Density shock waves in confined microswimmers

Abstract

Motile and driven particles confined in microfluidic channels exhibit interesting emergent behavior from propagating density bands to density shock waves. A deeper understanding of the physical mechanisms responsible for these emergent structures is relevant to a number of physical and biomedical applications. Here, we study the formation of density shock waves in the context of an idealized model of microswimmers confined in a narrow channel and subject to a uniform external flow. Interestingly, these density shock waves exhibit a transition from `subsonic' with compression at the back to `supersonic' with compression at the front of the population as the intensity of the external flow increases. This behavior is the result of a non-trivial interplay between hydrodynamic interactions and geometric confinement, and is confirmed by a novel quasilinear wave model that properly captures the dependence of the shock formation on the external flow. These findings can be used to guide the development of novel mechanisms for controlling the emergent density distribution and average population speed, with potentially profound implications on various processes in industry and biotechnology such as the transport and sorting of cells in flow channels.

References in corpus (6)

• Hydrodynamic attraction of swimming microorganisms by surfaces
• Emergent vortices in populations of colloidal rollers
• Phonons in a one-dimensional microfluidic crystal
• Transport of a dilute active suspension in pressure-driven channel flow
• Living on the edge: transfer and traffic of E. coli in a confined flow
• Active and driven hydrodynamic crystals

Cited by in corpus (10)

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• Purely hydrodynamic origin for swarming of swimming particles
• Phoretic and hydrodynamic interactions of weakly-confined autophoretic particles
• Quasiparticles, Flat Bands, and the Melting of Hydrodynamic Matter
• Strong confinement of active microalgae leads to inversion of vortex flow and enhanced mixing
• A minimal model for a hydrodynamic fingering instability in microroller suspensions
• Sedimentation of a Colloidal Monolayer Down an Inclined Plane
• Hydrodynamic bend instability of motile particles on a substrate