Nanotechnology and polymer nanocomposites — страница 3

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in the transformative possibilities of more ambitious and far-sighted work. The diversion of support based on the promises of proposals like molecular manufacturing to more mundane projects also risks creating a perhaps unjustifiedly cynical impression of the most ambitious goals: an investor intrigued by molecular manufacturing who invests in 'nano' only to find typical materials science advances result might conclude that the whole idea is hype, unable to appreciate the bait-and-switch made possible by the vagueness of the term. On the other hand, some have argued that the publicity and competence in related areas generated by supporting such 'soft nano' projects is valuable, even if indirect, progress towards nanotechnology's most ambitious goals. Potential benefits

Nanotechnology covers a wide range of industries, and therefore the potential benefits are also widespread. Telecommunications and Information technology could benefit in terms of faster computers and advanced data storage. Healthcare could see improvements in skin care and protection, advanced pharmaceuticals, drug delivery systems, biocompatible materials, nerve and tissue repair, and cancer treatments. Other industries benefits include catalysts, sensors and magnetic materials and devices. Potential risks For the near-term, critics of nanotechnology point to the potential toxicity of new classes of nanosubstances that could adversely affect the stability of cell membranes or disturb the immune system when inhaled, digested or absorbed through the skin. Objective risk

assessment can profit from the bulk of experience with long-known microscopic materials like carbon soot or asbestos fibres. Nanoparticles in the environment could potentially accumulate in the food chain. An often cited worst-case scenario is "grey goo", a hypothetical substance into which the surface objects of the earth might be transformed by self-replicating nanobots running amok. Societal risks from the use of nanotechnology have also been raised, such as hypothetical nanotech weapons (e.g., a nanomachine that consumed the rubber in tires would quickly disable many vehicles), and in the creation of undetectable surveillance capabilities. Manufacturing When the term "nanotechnology" was independently coined and popularized by Eric Drexler, who at the time

was unaware of Taniguchi's usage, it referred to a future manufacturing technology based on molecular machine systems. The premise was that molecular-scale biological analogies of traditional machine components demonstrated that molecular machines were possible, and that a manufacturing technology based on the mechanical functionality of these components (such as gears, bearings, motors, and structural members) would enable programmable, positional assembly to atomic specification (see the original reference PNAS-1981). The physics and engineering performance of exemplar designs were analyzed in the textbook Nanosystems. Because the term "nanotechnology" was subsequently applied to other uses, new terms evolved to refer to this distinct usage: "molecular

nanotechnology," "molecular manufacturing," and most recently, "productive nanosystems." One alternative view is that designs such as those proposed by Drexler and Merkle do not accurately account for the electrostatic interactions and will not operate according to the results of the analysis in Nanosystems. The contention is that man-made nanodevices will probably bear a much stronger resemblance to other (less mechanical) nanodevices found in nature: cells, viruses, and prions. This idea is explored by Richard A. L. Jones in his book Soft Machines: Nanotechnology and Life (ISBN 0-19-852855-8). Another view, put forth by Carlo Montemagno, is that future nanosystems will be hybrids of silicon technology and biological molecular machines, and his group's

research is directed toward this end. The seminal experiment proving that positional molecular assembly is possible was performed by Ho and Lee at Cornell University in 1999. They used a scanning tunneling microscope to move an individual carbon monoxide molecule (CO) to an individual iron atom (Fe) sitting on a flat silver crystal, and chemically bind the CO to the Fe by applying a voltage. Though biology clearly demonstrates that molecular machine systems are possible, non-biological molecular machines are today only in their infancy. Leaders in research on non-biological molecular machines are Dr. Alex Zettl and his groups at Lawrence Berkeley Laboratories and UC Berkeley. They have constructed at least three distinct molecular devices whose motion is controlled from the