Imagine charging your FitBit by simply wearing it while you walk.
While wearable devices are growing in popularity, they still share a common burden: The more complex the device, the shorter its battery life. Until perhaps now. In a paper published on Friday (June 17) in Science Advances, researchers outline a way to harvest energy from body movement using nothing more than salt water and a flexible rubber band.
To conduct their experiment, researchers at the Georgia Institute of Technology built a rubber shell and filled it with salt water. When the shell moved, the conductive salt water moved with it, generating an alternating current. That harvested energy can be stored in existing batteries or capacitors, and used to power anything from smartwatches to toys. The stored energy is capable of powering devices even when their wearers aren’t moving.
“It’s very robust because the surface material is nothing special,” says Zhong Lin Wang, a materials scientist at Georgia Tech and one of the authors of the study. The Georgia Tech prototypes—arm bands, rubber mats and mouse pads among them—were put through more than 500,000 cycles of deformation without any negative effects on energy storage. Every prototype was able to light up an LED panel after being tapped or pressed. Using this approach, manufacturers could conceivably create self-charging devices by combining salt water with commercially available rubber or plastic.
This is hardly the the first attempt to charge devices without plugging them in—see: solar panels—but it could be an important one. If wearables are ever truly going to take it off, it’s likely to be without a charging cord dragging behind them.