The biologist as a fuel cell

Larry Rome is a professor of biology at the University of Pennsylvania who studies how frogs and fish move. His latest project, however, is more of an engineering feat: A backpack that scavenges energy from its wearers as they walk. Rome's team developed the device with funding from the National Institutes of Health and the Office of Naval Research for soldiers to use in the field as a substitute for heavy replacement batteries. "If you ran out of batteries in the mountains of Afghanistan you can't go to the local drugstore" to replace them, Rome says.

Reported earlier this month in Science (309:1725–8, Sept. 9, 2005), the backpack combines a rigid frame with a metal load plate suspended from the frame by springs. As the user walks, the load moves up and down along vertical rods connected to the plate, and energy is generated by a rack-and-pinion device attached to...