Tough, Fatigue-Resistant Polyaniline Hydrogels with Multiple Reversible Physical Interactions for Wearable Sensors

Abstract

Conductive hydrogels have emerged as promising candidates for stretchable and flexible electronic devices. However, simultaneously maintaining high electrical conductivity, sensitive strain responsiveness, and fatigue resistance under extreme deformation remains a major challenge. In this study, MnO2 was embedded into the hydrogel matrix as an in situ oxidizing agent to initiate the in situ oxidative polymerization of aniline within the hydrogel network within 3 h. Lauryl methacrylate (LMA) and cetyltrimethylammonium bromide (CTAB) were introduced to cross-link the polyacrylic acid (PAA) hydrogel through hydrophobic association, while quaternized chitosan (QCS) was incorporated as a reinforcing component, thereby yielding the PALQMI hydrogel with integrated mechanical robustness, stretchability, and electrical conductivity. Through the rational regulation of multiple reversible physical interactions, including hydrogen bonding, electrostatic interactions, and metal–ion coordination, the optimized PALQ0.5M30I0.5 hydrogel achieved a tensile strength of 1.62 MPa, an elongation at break of 2833.2%, and a toughness of 20.119 MJ m–3. It also showed remarkable fatigue resistance during cyclic loading–unloading tests. The incorporation of polyaniline endowed the hydrogel with a high electrical conductivity of 161.49 mS cm–1. The hydrogel detected a broad strain range of 10–1000% and exhibited a maximum gauge factor (GF) of 5.667 in the 600–1000% strain range. Moreover, PALQMI enabled clear and reproducible detection of human-motion-related strains and could function as a pressure sensor for encrypted information transmission. These results demonstrate the considerable potential of PALQMI for wearable strain sensors and flexible electronic devices