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 interfere¹ with metabolism²（新陈代谢） or require a more drastic（激烈的） surgery, such as passing a wire from the limbs to the chest area. Aerospace³ engineers M. Amin Karami and Daniel J. Inman, from the University of Michigan in Ann Arbor⁴, have developed a prototype device that could power a pacemaker using a source that is surprisingly close to the heart of the matter: vibrations⁵ in the chest cavity that are due mainly to heartbeats.

The authors describe the technique and their progress developing it in a paper recently published in the AIP's Applied⁶ Physics Letters.

In their method, vibrations in the chest cavity deform⁷ a layer of piezoelectric（压电的） 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.