Hydrophobic association and ionic coordination dual crossed-linked conductive hydrogels with self-adhesive and self-healing virtues for conformal strain sensors

As a promising functional material, conductive hydrogel has attracted extensive attention, especially in flexible sensor field. Despite the recent developments, current hydrogels still experience several issues, such as limited stretchability, lack of self-recovery and self-healing capability, and insufficient self-adhesion. Herein, dual cross-linked (DC) poly (AA-co-LMA)_SDS/Fe³⁺ hydrogels are fabricated subtly on the basis of ionic coordination interactions and the poly (AA-co-LMA)_SDS hydrophobic association networks, which may provide one plausible routine to compensate the mentioned drawback of hydrogels. The hydrophobic association and ionic coordination networks work synergistically to endow the hydrogels remarkable stretchability (>1200%), high-fracture strength (≈ 820 kPa), and excellent self-healing capability. In addition, the DC hydrogel-based strain sensors displayed a broad sensing range (0 ～ 900%), conspicuous sensitivity (strain 0% ～ 200%, gauge factor = 0.53; strain 200% ～ 500%, gauge factor = 1.23; strain 500% ～ 900%, gauge factor = 2.09), and pronounced durability. What's more, the self-adhesive feature ensures the strain sensor always forming a good conformal contact with the skin during human movements and displaying remarkable bidirectional detection capability.