US scientists tout 'world's smallest fuel cell'

Chemical engineers from the University of Illinois at Urbana-Champaign say they've developed a working fuel cell measuring 3 millimeters across.

New Scientist reports that the device is the smallest working fuel cell in the world, potentially opening up applications in portable gadgets. 

The key to the 3 mm by 3 mm by 1 mm device is that it generates power without using a pump or control electronics, which increases its net power output.

Similarly, a researcher in France in late 2008 increased the efficiency of micro-sized direct methanol fuel cells to 75 percent by eliminating the pumps on the 0.18 cm² device (see French researcher boosts efficiency of methanol fuel cell).

New Scientist reports that the 9 mm³ system is designed for portable devices that move and rotate. Instead of gravity controlling the flow of water, the fuel cell uses surface tension, which is unaffected by the device moving.

The device generated 0.7 volts and a current of 0.1 milliamps for 30 hours before the fuel ran out, New Scientist reports.

Saeed Moghaddam and Mark Shannon developed the fuel cell with just four components: a membrane, water, metal hydride and electrodes. The thin membrane separates chambers holding water and metal hydride, with small holes allowing vapor to reach the metal hydride and form hydrogen. That hydrogen reacts with electrodes beneath the metal hydride chamber to form electricity.

Shannon is the director of University of Illinois' WaterCAMPWS Center (see California's drought could mean water boom, say experts).

Fuel cells can offer higher energy density than conventional batteries, but scientists across the globe are working to lower the cost and improve the efficiency.

In December, scientists at Wuhan University in Wuhan, China, said they developed a new membrane for fuel cells that operates in alkaline conditions, opening up the possibility of using cheaper catalyst (see Chinese researchers develop membrane for alkaline fuel cell).

In 2007, Japans' Daihatsu Motor said it developed a method to use alkaline instead of acid exchange membranes to enable the use of less-costly metals, such as cobalt or nickel (see Daihatsu makes platinum-free fuel cell). 

In October, India’s National Chemical Laboratory said it developed a polymer that could be 100 times cheaper to use than the industry-standard material for building hydrogen fuel cells. The substance is a variant of polybenzimidazole, which is used in making spacesuits (see India makes cheaper fuel cell part).

And in Japan, researchers say they've developed a smaller, cheaper fuel cell that can also generate power at room temperatures (see Japanese tout low-temp fuel cell). The researchers’ fuel cell uses a membrane composed of polybenzimidazole doped with phosphoric acid, allowing protons to migrate through the phosphoric acid.

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