Anti-Fatigue Ionogels for High-Performance Strain Sensing

Abstract

Ionically conductive gels have emerged as excellent candidates for strain sensing materials due to their exceptional stretchability, skin affinity, and freezing resistance. However, developing ionogel strain sensors with outstanding mechanical properties (particularly high fatigue resistance), a wide strain detection range, and a linear resistance response remains a significant challenge. In this study, we present a facile solvent evaporation-assisted annealing strategy to fabricate strong, anti-fatigue, anisotropic Polyvinyl Alcohol (PVA) ionogels. Solvent evaporation increases tensile stress during pre-stretching, promoting macromolecular alignment, while annealing optimizes macromolecular conformation, ensuring the maintenance of the anisotropic structure. The resulting anisotropic ionogels exhibit an exceptional fatigue threshold of 3232.87 ± 254.64 J·m-2, along with high tensile strength, toughness, and Young’s modulus of 45.40 ± 4.81 MPa, 30.78 ± 8.32 MJ·m-3, and 77.38 ± 15.07 MPa, respectively. The ionogel strain sensors, with cyclic sensing stability, can detect small strains (as low as 0.2%), provide a linear resistance response (up to 200% strain), and output stable and reliable strain sensing signals even in the presence of cracks in the ionogel. These strong, flaw-insensitive, and multifunctional ionogels are well-suited for stress-bearing materials and advanced wearable electronics.

Keywords: Anisotropic ionogel, Fatigue resistance, Mechanical properties, strain sensors