A Microphase-Separated Design Toward an All-Round Ionic Hydrogel with Discriminable and Anti-Disturbance Multisensory Functions

Abstract

Abstract Stretchable ionic hydrogels with superior all-round properties that can detect multimodal sensations with high discriminability to decouple multiple stimuli and high robustness against external disturbances are highly required for artificial electronic skin applications. However, some of the critical material parameters exhibit intrinsic tradeoffs with each other for most ionic hydrogels. Here, we demonstrate a microphase-separated hydrogel design by combining three strategies: (1) the use of a low crosslinker/monomer ratio to obtain highly entangled polymer chains as the first network; (2) the introduction of zwitterions into the first network; (3) the synthesis of a ultrasoft polyelectrolyte as the second network. This approach creates an all-round elastic ionic hydrogel with a skin-like Young’s modulus (< 60 kPa), large stretchability (> 900%), high resilience (> 95%), low hysteresis (< 5%), unique strain-stiffening behavior, excellent fatigue tolerance, high ionic conductivity (> 2.0 S/m), and anti-freezing capability, which were not achieved with previous ionic hydrogels. These comprehensive properties allow the ionic hydrogel to operate as a stretchable multimodal sensor that can detect and decouple multiple stimuli (temperature, pressure, and proximity) with both high discriminability and sensitivity. It also shows strong sensing robustness against large strains and subzero temperature perturbations. The ionic hydrogel sensor exhibits great potential for intelligent electronic skin applications such as reliable health monitoring and accurate object identification.