Fig. 3: Control of pDR1M platforms rolling.

A Representative optical microscopy images of 6 µm by 6 µm (top six images) and 6 µm by 9 µm (bottom six images) pDR1M platforms dispersed in water before and after illumination with light characteristics described in green (left: no polarization, middle: vertical polarization, right: horizontal polarization). The alignment of the microtubes along the polarization direction is clearly visible; moreover, it can be noticed that rectangles irradiated without polarization rolled along their long side. Scale bars: 10 µm. B Analysis of rolling direction: occurrence of microtubes formation along specific directions (shown on the x-axis) depending on the sheets’ aspect ratio and initial orientation (depicted in the legend) and light polarization (shown at the top). The data also includes structures that formed undefined shapes (as fifth column). The columns represent the mean ± s.e.m. of three samples (each sample including 20–40 structures per condition). The micrographs in (A) show a representative area of the analyzed images. C Snapshots during microtubes formation of pDR1M 6 μm-wide squares responding to the depicted light stimulus. An elongation along the polarization direction occurs prior rolling and continues even after the microtube is formed. At the bottom, SEM images, taken with a tilt angle of 30°, show dried samples found at the corresponding rolling stage. D Hypothesized molecular mechanisms responsible for pDR1M deformation and rolling: the Weigert effect, in which the azobenzene units reorient perpendicular to the linear polarization direction (i), could cause reorganization of the polymer molecules and elongation along the light polarization direction (ii). This elongation, together with releasing fabrication stresses thanks to photofluidization, could induce the rolling.