Fig. 4. Stimuli-responsive hydrogels. (A) Thermoresponsive sol–gel transition of gelatin. (B) pH-sensitive swelling–deswelling behaviour of acidic and basic hydrogels redrew from Kocak et al.42 (D) Influence of applied electric filed on hydrogel reconstructed from Qureshi et al.43 (C) Photosensitivity in the sol–gel transition of azobenzene-based hydrogel redrew from Zhao et al.41.
