UW Researchers Develop Battery-Free Pacemaker Powered by Heartbeats

Every heartbeat is a small engine of motion. At the University of Wisconsin–Madison, a team of researchers has figured out how to capture that motion and turn it into electricity—enough to power a pacemaker for the rest of a patient's life.

The device, developed by Pengfei Chen and overseen by materials science professor Xudong Wang, represents a fundamental shift in how implantable cardiac devices might work. Instead of relying on a battery that depletes over seven to ten years and requires surgical replacement, this pacemaker harvests energy directly from the heart's contractions. The research was published in Science Advances on August 19, 2026, and it addresses one of the persistent frustrations in cardiac care: the need to repeatedly open a patient's chest to swap out a dead battery.

The problem is real and immediate. Modern leadless pacemakers—small titanium capsules about the size of a large vitamin pill, implanted directly inside the heart—have revolutionized treatment for irregular heartbeats. They're less invasive than older chest-implanted models and cause fewer complications. But their batteries take up more than half the device's size and weight, and they fail predictably. For a 40-year-old patient, that means multiple surgeries over a lifetime. When the battery dies, removing the old pacemaker from inside the heart is difficult, so doctors often leave it in place and insert a new one alongside it—a workaround that accumulates risk and hardware in the body.

Wang and his team approached the problem by designing what's called a triboelectric nanogenerator—a system that produces electrical current when oppositely charged materials come into contact and then separate. They built specialized oscillating structures that fit inside the battery compartment of the Medtronic Micra, the most common leadless pacemaker on the market. The oscillators consist of electrode plates coated with copper on one side and a negatively charged fluorinated polymer on the other. When the heart beats, the motion compresses these plates together, and when they spring apart, the movement creates an electrical charge. That charge either powers the pacemaker directly or gets stored in a small onboard capacitor.

The engineering required obsessive attention to detail. Chen had to optimize the placement and thickness of every wire, every electrode plate, every substrate layer. The goal was to create something that could oscillate millions of times without losing its mechanical properties—flexible enough to move with the heartbeat, but stable enough to last a lifetime. Lab tests showed the nanogenerator could produce 276.6 microwatts per cubic centimeter, an order of magnitude higher than previous miniaturized energy-harvesting devices.

To test whether the concept actually worked inside a living body, the team implanted a prototype in a pig and monitored it for a month. The nanogenerator successfully powered the pacemaker's cardiac stimulation without triggering adverse reactions beyond what conventional battery-powered devices cause. But the real-world test also revealed challenges. Inside the pig's heart, the nanogenerator didn't reach the same power peak it achieved in the lab. Heart tissue is soft and dampens mechanical movement. The heart's natural motion is also more of a twisting action than the straight up-and-down compression the oscillator is designed to capture.

Dr. Daniel Modaff, a cardiac electrophysiologist at UW Hospital and Clinics who co-authored the paper, sees the clinical significance clearly. "One of the challenges in managing patients with pacemakers is the need for generator replacement procedures when the battery depletes, which involves reoperation to replace it," he said. "I look forward to a world in which we can implant a single device that will last a patient's lifetime, and this is a big step closer to realizing this dream."

Wang and Chen are continuing to refine the design to handle the heart's irregular motion more efficiently. The device has been registered with the Wisconsin Alumni Research Foundation, but commercialization and human clinical trials remain years away. Still, the implications extend beyond pacemakers alone. A reliable, self-sustaining power source embedded in the body could enable an entirely new generation of implantable cardiac devices—smaller, smarter, capable of more sophisticated monitoring and treatment. For patients, it means fewer surgeries, less accumulated hardware, and the possibility of a truly permanent solution to a problem that has required repeated intervention for decades.