Body temperature-triggered phase change dry electrode for long-term comfort electroencephalography monitoring

Electrodes are crucial for long-term electroencephalography (EEG) monitoring. Dry electrodes eliminate issues of dehydration, skin irritation, and non-reusability that are associated with wet electrodes. However, overly soft dry electrodes cannot penetrate dense hair, while overly hard electrodes compromise comfort and signal quality. Here, we report a body temperature-triggered, phase change dry electrode to address these problems. The electrode, made from a polymer composite with crystalline region and silver flakes, is rigid at room temperature, allowing it to pass through hair. Upon contact with the scalp, body temperature melts the crystalline region, significantly reducing the modulus, thereby enhancing comfort and reducing contact impedance. This phase transition also transforms the electrode into a pressure sensitive adhesive, ensuring the stable contact. Additionally, its shape memory effect enables the electrode to return to its original shape, making it reusable. The reported electrodes exhibit superior signal quality and stability in long-term EEG monitoring.