Knee brace generates power from walking

AN electricity-generating knee brace that can power mobile phones and medical devices has been developed by scientists.

Wearing the invention, an energetic brisk walk really can recharge the batteries.

The device borrows technology already used in some hybrid motor vehicles to produce power from braking.

“Regenerative brakes” collect kinetic energy that would otherwise be dissipated as heat when a car slows down.

In the same way, the “people power” brace harvests energy lost when a walker’s knee “brakes” after each step.

In tests, volunteers wearing a device on each leg were able to generate around five watts.

That is enough to run 10 mobile phones at the same time, and twice the amount of power needed for a laptop computer.

The braces could also operate a portable GPS satellite navigation locator, a robotic prosthetic joint, or a heart pacemaker.

Dr Arthur Kuo, from the University of Michigan in Ann Arbor, US, said: “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. During walking, you dissipate energy in various places, when your foot hits the ground, for example. You have to make up for this by performing work with your muscles.

“We’ve demonstrated proof of concept,” said Dr Kuo. “The prototype device is bulky and heavy, and it does affect the wearer just to carry it.”

A lighter version would be helpful to hikers or soldiers with no easy access to electricity, he added.

In medicine, the brace could supply power for devices such as pacemakers which currently require surgically implanted batteries.