Re-entrant bimodality in spheroidal chiral swimmers in shear flow

Abstract

We use a continuum model to report on the behavior of a dilute suspension of chiral swimmers subject to externally imposed shear in a planar channel. Swimmer orientation in response to the imposed shear can be characterized by two distinct phases of behavior, corresponding to unimodal or bimodal distribution functions for swimmer orientation along the channel. These phases indicate the occurrence (or not) of a population splitting phenomenon changing the swimming direction of a macroscopic fraction of active particles to the exact opposite of that dictated by the imposed flow. We present a detailed quantitative analysis elucidating the complexities added to the population splitting behavior of swimmers when they are chiral. In particular, the transition from unimodal to bimodal and vice versa are shown to display a re-entrant behavior across the parameter space spanned by varying the chiral angular speed. We also present the notable effects of particle aspect ratio and self-propulsion speed on system phase behavior and discuss potential implications of our results in applications such as swimmer separation/sorting.

Influence of cap weight on the motion of a Janus particle very near a wall

“…Predicting the dynamics of anisotropic colloids is important for applications in real systems, for example during processing when complex fluids are often not at equilibrium [23,24].…”

“…Janus particles are one class of anisotropic colloid, typically with some property difference in the hemispherical domain. Each hemispherical domain of a Janus particle may have its own surface chemistry, shape, or other properties [22].Predicting the dynamics of anisotropic colloids is important for applications in real systems, for example during processing when complex fluids are often not at equilibrium [23,24].Various parameters influence the dynamics of anisotropic colloids [25][26][27][28]. Particle confinement will strongly impact the hydrodynamic interactions between the colloid and boundary, thereby strongly influencing particle mobility.…”

Galvanotaxis of ciliates: spatiotemporal dynamics of Coleps hirtus under electric fields

“…Although C. hirtus exhibits bimodal swimming patterns (see figure 2(C)), no bimodal velocity distribution was observed, like for E. coli and other unicellular organisms [45][46][47][48]. Such so called run-and-tumble swimming patterns are observed by the change in speed and direction of cellular locomotion [49].…”

Behavior of active filaments near solid-boundary under linear shear flow

“…Despite their simplicity, they are able to capture various complex behaviors of microswimmers such as, surface accumulation [22,53,54], upstream swimming [35][36][37], and flow-induced angular alignment [55,56], etc. The population splitting from a unimodal to a bimodal phase is also reported in terms of chirality and angular speed [57]. Further, the upstream motion can be regulated using viscoelastic fluid [58].…”