Tough, self-healing double network hydrogels crosslinked via multiple dynamic non-covalent bonds for strain sensor

Double-network hydrogels have outstanding mechanical characteristics but mostly suffer from poor self-healing performance since most hydrogels are chemically crosslinked via covalent links for each network. In this work, a tough and self-healing double network hydrogel with multiple dynamic non-covalent bonds is developed by combining the hydrophobically modified polyacrylamide (HPAM) with a thermally reversible potassium ion crosslinked kappa-carrageenan (K+C) network through a dual physical crosslinked network strategy. Being the multiple dynamic non-covalent bond interactions and dual physical crosslink networks, the K+C/HPAM DN hydrogel exhibits excellent mechanical characteristics (tensile strength: 1.86 MPa, tensile strain: 1637%) and good self-healing ability (maximum stress self-healing efficiency: 87%, maximum tensile strength after self-healing: 0.95 MPa). Due to the three-dimensional pore structure and the conductive ions in the system, the K+C/HPAM DN hydrogel also achieves good strain sensing capabilities with a strain sensitivity of 2.98 (gauge factor, GF) in the 100% strain range. Even after being cut and self-healed, the gel still exhibits good strain sensing capabilities (GF = 2.79), which is still better than the most similar DN hydrogel strain sensors in sensitivity. We believe this work offers a new material for self-healing flexible strain sensors.