Diffusion of chiral active particles in a Poiseuille flow

TL;DR

This study investigates how chiral active particles behave in a microchannel flow, revealing controllable upstream drift, aggregation near walls, and flow-dependent diffusion, with implications for microfluidic device design.

Contribution

The paper provides a numerical analysis of how flow strength, diffusion, and chirality influence active particle transport, highlighting controllable drift and aggregation phenomena.

Findings

Particles can exhibit upstream drift with negative average velocity.

Chiral particles tend to aggregate near channel walls at optimal parameters.

Effective diffusion coefficient is enhanced or suppressed depending on particle chirality and flow conditions.

Abstract

We study the diffusive behavior of chiral active (self-propelled) Brownian particles in a two-dimensional microchannel with a Poiseuille flow. Using numerical simulations, we show that the behavior of the transport coefficients of particles, for example, the average velocity $v$ and the effective diffusion coefficient $D_{eff}$, strongly depends on flow strength $u_0$, translational diffusion constant $D_0$, rotational diffusion rate $D_\theta$, and chirality of the active particles $\Omega$. It is demonstrated that the particles can exhibit upstream drift, resulting in a negative $v$, for the optimal parameter values of $u_0$, $D_\theta$, and $\Omega$. Interestingly, the direction of $v$ can be controlled by tuning these parameters. We observe that for some optimal values of $u_0$ and $\Omega$, the chiral particles aggregate near a channel wall, and the corresponding $D_{eff}$ is enhanced. However, for the nonchiral particles ($\Omega = 0$), the $D_{eff}$ is suppressed by the presence of Poiseuille flow. It is expected that these findings have a great potential for developing microfluidic and lab-on-a-chip devices for separating the active particles.