Anion-Regulated Phase Separation Constructs Mechanically Tunable Ion Gels for Strain Sensing

Although ion gels are promising for flexible sensing, simultaneously achieving high mechanical strength, stretchability, ionic conductivity, and interfacial adhesion remains challenging. Here, we report the preparation of ion gels with tunable mechanical properties using two ionic liquids (ILs) with different compatibilities with poly(acrylic acid) (PAA) via a one-pot ultraviolet (UV)-initiated polymerization. Adjusting the mixing ratio of the two ILs can regulate the phase separation of the gel and promote the formation of a bicontinuous phase. The optimized ion gel exhibits a tensile strength of 11 MPa, high elongation at break (363%), excellent ionic conductivity (1.4 × 10^{- 2} mS cm^{- 1}), and robust interfacial adhesion. Ion gel-based strain sensors exhibit sensitive, reproducible resistance responses over a wide strain range and enable repeatable monitoring of human joint motions and daily activities. This work establishes a simple anion-regulated phase separation strategy for engineering high-performance ion gels for wearable sensing.