Research progress on double-network hydrogels

Recently, research on double-network (DN) hydrogels with good biocompatibility and mechanical properties has been flourishing. The main research directions have aimed to enhance the poor mechanical properties of conventional hydrogels and to broaden their potential applications in various fields. This paper reviews the recent research progress in the preparation of DN hydrogels, including fully chemically cross-linked DN hydrogels, hybrid physically/chemically cross-linked DN hydrogels, and fully physically cross-linked DN hydrogels. These DN hydrogels have significant advantages in mechanical properties, structure, biocompatibility and so on. Focus is placed on the enhancement mechanisms and preparation of different DN hydrogels. Besides, we also discussed the applications of DN hydrogels in drug and biomolecular carriers, flexible sensors and actuators, tissue engineering, medical dressings, ions/pollutant removal, and supercapacitors (SCs). These research advances are rapidly breaking away from the current limitations of DN hydrogels and providing new ideas for their future development.