Batteries are a notorious weak link for many portable devices, such as laptop computers and cellular phones. They are expensive, heavy and cumbersome, often requiring recharging at the most inopportune times. Recent advances in fuel-cell technology might bring relief. Several research groups are developing "microfuel cells" that could, for example, result in mobile phones running continuously for weeks on standby power.

Fuel cells are simple devices, basically consisting of a nonmetallic conductor called an electrolyte sandwiched between two electrodes. Hydrogen from a fuel, such as methanol, flows through the electrolyte to mix with an oxidizer, such as oxygen from air, and the chemical reaction produces an electric current between the two electrodes. The cells can be replenished easily-and quicklyby adding more fuel. Fuel cells also run cleanly, their main-byproduct being water from the combination of hydrogen and oxygen, whereas batteries, which eventually wear out from repeated recharging, present a disposal problem.

While various laboratories have been busy developing large, powerful fuel cells to replace automotive combustion engines, other work has concentrated on miniaturization. Robert G. Hockaday, a researcher on leave from Los Alamos National Laboratory, where he worked in diagnostic physics, has patented a micro-fuel cell that he predicts will be able to provide power for up to 50 times longer than traditional nickelcadmium batteries-all for a comparably sized and priced package but at half the weight. With this technology, Hockaday envisions cell phones running continuously for 40 days on standby while consuming less than two ounces of methanol.

The invention is more a triumph of engineering than a wonder of science. Hockaday has taken modern techniques for fabricating electronic circuitry and applied them to the time-honored technology of fuel cells. The key was in the packaging. Whereas most fuel-cell researchers start with the design of the electrolyte and electrodes, Hockaday realized that be could best achieve miniaturization and mass production by using a thin film of plastic as the basic container for microscopic fuel cells. The plastic membrane, only 25 microns thick, is bombarded with nuclear particles and then chemically etched to form fine pores through which a liquid electrolyte is later poured. The metal electrode plates, a catalyst material and a conductive grid to connect the individual cells can then be layered and etched on the plastic structure by using proved chipmaking techniques such as vacuum deposition. "I'm basically building fuel cells like circuit boards," Hockaday says.

To complete his research, Hockaday is receiving $1 million from Manhattan Scientifics, a New York City-based holding company. He expects to have a prototype ready for production in a year.

Hockaday's invention is not the only game in town. Christopher K. Dyer of Bell Communications Research (Bellcore) has brought forth an innovative design that draws the hydrogen and oxygen from the same source. (In most fuel cells, as with Hockaday's, the two substances need to be kept separate, which complicates the internal plumbing of the devices.) Meanwhile DTI Energy in Los Angeles is working on commercializing its fuel-cell technology from the jet Propulsion Laboratory in Pasadena, Calif,, and the University of Southern California. DTI claims its device can use methanol directly instead of having the hydrogen extracted beforehand from the alcohol. Although the different groups boast competing approaches, Bellcore's Dyer asserts they share a common enemy: "We really should replace batteries because they're awful things." -Alden M. Hayashi