Dual-Working-Pattern Nanosheet-Based Hydrogel Sensors for Constructing Human-Machine and Physiological-Electric Interfaces.

While hydrogels are ideal building blocks for fabricating next-generation epidermal electronics to acquire high-fidelity electrical signals induced by motion and physiological activities, an unresolved issue remains: the differentiation and selection of sensing modes in hydrogel sensors. The novel design leverages numerous conductive nanosheets, randomly arranged in a series-parallel configuration, embedded within a highly compliant dielectric hydrogel. For the nanosheets, poly(3,4-ethylenedioxythiophene) (PEDOT) is deposited on the surface of sulfonated cellulose nanosheets (SCNS) to function as microelectrodes (PEDOT@SCNS). The resulting nanosheet-based hydrogel (NSH) demonstrates remarkable stretchability (1356%), excellent adaptability (storage modulus of 102 Pa), and self-adhesiveness (21.7 kPa on pigskin). The nanosheet microelectrodes enable the formation of both microcapacitor arrays and conductive paths within the ultrasoft hydrogel, facilitating the construction of high-fidelity capacitive sensors and bioelectrodes for the real-time monitoring and classification of human activities and physiological states, respectively. This NSH, which significantly reduces skin-interfacial impedance, has demonstrated strong potential as candidate sensors for advanced applications in EMG, facial nerve monitoring, ECG, and brain activity monitoring, achieving reduced RMS noise (9.7 µV) and minimal motion artifacts.