Ultradurable Noncovalent Cross-Linked Hydrogels with Low Hysteresis and Robust Elasticity for Flexible Electronics

Development of hydrogel-based flexible electronics with robust elasticity, low hysteresis, and excellent durability is still challenging. Herein, for the first time, B–N coordination was employed as the main driving force to promote gelation by free radical polymerization of acrylamide and 3-acrylamidophenylboronic acid. Owing to the outstanding stability of B–N coordination, the hydrogels could retain their initial stress (>95%) during 500 tension cycles (strain of 200%) with <10% hysteresis. Moreover, the addition of NaCl elevated the mechanical properties (break stress of 0.21 MPa and fracture strain of 1600%) and imparted high electrical conductivity (4.8 S/m) and superior gauge factor (10.2) to the hydrogels. The conductive hydrogels could accurately distinguish various deformations (2.5–200% tensile strain and 1–25 kPa compressive stress) and successively output reliable electrical signals with super durability (1000 tensile cycles with a strain of 100% and 1000 compressive cycles with a stress of 15 kPa). Combined with moderate tissue adhesiveness, the conductive hydrogels can monitor various human activities with constant outputs. This work offers a new solution to integrate high stretchability, robust elasticity, and low hysteresis into noncovalent cross-linked hydrogels, and may show vast potential in the development of flexible electronic devices.