Powering pacemakers with heartbeat vibrations

Though pacemakers require only small amounts of energy (about 1 millionth of a Watt), their batteries have to be replaced periodically, which means multiple surgeries for patients. Researchers have searched for ways to prolong battery life — trying to generate energy to power a pacemaker using blood sugar, or the motion of the hands and legs — but these methods either interfere with metabolism or require a more drastic surgery, such as passing a wire from the limbs to the chest area.
Aerospace engineers M. Amin Karami and Daniel J. Inman, from the University of Michigan in Ann Arbor, have developed a prototype device that could power a pacemaker using a source that is surprisingly close to the heart of the matter: vibrations in the chest cavity that are due mainly to heartbeats.
In their method, vibrations in the chest cavity deform a layer of piezoelectric material, which is able to convert mechanical stress into electrical current. Tests indicate that the device could perform at heart rates from 7 to 700 beats per minute (well below and above the normal range), and that it could deliver eight times the energy required for a pacemaker. Furthermore, the authors write, the amount of energy generated is always larger than the amount required to run a pacemaker, regardless of heart rate.
Though the team has yet to develop a prototype that is biocompatible, they say that the potential to package this energy harvester with pacemakers gives it an advantage over competing methods.
U-M Department of Aerospace Engineering