Incorporation of cupric sulfate and vanillin empowered poly (vinyl alcohol) hydrogel as flexible sensing device

Abstract

Poly (vinyl alcohol) (PVA) attracts increasing interest in hydrogel field, but it suffers from some obstacles including multi-component, complex preparation process, inadequate mechanical properties, and poor bacteriostatic properties, which hinder its application such as flexible electric devices. In the study, a novel strategy was put forward to make the conductive hydrogel by a combination of coupling vanillin onto PVA and immersing CuSO₄ solution. Coupled vanillin as an accelerator regulates the formation of hydrophobic microcrystal network to enhance the mechanical properties of the hydrogel. CuSO₄ as conductive medium improves the amorphous network by the salting-out effect to further reinforce the mechanical properties of the hydrogel. The optimized hydrogel is super-tough, and its toughness, tensile strength, and elongation at break are 15.05 MJ∙m⁻³, 4.72 MPa, and 737.80 %, respectively. The conductive hydrogel was assembled into a flexible sensing device and exhibits reliable sensitivity (GF = 2.94, Response time = 0.22 s), stability, and durability for monitoring human activities. In addition, conductive hydrogel possesses frost resistance at −20 °C without the introduction of cryoprotectants, and good antimicrobial activity. It provides a general method and reference example for the development of multifunctional hydrogel electronic materials.