The idea of capturing some energy from you constant writhing and wriggling ins't new -- but this small, flexible device certainly is. The postage stamp-sized circuitry, once attached to the skin, could generate electricity to power the gadgets secreted about your person.
The device captures the piezoelectric effect -- where electrical energy is generated by mechanical stress. A thin rubber sheet is bound to a 50 nanonmeter-thick gold film that acts as the device's electrode, held away from the skin by tiny pillar-like structures. Friction between the skin and pillars induce currents in the gold film, in turn generating a voltage. The more pillars, the greater the effect.
In tests, prodding it with a finger has been shown to create 90V and power of 0.8mW. But in a more realistic use case -- attached to a subject's forearm or throat -- the device still generates 7.3V and 7.5V respectively. That's fairly significant output for a simple piece of flexible adhesive, though it would still take a while to charge a phone, say, with those power levels.
Still, the device is progress and next the team plans to make their creation even more flexible. In theory, it could create a sheet of any size that in the future, so that they can create one in any size and still confirm to the contours of the human body. Piezoelectric spandex, anyone? [IEEE via Engadget]