Injectable eutectogel for high-quality scalp electroencephalogram monitoring

Abstract Hydrogels emerge as a promising electrode material for scalp electroencephalogram monitoring, which stands as a pivotal technique in neuroscience, enabling real-time monitoring of brain activity. However, conventional hydrogel-enabled electrodes suffer from low scalp compliance, high scalp-electrode impedance, and inferior interfacial stability. Here, we propose an injectable eutectogel-enabled electrode for high-quality, long-term scalp electroencephalogram monitoring. This gelatin-based eutectogel exhibits temperature-controlled reversible phase transitions, enabling rapid in-situ gelation on the scalp and forming a robust self-adhesive interface. It demonstrates exceptional mechanical durability (1000 cycles at 100% strain), robust adhesion (0.7 N cm−1 on human epidermis and 1.7 N cm−1 on Ag/AgCl electrode), and outstanding anti-drying properties (negligible water loss after 7 days). Additionally, the eutectogel shows superior healing properties, antibacterial properties, and recyclability. Furthermore, it exhibits remarkably low scalp-electrode contact impedance (<20 kΩ at 16 Hz). The eutectogel is injected on the human scalp with dense hair for high-fidelity electroencephalogram recording, enabling long-term monitoring. Its practical applications include monitoring visual evoked potentials, steady-state visual evoked potentials, somatosensory evoked potentials, slow vertex response, auditory brainstem response, multi-channel cognitive electroencephalogram during various daily activities, and event-related potentials P300 signals. The eutectogel-enabled electrode provides a versatile and reliable solution for long-term electroencephalogram monitoring in diverse clinical and research settings.