Figure 4.

(A-C): Images showing the micromotors right before the light was applied (A), right before it was turned off (B), and 10 seconds after it was turned off (C). The dashed lines in (B) are a visual aid to help better distinguish the illuminated region. The micromotors inside the illuminated region increase their speed and collide, forming aggregates. (D): A plot of the number of micromotor clusters within various size ranges inside the annulus region as a function of time. The vertical dashed lines correspond to when the light was turned on and the micromotors began to aggregate (at 5 seconds) and when it was turned off and the aggregates dissolved (76 seconds). (E): A color bar plot of the number of clusters as a function of their size within the illuminated region. The blue colored data correspond to times just after the light was applied and the green colored data correspond to later times up to the moment the light was turned off.