So far your footsteps, breath and nervous energy have all been tapped to charge up batteries, and now researchers from the Georgia Institute of Technology scientists have pulled it off using thermal changes. They did it with so-called pyroelectric nanogenerators, which use polarization changes to harvest heat energy from temperature fluctuations. Normally output current is too low for commercial electronics, but by making one with lead zirconate titanate (PZT), the team was able to create a device that could charge a Li-ion coin battery to power a green LED for a few seconds. The researchers predict that by doubling the surface area, they could drive wireless sensors or LCDs using only environmental temperature changes from an engine or water pipe, for instance. The result could be green power, but without all that pesky moving around.