Multifunctional ionic conductive hydrogels based on gelatin and 2-acrylamido-2-methylpropane sulfonic acid as strain sensors

Abstract

Stretchable hydrogels have the potential as alternatives to wearable flexible sensors and electrolyte membranes for soft energy storage devices. However, a challenge in the design of functional hydrogel with comprehensive performances including anti-freezing, favorable reusability, conductivity, flexibility, antibacterial property, biocompatibility, and omnidirectional strain sensitivity, still exists. Herein, inspired by heparin-mimetic gel, a novel double-network conductive hydrogel simultaneous with good mechanical properties, adhesion properties, frost resistance, self-healing properties, and some antibacterial properties were prepared by adding 2-acrylamido-2-methylpropanesulfonic acid, gelatin (Gel) as interpenetrating chains, and glycerol in the presence of lithium chloride and N,N'-methylenebisacrylamide as crosslinker. The hydrogels have high tensile properties (1750%) and fatigue resistance. In addition, the Gel-based sulfonated hydrogel has high electrical conductivity (2.04 S/m), a faster response time (290 ms), and significant frost resistance (−32 °C). The resulting transparent composite hydrogel successfully brings a strong synergistic advantage of adhesion strength between multiple substrates. Meanwhile, the high sensitivity of the hydrogel allows monitoring of various human movements, including large-scale joint flexion, and minute articulation, breathing, heartbeat, and pulse beat. This antibacterial, self-adhesive, and conductive composite hydrogel has promising applications in the field of flexible wearable and electronic skin.