This was a big deal in the world of medicine. Before the implanted technology, pacemakers were hooked to bulky external devices that literally shocked patients. Having a self-contained pacemaker was a significant step forward in medicine. But the pacemaker still needed a source of power, and Greatbatch ended up getting into the lithium battery business in order to create a better, longer-lasting power supply for the pacemaker [source: MIT]. Greatbatch died in 2011, but the need for a more satisfactory source of energy for the pacemaker continued.

In 2014, researchers made it sound like that search might be over. An interdisciplinary research team (including scientists and cardiologists from Northwestern University, University of Illinois and the University of Arizona) developed a device that uses the motion of heartbeats (as well as the motion of the lungs and diaphragm) to power an implanted pacemaker. While the self-powered pacemakers haven’t yet been tested on humans, they have so far had successful trials with cows, sheep and pigs.

Even better? Although the technology was tested for a pacemaker, it could have broad uses for any implanted device that uses battery power. Think cochlear implants, implanted defibrillators, even heart rate monitors — all of these devices use batteries that require changing. Replacing those batteries usually means a potentially risky surgical procedure [source: Dagdeviren et al.]. So how does our body produce enough voltage to keep a pacemaker in working order? Read on for the nitty-gritty.