If you've ever been frustrated when your iPod battery runs out in the middle of a workout, help may be on the way.  Nanotechnology researchers at the Georgia Institute of Technology are developing a shirt that harvests energy from the wearer's physical motion and converts it into electricity for powering small electronic devices like iPods, global positioning systems, or radio devices.

The researchers have demonstrated that pairs of textile fibers covered with zinc oxide nanowires generate electricity in response to applied mechanical stress. Known as "the piezoelectric effect," the resulting current flow from many fiber pairs woven into a shirt or jacket could allow the wearer's body movement to power a range of portable electronic devices.  The fibers could also be woven into tents or other structures to capture energy from wind motion, sound vibration or other mechanical energy.

"The two fibers scrub together just like two bottle brushes with their bristles touching, and the piezoelectric-semiconductor process converts the mechanical motion into electrical energy," says Zhong Lin Wang, a Regents professor in the School of Materials Science and Engineering at the Georgia Institute of Technology.  "Many of these devices could be put together to produce higher power output."

The researchers have measured current of about four nanoamperes and output voltage of about four millivolts from a nanogenerator that included two fibers that were each one centimeter long. With a much improved design, Wang estimates that a square meter of fabric made from the special fibers could theoretically generate as much as 80 milliwatts of power--enough to power an iPod.

The only drawback to the design thus far is that it can't be washed without damaging the nanowires, so the researchers must come up with a way to keep the wire protected while cycling through a washing machine before the product is commercially viable.  

The research was funded by NSF's Division of Materials Research and sponsored by the U.S. Department of Energy and the Emory-Georgia Tech Nanotechnology Center for Personalized and Predictive Oncology.