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Grazing the Nanograss

Adaptable substance may cool computers and put a zoom lens in your cell phone.

By Gary Anthes
October 11, 2004 12:00 PM ET

Computerworld - A drop of water glides across the flat surface like quicksilver, moving effortlessly from place to place as the surface is tilted. It's hard to believe that the little bead is water, for it doesn't wet the surface as it races around, seemingly without friction.
The little drop in this impromptu laboratory demonstration isn't on an ordinary surface. It's riding on "nanograss," a bed of upright silicon posts a thousand times thinner than a human hair. Bell Labs, the research and development arm of Lucent Technologies Inc., is betting that nanograss will find its way into commercial products ranging from low-friction boat hulls to heat sinks for computer processors and batteries with a shelf life of 25 years. It will be one of the first nanoscale technologies commercialized by Bell Labs and its partner, the New Jersey Nanotechnology Consortium (NJNC).
"Nanograss is a whole new class of structure, where we are nanoengineering the surface of a material," says David Bishop, a research vice president at Bell Labs and president of the NJNC. "By adjusting the area of these posts and their density, and how you pattern them, you can engineer how the fluid interacts with the substrate. So you are not stuck with what nature gave you, and you can do lots of amazing things."
It is also possible to alter the properties of nanograss on the fly by changing the temperature, applying ultrasound or a small voltage, or other means. A voltage builds up an electrical field at the tips of the nanograss, and that changes its wettability through an effect called electrowetting.

Grazing the Nanograss
That could allow the electrodes and electrolytes in a battery to remain separated until the battery is needed, extending its shelf life indefinitely. Conventional batteries discharge at the rate of 3% to 5% a month, even when not in use. Nanograss batteries will cost less and have far higher power-to-weight ratios, researchers predict.
Bishop says other applications of nanograss include the following:
Heat sinks for computer processors and other devices. "It's very hard to get high fluid flows through small silicon channels; it kind of jams up," Bishop says. "But nanograss allows much higher fluid flow because the liquid is only interacting with one-hundredth as much surface."
Commercialization of the nanograss heat-sink idea is two to three years away, but Bell Labs is about to sign a contract with a company to develop a "smart" heat sink that can change its cooling properties as needs change, he says. The idea is noteworthy because chip makers have found that heat dissipation is one

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