Power your phone with your body heat

Someday soon, we may have eminently portable phone battery rechargers on us at all times -- and they may be our pants pockets.

Power Felt is a "thermoelectric" device, which means that it can take the difference in temperature between, say, your body temperature and the room temperature, and use that to create a charge. Theoretically, it could be put into our clothing -- pants, jackets, etc. to charge our phones or iPods.

Developed by Wake Forest University researchers at the Center for Nanotechnology and Molecular Materials, Power Felt is "comprised of tiny carbon nanotubes locked up in flexible plastic fibers and made to feel like fabric," according to the university press release. Carbon nanotubes are tiny cylinder-shaped molecules of linked carbon atoms.

Their research appears in the current issue of Nano Letters.

Researcher and Wake Forest graduate student Corey Hewitt says:

“We waste a lot of energy in the form of heat. For example, recapturing a car’s energy waste could help improve fuel mileage and power the radio, air conditioning or navigation system. Generally thermoelectrics are an underdeveloped technology for harvesting energy, yet there is so much opportunity.”

Power Felt could be used many ways. It could:

line car seats to boost car battery power
insulate pipes or collect heat under roof tiles to help reduce gas or electricity bills
be wrapped around IV or wound sites to help in medical monitoring
line sports clothing to monitor athletic performance

“Imagine it in an emergency kit, wrapped around a flashlight, powering a weather radio, charging a prepaid cell phone,” adds David Carroll, director of the Center for Nanotechnology and Molecular Materials. “Power Felt could provide relief during power outages or accidents.”

Thermoelectrics are currently too expensive to be used widely in consumer products, because they use bismuth telluride, a substance that is much more efficient, but that can cost as much as $1,000 a kilogram. Power Felt could someday be as cheap as $1 to add to a cell phone cover.

Power Felt needs more work before it can be brought to market, but Hewitt says,

"I imagine being able to make a jacket with a completely thermoelectric inside liner that gathers warmth from body heat, while the exterior remains cold from the outside temperature. If the Power Felt is efficient enough, you could potentially power an iPod, which would be great for distance runners. It’s definitely within reach."