Lipophilic Self‐Wetting Ionogel Electrodes for Long‐Term High‐Fidelity Electroencephalogram Recording

ABSTRACT Establishing a long‐term stable electrode‐scalp interface to ensure high‐quality electroencephalogram (EEG) signal acquisition is crucial for advancing the practical application of brain‐computer interfaces (BCIs). However, most non‐invasive electrodes face issues such as dehydration or mechanical mismatch, making them difficult to maintain stable and efficient contact with the hairy scalp during prolonged recordings. Inspired by the natural perspiration mechanism of the skin, this study develops a body temperature‐responsive self‐wetting ionogel electrode (SWIGE) to overcome these limitations. Through microphase separation, SWIGE continuously releases electrolyte, improving interfacial contact by filling microgaps. Concurrently, the choline geranate (CAGE) in electrolyte swells the stratum corneum, significantly improving the ionic conductivity across the skin‐electrode interface and thus strengthening bioelectrical signal transmission. Synergistically combined with the inherent fatigue resistance and low mechanical hysteresis of the ionogel matrix, this strategy establishes a highly reliable biointerface with an impedance of 10.3 ± 0.6 kΩ at 7.8 Hz. The SWIGE enables sustained, high‐fidelity EEG monitoring and demonstrates robust capabilities in capturing and classifying evoked potentials. Crucially, SWIGE maintains performance parity with daily‐replaced commercial conductive pastes during the 50‐day reuse, validating its exceptional durability for brainprint authentication systems.