Nanotechnology - Unbounding the future

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.
Todays manufacturing methods are very crude at the molecular level. Casting, grinding, milling and even lithography move atoms in great thundering statistical herds. It's like trying to make things out of LEGO blocks with boxing gloves on your hands. Yes, you can push the LEGO blocks into great heaps and pile them up, but you can't really snap them together the way you'd like.

In the future, nanotechnology will let us take off the boxing gloves. 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.

It's worth pointing out that the word "nanotechnology" has become very popular and is used to describe many types of research where the characteristic dimensions are less than about 1,000 nanometers. For example, continued improvements in lithography have resulted in line widths that are less than one micron: this work is often called "nanotechnology." Sub-micron lithography is clearly very valuable (ask anyone who uses a computer!) but it is equally clear that lithography will not let us build semiconductor devices in which individual dopant atoms are located at specific lattice sites. Many of the exponentially improving trends in computer hardware capability have remained steady for the last 50 years. There is fairly widespread belief that these trends are likely to continue for at least another several years, but then lithography starts to reach its fundamental limits.

If we are to continue these trends we will have to develop a new "post-lithographic" manufacturing technology which will let us inexpensively build computer systems with mole quantities of logic elements that are molecular in both size and precision and are interconnected in complex and highly idiosyncratic patterns. Nanotechnology will let us do this.


NANOTECHNOLOGY:
What Will it mean ?

Nanotechnology will make us healthy and wealthy though not necessarily wise. In a few decades, this emerging manufacturing technology will let us inexpensively arrange atoms and molecules in most of the ways permitted by physical law. It will let us make supercomputers that fit on the head of a pin and fleets of medical nanorobots smaller than a human cell able to eliminate cancer, infections, clogged arteries, and even old age. People will look back on this era with the same feelings we have toward medieval times--when technology was primitive and almost everyone lived in poverty and died young.

Besides computers billions of times more powerful than today's, and new medical capabilities that will heal and cure in cases that are now viewed as utterly hopeless, this new and very precise way of fabricating products will also eliminate the pollution from current manufacturing methods. Molecular manufacturing will make exactly what it is supposed to make, no more and no less, and therefore won't make pollutants.

When nanotechnology pioneer Eric Drexler first dared to publish this vision back in the early 1980s, the response was skeptical, at best. It seemed too good to be true, and many scientists pronounced the whole thing impossible. But the laws of physics care little for either our hopes or our fears, and subsequent analysis kept returning the same answer: it will take time, but it is not only possible but almost unavoidable.

The progress of technology around the world has already given us more precise, less expensive manufacturing technologies that can make an unprecedented diversity of new products. Nowhere is this more evident than in computer hardware: computational power has increased exponentially while the finest feature sizes have steadily shrunk into the deep submicron range. Extrapolating these remarkably regular trends, it seems clear where we're headed: molecular computers with billions upon billions of molecular switches made by the pound. And if we can arrange atoms into molecular computers, why not a whole range of other molecularly precise products?

It has taken decades for the bulk of the research community to accept the feasibility of this vision. But when the President of the United States in January 2000 called for a US $500 million National Nanotechnology Initiative, we knew nanotechnology had reached critical mass.



Visions of good, visions of harm
Some people have recently, publicly (and belatedly) realized that nanotechnology might create new concerns that we should address. Any powerful technology can be used to do great harm as well as great good. If the vision of nanotechnology sketched earlier is even partly right, we are in for some major changes--as big as the changes ushered in by the Industrial Revolution, if not bigger. How should we deal with these changes? What policies should we adopt during the development and deployment of nanotechnology?



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

APPLCATIONS OF MOLECULAR NANOTECHNOLOGY

1) NANOELECTRONICS
(A) Nanotubes makes Metal Transistor
The field-effect transistors that underlie electronics are made from semi conducting materials rather than conductors like metals because it is possible to use an electric field to block or allow the flow electricity in semiconductor, and thus turn the transistor on or off. It is difficult to make tiny semiconductor devices that conducts efficiently, howere Metals are much more efficient at conducting electricity but the flow of electricity through a metal is not easy to shunt off because the flow is not ordinarily sensitive to electric field . Researchers from the university of Illinois at Urbana-Champaign have found a way to produce a field effect in a metallic single-wall carbon nanotube that conducts electricity 40 times more efficiently than copper.Carbon nanotubes are rolle-up sheets of carbon atoms
That can be smaller than a single nanometer in diameter and are either metallic or semiconducting . A nanometer is the span of 10 hydrogen atoms. The metal field effect transistor has the potential to consume less energy, operate at higher frequencies, and dissipate heat more readily than traditional
Semiconducting field effect transistors. The researchers took advantage of the nanotubes’small size and a special type of electric field to produce the effect.


