For years, researchers have tried to harvest the energy that is lost with each walking stride (as much as 20 watts per foot). In the past, scientists have used electrostatic capacitors made up of two thin, solid metal electrodes, which only generate microwatts or hundreds of milliwatts of power, nowhere near enough the charge needed to recharge portable electronics.
Now, two engineers from the University of Wisconsin, Madison, Tom Krupenkin and J. Ashley Taylor, however, have figured out a way to effectively harvest mechanical energy.
The researchers decided to replace one of the solid electrodes with an electrically conductive liquid in order to eliminate some of the space between the electrodes. By placing the solid electrode within 10 to 50 nanometers of the conductive material, the electrostatic capacitor was able to generate a much larger voltage than previously achieved.
The Wisconsin researchers believe that enlarging their technology would create a device that could completely recharge a cell phone battery, camera, or any other portable electronic device while being worn during a 2-hour walk.
In order to commercialize their findings, Krupenkin and Taylor have created a company called InStep NanoPower. They are currently working on a prototype device for the sole of a shoe, which should be ready in about 2 years.