Dynamic Flexible Hydrogel Network with Biological Tissue-like Self-Protective Functions

Biological tissues are capable of stiffening and self-healing as they are strained or damaged in order to preserve their integrity and functionalities. However, mimicking both strain-stiffening and self-healing functions of biological tissues in biocompatible flexible hydrogels remains a challenge. Here, we report a flexible hydrogel constructed by two biocompatible polymers, which can smartly adopt biological strain-stiffening or self-healing strategy to maintain the structural integrity and functionalities in response to mechanical deformation. The hydrogel can be reversibly and repeatedly stiffened up to eight times of its original modulus as it is strained, without showing mechanical hysteresis. Besides, the damaged hydrogel can repeatedly self-heal within seconds and fully retains the strain-stiffening capability. In addition, benefitting from the excellent biocompatibility and dynamic nature, the biomimetic hydrogel can be facilely applied for 3D cell encapsulation. This work provides novel insights into the molecular design of tissue-like self-protective soft materials, which may also inspire the development of biomimetic cell culture matrices, artificial tissues, as well as soft machines and robotics for various biomedical and engineering applications.