Ionically Conductive and Self-Healing Polyampholyte Hydrogels for Wearable Resistive Strain Sensors and Capacitive Pressure Sensors

Hydrogels are promising materials for flexible wearablesensors,but they often suffer from unpredictable mechanical damage. In thiswork, self-healing polyampholyte hydrogels are developed and exploredin constructing wearable mechanosensors including resistive strainsensors and capacitive pressure sensors. In order to prepare the polyampholytehydrogels, sodium p-styrenesulfonate (NaSS) and (methacryloxyethyl)trimethylammoniumchloride (DMC) are used as the anionic and cationic monomers, respectively,and N,N & PRIME;-methylenebis(acrylamide)(MBAA) is used as the chemical cross-linking agent. The resultinghydrogels, denoted as NaSS/DMC polyampholyte hydrogels, exhibit outstandingself-healing ability, transparency, ionic conductivity, and stretchability.Resistive strain sensors assembled from such polyampholyte hydrogelsexhibit a gauge factor (GF) of 2.9 over a strain range of 0-350%,a low response time of 250 ms, and excellent cycling stability. Moreover,sandwich-structured capacitive pressure sensors are assembled utilizingpolyampholyte hydrogels containing reliefs as the electrodes. Thepressure sensors achieve a GF of 2.17 kPa(-1), a sensingrange of 0-7.35 kPa, and high cycling stability. The applicationsof such wearable mechanosensors in monitoring various strains andpressures in daily life are demonstrated. Overall, this work not onlydevelops a smart hydrogel with outstanding self-healing ability butalso provides a clue to construct soft electronics for wearable devices.