Wearable devices that harvest energy from movement are not a new idea, but a material created at Rice University may make them more practical.

The Rice lab of chemist James Tour has adapted laser-induced graphene (LIG) into small, metal-free devices that generate electricity. Like rubbing a balloon on hair, putting LIG composites in contact with other surfaces produces static electricity that can be used to power devices.

For that, thank the triboelectric effect, by which materials gather a charge through contact. When they are put together and then pulled apart, surface charges build up that can be channeled toward power generation.

In experiments, the researchers connected a folded strip of LIG to a string of light-emitting diodes and found that tapping the strip produced enough energy to make them flash. A larger piece of LIG embedded within a flip-flop let a wearer generate energy with every step, as the graphene composite’s repeated contact with skin produced a current to charge a small capacitor.

“This could be a way to recharge small devices just by using the excess energy of heel strikes during walking, or swinging arm movements against the torso,” Tour said.

The project is detailed in the American Chemical Society journal ACS Nano.

Read more at Rice University