Hair-compatible adhesive hydrogel electrodes for electroencephalography-based cybersickness detection and closed-loop mitigation

Cybersickness develops dynamically during virtual reality (VR) exposure, creating a need for continuous electroencephalography (EEG) monitoring. However, wearable EEG remains limited by the difficulty of establishing low-impedance, conformal, and mechanically stable electrode-scalp interfaces on hair-covered skin, especially under sweating and head motion. Here, we report a shell-assisted adhesive hydrogel electrode that combines hair penetration with stable scalp adhesion for rapid EEG acquisition. Poly (3,4-ethylenedioxythiophene)-modified polydopamine particles (PDA/PEDOT) are incorporated into an adhesive hydrogel to achieve high conductivity, strong adhesion, and mechanical compliance while preserving PEDOT conductivity without poly (styrene sulfonate) incorporation or additional treatment. A flexible silicone shell guides the hydrogel through hair, prevents unwanted hydrogel-hair adhesion, and enables intimate scalp contact. The electrode achieves an EEG signal-to-noise ratio (SNR) of 11.66 dB, while motion-induced interference under sweating is only 22.8% of that observed with traditional wet electrodes. Integrated into a wearable headband, the system detects cybersickness with 92.5% accuracy and enables closed-loop noisy galvanic vestibular stimulation (nGVS), increasing users' tolerance time by 52.3%. This work provides a practical strategy for hair-compatible soft biointerfaces and wearable neurotechnology for immersive human-machine interaction.