Biological tissues can accurately differentiate external mechanical stresses and actively select suitable strategies (e.g., reversible strain-stiffening, self-healing) to sustain or restore their integrity and related functionalities as required. Synthetic materials that can imitate the characteristics of biological tissues have a wide range of engineering and bioengineering applications. However, no success has been demonstrated to realize such strain-stiffening behavior in synthetic networks, particularly using flexible polymers, which has remained a great challenge. Here, we present one such synthetic hydrogel material prepared from two flexible polymers (polyethylene glycol and branched polyethylenimine) that exhibits both strain-stiffening and self-healing capabilities. The developed synthetic hydrogel network not only mimics the main features of biological mechanically responsive systems but also autonomously self-heals after becoming damaged, thereby recovering its full capacity to perform its normal physiological functions.
Keywords: dynamical covalent bonds; flexible network; hydrogel; self-healing; strain-stiffening.