Preparation of Adhesive Conductive Hydrogels with Desirable Mechanical Properties

Conductive hydrogels are innovative materials that combine the properties of hydrogels—high water content, flexibility, and biocompatibility—with electrical conductivity. These hydrogels are typically composed of polymer networks that are crosslinked with conductive components such as metallic nanoparticles, carbon-based materials (e.g., graphene or carbon nanotubes), or conductive polymers (e.g., polypyrrole, polyaniline). This dual functionality allows them to mimic the physical properties of biological tissues while enabling electrical communication, making them highly valuable in bioelectronics, tissue engineering, and medical devices. However, their practical application is hindered by the insufficient and unstable adhesion of these hydrogels to substrates, posing significant limitations to their utility and reliability. Most methods for synthesizing adhesive conductive hydrogels involve combining conductive materials with adhesive but insulating components, which compromises both mechanical strength and electrical conductivity. This study aims to overcome these limitations in adhesive bioelectronic interfaces by optimizing mechanical, electrical, and adhesive properties for improved integration into devices and biological systems. A versatile approach is developed to incorporate a conductive PEDOT-derived polymer, specifically polyethylene dioxythiophene with a diethylene glycol side chain (PEDOT-DEG), into preformed adhesive hydrogels. These hydrogels contain a zwitterionic monomer, [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl) (SBMA), that provides inherent adhesive properties. The as-prepared hydrogel is uniform, with electrical conductivity ~0.1 S/m, ionic conductivity ~1 S/m, elastic modulus ~50 kPa and strain at break of 35%. The hydrogels exhibit strong adhesion with pig skin based on strong dipole–dipole interactions between zwitterionic units and polar functional groups on skin. These hydrogels therefore have potential for on-skin-adhesive electrodes in bioelectronics.