Fig. 2

Preparation and morphology of the self-healing hydrogels. A The COA hydrogels can be injected through 34-gauge syringe needles with 80 μm internal diameter into the heart-shaped mold (A). An integrated heart-shaped hydrogel with smooth and homogenous appearance formed after self-adaption and self-healing for 30 min at 25 °C. B The integrated hydrogel was chopped into small pieces and then refilled the heart-shaped mold. The heart-shaped hydrogel self-healed for 30 min and recovered into its original shape. C The SEM image for the cross-section of the COA2 hydrogel. D Remaining weights of the CO and COA2 hydrogel in PBS at 37 °C. E Schematic diagram for the possible gelation mechanism of COA hydrogels