Design of Injectable, Self-Adhesive and Highly-Stable Conductive Polymer Electrode for Sleep Recording

High-quality and continuous EEG monitoring is desirable for sleep research, sleep monitoring and the evaluation and treatment of sleep disorders. Existing continuous EEG monitoring technologies suffer from fragile connections, long-term stability, and complex preparation for electrodes in real-life conditions. Here, we report an injectable and spontaneously-crosslinked, conductive polymer hydrogel electrode for long-term EEG applications. Specifically, our electrodes have a long-term low impedance on hairy scalp regions of 17.53 kΩ for > 8 hours of recording, high adhesiveness on the skin of 0.92 N cm^-1 with repeated attaching capability, and long-term wearability during daily activities and overnight sleep. In addition, our electrodes demonstrate a superior signal-to-noise-ratio of 23.97 dB in comparison to commercial wet electrodes of 17.98 dB and share a high agreement in sleep stage classification with commercial wet electrodes during multi-channel recording. These results exhibit the potential of our on-site formed electrodes for high-quality, prolonged EEG monitoring in various scenarios.