Heartbeat-powered pacemaker prototype tested in a pig

Inside a pig’s heart, a prototype pacemaker ran on the motion of the heartbeat for one month. The device, built by Pengfei Chen and professor Xudong Wang at the University of Wisconsin–Madison, is a triboelectric nanogenerator designed to fit inside the battery compartment of Medtronic’s Micra, a leadless pacemaker implanted directly in the heart.

The engineering target is small but consequential. In the Micra, the battery makes up more than half the device’s size and weight, yet lasts only seven to 10 years. Removing a depleted pacemaker from inside the heart is difficult, so an expired implant is often left in place while another is inserted. For younger patients, that can mean several replacement procedures over a lifetime.

The Wisconsin design places oscillating structures above and below the pacemaker’s electronics inside its titanium shell. Each structure contains electrode plates coated with copper on one side and a fluorinated polymer film on the other. As the heart beats, the plates are pushed together and then separate; their changing contact generates electricity, which can run the pacemaker or be stored in a small capacitor.

Laboratory tests measured 276.6 microwatts per cubic centimeter, which the researchers describe as an order of magnitude higher than previous nanogenerator designs and sufficient to power the pacemaker. The prototype also powered cardiac stimulation in the pig without complications beyond those seen with conventional battery-powered pacemakers. But its output in the heart fell short of the laboratory peak: soft tissue dampened the motion, while the heart’s twisting movement differed from the straight compression that maximized generation on the test bench.

So what changes in practice? If the design can be refined and later validated in people, a single leadless pacemaker could potentially avoid repeated battery-replacement procedures. That prospect is still distant: the team is adapting the generator to the heart’s irregular motion, the device is at the prototype stage, and human clinical trials remain years away.