World's smallest pacemaker is set to revolutionize heart health

In a remarkable medical breakthrough, engineers have developed a light-activated pacemaker so tiny that doctors can inject it into the body through a syringe. Remarkably, the device simply dissolves after it’s no longer needed. 

Designed for newborns, the pacemaker could transform temporary heart care after congenital defect surgeries.

Controlling the heart with light

The new pacemaker is smaller than a grain of rice. It’s wirelessly activated through pulses of light which are delivered by a soft, wearable device mounted on the patient’s chest.

The external controller detects abnormal rhythms and sends light through the body to activate the pacemaker and restore heartbeat. The study demonstrates the device’s effectiveness across animal and human donor hearts. 

The development of the pacemaker was led by John A. Rogers, a professor of material science, biomedical engineering, and neurological surgery at Northwestern University. 

“We have developed what is, to our knowledge, the world’s smallest pacemaker,” said Professor Rogers.

“There’s a crucial need for temporary pacemakers in the context of pediatric heart surgeries, and that’s a use case where size miniaturization is incredibly important. In terms of the device load on the body – the smaller, the better.”

Solution designed for newborns

Though the light-activated pacemaker can function in patients of all sizes, its miniaturized design was motivated by the needs of infants.

Igor Efimov is a co-leader of the study and experimental cardiologist at Northwestern. 

“About 1% of children are born with congenital heart defects. The good news is that these children only need temporary pacing after a surgery. In about seven days or so, most patients’ hearts will self-repair. But those seven days are absolutely critical,” said Efimov.

Traditional pacemakers require surgery and have wires sticking out of the chest to connect to an external device. When they are no longer needed, the wires are removed – risking bleeding, tissue damage, or even death.

“Wires literally protrude from the body, attached to a pacemaker outside the body,” Efimov explained. “When the pacemaker is no longer needed, a physician pulls it out. The wires can become enveloped in scar tissue. That’s actually how Neil Armstrong died.”

The new injectable pacemaker addresses these risks. All of its components are biocompatible and bioresorbable, meaning they safely dissolve in the body’s fluids without needing surgical removal. Once the device has served its purpose, it simply disappears.

Refining the light-activated pacemaker

This innovation builds on earlier work by Rogers and Efimov, who developed a quarter-sized dissolvable pacemaker in 2021. Surgeons asked for a smaller version to allow easier placement and suit the smallest patients. 

The original device used near-field communication (NFC), but its antenna limited how small the device could be made. To overcome this, the team replaced the NFC system with a novel light-based mechanism.

“Instead of using the radio frequency scheme for wireless control, we developed a light-based scheme for turning the pacemaker on and delivering stimulation pulses to the surface of the heart. This is one feature that allowed us to dramatically reduce the size,” said Professor Rogers.

Powered by the body’s own fluids

The engineers also reimagined how to power the tiny pacemaker. Rather than requiring a battery or external power source, the device uses a simple galvanic cell – a chemical battery formed by two different metals as electrodes. 

When the device is inside the body, surrounding biofluids act as the electrolyte, allowing electrical current to flow and stimulate the heart.

“A very tiny light-activated switch on the opposite side from the battery allows us to turn the device from its ‘off’ state to an ‘on’ state upon delivery of light that passes through the patient’s body from the skin-mounted patch,” explained Professor Rogers.

Reducing trauma and risk

Using infrared light, which can safely penetrate deep into the body, the wearable controller detects when a patient’s heart rate falls too low. It then triggers a light-emitting diode (LED) to flash on and off at the desired pacing rhythm. 

“Infrared light penetrates very well through the body,” Efimov said. “If you put a flashlight against your palm, you will see the light glow through the other side of your hand. It turns out that our bodies are great conductors of light.”

Despite its microscopic size – just 1.8 mm wide, 3.5 mm long, and 1 mm thick – the pacemaker delivers stimulation on par with traditional devices. “The heart requires a tiny amount of electrical stimulation,” Rogers said. 

“By minimizing the size, we dramatically simplify the implantation procedures, we reduce trauma and risk to the patient, and, with the dissolvable nature of the device, we eliminate any need for secondary surgical extraction procedures.”

A new era of heart care

Because these light-activated pacemakers are so small and wireless, doctors could one day deploy multiple units on different parts of the heart to create more advanced pacing systems.

Each device could be controlled independently using different light wavelengths, enabling personalized and precisely timed stimulation across the heart’s surface.

“We can deploy a number of such small pacemakers onto the outside of the heart and control each one,” Efimov said. “Then we can achieve improved synchronized functional care.”

Professor Rogers noted that because it’s so small, the pacemaker can be integrated with almost any kind of implantable device.

“We also demonstrated integration of collections of these devices across the frameworks that serve as transcatheter aortic valve replacements to address complications that can occur during a patient’s recovery process,” said Rogers.

Future of bioelectronic medicine

While this breakthrough has clear implications for pediatric heart care, the technology could pave the way for a new generation of bioelectronic medicine. 

These tiny, dissolvable devices could one day be adapted to promote nerve and bone regeneration, manage pain, support wound healing, and more.

Northwestern engineers shrank the device and removed risks by making it dissolve after use. In doing so, they’ve created a tool that could reshape how doctors care for the heart – from the tiniest patients to adults.

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Click here to watch a video interview…

The study is published in the journal Nature.

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