A High Strength Hydrogel with a Core–Shell Structure Simultaneously Serving as Strain Sensor and Solar Water Evaporator

Abstract A super‐strong poly (acrylic acid)‐ poly(3,4‐ethylene dioxythiophene) (PAA‐PEDOT) hydrogel with a unique core‐shell structure is successfully constructed and studied. The shell composed of the conductive polymer PEDOT makes the composite hydrogel possess mechanical strength, electrical conductivity, and photothermal conversion properties, while the PAA hydrogel core ensures the flexibility, recovery, and water absorption of the composite hydrogel. The prepared PAA‐PEDOT hydrogel displays outstanding tensile strength (up to 780 KPa) and satisfactory conductivity (6.6 S m −1 ). Notably, the flexible strain sensor made of PAA‐PEDOT composite hydrogel presents both high sensitivity (gauge factor up to 8.87) and short response time (<200 ms), demonstrating that the composite hydrogel can accurately and timely detect the movement of human joints. In addition, PAA‐PEDOT composite hydrogel also has excellent photothermal conversion properties and can be used as a highly efficient solar water evaporator, which has a water evaporation efficiency of up to 3.05 kg m −2 h and an excellent photothermal conversion efficiency of 95% under 1‐sun irradiation (1kW m −2 ). These features make the composite hydrogel has great potential in many fields such as motion sensing, seawater desalination, and wastewater treatment.