In Situ Forming Dual-Conductive Hydrogels Enable Conformal, Self-Adhesive and Antibacterial Epidermal Electrodes

Conductive hydrogels (CHs) are regarded as one of the most promising materials for bioelectronic devices on human-machine interfaces (HMIs). However, conventional CHs cannot conform well with complex skin surfaces, such as hairy or wrinkled skin, due to pre-formation and insufficient adhesion; they also usually lack antibacterial abilities and require tissue-harm and time-consuming preparation (e.g., heating or ultraviolet irradiation), which limits their practical application on HMIs. Herein, an in situ forming CH is proposed by taking advantage of the PEDOT:PSS-promoted self-polymerization of zwitterionic [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl) (SBMA). The hydrogel is formed spontaneously after injection of the precursor solution onto the desired location without any additional treatments. The as-prepared hydrogel possesses excellent elasticity (elastic recovery >96%), desirable adhesive strength (approximate to 6.5 kPa), biocompatibility, and intrinsically antibacterial properties. Without apparent heat release (<5 degrees C) during gelation, the hydrogel can form in situ on skin. Additionally, the obtained hydrogel can establish tight contact with skin, forming highly conformal interfaces on hairy skin surfaces and irregular wounds. Finally, the in situ forming hydrogels are applied as conformal epidermal electrodes to record stable and reliable surface electromyogram signals from hairy skin (with high signal-to-noise ratio, SNR approximate to 32 dB) and accelerate diabetic wound healing under electrical stimulation.