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

Wearing the invention for a brisk walk really can re-charge 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 of electricity - enough to run 10 mobile phones and twice the amount of power needed for a laptop.

Dr Arthur Kuo, from Michigan university, said "The prototype device is bulky and heavy, and it does affect the wearer just to carry. But the energy generation part itself has very little effect on the wearer, whether it is turned on or not.

"We hope to improve the device so that it is easier to carry, and to retain the energy-harvesting capabilities."

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

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