Activity-induced microswimmer interactions and cooperation in one-dimensional environment*

Cooperative motion in biological microswimmers is crucial for their survival as it facilitates adhesion to surfaces, formation of hierarchical colonies, efficient motion, and enhanced access to nutrients. Here, we confine catalytic microswimmers along one-dimensional paths and demonstrate that they, too, show a variety of cooperative behaviours. We demonstrate that their speed increases with the number of swimmers, and find a preferred distance between swimmers. Using a minimal model, we ascribe this behaviour to an effective activity-induced potential that stems from a competition between chemical and hydrodynamic coupling. These interactions further induce active self-assembly into trains as well as compact chains that can elongate, break-up, become immobilized and remobilized. The cooperative behaviour of catalytic microswimmers opens the door to applications that need more efficient motion, with temporal and spatial control in complex environments.