Hydrodynamics of chiral squirmers

Abstract

Many microorganisms take a chiral path while swimming in an ambient fluid. In this paper, we study the combined behavior of two chiral swimmers using the well-known squirmer model taking into account chiral asymmetries. In contrast to the simple squirmer model, which has an axisymmetric distribution of slip velocity, the chiral squirmer has additional asymmetries in the surface slip, which contribute to both translations and rotations of the motion. As a result, swimming trajectories can become helical and chiral asymmetries arise in the flow patterns. We study the swimming trajectories of a pair of chiral squirmers that interact hydrodynamically. This interaction can lead to attraction and repulsion, and in some cases even to bounded states where the swimmers continue to periodically orbit around a common average trajectory. Such bound states are a signature of the chiral nature of the swimmers. Our study could be relevant to the collective movements of ciliated microorganisms.

Diffraction and Interference with Run-and-Tumble Particles

“…Therefore, the interference of fermions can be embedded in a larger class of stochastic particle dynamics showing these wave effects. See also [23,24] for similar points. From the point of view of soft condensed matter, it remains perhaps surprising that run-and-tumble particles, in a classical simulation of trajectories, may show an interference pattern.…”

“…Here also, an implicit relation between pure quantum processes such as in spin-orbit coupling and (classical) run-and-tumble particles was formulated before. References with such analogies and similar inspiration include [23,24]. The recent [25] gives a mathematical (spectral) analysis of the zig-zag process within classical probability.…”