Pressure-Activated Breathable Liquid-Metal Electrodes for Long-Term Sleep Electroencephalogram Monitoring

Sleep electroencephalography monitoring has become an effective strategy for health evaluation. However, conventional gel electrodes suffer from inherent limitations such as moisture loss and poor breathability, compromising long-term signal stability and wear comfort. Here, we present a facile strategy for fabricating breathable, biocompatible liquid-metal electrodes with enhanced interfaces. Eutectic gallium-indium particles fabricated via ultrasonication are coordinated with (3-mercaptopropyl) triethoxysilane and patterned onto a fiber matrix. During ambient drying, thiol-silane dehydration and condensation generates a polymer network that entangles with the fiber matrix while encapsulating the liquid-metal droplets. When pressure is applied, the encapsulated liquid metal exudes to form the interface-enhanced electrode, demonstrating exceptional tolerance to water washing, air exposure, and mechanical deformations, along with superior skin compatibility and lower interface impedance compared with those of commercial gel electrodes. As a proof of concept, the integrated head-worn epidermal electrodes achieved continuous sleep electroencephalography monitoring for 6 h, highlighting their potential for unobtrusive and long-term wearable health surveillance.