The device is inspired by technology used in hybrid cars which store the power from braking to generate electricity. So-called regenerative brakes can collect energy that would otherwise be dissipated as heat when a car slows. In the same way, the knee brace uses the energy dissipated at the knee as the leg slows after a step.
In tests, volunteers generated five watts of power when they wore a brace on each leg. The researchers said it was enough to operate a portable GPS navigation unit, a robotic prosthetic joint or a heart pacemaker.
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