 controlSelf AssemblyThe ability of chemists to synthesize what they want by stirring things together is trulyremarkable. Imagine building a radio by putting all the parts in a bag, shaking, and pullingout the radio -- fully assembled and ready to work! Self assembly -- the art and science ofarranging conditions so that the parts themselves spontaneously assemble into the desiredstructure -- is a well established and powerful method of synthesizing complex molecularstructures.A basic principle in self assembly is selective stickiness: if two molecular parts havecomplementary shapes and charge patterns -- one part has a hollow where the other part has abump, and one part has a positive charge where the other part has a negative charge -- thenthey 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 andcombine 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 togetherand shaking.Many viruses use this approach to make more viruses -- if you stir the parts of the T4bacteriophage together in a test tube, they will self assemble into fully functional viruses.Positional devices and positionally controlled reactions
  • 101seminartopics.comWhile self assembly is a path to nanotechnology, by itself it would be hard pressed to makethe very wide range of products promised by nanotechnology. During self assembly the partsbounce around and bump into each other in all kinds of ways, and if they stick together whenwe dont want them to stick together, well get unwanted globs of random parts.Many types of parts have this problem, so self assembly wont work for them. These partscant be allowed to randomly bump into each other (or much of anything else, for that matter)because theyd stick together when we didnt want them to stick together and form messyblobs instead of precise molecular machines.We can avoid this problem if we can hold and position the parts. Even though the molecularparts that are used to make diamond are both indiscriminately and very sticky (moretechnically, the barriers to bond formation are low and the resulting covalent bonds are quitestrong), if we can position them we can prevent them from bumping into each other in thewrong way.When two sticky parts do come into contact with each other, theyll do so in the rightorientation because were holding them in the right orientation. In short, positional control atthe molecular scale should let us make things which would be difficult or impossible to makewithout it.If we are to position molecular parts we must develop the molecular equivalent of "arms" and"hands." Well need to learn what it means to "pick up" such parts and "snap them together.
  • 101seminartopics.comOne of the first questions well need to answer is: what does a molecular-scale positionaldevice look like? Current proposals are similar to macroscopic robotic devices but on a muchsmaller scale. The illustrations show a design for a molecular-scale robotic arm proposed byEric Drexler, a pioneering researcher in the field. Only 100 nanometers high and 30nanometers in diameter, this rather squat design has a few million atoms and roughly ahundred moving parts. It uses no lubricants, for at this scale a lubricant molecule is more likea piece of grit.StiffnessOur molecular arms will be buffeted by something we dont worry about at the macroscopicscale: thermal noise. This makes molecular-scale objects wiggle and jiggle, just as Brownianmotion makes small dust particles bounce around at random.The critical property we need here is stiffness. Stiffness is a measure of how far somethingmoves when you push on it.Unfortunately, as we make our positional devices smaller and smaller, they will be more andmore subject to thermal noise. To make something thats both small and stiff is morechallenging. It helps to get the stiffest material you can find. Diamond, as usual, is stifferthan almost anything else and is an excellent material from which to make a very small, verystiff positional device. Theoretical analysis gives firm support to the idea that positionaldevices in the 100 nanometer size range able to position their tips to within a small fractionof an atomic diameter in the face of thermal noise at room temperature should be feasible.STEWART PLATFORMWhile Drexlers proposal for a small robotic arm is easy to understand and should beadequate to the task, more recent work has focused on the Stewart platform. This positionaldevice has the great advantage that it is stiffer than a robotic arm of similar size.
