An Implantable and Biodegradable Thermosensitive MXene Supercapacitor for Simultaneous In Vivo Energy Storage and Thermal Sensing

ABSTRACT Integrating energy storage with physiological sensing in a single, biodegradable device is a central goal for advanced bioelectronics. While multifunctional supercapacitors have emerged, a device capable of simultaneous power delivery and in situ thermal sensing has remained elusive. Here, we report an implantable, biodegradable supercapacitor that functions as a thermosensitive energy storage device system. This dual functionality is enabled by a novel MXene/liquid metal (LM) composite film, where LM nanodroplets synergistically enhance electrochemical performance while imparting intrinsic thermosensitivity. The device exhibits a high areal capacitance of 61.5 mF cm −2 (corresponding to a specific capacitance of 39.5 F g −1 ) and demonstrates exceptional cycling stability, retaining 91% of its initial capacitance over 16 000 cycles. Concurrently, it exhibits a highly linear thermal response (α T‐C ≈ 0.050°C −1 ) in the 35°C–40°C physiological range. Crucially, in vivo studies confirmed its excellent biocompatibility and showcased its ability to perform real‐time thermal mapping of inflammation, validating its diagnostic potential. Furthermore, the core of device is biodegradable, eliminating the need for surgical retrieval. This work presents an integrated strategy for smart, transient bioelectronic systems, merging energy storage and diagnostics into a single platform.