Polydopamine-Mediated Nanofillers Reinforced Zwitterion Hydrogel Electrodes for Supercapacitors in Bioelectronics

Supercapacitors that can function when in direct contact with human tissue are of paramount importance for wearable bioelectronics but face mismatching with biological tissue and its movement. Herein, we developed a zwitterion hydrogel elastomer electrode-based all-hydrogel supercapacitor (AHSC) characterized by good energy storage properties, bioadhesion, body movement-matching mechanical properties, and biocompatibility. These functions were realized by integrating a [2-(methacryloyloxy)ethyl]dimethyl-(3-propylsulfonate)ammonium hydroxide (DMAPS) and hydroxyethyl acrylate (HEA)-copolymerized zwitterion hydrogel electrode (DMAPS-HEA) with redox-active nanofillers. This hydrogel electrode endowed AHSC with body movement-matching mechanical properties and biocompatibility. Redox-active nanofillers were designed with the structure of a reduced graphene oxide (rGO)-anchored cobalt/nickel bimetallic metal-organic framework (Co/Ni MOF) using polydopamine (PDA). The Co/Ni MOF contributes to the high energy storage performance. rGO enhances the conductivity, whereas PDA introduces catechol groups, contributing to the bioadhesion. This AHSC serves as a flexible alternative to traditional rigid and low-tissue-affinity power supply devices in bioelectronics.