A pacemaker’s battery needs to be swapped out about every five to eight years, requiring surgery. Engineers are now working on a device that converts the mechanical energy of a beating heart into electrical energy and could last indefinitely. A prototype tested in farm animals has generated a microwatt of power, enough to keep a pacemaker going.

The Parts

A) Flexible polymer holds system in place.

B) Piezoelectric ribbons harvest energy.

C) Rectifier switches current.

D) Micro­battery stores energy.

E ) Leads connect battery to pacemaker.

F) Pacemaker controls heart rhythm.

Source: John A. Rogers, professor of materials science and engineering, University of Illinois at Urbana-Champaign

This article originally appeared in the April 2014 issue of Popular Science.