Figure 3: Measurements of rotational speed and diffusivity.

(a) Angular displacement as a function of time for a single gear under different illumination power levels. The arrow points towards increasing illumination powers. The bottom panel displays the corresponding angular deviations from a linear fit. (b) Angular speed as a function of the illumination power for ten different gears. All curves scale on top of each other when rescaling power by an arbitrary factor accounting for absorption variations (inset). (c) Mean squared angular displacement for a gear at the liquid–air interface is shown in blue together with a best fit curve in equation (1). Red data refer to a gear at the liquid–solid interface. The dashed line represents the expected behaviour assuming that a comparable light-induced torque was present in the bulk.