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If cars of the future are powered by fuel cells, as many predict
(see 鈥淎 tankful of sunshine鈥�),
they will undoubtedly require sensors to detect leaks of the
potentially explosive hydrogen fuel. Now scientists at France鈥檚 National Centre
for Scientific Research (CNRS) in Montpellier and the University of California
at Irvine have created a new type of hydrogen sensor using arrays of nanoscopic
palladium wires (Science, vol 293, p 2227). They鈥檝e found that the arrays鈥�
electrical resistance rapidly decreases when they are exposed to
hydrogen鈥攁nd the decrease is proportional to the gas鈥檚 concentration, even
in the presence of other gases such as oxygen and methane. They believe the
arrays of wires, each just 55 nanometres thick, absorb hydrogen and swell up.
This closes minute gaps between them, allowing current to flow more easily.