David Carroll Turns Fabric Into an Energy Source

The women in David Carroll’s life are big talkers, and that takes a toll on his cell phone battery. “My wife likes to call me, and she does take her time when she tells her stories,” he says. “You can watch the power meter just go down.” Carroll, a physicist and head of Wake Forest University’s Center for Nanotechnology and Molecular Materials, was discussing this problem last year with his 10-year-old daughter, Lauren, when she came up with a suggestion: What if Carroll could design something that harnessed the heat from someone’s hand, or from the phone itself, to give a cell phone battery more power? Carroll agreed that would be pretty cool.

Last month, Carroll’s lab unveiled a fabric that does just that. Called Power Felt, it generates electricity from heat. Wrap your cell phone in Power Felt, and it feeds off your body heat to recharge while it’s in your pocket. Carroll is a lifelong Southerner—he’s descended from some of North Carolina’s first white settlers, and his family donated some of the land that Wake Forest sits on—and he’s acutely aware of how powerful summer heat can be. He says Power Felt installed just under the roof of a house could be used to power household appliances. Lay it on the floor of a car and it could use the heat generated from sitting in a midday parking lot to run air conditioning and the radio. In an electric or a hybrid car, the Power Felt might even boost mileage.