Soy protein derived double network (DN) ionic conductive organohydrogel toward flexible strain sensor

Ionic conductive hydrogels, which respond electronically to mechanical inputs, have emerged as promising materials for flexible strain sensors. However, achieving simultaneous high strength and stretchability, high ionic conductivity, strong environmental tolerance (e.g., drying and freezing) remains a significant challenge for these hydrogels. Here, a biocompatible soy protein based ionic conductive organohydrogel possessing the aforementioned characteristics is developed for the first time through the combination of a methacrylated soy protein isolate and poly(vinyl alcohol) (MSPI/PVA) double network (DN) structure, tannic acid-coated cellulose nanocrystals (TCNC) reinforcement, and infiltration with saturated NaCl solution in a glycerol/water binary solvent system. The ionic conductive organohydrogel offers high gel strength (1.07 MPa) and strain (1321 %), high room temperature conductivity (3.23 S/m), remarkable low-temperature performance (flexible and conductive at -70 °C and a high conductivity of 0.63 S/m at -40 °C), and anti-drying properties (a mass retention of 82 % and a conductivity of 0.3 S/m after 15 days). Moreover, the organohydrogel shows good sensitivity, fast responsiveness, and stability under various tensile deformations and based on which a wearable sensor is fabricated to detect human body movements with good accuracy and reliability. This organohydrogel is envisioned to be a promising candidate in the field of flexible strain sensors.