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Implications and Applications of Nanotechnology

Varied approaches to fabricating nanostructures have emerged in the nanoworld. Like sculptors, so-called top-down practitioners chisel out or add bulk material to a surface. Microchips, which now boast circuit lines of little more than 100 nanometers, are about to become the most notable example. In contrast, bottom-up manufacturers use self-assembly processes to put together larger structures-atoms or molecules that make ordered arrangements spontaneously, given the right conditions. Nanotubes-graphite cylinders with unusual electrical properties-are a good example of self-assembled nanostructures [see "The Art of Building Small," by George M. Whitesides and J. Christopher Love, on page 38].

Beyond Silicon

Once conventional silicon electronics goes bust, new nanoelectronic devices are a good bet to replace them. A likely wager, though not a sure one.

The dwindling size of circuits in electronic chips drives much of the interest in nano. Computer companies with large research laboratories, such as IBM and Hewlett-Packard, have substantial nano programs. Once conventional silicon electronics goes bust-probably sometime in the next 10 to 25 years-it's a good bet that new nanotechnological electronic devices will replace them. A likely wager, though not a sure one. No one knows whether manufacturing electronics using nanotubes or some other novel material will allow the relentless improvements in chip performance without a corresponding increase in cost that characterizes silicon chipmaking [see "The Incredible Shrinking Circuit," by Charles M. Lieber, on page 58].

Even if molecular-scale transistors don't crunch zeroes and ones in the Pentium XXV, the electronics fashioned by nanotechnologists may make their way into devices that reveal the secrets of the ultimate small machine: the biological cell. Bio-nano, in fact, is finding real applications before the advent of postsilicon nanocomputers [see "Less Is More in Medicine," by A. Paul Alivisatos, on page 66]. Relatively few nanotags made of a semiconductor material are needed to detect cellular activity, as opposed to the billions or trillions of transistors that must all work together to function in a nanocomputer. One company, Quantum Dot Corporation, has already emerged to exploit semiconductor quantum dots as labels in biological experiments, drug-discovery research, and diagnostic tests, among other applications.

UPTICK: The National Nanotechnology Initiative (NNI), begun in fiscal year 2001, helps to keep the U.S. competitive with world spending (top). It also provides a monetary injection for the physical sciences and engineering, where funding has been flat by comparison with the life sciences (bottom).

Outside biology, the earliest wave of products involves using nanoparticles for improving basic material properties. For instance, Nanophase Technologies, one of the few companies in this field that are publicly traded, produces nano-size zinc oxide particles for use in sunscreen, making the usually white-colored cream transparent because the tiny particles don't scatter visible light.

The government's nanotech initiative goes beyond sunscreen. It envisages that nanostructured materials may help reduce the size, weight and power requirements of spacecraft, create green manufacturing processes that minimize the generation of unwanted by-products, and form the basis of molecularly engineered biodegradable pesticides. The field has such a broad scope-and basic research is still so new in some nanosubspecialties-that worries have arisen about its ability to deliver on ambitious technology goals that may take 20 years to achieve. "While nanotechnology may hold great promise, some scientists contend that the field's definition is too vague and that much of its 'hype' may not match the reality of present scientific speculation," noted a Congressional Research Service report last year.

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