Implantable pacemakers have without doubt altered modern medicine, saving countless lives by regulating heart rhythm. But they have one serious shortcoming: Their batteries last only five to 12 years, at which point they have to be replaced surgically. Now, researchers have surmounted this issue by designing a pacemaker powered by the energy of heartbeats, according to a report in ACS Nano. The device was successfully tested in pigs, which have a similar physiology to humans.