WASHINGTON - Call it the ultimate power walk.
Researchers have developed a device that generates electrical power from the swing of a walking person's knee.
With each stride the leg accelerates and then decelerates, using energy for moving and braking.
Max Donelan and colleagues reasoned that a device that helps the leg decelerate could generate power without requiring much additional energy from the person.
It's sort of like the way that some hybrid-electric cars produce electricity from braking.
With the device, a minute of walking can power a cellphone for 10 minutes, Donelan, of Simon Fraser University in Burnaby, British Columbia, said in a telephone interview. Other potential uses include powering a portable Global Positioning System device, a motorized prosthetic joint, or implanted drug pumps.
Donelan and colleagues at the University of Pittsburgh and the University of Michigan reported the development of the device in today's edition of the journal Science.
The first practical use for the generator is likely to be in producing power for artificial limbs, said Donelan, who with his coauthors has founded a company to develop the device commercially.
The generator weighs about 3 1/2 pounds so users do burn energy carrying it on their knee, but they don't notice whether it is switched on or off when walking on a treadmill, he said.
They miss it when it's removed, however, because they get used to its extra braking action, he added.
With one generator on each knee, people walking on a treadmill were able to generate about 5 watts of power.