In 2012, Neil Armstrong, the first human to walk on the moon, died from complications following heart surgery. His doctors had implanted a temporary pacemaker. When the pacemaker wires were later removed, Armstrong suffered internal bleeding — an outcome more common than many patients realize.
Now, engineers at Northwestern University have developed what could have saved Armstrong’s life: the world’s smallest pacemaker, smaller than a single grain of rice. Unlike traditional pacemakers, this one is injectable, wireless, and dissolves harmlessly into the body at the end of its mission.
It’s a technological leap that might transform cardiac care, especially for newborns with fragile hearts and adults recovering from surgery.
Tiny Pacemaker, Huge Potential
Although temporary pacemakers are now routine, they come with risks. They rely on wires sewn directly onto the heart muscle during surgery. These wires extend outside the body and connect to an external pacing box. Removing them often causes injuries: infection, tissue damage, or internal bleeding.
“When the wires are pulled out, that can potentially damage the heart muscle,” explained Igor Efimov, an experimental cardiologist at Northwestern. “That’s actually how Neil Armstrong died.”
The new device bypasses this hazard completely. At only 1.8 millimeters wide and 3.5 millimeters long, it fits comfortably into the tip of a syringe. Doctors can inject it directly into the heart muscle, entirely avoiding open-chest surgery.
“There’s a crucial need for temporary pacemakers in pediatric heart surgeries,” said John A. Rogers, who led the research at Northwestern University. “Our major motivation was children. About 1% of children are born with congenital heart defects — regardless of whether they live in a low-resource or high-resource country.”
After heart surgery, these babies typically need temporary pacing for about a week until their hearts stabilize. “Now, we can place this tiny pacemaker on a child’s heart and stimulate it with a soft, gentle, wearable device,” Efimov said. “No additional surgery is necessary to remove it.”
Powering a Heartbeat with Light
But how can something so small work as effectively as traditional pacemakers? The answer, remarkably, is found in the body itself.
The device doesn’t rely on batteries or external wiring. Instead, it uses a galvanic cell, a type of simple battery that transforms chemical reactions in bodily fluids into electricity. When two tiny metal pads on the device come into contact with fluids surrounding the heart, they create a natural battery, providing enough electrical current to regulate heartbeats.
But the true innovation is how the pacemaker is controlled. A small, wearable patch on the patient’s chest monitors the heartbeat. When it detects irregular rhythms, the patch automatically flashes pulses of infrared light through the patient’s skin. This infrared light travels deep into the body, turning on the pacemaker remotely.
“Infrared light penetrates very well through the body,” Efimov noted. “If you put a flashlight against your palm, you will see the light glow through the other side of your hand. Our bodies are great conductors of light.”
This combination of biological power and wireless control allowed the team to shrink the device dramatically, eliminating bulky antennas that older models required.
Dissolvable and Versatile
One of the device’s most remarkable features is how to dispose of it. The pacemaker dissolves naturally into bodily fluids once it’s no longer needed, similar to absorbable stitches. There’s no need for invasive removal surgeries, drastically reducing patient risk.
“The heart requires only a tiny amount of electrical stimulation,” Rogers explained. “By minimizing the size, we dramatically simplify implantation, reduce trauma and risk, and eliminate secondary surgical extraction procedures.”
The researchers have successfully tested their pacemaker in mice, rats, pigs, dogs, and even human heart tissue from organ donors. Although human trials are still two to three years away, the researchers are optimistic about its potential.
Bozhi Tian, a bioelectronics expert at the University of Chicago who was not involved in the study, described the device as a “significant leap forward.”
“This new pacemaker is a transformative breakthrough in medical technology,” Tian told AFP. “It’s a paradigm shift in temporary pacing and bioelectronic medicine, opening up possibilities far beyond cardiology — including nerve regeneration, wound healing, and integrated smart implants.”
Indeed, Rogers suggests the pacemaker’s tiny size could allow multiple devices to be placed across the heart, each controlled independently by different colors of light. This method could synchronize pacing in complex heart conditions, treating arrhythmias far more effectively than current techniques.
“Because it’s so small, this pacemaker can be integrated with almost any kind of implantable device,” Rogers added. “We could incorporate our pacemakers into other medical devices like heart valve replacements, which can cause heart block.”
The findings were published in the journal Nature.
