Fig. 2. (A) Schematic preparation of a triangle-shaped CMC hydrogel crosslinked by the (1)/(1) duplexes and trans-azobenzene/β-CD complexes, and light-induced reversible transitions between the stiff shaped hydrogel I and the shapeless quasi-liquid hydrogel II that is only crosslinked by the (1)/(1) bridges. (B) Macroscopic images of the reversible light-induced transitions of the hydrogel between the triangle-shaped hydrogel I and the quasi-liquid shapeless hydrogel II, respectively.