Fig. 2: Photochemical actuation and light tuning in artificial seeds.

a Chemical composition of the photomechanical actuator. b UV–Vis spectra of a solid actuator film. The thickness of the film: 5 µm. Alignment: splayed. c The change of trans-isomer content in the azo-LCN film upon irradiation of different UV intensities. Superimposed images of a free-falling artificial seed as an initial state (d), after UV (240 mW cm⁻², 12 s) illumination (e) and then after blue light (300 mW cm⁻², 20 s) irradiation (f). The shape of the artificial seed wing before (g) and after (h) UV irradiation. UV: 240 mW cm⁻², 12 s. i Deformation kinetics of the azo-LCN film under different UV intensities, insets: photographs of azo-LCN strip bending after UV illumination. j Change of terminal velocity (V_T, red ring) and spinning rate (Ω, blue dot) of the artificial seed after receiving different UV doses. k Change of the deflection angle α (red ring) of the wing and corresponding descent factor (D_F, blue dot) upon different doses of UV irradiation. The error bars are displayed as mean values +/- standard deviation (n  =  3). The same sample was measured repeatedly. UV wavelength: 360 nm. After each experiment, the film is illuminated by blue light (460 nm, 300 mW cm⁻², 30 s) for complete shape recovery. All scale bars are 5 mm.