Thermo-Switchable Bioadhesive Electrodes for Multimodal Electrophysiological Monitoring and Human-Machine Interaction

Conductive hydrogel-based bioelectrodes, featuring superior biocompatibility and soft tissue-conformal elasticity and adhesion, enable precise monitoring of subtle physiological signals while minimizing motion-induced interference. However, persistent strong interfacial adhesion may cause tissue anaphylaxis and serious damage during peeling, especially in the practical scenarios requiring long-time epidermal monitoring and possible intraoperative electrode reposition. Herein, we developed a smart hydrogel-based electrode that integrates gelatin alongside an upper critical solution temperature (UCST)-type polymer. Benefiting from a reversible temperature-controlled phase-transition, the hydrogel exhibits strong adhesion at body temperature and gentle detachment after cooling (e.g., with an ice bag for several seconds). This thermo-switchable adhesion ensures robust interfacial contact that reduces electrode-tissue impedance and enhances the signal-to-noise ratio, while allowing atraumatic removal from skin and subcutaneous tissues. The hydrogel electrode can accurately capture electromyography (EMG) signals of hand muscles, enabling high-fidelity gesture recognition for non-contact remote control of robotic devices. The electrode is suitable for high-precision monitoring of deep subcutaneous muscle activity. Under simulated intraoperative conditions, it reliably recorded both spontaneous and evoked EMG signals from subcutaneous muscles. The proposed hydrogel-based electrodes enables multimodal electrophysiological recording, including epidermal and subcutaneous healthcare sensing, thereby validating their promising application scenarios under wearable and implantable conditions.