U.S. nanotechnology researchers have developed a microfiber fabric that generates its own electricity, making enough current to recharge an iPod.
If made into a shirt, the fabric could harness power from its wearer simply walking around or even from a slight breeze, they reported on Wednesday in the journal Nature.
"The fiber-based nanogenerator would be a simple and economical way to harvest energy from the physical movement," Zhong Lin Wang of the Georgia Institute of Technology, who led the study, said in a statement.
The nanogenerator takes advantage of the semiconductive properties of zinc oxide nanowires -- tiny wires 1,000 times smaller than the width of a human hair -- embedded into the fabric. The wires are formed into pairs of microscopic brush-like structures, shaped like a baby-bottle brush.
One of the fibers in each pair is coated with gold and serves as an electrode. As the bristles brush together through a person's body movement, the wires convert the mechanical motion into electricity.
Researchers in the Georgia Institute of Technology made the nanogenerator by first coating fibers with a polymer, and then a layer of zinc oxide. They dunked this into a warm bath of reactive solution for 12 hours. This encouraged the wires to multiply, coating the fibers.
They added another layer of polymer to prevent the zinc oxide from being scrubbed off. And they added an ultra-thin layer of gold to some fibers, which works as a conductor.
To ensure all that friction was not just generating static electricity, the researchers conducted several tests. The fibers produced current only when both the gold and the zinc oxide bristles brushed together.
So far, the researchers had demonstrated the principle and developed a small prototype. They 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, they estimate that a square meter of fabric made from the special fibers could theoretically generate as much as 80 milliwatts of power.
The material could be used by hikers and soldiers in the field and also to power tiny sensors used in biomedicine or environmental monitoring.
However, one major hurdle remains: zinc oxide degrades when wet. The researchers are working on a process that would coat the fibers to protect the fabric in the laundry.
For additional information visit http://www.gatech.edu