A new development in passively harvesting human power was featured in a recent NY Times article. Using piezoelectric crystals to generate electricity from human movement isn’t a novel idea. Its varied applications are described in Chapter 1 of The Human-Powered Home. But now scientists at Princeton have printed the crystals onto a flexible rubberlike material that’s also biocompatible, so it can be implanted in the body. As you move, the material could generate enough electricity to run a medical sensor. Outside of the body–for example, embedded in clothing–a flexible generator could charge your cell phone or portable music player.