Ultra-robust, repairable and smart physical hydrogels enabled by nano-domain reconfiguration of network topology

Abstract

Unlike natural load-bearing tissues such as tendon and cartilage, artificial hydrogels usually lack the combination of high strength, high toughness, self-healing and stimuli-responsive abilities. Herein, we design a network topology featured by nano-domain reconfiguration to construct ultra-robust, repairable and smart physical hydrogels. The network is formed by crosslinking the linear carboxyl-bearing polyacrylamide chains interpenetrated in the poly(N-isopropylacrylamide-co-acrylic acid) nanogels through coordination bonds. Such design increases the local network density around the nanogels, enabling the sticky slipping motion of the interpenetrated chains upon small deformation. Under large deformation, the coordination network and nanogels can break and reform. These behaviors progressively dissipate mechanical energy and redistribute stress concentration. Thus, the hydrogels show tensile strength up to 10.8 MPa, strain at break up to 2048 %, and toughness up to 111.8 MJ/m3. Moreover, the sinherent dynamic nature of the coordination bonds and the temperature-responsive ability of the nanogels impart the hydrogels with mending and sensing abilities. Such tough-tissue like mechanical properties and physiological functions enables the material to serve as durable soft robots and wearable devices.