A dual chemical cross-linking strategy for PVA hydrogels with high tensile strength, low hysteresis and versatile sensing applications

Research on conductive elastomer with low hysteresis holds significant scientific importance for accelerating technological development of stable sensing electronic skin. Traditional polyvinyl alcohol (PVA) hydrogel is weak in mechanical properties and has serious hysteresis, which hampers its applications as tensile consecutive cycle sensors. Here, a covalent cross-linking network of PVA hydrogel was constructed through a condensation reaction by PVA and dimethylol dihydroxy ethylene urea (2d resin). On the other hand, a dynamic cross-linking network of PVA hydrogel was formed by the two-step reaction of borax with PVA, which acts as a sacrificial bond to dissipate energy during the loading-unloading process. In brief, the introduction of dual chemical cross-linking structure can adjust the mechanical properties of hydrogels (PVA/2d DN) in the range of 623–954 % and 35–86 kPa, with low hysteresis (residual strains of 4.13 % at 0–500 %), and fatigue resistance. The PVA/2d DN hydrogel was used as resistance strain sensor, capacitive pressure sensor, and triboelectric self-power sensor, which showed low detection limit, high sensitivity, and cycle stability. It has a wide application in human motion monitoring and metal recognition, etc. This work provided a versatile and effective way to design PVA hydrogel with high tensile strength and low hysteresis.