Enhanced mechanical strength and stretchable ionic conductive hydrogel with double-network structure for wearable strain sensing and energy harvesting

Abstract

The conductive hydrogels with skin-like modulus have flourished as a promising soft electronic material for health monitoring and human-machine interface systems. Nevertheless, it is still a challenge to achieve excellent mechanical properties, high ionic conductivity, outstanding structural homogeneity, and biocompatibility of hydrogels through a simple method. Herein, a biocompatible polyacrylamide/calcium alginate/ethanol double-network hydrogel (PAM/CA/EtOH₃₀ DN hydrogel) was prepared via free radical polymerization and solvent-exchange strategy. Benefiting from the synergistic effect of solvent replacement and the dissipating energy of the double-network structure, the resultant PAM/CA/EtOH₃₀ hydrogel showed excellent mechanical properties. In addition, the prepared hydrogels exhibited remarkable stretchability (>1500 %), fracture energy (1917 J m⁻²), and ionic conductivity (1.53 S m⁻¹). The PAM/CA/EtOH₃₀-based wearable strain sensor displayed a strain sensing capability with a wide operating range (0%–250 %), good sensitivity (GF = 1.63), and fast response time. Furthermore, the triboelectric nanogenerator for mechanical energy harvesting was created using the PAM/CA/EtOH₃₀ double-network hydrogel as the electrode, which demonstrated exceptional electrical output performance (up to 236.8V). The proposed PAM/CA/EtOH₃₀ hydrogels with integrated strain sensing and energy harvesting capabilities indicate a valuable potential to be applied to self-powered wearable sensing devices.