Skin-inspired environment-tolerant organohydrogel sensors with balanced mechanical and electrical properties for human motion and physiological signal monitoring

Hydrogel-based sensors have gained great attention owing to their potential applications in flexible and wearable electronics, whose excellent comprehensive performances are highly desirable and remain a research hotspot. However, the stability and durability of hydrogel sensors have always been achieved by sacrificing mechanical and/or electrical properties. Herein, inspired by the skin, we proposed an inner-outer synergistic strategy for developing sodium alginate (Alg)/polyvinyl alcohol (PVA) organohydrogels in glycerol/water solvent with the surface region tightened by the chelation between Ca 2+ and Alg chains. Excellent water retention (95% after 10 days) and anti-freezing abilities (−20 °C) of the organohydrogels were achieved through the synergistic effect of adding glycerol and soaking in CaCl 2 solution while the trade-off between two treatments endowed balanced mechanical and conductive properties. Besides, the as-prepared organohydrogels exhibited high transparency (85%), strong adhesion (35.4 kPa), and efficient self-healing (93.8% after three cycles). As strain sensors, they possessed a broad strain range (0-400%), short response time (360 ms), and good sensing stability (5000 cycles), which could accurately detect multiple human motions and physiological signals like pulse and heartbeat. Therefore, this work provides a new strategy for preparing multifunctional organohydrogel-based sensors with balanced comprehensive properties. A skin-inspired inner-outer synergistic strategy was proposed for preparing environment-tolerant organohydrogel sensors, where trade-off effects and synergistic effects co-contributed to their balanced comprehensive performances.