Adhesive, biocompatible, and conductive reduced graphene oxide hydrogel-based bioelectrodes for epidermal electrophysiological signal monitoring†

Conductive hydrogel bioelectrodes that acquire human physiological information are vital in continuously monitoring various electrophysiological (EP) signals. However, poor adhesion during human physical/chemical activities limits their performance, adversely affecting the accuracy and continuity of biosignals. Herein, we report reduced graphene oxide (RGO) hydrogel-based epidermal bioelectrodes that can conformably adhere to the living skin and reliably record multiple EP signals during human activities. The RGO hydrogel bioelectrodes comprised polyvinyl alcohol (PVA) as the backbone material, RGO flakes as the conductive material, and polyacrylic acid (PAA) as the bioadhesive material. We have successfully developed RGO hydrogel-based EP bioelectrodes that exhibit several unique properties, including good adhesion strength (∼6.506 kPa), high electrical conductivity (∼0.11 S m⁻¹), and excellent in vitro biocompatibility (>90% cell viability). In addition, these adhesive bioelectrodes adhered firmly to different types of skin and could be reattached more than 10 times. The exceptional properties of our adhesive, biocompatible, and conductive graphene bioelectrodes were used to successfully monitor the electrooculogram, electromyogram, and electrocardiogram with human movements and sweat secretion. Our study provides a practical approach for monitoring high-fidelity EP biosignals from the skin, thus, overcoming the bottleneck of wearable bioelectronics.