To turn or not to turn: Slender body analysis for a self-propelling axially asymmetric bent rod

Synthetic microswimmers have gained attention due to their ability to mimic biological motion. However, the interplay between phoretic and geometric effects isn’t fully understood for axially asymmetric particles. To this end, we investigate the self-diffusiophoretic motion of a two-dimensional bent rod by employing slender body theory.

Our framework to predict the motion of the particle consists of two steps. First, we first calculate the diffusiophoretic slip velocity by solving the species conservation equation. Second, we employ the reciprocal theorem to obtain the particle translational and angular velocity. We analyze the particle motion for two scenarios: (1) both arms of the bent rod are active, and (2) one arm is active and the other is passive. In each case, we study the impact of geometry, i.e., the relative lengths and the angle between the two arms. Our study reveals that the particle typically follows a circular trajectory with a constant radius and a turn frequency. We quantify the impact of geometry on speed, turn frequency, and radius of the particle trajectory. We find that particle geometry in the second scenario, i.e., when only one arm is active, provides a higher degree of control over particle motion.