Wouldn't it be great if you could walk down the street listening to your iPod or using your smartphone without ever worrying about the battery dying?

Zhong Lin Wang, a professor and nanotechnology researcher at the Georgia Institute of Technology, says that within five years, you might be able to do just that. According to Wang, instead of using a battery to power phones, MP3 players and other portable devices, you could harvest the energy generated by the movement of your shirt. Yup, you read that right - a "power shirt," which would provide users with a flexible, foldable and wearable power source.

Georgia Tech detailed the potential development of power shirts and other fibre-based power generators last week. And Wang, a Regents professor in the Atlanta-based college's School of Materials Science and Engineering, said this week that he's using nanotechnology to try to help soldiers, hikers and other people harness the energy generated by physical motion and convert it into usable electrical power.

"For the last few years, we've been looking for energy harvesting technology," Wang said. "Body movements. Heart beating. Blood flow. Sonic waves created when you're talking. These are all energies available in our environment. We wanted to know how to convert them into use. Body movement is the most conventional choice."

Weaving numerous pairs of textile fibres covered with zinc oxide nanowires into a shirt could enable the wearer's body movements to power portable devices, Wang explained. The nanowire-covered fibres also could be woven into curtains, tents or other structures to capture energy from sound vibrations, or from wind motion, he said.

Wang noted that the fibre pairs being used by him and his team of researchers are each one centimetre long and can produce four nanoamperes of current and an output voltage of about four millivolts.

Millions of the fiber pairs - which would take up about one square metre of space on a shirt - would be needed to harvest enough energy to power an iPod, Wang said. He added that the nanowires stick out of the fibres like bristles on a brush. When the wearer of a power shirt began to walk, the fibre pairs would rub against each other, creating electricity via the nanowires.

The shirt could be connected to an electronic device via a separate wire, enabling the device to be powered directly by the wearer's movements, Wang said.

The Georgia Tech researchers have developed more than 200 nanofibres, along with their first prototype of a power shirt. But there is still plenty of work to do before the vision becomes reality, according to Wang.

"I think we are five years away from this [becoming viable], because there are a lot of technical challenges to overcome," he said. "How do we link all these fibres together? How do we protect them when the shirt is out in the rain? How do we make sure the power is effectively stored and [then] output?"

Washing power shirts and other materials with the fibres built into them also is an issue. Zinc oxide is sensitive to moisture, so it would have to be safeguarded from water not only during storms but also during the wash cycle, Wang acknowledged.

Georgia Tech said the nanogenerator research work was sponsored by the National Science Foundation, the US Department of Energy and the Emory-Georgia Tech Nanotechnology Center for Personalized and Predictive Oncology.