Cross-stream migration of active particles

Abstract

For natural microswimmers, the interplay of swimming activity and external flow can promote robust motion, e.g. propulsion against ("upstream rheotaxis") or perpendicular to the direction of flow. These effects are generally attributed to their complex body shapes and flagellar beat patterns. Here, using catalytic Janus particles as a model experimental system, we report on a strong directional response that occurs for spherical active particles in a channel flow. The particles align their propulsion axes to be nearly perpendicular to both the direction of flow and the normal vector of a nearby bounding surface. We develop a deterministic theoretical model of spherical microswimmers near a planar wall that captures the experimental observations. We show how the directional response emerges from the interplay of shear flow and near-surface swimming activity. Finally, adding the effect of thermal noise, we obtain probability distributions for the swimmer orientation that semi-quantitatively agree with the experimental distributions.

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• Theory of light-activated catalytic Janus particles
• Near-wall hydrodynamic slip triggers swimming state transition of microorganisms
• Jeffery's orbits and microswimmers in flows: A theoretical review
• Axisymmetric spheroidal squirmers and self-diffusiophoretic particles
• Self-Propelled Janus Colloids in Shear Flow
• Rheotaxis of Active Droplets
• Behavior of active filaments near solid-boundary under linear shear flow
• Transport barriers to self-propelled particles in fluid flows
• Interaction of Active Janus Particles with Passive Tracers
• Microtransformers: controlled microscale navigation with flexible robots
• Selecting active matter according to motility in an acoustofluidic setup: Self-propelled particles and sperm cells
• Self-propulsion in 2D Confinement: Phoretic and Hydrodynamic Interactions
• Phase coexistence in a monolayer of active particles induced by Marangoni flows
• Rotation Control, Interlocking and Self-positioning of Active Cogwheels
• Janus microswimmers are poor hydrodynamic mixers
• Active dipolar spheroids in shear flow and transverse field: Population splitting, cross-stream migration and orientational pinning
• Localization due to topological stochastic disorder in active networks
• Effective squirmer models for self-phoretic chemically active spherical colloids