Scientists at the University of Michigan have created a new energy-capturing knee brace that can generate enough electricity from walking to operate a portable GPS locator, cell phone, motorized prosthetic joint, or implanted neurotransmitter. The wearable mechanism works similarly to how regenerative braking charges a battery in hybrid vehicles, said Arthur Kuo, an associate professor of mechanical engineering at UM.

Regenerative brakes collect the kinetic energy that would otherwise be dissipated as heat when a car slows down. This knee brace harvests the energy lost when a human brakes the knee after swinging the leg forward to take a step. "There is power to be harvested from various places in the body, and you can use that to generate electricity. The knee is probably the best place," Kuo said.

The 3.5-pound prototype device is bulky, but the energy harvester itself has little effect on the wearer. Similar mechanisms could be built into prosthetic knees and other implantable devices like pacemakers that today require a battery and periodic surgery to replace that battery. A future energy harvester might be implanted along with such a device and generate its own power from walking.

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