Human Gait Could Soon Power Portable Electronics

If the vision of Tom Krupenkin and J. Ashley Taylor comes to fruition, one day soon your cellphone -- or just about any other portable electronic device -- could be powered by simply taking a walk. In a paper appearing in the journal Nature Communications, Krupenkin and Taylor, both engineering researchers at the University of Wisconsin-Madison, describe a new energy-harvesting technology that promises to dramatically reduce our dependence on batteries and instead capture the energy of human motion to power portable electronics.

"Humans, generally speaking, are very powerful energy-producing machines," explains Krupenkin, a UW-Madison professor of mechanical engineering. "While sprinting, a person can produce as much as a kilowatt of power."

Grabbing even a small fraction of that energy, Krupenkin points out, is enough to power a host of mobile electronic devices -- everything from laptop computers to cell phones to flashlights. "What has been lacking is a mechanical-to-electrical energy conversion technology that would work well for this type of application," he says.

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 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.

In their Nature Communications report, Krupenkin and Taylor describe a novel energy-harvesting technology known as "reverse electrowetting," a phenomenon discovered by the Wisconsin researchers. The 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.