Schematic of the experimental setup: Depending on whether the coated glass beads have many or few neighbours within their field of vision (red), they are either illuminated by a laser beam or not. Researchers can use such an experiment to investigate the effects of visual information on the collective behaviour and swarming of swimming microparticles.
Photo: Noemi Furlani

Microscopic swimmers with visual perception of group members form stable swarms

Birds, fish and bacteria often gather into groups or swarms. This so-called collective behaviour requires all group members to continuously and reciprocally adapt their movements. It can be a challenging task, however, for researchers to ascertain the specific environmental stimuli that individuals respond to within the context of their group; in addition to optical and acoustic information, flow resistances or chemical messengers can also play a role. By designing experiments with artificial microswimmers, we were able to show that the formation of stable groups requires only few skills: forward visual perception over large distances and regulation of the speed according to the number of perceived individuals. In addition to providing more insight into collective phenomena, the experiments can also be used for research on autonomous systems.