Bioinspired Self-Growing Layered Hydrogel Enabled by Catechol Chemistry-Mediated Interfacial Catalytic System.

Tissue-inspired layered structural hydrogel has attracted increasing attention in artificial muscle, wound healing, wearable electronics, and soft robots. Despite numerous efforts being devoted to developing various layered hydrogels, the rapid and efficient preparation of layered hydrogels remains challenging. Herein, inspired by the self-growth concept of living organisms, an interfacial catalytic self-growth strategy based on catechol chemistry-mediated self-catalytic system of preparing layered hydrogels is demonstrated. Typically, the tannic acid-metal ion (e.g., TA-Fe) complex embedded in the hydrogel substrate would catalytically trigger rapid solid-liquid interfacial polymerization to grow the hydrogel layer without bulk solution polymerization. The self-growth process can be finely controlled by changing the growth time, the molar ratio of Fe/TA, and so on. The strategy is applicable to prepare various layered hydrogels as well as complex layered hydrogel patterns, allowing the customization of the physicochemical properties of the hydrogel. In addition, the self-adhesive layered hydrogel was prepared and can be utilized as a wearable strain sensor to monitor physiological activities and human motions. The demonstrated interfacial catalytic self-growth strategy will provide a route to design and fabricate layered hydrogel materials.