Rachel Segalman, 31

Most of the energy in fuels is wasted as heat. But much of that heat could be converted to electricity by "thermoelectric" materials--if they were cheaper and more efficient. Now Rachel Segalman, an assistant professor of chemical engineering, has discovered that cheap organic molecules can be used to generate electricity from heat. So far, the voltage produced is small, but Segalman and colleagues are modifying the molecules and inventing new devices to harness them. Such devices could harvest heat in, say, computers, to extend laptop battery life.

Electricity from heat: Segalman's thermoelectric material consists of metallic or semiconducting nanoparticles linked together by molecules of benzenedithiol, an inexpensive organic compound comprising sulfur and hydrogen atoms attached to a carbon ring.

A material combining nanoparticles and organic molecules conducts electricity but not heat--a vital property of thermo­electric materials, since it is the heat differential that creates the electrical voltage. In a thermoelectric device, the material is sandwiched between two electrodes. As one electrode is heated and the other kept cool, a voltage is produced. Hooking the electrodes to an external circuit generates a current.

--Kevin Bullis