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Journal Articles Journal of Fluid Mechanics Year : 2021

Path selection of a train of spherical capsules in a branched microchannel

Abstract

Microfluidic systems consisting of a square microchannel with an orthogonal side branch are promising tools to enrich or sort suspensions of deformable capsules. To allow their operating control, we numerically consider a train of initially spherical identical capsules, equally spaced along the axis of the feeding channel. The capsules have a strain-hardening membrane, an internal fluid viscosity identical to that of the external fluid and a size comparable to that of the channel. We study the influence of the interspacing on the capsule path selection at the channel bifurcation using a three-dimensional immersed boundary–lattice Boltzmann method. Our objectives are to establish a phase diagram and identify the critical interspacing above which hydrodynamic interaction between capsules no longer affects their path selection. We find two main regimes. At low interspacing, strong capsule interaction leads to an unsteady regime for which the capsule path selection follows either a periodic or a disordered state. Above a critical initial interspacing $d_{ct}$ , a steady regime is achieved where interaction between capsules is too weak to affect their path selection. The capsules then follow an identical steady trajectory. We find that the dependence of the interspacing $d_{ct}$ , normalised by the capsule radius, on the flow split ratio falls onto a universal curve regardless of the flow strength, capsule size and membrane shear elasticity. We also compare the path selection of a capsule train with that of a two-capsule system, and discuss applications of the present results in controlling capsule trains in microfluidic suspension enrichment devices.
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Dates and versions

hal-03310771 , version 1 (30-07-2021)

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Cite

R.X. X Lu, Z. Wang, Anne-Virginie Salsac, D. Barthès-Biesel, W. Wang, et al.. Path selection of a train of spherical capsules in a branched microchannel. Journal of Fluid Mechanics, 2021, 923, ⟨10.1017/jfm.2021.571⟩. ⟨hal-03310771⟩
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