Fig. 7

Particle spinning for polarizations of excitation light at θ ≈ −60° and θ ≈ 45°. a, c Sequences of images showing a micro-platelet at different orientations during one rotation period under polarization of excitation light at θ ≈ −60° a and θ ≈ 45° c. Polarizing optical images were taken under parallel polarizers shown with two adjacent white double arrows. Polarization direction of the blue excitation light is shown using a blue double arrow. The particle rotates counterclockwise a and clockwise c, as indicated by the yellow dashed arrow. Its angular positions in each image are shown using yellow arrows. Scale bars are 5 µm. b, d The net azimuthal rotation angle φ (black curve) and angular speed (red curve) versus time during five periods of platelet rotation corresponding to platelet rotation shown in a and c, respectively