Long/Short chain Crosslinkers-optimized and PEDOT:PSS-enhanced covalent double network hydrogels rapidly prepared under green LED irradiation as flexible strain sensor

Hydrogel-based soft materials have great potential in flexible sensors and wearable devices. Herein, a novel covalent double network (C-DN) conductive hydrogel with excellent mechanical properties and great sensing performances was facilely prepared through photopolymerization under green light emitting diode (LED) irradiation. Two types of crosslinking agents were used to optimize the construction of C-DN poly(2-acrylamido-2-methylpropanesulfonic acid sodium salt) /polyacrylamide (P(AMPS-Na)/PAM) hydrogels, which were further reinforced by poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS). The effect of monomer ratio on the mechanical properties of hydrogels was investigated. Notably, the asymmetric double network from hybrid long/short chain crosslinkers and physical interactions from PEDOT:PSS enabled hydrogels to show satisfactory stretchability of 1228%, high tensile strength of 1.502 MPa, strong toughness of 7.209 MJ m−3, and good fatigue resistance. Moreover, the synergistic transport of well-dispersed PEDOT:PSS and Na+ provided a rich conductive network for hydrogels. The P(AMPS-Na)/PAM/PEDOT:PSS hydrogels exhibited stable and reproducible resistance responses under different strains, showing excellent strain sensitivity (Gauge factor (GF) = 1.30 and 2.72 at 0–50% and 50%-300% strains, respectively). These conductive hydrogels are promising in wearable sensors and human–computer interfaces.