  • 101seminartopics.comIf we want a full six degrees of freedom (X, Y, Z, roll, pitch and yaw) then we must be ableto independently adjust the lengths of six different edges of the polyhedron. If we furtherwant one triangular face of the polyhedron to remain of fixed size and hold a "tool," and asecond face of the polyhedron to act as the "base" whose size and position is fixed, then wefind 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-lengthedges are either in pure compression or pure tension and are never subjected to any bendingforce, this positional device is stiffer than a long robotic arm which can bend and flex. TheStewart platform is also conceptually simpler than a robotic arm, having fewer different typesof parts; for this reason, we can reasonably expect that making one will be simpler thanmaking a robotic.Self replication: making things inexpensivelyPositional control combined with appropriate molecular tools should let us build a trulystaggering range of molecular structures -- but a few molecular devices built at great expensewould hardly seem to qualify as a revolution in manufacturing. How can we keep the costsdown?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
  • 101seminartopics.comproducts. If we can design and build one such system the manufacturing costs for more suchsystems and the products they make (assuming they can make copies of themselves in somereasonably inexpensive environment) will be very low.Once the product has been assembled by assemblers and time of production quickened usingreplicators, the assemblers are no more needed in them. The miniature devices used todissemble these assemblers are known as DISSEMBLERS. They function opposite to theassemblers by breaking bonds between the atoms of assemblers and reducing them to junkatoms.VISUAL IMAGES IN NANOTECHNOLOGYNanogears no more than a a nanometer wide could be used to construct a matter compiler, Nanogears no more than nanometer wide could be used to construct a matter compiler, whichcould becould be materialmaterial to arrange atoms andmacro-scale structure. which fed raw fed raw to arrange atoms and build a build a macro-scale structure.
  • 101seminartopics.com A NANO-PUMP A NANO PUMP A DIFFERENTIAL A DIFFERENTIAL GEAR A FINE MOTION A FINE MOTION CONTROLLER GEAR CONTROLLER A BEARING A HYDROCARBON JOINTAPPLICATIONSDip_Pen Nanolithography"One molecule thick letters written usingDip-Pen Nanolithography:Octadecanethiol is the ink and gold is thesubstrate. Visualized with an atomic forcemicroscope.
  • 101seminartopics.comNANOTECHNOLOGY AS AN ANALOGYNanotechnology is likely to change the way almost everything, including medicine,computers and cars, are designed and constructed. Nanotechnology is anywhere from five to15 years in the future, and we wont see dramatic changes in our world right away. But letstake a look at the potential effects of nanotechnology:  The first products made from nanomachines will be stronger fibers. Eventually,Technology Function Molecular Examplesstruts, beams, casins transmit force, hold positions cell walls, microtubulescables transmit tension collagen, silkfasteners, glue connect parts intermolecular forcessolenoids, actuators move things muscle actin, myosinmotors turn shafts flagellar motordrive shafts transmit torque bacterial flagellabearings support moving parts single bondsclamps hold workpieces enzymatic binding sitestools modify workpieces enzymes, reactive moleculesproduction lines control devices enzyme systems, ribosomesnumerical control systems store and read programs genetic system
  • 101seminartopics.com 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.  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.  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. Theres 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.  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
  • 101seminartopics.com  New findings suggest that artificial leaves comprised of nanocrystals may one day remove carbon dioxide from the atmosphere--even in the dark  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 ones 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?"  “Will Quantum Uncertainty Mess Things Up?"  "Will Loose Molecules Mess Things Up?"  “Will Chemical Instability Mess Things Up?”ETHICAL ISSUESSome people have recently, publicly (and belatedly) realized that nanotechnology might create newconcerns that we should address.Deliberate abuse, the misuse of a technology by some small group or nation to cause great harm, isbest prevented by measures based on a clear understanding of that technology. Nanotechnologycould, in the future, be used to rapidly identify and block attacks. Distributed surveillance systemscould quickly identify arms buildups and offensive weapons deployments, while lighter, stronger, andsmarter materials controlled by powerful molecular computers would let us make radically improvedversions 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 clearunderstanding of the potential threats and countermeasures available.
  • 101seminartopics.comBesides deliberate attacks, the other concern is that a self-replicating molecular machine couldreplicate unchecked, converting most of the biosphere into copies of itself. Some precautionarymeasures include such common sense principles as: artificial replicators must not be capable ofreplication in a natural, uncontrolled environment; they must have an absolute dependence on anartificial fuel source or artificial components not found in nature; they must use appropriate errordetection codes and encryption to prevent unintended alterations in their blueprints; and the like.CONCLUSIONThe promises of nanotechnology sound great, dont they? Maybe even unbelievable? Butresearchers say that we will achieve these capabilities within the next century. And ifnanotechnology is, in fact, realized, it might be the human races greatest scientificachievement yet, completely changing every aspect of the way we live.Nanotechnologys potential to improve the human condition is staggering: we would beshirking 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