This Miniature Hydrogel-Based Battery for Medical Implants Is Soft, Body-Safe, and Biodegradable

A team of researchers from the University of Oxford and the École Polytechnique Fédérale de Lausanne have developed a new approach to building batteries for implantable devices and miniature soft robotics — creating a biocompatible lithium-ion battery from hydrogel droplets.

"Our droplet battery is light-activated, rechargeable, and biodegradable after use. To date, it is the smallest hydrogel lithium-ion battery and has a superior energy density," claims Yujia Zhang, PhD, the lead researcher on the project and starting assistant professor at the École Polytechnique Fédérale de Lausanne. "We used the droplet battery to power the movement of charged molecules between synthetic cells and to control the beating and defibrillation of mouse hearts. By including magnetic particles to control movement, the battery can also function as a mobile energy carrier."

The battery is designed for use in implantable medical devices, including pacemakers and automated defibrillators, delivering enough power to stimulate tissue despite its small size. It's built using a lipid-supported assembly of silk hydrogel droplets — an approach which has already been proven in the past but has never been demonstrated with a rechargeable, rather than single-use, battery design.

"Cardiac arrhythmia is a leading cause of death worldwide," says Ming Lei, a senior electrophysiologist whose lab carried out experimental heart treatments with the device. "Our proof-of-concept application in animal models demonstrates an exciting new avenue of wireless and biodegradable devices for the management of arrhythmias."

"The tiny soft lithium-ion battery is the most sophisticated in a series of microscale power packs developed by Dr Zhang," claims research group lead Hagan Bayley, a professor in the University of Oxford's department of chemistry, of the team's work, "and points to a fantastic future for biocompatible electronic devices that can operate under physiological conditions."

The researchers' work has been published in the journal Nature Chemical Engineering under open-access terms.