2) COMPUTER TECHNOLOGY

) Data Storage on Diamond
[Bauschlicher 97a] computationally studied storing data in a pattern of fluorine and hydrogen atoms on the (111) diamond surface . If write-once data could be stored this way, 1015 bytes/cm2 is theoretically possible. By comparison, the new DVD write-once disks now coming on the market hold about 108 bytes/cm2. [Bauschlicher 97a] compared the interaction of different probe molecules with a one dimensional model of the diamond surface. This study found some molecules whose interaction energies with H and F are sufficiently different that the force differential should be detectable by an SPM. These studies were extended to include a two dimensional model of the diamond surface and two other systems besides F/H [Bauschlicher 97b]. Other surfaces, such as Si, and other probes, such as those including transition metal atoms, have also been investigated [Bauschlicher 97c].
Among the better probes was C5H5N (pyridine). Quantum calculations suggest that pyridine is stable when attached to C60 in the orientation necessary for sensing the difference between hydrogen and fluorine. Half of C60 can form the end cap of a (9,0) or (5,5) carbon nanotube, and carbon nanotubes have been attached to an SPM tip [Dai 96]. Thus, it might be possible using today's technology to build a system to read the diamond memory surface.
[Avouris 96] has shown that individual hydrogen atoms can be removed from a silicon surface. If this could be accomplished in a gas that donates fluorine to vacancies on a diamond surface, the data storage system could be built. [Thummel 97] computationally investigated methods for adding a fluorine at the radical sites where a hydrogen atom had been removed from a diamond surface

) NANOMEDICINES
Medical Nanomaterials
Initial medical applications of nanotechnology, using nanostructured materials, are already being tested in a wide variety of potential diagnostic and therapeutic areas. A short list follows:

Building new organs and bones
Researchers at MIT and Harvard Medical School have built a functioning vascular system. By etching networks of paths (from three millimetres to 10 microns) onto silicon wafers, and using it as a mould for a layer of biodegradable polymer, they were able to produce mini artificial vascular system. "Eventually, we want to be able to replace whole organs with several layers of these constructs. So in the next 10-15 years, we will hopefully have reached a point where we can do this procedure clinically in human patients," said lead researcher Mohammad Kaazempur-Mofrad to NewScientist.com.
By decreasing the size of calcium phosphorus (two of the primary constituents of bone) to the nanoscale (30 nanometers in thickness and 60 nanometers in width), Cui Fuzhai (a materials science professor at Tsinghua University) has created "nano bone" - a replacement for damaged bone. "At this size, the properties of calcium phosphorus change. 'On a large scale (the calcium phosphorus) won't degrade, but on a nanoscale it will,' Cui said." What changes? Nanoscale calcium phosphorus degrades after a time (6 months), at which time the space has been filled with natural bone. A scales above the nano, calcium phosphorus does not degrade, so scale does matter. To-date Cui and his team has successfully implanted nano bones in dozens of patients, and received approval from China's FDA in November 2002. Hospitals are the first likely recipient of this new technology, and may start using it within months.
"Imagine having bones woven with a fabric such that one could fall out of a building and walk away. Imagine that in the event of a fire, microscopic vessels just ten billionths of a meter wide, pressurized with 1,000 atmospheres of pure oxygen could sense oxygen levels in the blood and provide hours of respiratory requirements for the body. Imagine medical nanites being injected into the bloodstream, consuming atherosclerotic plaques in the walls of the blood vessels; repairing cell damage caused by cancer. Or imagine nanomouthwashes that could eliminate gum disease and tooth decay - nanomachines acting as security guards and attacking any foreign entity in the body. Sounds like something from a science fiction movie? Absolutely not. Welcome to the world of nanomedicine." Albert Tsai


The Nanopill Credit researchers at McGill for creating the "nanopill"- a new way to deliver drugs inside cells. Researchers at McGill University in Montreal recently created a "nanopill" from two polymer molecules - one water-repellant, the other hydrophobic - that self-assemble into a sphere called a micelle. In tests, the 20-45 nanometer structures were small enough to pass through the wall of an animal cell and deliver their cargo of drugs to specific structures within the cell. Two of the companies currently working on a drug-delivery system based on this type of molecule are Insert Therapeutics Inc. in Pasadena, Calif., and Berlin-based Capsulution NanoScience AG