Harnessing the power of movement to run portable electronics

The brace harvests the energy lost when a human brakes the knee after swinging the leg forward to take a step in much the same way that a hybrid-electric car recycles power from braking.

"There is power to be harvested from various places in the body, and you can use that to generate electricity," said Arthur Kuo, a co-author of the paper and an associate professor of mechanical engineering at the University of Michigan in Ann Arbor.

"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."

In preliminary testing, volunteers with a device on each leg generated 5 watts of electrical power without breaking a sweat and they only used 1 watt of extra metabolic energy for each watt of electricity they generated.

The power the walkers generated was enough to power 10 cellphones at the same time and twice the power needed for computers in developing countries.

Expressed another way, one minute of walking would provide 10 minutes of talk time on a cellphone.

The prototype is a bulky 1-kilo brace equipped with a generator, but its creators hope to have something much lighter ready for tests in field trials in a year. They believe the device could be helpful to hikers or soldiers who don't have easy access to electricity.

"One of the biggest technological challenges for the military is developing a portable power source so dismounted soldiers can power their navigation devices, their night-vision goggles, and everything else they carry," said Max Donelan, a professor of kinesiology at Simon Fraser University in British Columbia, Canada.

The brace is the latest innovation in the field of energy-harvesting, which seeks to harness mechanical energy and convert it to electrical energy to drive portable electronics.

Researchers at the University of Pennsylvania, for example, are working on a backpack that converts the mechanical strain on the straps into electrical energy. The straps are made with a material that converts an applied stress into an electrical charge.

The study appears in the journal Science. Researchers from the University of Pennsylvania also worked on the project.

Vocabulary

multitasking, n: doing several things at the same time

brace, n: something that holds parts in place

portable, adj: can be moved about

modest, adj: limited; moderate; small

juice, n: electricity

to dissipate, v: to expend wastefully

preliminary, adj: initial; in advance

metabolic, adj: relating to all the physical and chemical processes of the body

to dismount, v: to get off a means of transport

kinesiology, n: science studying how the organs and bones of the human body make movement possible

to harness, v: to capture and make usable

Questions

1. What can the new brace do?

a. disarm enemies

b. fly at low altitudes

c. generate electricity

d. double up as parachute

2. How does the new brace work?

a. It multiplies dynamical energy.

b. It uses electricity for movement.

c. It suspends the effects of gravity.

d. It changes kinetic energy into electricity.

3. Who might want to use it?

a. pilots

b. soldiers

c. dentists

d. train drivers

4. What part of the body is the brace attached to?

a. neck

b. knee

c. head

d. elbow

5. What is the biggest problem with the brace?

a. It is big and heavy.

b. It is not waterproof.

c. It's colour is unattractive.

d. It freezes in cold weather.

Synonyms

Which of the following words or phrases replace the ones from the passage best

1. devise

a. use

b. target

c. create

d. destroy

2. generate

a. alter

b. store

c. produce

d. condense

3. various

a. internal

b. external

c. different

d. stationary

4. bulky

a. heavy

b. dynamic

c. functional

d. innovative

5. convert to

a. absorb

b. eliminate

c. free from

d. change into

KEY

Questions                 1. c, 2. d, 3. b, 4. b, 5. a

Synonyms                 1. c, 2. c, 3. c, 4. a, 5. d

By Ajarn Horst Baelz