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.