Millions of people around the world live with cardiac arrhythmia—a condition where the heart's rhythm goes too fast, too slow, or falls out of sync entirely. The standard fix has long been a surgically implanted pacemaker, complete with leads threaded into the heart itself. Effective, yes, but not without risk: infection and tissue damage are real possibilities whenever you're cutting someone open. Now, a joint team from MIT and USC has come up with something that skips the scalpel altogether—a wearable patch, applied like a sticker to the chest, that regulates heartbeat using nothing but ultrasound.
"Ultrasound offers a unique combination of deep tissue penetration, spatial focusing and non-invasive delivery," says Chen Gong, the study's first author and a researcher at USC. Earlier attempts at ultrasound-based pacing had stumbled—either the results weren't consistent, or the method depended on injected microbubbles to work at all. Gong's team took a different route, borrowing from a field called sonogenetics. The idea: genetically tweak heart cells so they become responsive to sound waves. Once those modified cells pick up an ultrasound pulse, ion channels swing open, calcium rushes in, and the cell contracts—essentially giving researchers a remote switch for heartbeat, reports Physics World.
"Our central motivation was to address the limitations of conventional pacemakers, while preserving precise control of cardiac rhythm," Gong explains.
Testing It Out
Before building any hardware, the team checked whether the concept even held up in a dish. Using human heart muscle cells that had been sonogenetically altered, they found that ultrasound pulses got roughly 75% of the engineered cells beating in lockstep with the sound waves. Cells that hadn't been modified simply ignored the signal. Just as important, the ultrasound exposure didn't trigger any red flags in the cells—no spike in inflammation markers, no signs of injury or oxidative stress—suggesting the approach is safe, at least at this stage.
Introducing the Device
Building on those results, the researchers engineered what they call a non-invasive ultrasound pacemaker, or NUP—detailed in a paper published in Nature Biomedical Engineering. It's roughly the size of a postage stamp, adheres to skin using a bioadhesive layer, and packs in a 64-channel phased-array transducer alongside modules for data collection, wireless transmission, and power.
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To see whether it actually worked in a living animal, they tested it on sonogenetically modified rats, sticking the device onto each rat's chest and firing ultrasound through the chest wall toward the heart. At 2 MPa of acoustic pressure with 40-millisecond pulses, the device pushed heart rates up from a baseline of 240 bpm to somewhere between 360 and 540 bpm—and cranking up the pulse repetition frequency pushed rates even higher. The moment the ultrasound stopped, hearts reverted to their normal rhythm on their own. Rats without the genetic modification, by contrast, showed no response to the device at all.
The team also showed off the NUP's precision: it can electrically steer its ultrasound beam to hit targets less than a millimeter apart, meaning it can selectively pace different chambers of the heart. When they induced arrhythmias in the modified rats, the device successfully restored normal rhythm—something that didn't happen in unmodified control animals exposed to the same stimulation.
"A major objective of this work was to move beyond proof-of-concept stimulation and demonstrate a wearable system that could realistically support daily use," notes Qifa Zhou, who leads a research group at USC. "The current prototype integrates imaging, stimulation, wireless communication and battery-powered operation into a wearable format."
Looking Toward the Clinic
A real-world version of this device would need to handle a lot on its own—tracking heart rate, pinpointing the heart's chambers, and delivering stimulation, all without a technician manually steering things. To move toward that, the team built a cloud-based AI system that reads heart rate and calculates targeting coordinates, then adjusts the ultrasound beam accordingly.
They also had to answer a harder question: would this actually work on a human-sized chest? Using simulations plus experiments on a pig heart buried under multiple layers of tissue, they found that even after the ultrasound weakened passing through tissue, it still arrived at roughly 2 MPa—enough to stimulate the heart at clinically meaningful pacing sites.
Safety checks turned up encouraging results too. The ultrasound energy delivered stayed under approved exposure limits, generated barely any heat, and the genetic modification itself didn't cause unwanted immune reactions, off-target effects, or tissue damage in the rats.
"In the long term, we are optimistic about applying sonogenetics in humans," says Gengxi Lu, a co-author from MIT. He's careful to draw a distinction here: sonogenetics isn't gene editing in the sense of permanently altering DNA. Instead, it gets cells to temporarily produce proteins that respond to ultrasound. Still, he cautions, plenty of clinical testing lies ahead before anyone can call it safe or effective long-term in people.
Next on the agenda: refining how the genetic material gets delivered, running trials in larger animals, and building closed-loop systems that pair real-time sensing with adaptive stimulation. There's also the unglamorous engineering side—shrinking the device further, stretching battery life, and making sure it stays put and functions well even as a person moves around.
"For cardiac pacing, we envisage that the final goal of NUP technology is to be a permanent alternative to a long-term implanted pacemaker," Xuanhe Zhao of MIT told Physics World. "More broadly, we are interested in expanding ultrasound-enabled bioelectronic medicine beyond cardiac pacing toward other organs and therapeutic applications where non-invasive, spatially precise modulation could have clinical impact."
