Washington: An experimental device could use the energy of the beating heart to keep the pacemaker going, doing away with battery replacements every five to seven years.

A preliminary study by researchers at the University of Michigan Ann Arbor tested an energy-harvesting device that uses piezoelectricity - electrical charge generated from motion.

The approach is an innovative solution for pacemakers, because they require only small amounts of power to operate, said M. Amin Karami, research fellow in aerospace engineering at Michigan, who led the study.

"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," added Karami, according to a Michigan statement.

Researchers measured heartbeat-induced vibrations in the chest. Then, they used a "shaker" to reproduce the vibrations in the lab and connected it to a prototype cardiac energy harvester they developed.

Measurements of the prototype's performance, based on sets of 100 simulated heartbeats at various heart rates, showed the energy harvester performed as the scientists had predicted - generating more than 10 times the power that modern pacemakers require.

The next step will be implanting the energy harvester, which is about half the size of batteries now used in pacemakers, Karami said.

Researchers hope to integrate their technology into commercial pacemakers.

Two types of energy harvesters can power a typical pacemaker: linear and nonlinear. Linear harvesters work well only at a specific heart rate, so heart rate changes prevent them from harvesting enough power.

Conversely, a nonlinear harvester - the type used in the study - uses magnets to enhance power production and make the harvester less sensitive to heart rate changes.

The nonlinear harvester generated enough power from heartbeats ranging from 20 to 600 beats per minute to continuously power a pacemaker.

Devices such as cell phones or microwave ovens would not affect the nonlinear device, Karami said. His co-authors are David J. Bradley and Daniel J. Inman.

These findings were presented at the American Heart Association's Scientific Sessions 2012.