Scientists have developed a battery-free pacemaker with the potential to last a patient’s entire lifetime, reducing risks and costs of replacement. In a study published in Science Advances, researchers at the University of Wisconsin-Madison (UW-Madison) report the first heartbeat-powered pacemaker capable of generating enough energy to offer a feasible alternative to conventional battery-powered devices.
“One of the clinical challenges in managing patients with pacemakers is the need for generator replacement procedures when the battery depletes, which involves reoperation to replace it,” said Daniel Modaff, MD, cardiac electrophysiologist at UW Hospital and Clinics. “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.”
For decades, the standard of care has been the transvenous pacemaker, a battery-powered device implanted near the collarbone with leads threaded through a vein into the heart. Over the past decade, however, clinics have increasingly adopted leadless intracardiac pacemakers that are implanted directly inside the heart. These devices can speed recovery, reduce certain complications, and remove the need for a chest implant.
The main drawback is the battery, which accounts for more than half of the device’s size and weight and typically lasts just 7–10 years. When the battery is empty, the pacemaker is often left inside the heart as a new one is implanted, because surgical removal can be difficult and carries additional risks. This can be particularly problematic for younger patients who may need multiple pacemaker replacements over their lifetimes.
Although researchers have long been looking for alternatives to power these pacemakers, none could yet produce enough energy. Modaff and colleagues designed a nanogenerator that harvests energy from oscillators, each made of a pair of oppositely charged electrode plates. As the heart beats, the motion brings the plates together and pulls them apart, generating an electrical charge that can either power the pacemaker directly or be stored in a small capacitor.
“We had to think about how to balance stability and flexibility so it could oscillate millions and millions of times but maintain the desired mechanical behavior,” said Pengfei Chen, PhD, postdoctoral scholar in materials science and engineering at UW–Madison. “We had to optimize the placement and width of every wire, and the thickness of every electrode plate and substrate.”
Laboratory tests showed that the nanogenerator could generate enough energy to operate the pacemaker, outperforming previous miniaturized solutions. The researchers then implanted the device in a pig for one month, where it successfully provided cardiac stimulation without causing additional adverse reactions compared to conventional battery-powered pacemakers.
“For a device like this, it’s not just about producing energy,” said Xudong Wang, PhD, professor of materials science and engineering at UW-Madison. “You need to get enough power in a small enough volume. With our technology, we achieved a power output density an order of magnitude higher than previous nanogenerators.”
The oscillator’s simple design makes it relatively inexpensive to produce while also providing the mechanical robustness needed to potentially last a patient’s lifetime. However, several engineering challenges remain before the device can advance to clinical trials.
In the pig’s heart, the nanogenerator produced less energy than it did in laboratory tests. The softer tissue dampened its movement, while the heart’s complex motion prevented the oscillator from moving in the straight up-and-down pattern that produced its maximum output under laboratory conditions.
“We want to figure out how to transfer the more irregular movement of the heart into this mechanical oscillation efficiently,” said Wang. “This will lead to our goal by demonstrating sufficient and stable energy generation from hearts in vivo.”
As the researchers address these challenges and refine the pacemaker’s design, they hope to lay the groundwork for a new generation of self-powered cardiac devices that could eliminate the need for battery replacement.
“From a translational standpoint, a reliable self-sustaining power source gives device developers greater freedom to design smaller implants with enhanced diagnostic and therapeutic capabilities,” said Eric Schmuck, PhD, research assistant professor at the Center for Biomedical Swine Research and Innovation at UW–Madison. “As we continue to move toward smarter, more personalized cardiac care, technologies that harvest energy directly from the body could play a critical role in bringing these innovations from the laboratory to the patient.”
