You Could Power Up Future Gadgets by Walking

If you’re heading out for a hike in the future, you might not have to worry about whether or not your GPS will run out of juice while you’re still on the trail. In fact, keeping future gadgets powered up could be as simple as wrapping a portable electrical generator to your knee before heading out. A new technology aims to leverage the swinging motions of your knee as you walk to generate sufficient power to keep your gadgets juiced—you’ll just have to keep moving.

The prototype energy harvester mounted on a knee simulator.

A team of scientists from the United Kingdom’s Cranfield University, University of Liverpool and University of Salford are currently working to make such a system a reality. The researchers built a circular device, called a “pizzicato knee-joint energy harvester,” that fits onto the outside of the knee. It consists of four arms that extend from a central hub. To generate current, the harvester is surrounded by an outer ring made of 72 “plectra,” or plucking implements.

As described in a report published on Gizmag:

“The ring rotates about a quarter of a turn with every bend of the knee, causing the plectra to pluck the arms. This causes the arms to vibrate (not unlike a guitar string), and it’s those vibrations that are used to generate electrical energy.”

The research is funded by the U.K. Ministry of Defense, which wants to reduce the number of heavy batteries its soldiers must lug around to power their various gadgets.

The device is currently able to harvest about two milliwatts of power, though the researchers believe the output can be elevated to at least 30 milliwatts. This isn’t a large amount of power, but it should be adequate to juice up your average GPS unit.

I can’t help but wonder if the harvester makes it harder to walk. According to the report, “the muscles of the leg perform negative work during the swing extension phase; the device would harvest energy which otherwise must be dissipated by the muscle.” In other words, the technology may not necessarily make walking harder.

A smaller production model could eventually cost as little as $16, according to the researchers. You can read more in the related white paper titled “The pizzicato knee-joint energy harvester: Characterization with biomechanical data and the effect of backpack load.”