Ion-shielding ultrathin encapsulation with hot-press bonded interface enables chronic stretchable bioelectronics

Stretchable physiological electrodes are indispensable for continuous, high-fidelity bio-signal monitoring, yet liquid water and ions invade nano/microscopic interfacial defects and silence signals within weeks. We introduce an ion-shielding ultrathin encapsulation that is molecularly fused to the stretchable conductor with a hot-press bonded interface to block aqueous ingress. A single-step hot pressing expels trapped air and interdiffuses polymer chains, erasing interfacial defects. The hot-press bonded interface exhibits exceptional resistance to water and ion penetration of >12 months in solution, more than 10 times longer than untreated interfaces (less than a month). Stretchable physiological electrodes with ~10-micrometer-thick encapsulation achieved stable, high-fidelity electrophysiological recordings in demanding environments, as demonstrated by continuous monitoring of cardiomyocytes for 29 days in vitro and long-term signal recording in rat spinal cords spanning 12 weeks in vivo.