Autonomous self-healing hydrogel with anti-drying properties and applications in soft robotics

Abstract Mimicking nature's self-healing ability has always been desired in science, especially when devices accumulate damage over time with performance, including the loss of function due to deterioration. SHAP (Self-Healing AETA([2-(acryloyloxy)ethyl]trimethylammonium chloride)-based Polymer), a hydrogel with autonomous self-healing ability that can be applied for the development of a pneumatic artificial muscle, is presented here. Unlike other self-healing hydrogels, SHAP does not require any external stimulus to self-heal and it presents outstanding anti-drying properties. Few-layer graphene is also incorporated into the polymer network of the hydrogel in order to study the possible influence that the nanomaterial has on the properties of the scaffolds. The mechanical behavior and the self-healing abilities of the resulting hydrogels are analyzed. Moreover, the mechanism of self-healing is discussed in terms of experimental results and theoretical calculations. The data suggest a mechanism based on strong hydrogen-bonding interactions between the water molecules that remain inside SHAP, which keeps the material wet and soft under ambient conditions. Finally, the development of a SHAP-based artificial muscle is presented. The results show good performance of the healed artificial muscles after damage, even with healing periods as short as 10 minutes.