Preparation of strong, tough and conductive soy protein isolate/poly(vinyl alcohol)-based hydrogel via the synergy of biomineralization and salting out.

Conductive hydrogels have shown a great potential in the field of flexible electronic devices. However, conductive hydrogels prepare by traditional methods are difficult to combine high strength and toughness, which limits their application in various fields. In this study, a strategy for preparing conductive hydrogels with high strength and toughness by using the synergistic effect of biomineralization and salting-out was pioneered. In simple terms, by immersing the CaCl doped soy protein isolate/poly(vinyl alcohol)/dimethyl sulfoxide (SPI/PVA/DMSO) hydrogel in NaCO and NaCit complex solution, the biomineralization aroused by Ca and CO, and the salting-out effect of both NaCl and NaCit would enhance the mechanical properties of SPI/PVA/DMSO hydrogel. Meanwhile, the ionic conductivity of the hydrogel would also increase due the introduction of cation and anion. The mechanical and electrical properties of SPI/PVA/DMSO/CaCO/NaCit hydrogels were significantly enhanced by the synergistic effect of biomineralization and salting-out. The optimum tensile strength, toughness, Young's modulus and ionic conductivity of the hydrogel were 1.4 ± 0.08 MPa, 0.51 ± 0.04 MPa and 1.46 ± 0.01 S/m, respectively. The SPI/PVA/DMSO/CaCO/NaCit hydrogel was assembled into a strain sensor. The strain sensor had good sensitivity (GF = 3.18, strain in 20 %-500 %) and could be used to accurately detect various human movements.