(438j) Control of Phoretic Self-Propulsion through Particle Geometry: Slender-Body Analysis for an Asymmetric Bent Rod

Synthetic microswimmers have a wide range of applications such as non-invasive medicine, targeted drug delivery, and lab-on-chip devices. Over the last two decades, theoretical research has focused on predicting the motion of microswimmers, which are generally assumed to be spheroidal or cylindrical. The motion of these microswimmers is driven due to an asymmetry in the activity on the particle surface. However, in recent years, there has been an increasing interest in understanding the impact of geometric asymmetry of particles, and if the geometric design of the particle can provide an additional degree of freedom to tune the particle trajectory. A standard boundary element method could be used to resolve particle trajectories but soon become computationally expensive for particles with extremely high aspect ratios like active needles or filaments. Some asymptotic theories have been developed to describe the motion of slender phoretic rods. However, they are inadequate in describing the motion of bent particles with no axial symmetry.

To this end, we theoretically investigate the motion of an active bent rod under the slender-body limit. Specifically, we vary the angle between the two rods, relative arm lengths and the activity along the surface of the particle, and evaluate particle trajectories under different geometric and surface activity conditions. We find that under specific geometric and surface patterning conditions, particles move along a circular trajectory, which is in qualitative agreement with previous experimental data. Using particle trajectories, we evaluate the relative contribution of the geometric asymmetry in driving such active particles which would enable us to fine tune the design of these active particles for specific use cases.