Typhoon eye-shaped global convective flow field-induced colloidal motor swarm

Abstract

In nature, living individuals such as fish, gather as much as possible in the wild to carry out life activities to improve their survival rate and environmental adaptability. Colloidal motors are often used as models to form various swarms and reveal their intrinsic mechanisms. Here, we rely on a global convective flow field to prompt the formation of a colloidal motor swarm that can absorb all motors in the range of light radiation without assembly limits. The peanut-shaped colloidal motor photocatalytically decomposes hydrogen peroxide and generates the chemical concentration gradient, which triggers convective flows at its waist in the x-z plane and attracts nearby motors. When motors converge towards the center of the light gradient field due to their positive phototaxis, the chemical gradient fluid resulting from motors’ non-uniform distribution in the entire domain induces a typhoon eye-shaped global convective flow field that flows from the edge of the light to the center. Compared with individuals, the global convective flow has a wider attraction range and gathers motors into a swarm. Moreover, with the number of collected motors increasing, the convective flow integrated in the x-z plane is stronger and ceaselessly accumulates more motors toward the z-axis. The formed swarm can also move to other areas under light control to collect more motors. Such collective phenomena provide a chance for understanding the emergence mechanism of biological swarms and applying artificial swarms to environmental governance, information collection, and drug release.