Researchers think small

0 Comments | Insight on the News, April 1, 1996 | by Kenneth Silber

Nanoclusters -- tiny specks of matter -- could improve products from lasers to sunscreen.

Researchers at university and corporate laboratories are delving ever-deeper into the world of "nanoclusters," objects so small they are measured in nanometers, or billionths of a meter. While only a handful of such products have reached the market, scientists are experimenting with nanoclusters in areas ranging from lasers to cosmetics.

"I suspect we're at the beginning of a real revolution in the way we make materials and devices," says Richard W. Siegel, head of the materials science and engineering department at Rensselaer Polytechnic Institute in Troy, N.Y., and cofounder of Nanophase Technologies Corp., an Illinois-based company that produces nanocluster ceramics and other materials.

Because of their ultra-small size -- a few dozen to a few thousand atoms -- nanoclusters possess different physical and chemical properties than ordinary matter. Ceramic powders composed of nanoclusters, for example, can be molded more readily into engine parts than conventional ceramics. Cluster-based quantum-dot lasers may facilitate high-speed data transmissions along fiber-optic cables. Crystalline nanocluster films sprayed onto the surface of microchips, solar cells and other devices could make electrical conduction cheaper and more efficient.

Cluster particles dispersed through a fluid medium also show promise. Sun-screen could be composed of particles precisely the right size to filter out harmful ultraviolet rays. Nanocluster-based makeup would absorb light to produce a desired skin tone; at least one brand is already on the market.

By focusing on the very small, cluster researchers are entering a realm previously dominated by science-fiction writers who for decades have presented visions of "nanotechnology" -- ultrasmall machines capable of performing all sorts of marvelous tasks. Nanotechnology enthusiasts have written about microscopic factories that could turn dirt into food, or molecule-sized robots that could be injected into a person's bloodstream to cure disease. The late Nobel Prize-winning physicist Richard Feynman outlined the field's potential in a 1959 speech titled "There's Plenty of Room at the Bottom."

Nanocluster researchers still shun the "nanotechnology" label for fear of being associated with fantasy, but they have taken seriously the potential technological benefits of ultrasmall objects since the eighties -- especially with the discovery of fullerenes, soccer-ball shaped carbon molecules also named "buckyballs" because of their resemblance to the geodesic domes constructed by architect Buckminster Fuller. These extremely stable carbon clusters can serve as electrical conductors, semiconductors or insulators and are readily combinable with a variety of molecules. A number of laboratories are investigating the possibility of using fullerene-based filaments to create highly efficient flat-panel displays for computers and other electronic devices.

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In addition to its technological potential, cluster research promises to fill long-standing gaps in science's understanding of natural phenomena. Astrophysicists have been puzzled by the large quantities of carbon created by nuclear-fusion reactions in the sun and other stars; traditional calculations predicted that much of the carbon would break down rapidly into other elements. Scientists now speculate that carbon atoms can form chain-like clusters that remain stable even in the intense heat and pressure of stars.