The military deploys many commercial-off-the-shelf (COTS) portable electronic devices in the field for advanced networking operations, communications, surveillance, and other activities. Soldiers using these devices are often in remote locations and do not have access to a power grid to re-charge their batteries. When their devices go down, their jobs become more difficult.

Zhong Lin Wang, a Regents professor in the School of Materials Science and Engineering, Georgia Institute of Technology, developed a method of generating renewable power to charge portable electronic devices for soldiers and other people on-the-move.

“The fiber-based nanogenerator would be a simple and economical way to harvest energy from physical movement,” said Wang. “If we can combine many of these fibers in double or triple layers in clothing, we could provide a flexible, foldable, and wearable power source that, for example, would allow people to generate their own electrical current while walking.”

Wang’s system is a hybrid of microfiber and nanowire generators. His nanowire nanogenerator generates current from vertically aligned zinc oxide (ZnO) nanowires, which produce small electrical charges when they flex. This occurs beneath an electrode containing conductive platinum tips. The nanogenerators, which are 2 x 3 mm2, can produce up to 800 nA and 20 mV of power.

The microfiber generators are made from soft, DuPont Kevlar fibers and capture current from low-frequency mechanical energy. Zinc oxide nanowires have been grown radially and embedded in a polymer at the roots of the fibers. The structures look like microscopic baby-bottle brushes with billions of bristles. One fiber in each pair is coated with gold to serve as the electrode and to deflect the nanowire tips.

Zinc oxide coated nanowires rub against gold fiber to produce a small electric current. Image courtesy Zhong Lin Wang and Xudong Wang.

What’s more, the fibers could also be woven into curtains, tents, or other structures to capture energy from wind motion, sound vibration, or other mechanical sources.
Wang’s next challenge is the washing machine. Zinc oxide is sensitive to moisture, so in real shirts or jackets, the nanowires would need protection from water, he said.