Tom Krupenkin and Ashley Taylor at the University of Wisconsin at Madison's mechanical engineering program have invented a shoe insert that generates electrical energy from people's footsteps. According to the journal Nature Communications, the engineering researchers say their technology may eventually charge cell phones during a 2-hour walk.
Krupenkin and Taylor's “in-shoe technology” works by harnessing the thermodynamic power people generate with each footfall.
To make the device, the duo reversed a process called electrowetting, in which conductive liquid applied to the surface of an electrode changes with exposure to an electrical charge. By running this reaction backwards, Taylor and Krupenkin realized they could generate electrical charge by using the changing physical form of liquid drops.
In simpler terms, “If you run a motor in reverse you get an electrical generator,” explains Krupenkin.
The team has so far gotten 150 droplets to produce several milliwatts of power. But if they coat a 40-centimeter-thick electrode with 1,000 droplets, Krupenkin predicts the device will produce 10 watts.
Taylor and Krupekin's experiment is the first of its kind, though Samsung in 2008 debuted a water-powered battery.
The two students formed a company called InStep NanoPower and are working on a prototype for sale within two years.
