A one-step polyvinyl alcohol/polyacrylamide/polyacrylic acid/dimethyl sulfoxide/CaCl2 hybrid hydrogel enabling anti-fatigue, anti-freeze and anti-dehydration for wearable strain sensor

Abstract

Hydrogel with fatigue resistance, freezing tolerant and dehydration resistance are peculiarly attractive in strain sensors. The hydrogel soaked in organic solvent is an effective strategy to improve freezing resistance and dehydration resistance, while this may result in poor conductivity. Moreover, ion-incorporation is considered to be the most feasible method for solving above concern, while high concentration of salt ions will result in weak mechanical properties. Therefore, the facile preparation of anti-freezing and anti-dehydration hydrogels with excellent fatigue resistance remains a challenge. Herein, a polyvinyl alcohol/polyacrylamide/polyacrylic acid/dimethyl sulfoxide/CaCl₂ hybrid hydrogel was designed and fabricated through a facile one-step method to balance a variety of outstanding properties. On account of the hybridization design of multi-materials, the hybrid hydrogel exhibited high ionic conductivity (∼0.2 S/m), strength (∼0.36 MPa) and stretchability (∼825 %). Meanwhile, the hybrid hydrogel demonstrated prominent freezing resistance, dehydration resistance and fatigue resistance. The mechanical properties almost no deterioration after 1000 stretching cycle at 100 % strain, exposure to environment for 30 days or freeze at low temperature. Besides, the hybrid hydrogel-based stain sensor showed a linear sensitivity (GF = 1.12 over 0–400 % strain), quickly responsivity (200 ms), and could monitor various human activities steadily, demonstrating distinguished potential for use in wearable health monitoring and flexible electric skins.