article 1 on nanotech - 1 Introduction The properties of...

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1. Introduction The properties of manufactured products depend on how the atoms are arranged. Contemporary manufacturing methods provide limited control over the position of specific atoms in the final product. For example, continuing improvements in lithography have resulted in line widths that are less than 100 nm (100 × 10 9 m). Although submicron lithography is very valuable, it is clear that current lithography will not lead to the building of semiconductor devices in which individual atoms are located at specific unit cell sites. A manufacturing capability able to assemble atoms precisely in patterns chosen to improve material properties would permit radical improvements in product performance and capabilities. Nanotechnology allows this. When Eric Drexler ( 1 ) introduced the term nanotechnology in mid 1980s, he was discussing manufacturing machines on the scale of molecules, nanometer-size motors, robot arms, and complete computers. The meaning of nanotechnology has altered over the years from machines that have been deliberately built from nanoscale components to mean “anything in the range of 0.1 to 100 nm,” such as powders and coatings, and other materials that are nanoscale. This altered version of the term is more accurately characterized as “nanoscale technology,” while the initial meaning should be labeled as molecular nanotechnology, molecular mechanics, or nanoengineering. Recently, the Foresight Institute suggested a novel term to represent the initial meaning of nanotechnology: zettatechnology ( 2 ). Whatever the name, nanotechnology allows for the movement of an individual atom to a desired place and almost any structure that agrees with the laws of chemistry and physics can then be built. Nanotechnology offers not just better products, but a new way of production. This is the authentic meaning of the term nanotechnology, and that is why it is frequently regarded as “the next industrial revolution”. In the 21 st Century, the societal impact of nanotechnology is expected to be far superior to the combined influences that the silicon chip, medical imaging, computer-aided engineering, and synthetic polymers have had in the preceding century. Thus,
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nanotechnology will change the nature of almost every man-made object. [ Top of Page ] 2. Properties at Nanoscale Once the material sizes are reduced below 100 nm, they begin demonstrating an array of unique properties based on quantum mechanical effects, rather than the familiar Newtonian mechanics that operates in the macroscopic scale. The quantum effects may influence a variety of material properties such as conductivity, heat transfer, melting temperature, magnetization etc, without changing the chemical composition. That is, the same molecules are present, but their physical assembly is different. For example, colloidal structures immersed in liquid are subjected to constant attack from the liquid molecules, causing them to move about and bend in a random manner (Brownian motion). Although the
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