Two engineers at the University of Wisconsin-Madison have developed a new energy-harvesting technology that they say can power a cellphone simply through walking.
"Humans, generally speaking, are very powerful energy-producing machines. While sprinting, a person can produce as much as a kilowatt of power," says professor Tom Krupenkin.
"What has been lacking is a mechanical-to-electrical energy conversion technology that would work well for this type of application."
Most current energy harvesting technologies are aimed at either high-power applications such as wind or solar power, or very low-power applications such as calculators, watches or sensors.
"What's been missing," says J Ashley Taylor, "is the power in the watts range. That's the power range needed for portable electronics."
Solar power, the researchers explain, can also be used to power portable electronics, but, unlike human motion, direct sunlight is usually not a readily available source of energy for mobile electronics users.
Using their newly-developed 'reverse electrowetting' technique, mechanical energy is converted to electrical energy by using a micro-fluidic device consisting of thousands of liquid micro-droplets interacting with a novel nano-structured substrate.
Embedding the technology into a pair of sneakers could capture energy produced during walking, which is normally lost as heat, and convert it into up to 20 watts of electrical power to fuel mobile electronic devices.
It can be also integrated with a Wifi hotspot that acts as a 'middleman' between mobile devices and a wireless network, dramatically reducing the power consumption of wireless mobile devices and allowing them to operate for much longer without a recharge.
"You cut the power requirements of your cellphone dramatically by doing this," says Krupenkin. "Your cellphone battery will last 10 times longer."
Krupenkin and Taylor are hoping to commercialize the technology through their new company, InStep NanoPower.