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]