Stretchable and Biodegradable Hydrogel‐Nanomembrane Electrodes for Conformal and Transient Bioelectronics

ABSTRACT Implantable cardiac bioelectronics are essential for continuous monitoring and therapeutic modulation in cardiovascular diseases, yet current platforms—typically constructed from rigid electronic materials—exhibit a substantial mechanical mismatch with the constantly deforming heart. Such permanent, rigid implants often induce tissue irritation and require additional surgeries for device removal. Here, we introduce a stretchable, mechanically soft, and fully biodegradable hydrogel–nanomembrane electrode (SBHNE) designed to adhere conformally to the epicardial surface, thereby enabling stable, high‐fidelity signal acquisition under persistent cardiac motion. The SBHNE integrates three functional components: (i) a tissue‐adhesive hydrogel layer for intimate and stable contact, (ii) a stretchable molybdenum nanomembrane conductor for reliable electrical performance, and (iii) a conductive polymer coating for impedance reduction and stable electrical performance. All components are designed to biodegrade in vivo after a programmed operational period. Leveraging these features, the SBHNE enables reliable epicardial electrophysiological monitoring and effective electrical modulation. When integrated with a wearable pulse generator, it enables sustained and on‐demand cardiac stimulation to terminate ventricular arrhythmias in a rat model. Collectively, these results establish a fully transient, mechanically compliant epicardial interfacing device that advances the prospects of soft, temporary cardiac bioelectronics.