Nanotech fabric that can harvest energy from motion could one day lead to clothing that can power portable electronics, researchers say.

Scientists at the Georgia Institute of Technology have designed the new fabric based on a phenomenon called the piezoelectric effect. This effect occurs when mechanical pressure is applied to certain materials that have crystalline structures in such a way that it produces a small electric charge.

The team lined textile fibres with piezoelectric nanowires arranged like the bristles on a bottlebrush. When a person walks around wearing the material, the wires rub together and generates electricity.
The scientists reportedly say that bending the wires creates a piezoelectric field potential. In fact, one of the developments has been a ‘knee-bracer generator’ which acts as a mobile power plant for few of our gadgets.

The researchers estimated that their material could eventually generate up to 80 milliwatts of power for each square meter (about 11 square feet) of fabric.

An average digital music player or cell phone, by contrast, uses a few hundred milliwatts or more.So while your future sweat suit may not charge up your iPod, it could power tiny sensors that keep track of your vital signs as you run. And the use is not limited to clothing, scientists add. The technique can be applied to any surface that picks up vibration, such as engines, tires, or even swaths of cloth ( flags , sails, etc) catching the wind or even the synthetic-turf on a playground !

Growing Wires

For their research, these scientists have grown nano-size wires of zinc oxide around Kevlar fibres.
The wires were 50 nanometers thick, or about a thousand times thinner than a single human hair.

The enhanced Kevlar was then woven to create fabric. As the material stretched, the wires bent, creating electric potential. Electrodes at the bases of the fibres collected the charge.

For decades nanotech researchers have speculated about potential applications for tiny electronics.

Nano-size sensors placed in the bloodstream could better detect early onset of diseases, for example.

Such devices could also be woven into soldiers' uniforms to monitor their health during combat. Other work has focused on a fleet of tiny sensors that could be spread across a geographic area to monitor environmental health.

One thing common among nano-sensors is that these things needs power & therefore the interest among scientists in nano-scale power generation as an area of study. Conventional batteries are still too large, but piezoelectric generation would be perfect for these applications, scientists have reasoned.