Pacemaker implants save many lives every year, but they have one inherent limitation. They run on electricity provided by a lithium coin battery which contains toxic materials and has to be changed every few years. Researchers are finding ways to harvest energy from the heart’s motion, but there remains the question of how to store that energy in a safe and reliable way.

One of the leading alternatives is supercapacitor (supercap) technology. These devices can store a lot of energy, like a battery, but like a capacitor they can quickly absorb or release energy. Also, they tend to be able to survive many more charge/discharge cycles than a chemical battery can. Researchers at UCLA and the University of Connecticut have worked together to create a bio-compatible supercap. Made from microscopically-thin layers of graphene, these devices use modified human proteins as electrolytes. The result is a energy storage device that is only 1 micrometer thick (much less than the thickness of a human hair) that is flexible and lightweight. As a result, it can bend and twist without mechanical damage.

When paired with an energy harvesting device, this system could be used to power an implanted pacemaker indefinitely. This would eliminate the small risk involved in swapping out the chemical battery every few years, as is the current practice. The same technology could be used to provide other types of implants as well.