Power walking could recharge batteries

Science : People may soon be able to recharge their cell phones and cameras as they walk. Two researchers at the University of Wisconsin–Madison are developing a device that harvests the mechanical energy produced by walking and converts it to electrical energy. Engineers Tom Krupenkin and J. Ashley Taylor modified an electrostatic capacitor by replacing one of a pair of solid electrodes with an electrically conductive liquid. The liquid electrode allows for a smaller gap between it and the solid electrode, and thus the pair achieves greater capacitance and voltage. If scaled up to the size that would fit a typical shoe, the device could harvest 2 watts of power, the researchers reported yesterday in Nature Communications. They have started a company, InStep NanoPower , to market their product. Although the device won’t eliminate batteries, it could lengthen the time between charges.