Cross-stream migration of active particles

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 patter...

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Bibliographic Details
Published in:arXiv.org 2018-01
Main Authors: Katuri, Jaideep, Uspal, William E, Simmchen, Juliane, Miguel-López, Albert, Sánchez, Samuel
Format: Article
Language:English
Subjects:
Catalysis
Channel flow
Migration
Nanoparticles
Shear flow
Swimming
Thermal noise
Online Access:Get full text
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Summary: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.
ISSN:2331-8422
DOI:10.48550/arxiv.1706.06817