Force-Induced Single-Ion Transport in Porous Polyelectrolyte Hydrogels for Dual-Mode Output Sensing

Ionic hydrogels can change the number of transient ions at low pressure to promote ion migration, similar to the sensory mechanism of human skin. Reported ionic hydrogel sensors have multiple ion migration characteristics, which is not conducive to the precise regulation of ion transport. In this paper, a double cross-linked anionic polyelectrolyte hydrogel (CPAM-IP6) with negative channels and internal cations was prepared with the main components of methacrylic acid (MAA), acrylic acid (AA), sodium carboxymethylcellulose (CMC), and inositol hexaphosphate (IP6). The prepared hydrogels show a unique interconnected porous structure due to the regular arrangement of chemical and hydrogen bonds. IP6 has high hydrogen bonding density, which provides the hydrogels with tunable mechanical properties and a large amount of dissociable proton H+. Optimized hydrogels exhibit excellent electrical conductivity (∼22 mS/cm), high tensile strength (∼0.56 MPa), and high strain at break (∼1030%). It has a modulus similar to that of human skin (E = 0.09–0.22 MPa) and has strain-hardening properties. In addition, the resistance changes and voltage signals of the hydrogel under different force modes (tension and compression) are monitored by dual-mode sensing with a high sensitivity and stability. Hydrogels are expected to be used for motion monitoring and energy collection and have broad application prospects in intelligent medical treatment.