Symbiotic biodegradable flexible supercapacitor in vivo

Biodegradable electronics dissolve in vivo , eliminating retention risks, but they are often not self-contained due to limited energy storage, relying on tethered or wireless power. Here, we report a biodegradable flexible supercapacitor (BFSC) that can be completely dissolved to achieve symbiosis with the body and modulate neural excitation and inhibition without external energy. Its low stiffness and favorable biocompatibility allow it to minimize interface mismatch and rejection to be integrated with the body like a biological tissue. The BFSC has a farad surface capacitance (0.36 F/cm 2 ), high energy density (73.1 μWh/cm 2 ), and 1-month operating life in vivo due to the MXene nanolayered electrode and solid-state hydrogel electrolyte. The BFSC can drive bioelectric stimulation circuits to enable neuromodulation and cardiac pacing in rats and pigs. The scaffold-like BFSC almost completely inhibits neural activity. These advances are expected to facilitate the development of self-contained biodegradable and symbiotic bioelectronics.