The advent of semiconductors in the 1950s paved the way for transistors that could squeeze onto a microchip, but similar dreams for small-scale temperature controllers never quite materialized. These dreams are now one step closer to fulfillment, thanks to a new material developed by researchers at the Research Triangle Institute in North Carolina.
Rama Venkatasubramanian and co-workers, publishing in today¿s Nature, built a faster and more powerful than ordinary thermoelectric device, which converts heat and electricity back and forth, by alternating very thin layers of two semiconducing materials. This film¿made of bismuth, antimony and tellurium¿is 2.4 times more efficient than conventional bulk devices, 23,000 times faster, and can be applied in tiny dots for pinpoint refrigeration. "This marks a major advance in a field that has stagnated for 30 years," says John Pazik of the Office of Naval Research, which provided funding for the research.
Thermoelectric devices are longer lasting and tougher than mechanical refrigerators. Their high cost and low efficiency, though, have generally confined them to niche markets: powering deep-space probes, cooling infrared detectors, and, lately, heating and cooling luxury car seats. Cheaper, more convenient thermoelectrics could speed up microprocessors and fiber-optic lines, make possible miniature biotech tools capable of stopping and starting small biochemical reactions, or running a car's air conditioner with waste heat from the engine.
But don¿t throw away your fridge just yet, says Cronin B. Vining of ZT Services in Auburn, Ala., in a commentary from the same issue of Nature. "As promising as these new results are, the efficiency . . . remains significantly less than that of conventional refrigerators. And there is no telling when, or if, costs and various engineering issues can be resolved." On the other hand, he adds, "this result may be good enough to greatly expand the range of practical applications."