Getting electricity from your walking/running shoes

Individuals waste, on average, 20 watts of energy per second when talking. Instead of turning all calories into lift or forward motion, we turn most of them into heat that's quickly dissipated. Tony Krupenkin, an engineer at the University of Wisconsin, and his colleagues have come up with a way to harvest the wasted energy from human motion and convert it into about 10 watts of electricity. Their device is based on a physical penomenon called electrowetting: If you apply electrical voltage to certain liquids, the liquid moves. They reverse the process, forcing liquid to move over electrodes. In the shoes are two flexible plastic bladders one under the heel and the otherunder the toe. The bladders are filled with a mixture of oil and water and connected by a thin, snaking tube. When stepping down on the heel therear bladder is compressed and several milliters of liquid travel through the tube to the front bladder. Step on the toe and the process is reversed. The tube is lined with a thin film of electrodes, and as the liquid slides back and forth, the electrodes charge. A small battery stores the energy, and you can access that energy by way of a micro-USB port on the heel of the shoe. The power can be transferred from shoe to cellphone battery. This approach does require wiring up your feet - but futre solutions will be more elegant.