“…For instance, the curved photonic hydrogel actuator prepared with 784 nm PNIPAM microspheres turned red and green in 10% and 40% (v/v) ethanol–water mixtures, respectively. In the meantime, the shape of the curved photonic hydrogel actuator was changed in the ethanol–water mixture, owing to its asymmetric microstructure-induced anisotropic strain. ,,, The photonic hydrogel actuator presents the low cross-linking density at the nonirradiation side and thus possesses higher swelling/deswelling ratios in good/poor solvents at this side, compared to that of UV-irradiation side . Therefore, the curved hydrogel actuator unrolled in the good solvent (i.e., ethanol–water mixture with a low ethanol concentration lower than 50 v/v%), while it further rolled up toward the nonirradiated side in water/ethanol mixture with a high ethanol concentration (≥50 v/v%), as shown in Figure d.…”