No doubt you spend a lot of your time walking places—to and from work, the sandwich shop, the bar, etc. So wouldn’t it be nice if you could harvest that energy your knees generate as you stroll about, and convert it into electricity to charge your smartphone?
Scientists at Cranfield University, University of Liverpool, and University of Salford have created a piezoelectric device that does something similar. Just by walking, a user could power devices like heart rate monitors, pedometers, and accelerometers. But not quite your smartphone just yet, though it could be in the cards for the future. Devices attached to the knee joint have the capability to generate large amounts of power, as the knee has quite a significant—and fast—angle change during walking.
The circular energy harvester is placed onto the outside of the knee and has a central hub along with an outer ring which is fitted with 72 plectra. As you walk, the outer ring rotates and plucks at four protruding arms attached to the inner hub which vibrate. These vibrations are used to generate electricity. Currently the device can harvest two milliwatts of power, but the researchers say it could exceed 30 milliwatts with some improvements.