Hydrodynamic pursuit by cognitive self-steering microswimmers

Abstract

The properties of biological microswimmers are mostly determined by fluid-mediated interactions, which govern their propulsion, perception of their surrounding, and the steering of their motion for pursuit. Transferring similar functionalities to synthetic microswimmers poses major challenges, and the design of favorable steering and pursuit strategies is fundamental in such an endeavor. Here, we employ a squirmer model to investigate the pursuit of pursuer-target pairs with an implicit sensing mechanism and limited hydrodynamic steering abilities of the pursuer. Two hydrodynamic steering strategies are studied for the pursuer’s propulsion direction by adaptation of its surface flow field: reorientation toward the target with limited maneuverability, and alignment with the target’s propulsion direction combined with speed adaptation. Depending on the nature of the microswimmer propulsion (puller, pusher) and the velocity-adaptation scheme, stable cooperatively moving states can be achieved, where pursuer and target mutually affect their motion and trajectories.