Locomotion of active matter over a circular cylinder in a microchannel

This study numerically investigates the locomotion of active matter over a circular cylinder in a confined microchannel. We consider the effects of cylinder size, swimming Reynolds number on the motion characteristic of three kinds of swimmers. The swimmer’s motion over a cylinder in a microchannel can be classified into seven modes. The cylinder diameter and swimming Reynolds number have no impact on the motion mode of neutral swimmers. When approaching the cylinder, pullers mainly perform periodic motion near the left side of cylinder, the pushers primarily perform periodic motion near the right side of cylinder. The mechanism of the periodic motion is mainly induced by the hydrodynamic interaction between the cylinder, channel walls, and the pressure near the swimmer. As cylinder diameter increases, pushers are more likely to exhibit periodic motion on the surface of cylinder than the pullers. Puller is unable to stabilize on the surface of cylinder at low Reynolds number, it migrates to the right side of cylinder at high Reynolds number, showing a pattern opposite to that observed for pushers. The results provide a possible new path for controlling active matter in microfluidic devices.