By Peter Weiss
As scientists increasingly realize, everyday materials tend to act weird at small scales. Microstreams of water, for instance, behave like viscous flows of honey.
Recently, a team of engineers and chemists found a way to exploit a consequence of that microscale sluggishness. The result, reports Paul A.J. Kenis of the University of Illinois at Urbana-Champaign, is a fuel cell that does away with a particularly troublesome and expensive component: the membrane usually needed to split the cell into two parts.
The no-membrane design is a “neat concept,” says Piotr Zelenay of Los Alamos (N.M) National Laboratory.
Fuel cells intended for use in laptops and other portable electric devices typically generate power in a process that sends protons from a hydrogen-rich fuel solution, such as methanol in water, through a membrane to meet up with oxygen gas and form water (SN: 9/7/02, p. 155, Pocket Sockets). The membrane must keep the fuel contained while letting through the protons.
But membranes don’t do this perfectly and often create troubles of their own, says Kenis. Many fuel molecules sneak through the barrier and so produce no energy. In other instances, the membrane dries out or becomes waterlogged.
To create a membranefree fuel cell, Kenis and his colleagues took advantage of the property called laminar, or layered, flow. In a channel about the diameter of a human hair, multiple streams of aqueous solutions can flow with almost no mixing.
Because only a little oxygen typically dissolves in water, previous versions of the group’s all-liquid design didn’t have enough of the gas to produce much power, Zelenay notes. The cell’s developers say, however, they’ve found a way to make the cell richer in oxygen.
On March 22, Kenis described the device and presented new performance figures at a meeting of the American Physical Society in Los Angeles, Calif.
“This is really great performance. There’s no doubt about that,” comments Paul A. Kohl of the Georgia Institute of Technology in Atlanta. Kohl cautions, however, that the team has released no details about how it attained such performance.
Kenis is affiliated with a company founded by Larry J. Markoski, who formerly worked as a researcher at the University of Illinois at Urbana-Champaign, to translate the laminar-flow principle into products. INI Power Systems in Cary, N.C., is developing a 20-watt prototype fuel cell for the U.S. Army, which intends to use the device to recharge batteries for laptops and radios.
