Highly Sensitive Pressure and Strain Sensors Based on Stretchable and Recoverable Ion-Conductive Physically Crosslinked Double Network Hydrogels

Ion conductive hydrogel sensors have attracted great research interests for applications in

wearable devices, electronic skins, and implantable sensors, but most such sensors are fragile,

with low conductivity and sensitivity. This study reports on novel ion conductive double network hydrogels crosslinked by helical structure, hydrophobic association and metal ion

coordination. The helical -carrageenan first network and the second network crosslinked by

Pluronic F127 diacrylate micelles and tridentate Fe³⁺-COO^- coordination work synergistically

to show tensile strength of 2.7 MPa, fracture strain of 1400%, and tensile toughness of 9.82 MJ m^-3, and fatigue resistance against cyclic loadings with high strains. The hydrogels show an ion conductivity of 1.15 S m^-1, a strain sensitivity up to 2.8, and a pressure sensitivity of 0.33 kPa^-1. Sensor arrays fabricated from the conductive hydrogels provide in-plane detection of pressures less than 200 Pa. Such hydrogel sensors have potential applications to electron skins and implantable sensors.