High-Sensitivity Conductive Copolymer Hydrogel for Multifunctional Flexible Wearable Sensors Based on Salting-Out after Freeze-Casting Assisted UV-Curing

High sensitivity, consistent conductivity, and suitable mechanical strength were essential for strain sensor performance in the field of flexible wearables. The hydrogel containing poly­(3,4-ethylenedioxythiophene)/lignosulfonate (PEDOT/LS) was bound to destroy the hydrogel network and affect its mechanical characteristics, even if it could safely and consistently increase conductivity. In this work, a salting-out after freeze-casting assisted UV-curing (SFUV) strategy was first offered as a solution to this problem. Waterborne polyurethane acrylate and polyacrylamide were copolymerized at low temperatures to form microcrystalline hydrogels with an anisotropic honeycomb channel stacking structure. When the solvent level was up to 70%, SFUV-Fe hydrogels outperformed typical hydrogels in terms of tensile properties (218 kPa), adhesion (13.9 kPa on plastics), gauge factor (5.07), and conductivity (2.31 S/m). Furthermore, the SFUV strategy provided the hydrogel with a variety of functionalities, including antifatigue, self-healing, and moisturizing capabilities, enabling for accurate and reliable detection of complicated human movements over time. As a result, this study presented a comprehensive solution for the development of sophisticated, strong, and resistant conductive soft materials appropriate for a variety of applications, establishing copolymer hydrogels as a promising candidate for flexible wearable electronic goods.