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Time for the energy industry to pull itself up by the knee straps: A group of scientists in the United Kingdom have developed a novel energy-harvesting device that attaches to the joint between the thigh and shin. Composed of piezoelectric materials, which generate power when they’re subjected to mechanical strain, the technology could spell self-powered heart monitors for athletes, lighter loads for soldiers, and gadgets that won’t run out of juice before you do.
The research, published in this month’s issue of Smart Materials and Structures, combines the expertise of scientists from Cranfield University, the University of Liverpool, and the University of Salford.
When the knee joint moves forward, the outer ring rotates, causing 72 plectra on its surface to “pluck” four energy-generating arms.
The device itself is circular, with an outer ring and a central hub. When the knee joint goes through a walking movement, the outer ring rotates, causing the 72 plectra on its surface to “pluck” four energy-generating arms on the inner hub. As each individual plectrum deflects off one of the arms, it causes a vibration not unlike a strummed guitar string. The resulting electric charge is then captured.
Although the generator currently harvests only 2 milliwatts of power, the researchers believe they can tweak it to exceed 30 milliwatts of power—enough to allow next-generation GPS tracking, more-advanced signal processing, and longer and more frequent wireless transmission.
The best part? The device could cost as little as £10 ($15) when it enters the mass market. “There is an on-going project looking at manufacturing a more compact and truly wearable harvester,” says Michele Pozzi, the lead author of the study. “At the moment we are using precise but cost-effective manufacturing techniques for the plectra and casing and anticipate that remaining parts will be molded industrially, slashing the cost.”