A heart-powered pacemaker may sound counter-intuitive, but in essence this is precisely what aerospace engineers from the University of Michigan are proposing. The engineers have come up with a prototype powered by vibrations in the chest cavity - vibrations which are caused mainly by the beating of the heart.
Unfortunately the explanation being circulated is somewhat hazy, but it seems that this prototype employs piezoelectric material which can generate electricity when undergoing mechanical stresses, such as those caused by these naturally occurring vibrations in the chest.
Better news still is that the energy harvested from the chest is always more than is required to power a pacemaker, and typically by a factor of eight. Since pacemakers apparently only require 1 millionth of a watt to run, perhaps this shouldn't be all that surprising. Further, the device operates at heart rates ranging from seven to 700 beats per minute, comfortably encompassing the required range.
If viable, one day the technology could conceivably negate the need for surgery to replace pacemakers with dead batteries. The prototypes to date are not biocompatible, so don't expect to see effectively self-powered pacemakers any time soon. The team's findings were published in the American Institute of Physics journal, Applied Physics Letters, on January 23.