Although it can work with hearts of all sizes, the pacemaker is particularly well-suited to the tiny, fragile hearts of newborn babies with congenital heart defects.

A pacemaker is an implantable device that helps maintain an even heart rate, either because the heart's natural cardiac pacemaker provides an inadequate or irregular heartbeat, or because there is a block in the heart's electrical conduction system.

Smaller than a single grain of rice, the pacemaker is paired with a small, soft, flexible, wireless, wearable device that mounts onto a patient's chest to control pacing. When the wearable device detects an irregular heartbeat, it automatically shines a light to activate the pacemaker.

These short light pulses, which penetrate through the patient's skin, breastbone, and muscles, control the pacing.

Designed for patients who only need temporary pacing, the pacemaker simply dissolves after it's no longer needed. All the pacemaker's components are biocompatible, so they naturally dissolve into the body's biofluids, bypassing the need for surgical extraction.

The paper demonstrates the device's efficacy across a series of large and small animal models as well as human hearts from deceased organ donors.

"We have developed what is, to our knowledge, the world's smallest pacemaker," said John A. Rogers, PhD, professor of Neurological Surgery, Dermatology, and in the McCormick School of Engineering, who led the device development.

"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."