Fig. 4: Angle-dependent actuation and phototropic moving.

a–c (Top) Schematics of the rotation direction of the sample with respect to the laser source. The sample was illuminated from either PDMS or SIO/SF side. (Bottom) Dependence of displacement of the bilayers on the rotation angle (θ) of the sample (I = 35 m cm⁻²). Same legend for a, b, and c. d Schematic (left) and photograph (right) of a photonic sunflower. e, f Schematics (e) and images (f) showing different deformation states of the artificial sunflower with different illumination angles (I = 35 m cm⁻²). Insert in f indicates the initial state of the sunflower before illumination. g Photograph of the self-tracking photovoltaics system made of a photonic bilayer strip and an array of transfer-printed solar cells. Enlarged image shows the structure of one of the transfer-printed solar cells. h Current (I)–voltage (V) curves of the solar cell at different angles of incidence of light. i Measured power conversion efficiency (PCE) and short-circuit current (I_sc) as a function of incident angle. Error bars indicate the standard deviation (n = 5).