New wireless pacemaker is powered by light

In a key advance toward wireless, minimally invasive temporary pacemakers, researchers have made a thin silicon device that lays flat on the heart’s surface and regulates heartbeat using light (Nature 2024, DOI: 10.1038/s41586-024-07016-9). The researchers used a slim endoscopic tube to deliver and control the device on the heart of a live pig.

Patients recovering from cardiac surgery sometimes get temporary pacemakers that use electrical pulses to help maintain heart rate and rhythm. Removing the device requires risky invasive surgery. Once the electrodes that deliver the pulses are embedded in the heart, targeting a different location of the organ is difficult without moving the electrodes, which can damage tissue.

“We can solve these issues because our cardiac pacemaker is operated by light,” says Bozhi Tian, a physical chemist at the University of Chicago. The new device is a 2 µm thick silicon membrane that does not pierce the heart. Light from multiple optical fibers could be used to stimulate tissue at various locations, Tian says. In addition, the membrane dissolves in the body after a few weeks—although the researchers do not report this in the paper.

The team etches the silicon membrane surface with a hydrofluoric and nitric acid solution to create a nanoporous layer on top of the silicon membrane. The difference in the two layers’ porosity creates a junction that separates charge carriers, much like the p-n junction that forms the heart of silicon solar cells. When light shines on the material, it converts light energy into an electrical impulse that causes heart tissue to contract under the spot where the light is shining.

Tian, cardiac surgeon Narutoshi Hibino, and their colleagues inserted a 2 × 2 cm membrane, folded like an umbrella, into a pig’s chest cavity through a 1 cm wide endoscopic tube. They opened the device before placing it on the heart, where it adheres via van der Waals forces. Medical glue could be used if needed, Tian says.

The researchers introduced an optical fiber through the same tube to regulate heartbeat using 1 ms light pulses, which were enough to fire off the cardiac cells. For clinical use, a wireless light-emitting diode (LED) could be implanted under the skin, Tian says. “That LED can have an optical fiber coupled to it, and the fiber tip can point to the surface of the silicon membrane.”

Emilia Entcheva, a biomedical engineering professor at George Washington University, calls the study “elegant.” In principle, optical cardiac pacing offers better resolution in space and time than electrical methods provide. Because of the porous, multilayer design, the new device needs less light energy to induce electrical activity and shows more precise localized biological response than other optical techniques. “Particularly important is the effort to make the implantation minimally invasive,” Entcheva says. Future milestones should include longer-term tests of the implanted device and a viable light delivery method.