Now that’s a power walk

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Now that's a power walk

Device produces electricity from a swinging knee

http://www.msnbc.msn.com/id/23052904/

A new energy-capturing knee device can generate enough electricity

from walking to operate a portable GPS locator, a cell phone, a

motorized prosthetic joint or an implanted neurotransmitter.

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 both 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 cell phone for 10

minutes, Donelan, of Simon Fraser University in Burnaby, British

Columbia, said in a telephone interview. Other potential uses include

powering a portable GPS locator, a motorized prosthetic joint or

implanted drug pumps.

Donelan and colleagues at the University of Pittsburgh and the

University of Michigan report development of the new device in

Friday'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 co-

authors has founded a company to develop the device commercially.

The generator weighs about 3.5 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.

However, they miss it when it's removed 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.

Lawrence C. Rome of the University of Pennsylvania called the

development " extremely clever. "

Other people have thought of rotational devices around joints, Rome

said, " but what's really clever is these guys only turn on resistance

when person trying to brake, so it helps you. "

Rome, who was not part of the research team, previously developed a

backpack that generates electricity from the movement of the person

carrying it.

The backpack was comfortable so it was an easy sell, he said. Whether

the new knee generator is practical will depend on it being

comfortable so people will want to wear it, he said in a telephone

interview.

Arthur Kuo, an associate professor of mechanical engineering at the

University of Michigan and a co-author of the report, called the

device " a cocktail-napkin idea. "