MrSeb writes: "It sounds like the theoretical impossibility of perpetual motion, but engineers at the University of Michigan have created a pacemaker that is powered by the beating of your heart — no batteries required. The technology behind this new infinite-duration pacemaker is piezoelectricity. Piezoelectricity is is literally “pressure electricity,” and it relates to certain materials that generate tiny amounts of electricity when deformed by an external force — which, in the case of the perpetual pacemaker, the vibrations in your chest as your heart pumps blood around your body. Piezoelectric devices generate very small amounts of power — on the order of tens of milliwatts — but it turns out that pacemakers require very power, too. In testing, the researchers’ energy harvester generated 10 times the required the power to keep a pacemaker firing. Currently, pacemakers are battery powered — and the battery generally need to be replaced every few years, which requires surgery. According M. Amin Karami, the lead researcher, “Many of the patients are children who live with pacemakers for many years,” he said. “You can imagine how many operations they are spared if this new technology is implemented.” This piezoelectric energy harvester is about half the size of a conventional battery, too, which is presumably a good thing."