Characterizing the membrane properties of capsules flowing in a square-section microfluidic channel: Effects of the membrane constitutive law

Hu, Xu-Qu; Sévénié, B.; Salsac, Anne‐Virginie; Leclerc, Éric; Barthès-Biesel, Dominique

doi:10.1103/physreve.87.063008

Cited by 48 publications

(55 citation statements)

References 21 publications

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“…Once inside the daughter channel, the capsule migrates towards the centreline over distances of several capsule diameters due to viscous shear forces, and regains symmetry about the centreline of the channel towards the end of the visualisation window (Figure 3(a)). Figure 3(a) shows that the rear of the capsule adopts a parachute shape in both main and daughter channels, consistent with previous studies (Risso et al 2006;Lefebvre et al 2008;Hu et al 2013). We find that its rear is deformed into a concave shape beyond a threshold value of the capillary number of Ca c = 0.07 ± 0.02 in the main channel, while in the daughter channel, Ca c = 0.05 ± 0.02.…”

Section: Capsule Motion Through the T-junctionsupporting

confidence: 90%

“…In-flow measurements are routinely performed on micrometric capsules suspended in a carrier liquid within a microchannel. Their shear modulus is typically determined by comparison with numerical simulations of the deformation in flow along a straight section of tube of capsules based on a membrane model (Hur et al 2011;Hu et al 2013). However, the range of deformations achievable in a straight section of tube is narrower than that in a T-junction, and thus the accuracy of the method could be enhanced by focusing on the flow through a T-junction.…”

Section: Discussionmentioning

confidence: 99%

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Deformation and sorting of capsules in a T-junction

2019

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We study experimentally the motion and deformation of individual capsules transported by a constant volume-flux flow of low Reynolds number, through the T-junction of a channel with rectangular cross-section. We use millimetric ovalbumin-alginate capsules which we manufacture and characterise independently of the flow experiment. Centred capsules travel at constant velocity down the straight channel leading to the T-junction where they decelerate and expand in the spanwise direction before turning into one of the two identical daughter channels. There, non-inertial lift forces act to re-centre them and relax their shape until they reach a steady state of propagation. We find that the dynamics of fixed-size capsules within our channel geometry are governed by a capillary number Ca defined as the ratio of viscous shear forces to elastic restoring forces. We quantify the elastic forces by statically compressing the capsule to 50% of its initial diameter between parallel plates rather than by the Young's modulus of the encapsulating membrane, in order to account for different membrane thickness, pre-inflation and nonlinear elastic deformation. We show that the maximum extension in the T-junction of capsules of different stiffness collapses onto a master curve in Ca. Thus, it provides a sensitive measure of the relative stiffness of capsules at constant flow rate, particularly for softer capsules. We also find that the T-junction can sort fixed-size capsules according to their stiffness because the position in the T-junction from which capsules are entrained into the daughter channel depends uniquely on Ca. We demonstrate that a T-junction can be used as a sorting device by enhancing this initial capsule separation through a diffuser. †

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Section: Capsule Motion Through the T-junctionsupporting

confidence: 90%

Section: Discussionmentioning

confidence: 99%

Deformation and sorting of capsules in a T-junction

2019

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“…The LBM mesh size is x = 0.04l. The membrane The bending stiffness of the membrane is, in this case, set to zero to be consistent with Hu et al (2013). Dotted line (blue online), profile C 1 , obtained with 32 768 flat triangular elements; solid line (red online), profile C 2 obtained with 8192 elements; dashed line (black online), profile obtained by Hu et al (2013) for Re = 0, using a boundary element method.…”

Section: Numerical Methods and Validationmentioning

confidence: 99%

“…The capsule has dimensions comparable to the side branch cross-section and is centred along the feeding channel axis by hydrodynamic forces or by some flow-focusing devices. This situation is pertinent for the design of particle/cell enrichment devices (Yang, Ündar & Zahn 2006;Gossett et al 2010;Kersaudy-Kerhoas et al 2010;Shields IV, Reyes & López 2015), for which it is essential that the branch collecting the particles receives as little suspending fluid as possible. Many questions still remain regarding the magnitude of the velocity difference that allows separation and the effect of the flow pattern in the bifurcation, since microfluidic technology allows for different bifurcation designs.…”

Section: Introductionmentioning

confidence: 99%

Path selection of a spherical capsule in a microfluidic branched channel: towards the design of an enrichment device

et al. 2018

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We computationally study the motion of an initially spherical capsule flowing through a straight channel with an orthogonal lateral branch, using a three-dimensional immersed-boundary lattice-Boltzmann method. The capsule is enclosed by a strain-hardening membrane and contains an internal fluid of the same viscosity as the fluid in which it is suspended. Our primary focus is to study the influence of the geometry of the side branch on the capsule path selection. Specifically, we consider the case where the side branch cross-section is half that of the straight channel and study various bifurcation configurations, where the branch is rectangular or square, centred or not on the straight channel axis. The capsule is initially centred on the axis of the straight channel. We impose the flow rate split ratio between the two downstream branches of the bifurcation. We summarise the results obtained for different capsule-to-channel size ratios, flow Reynolds number $Re$ (based on the parent channel size and average flow speed) and capsule mechanical deformability (as measured by the capillary number) in phase diagrams giving the critical flow rate split ratio above which the capsule flows into the side branch. A major finding is that, at equal flow rate split between the two downstream branches, the capsule will enter a branch which is narrow in the spanwise direction, but will not enter a branch which is narrow in the flow direction. For $Re\leqslant 5$, this novel intriguing phenomenon primarily results from the background flow, which is strongly influenced by the side branch geometry. For higher values of $Re$, the capsule relative size and deformability also play specific roles in the path selection. The capsule trajectory does not always obey the classical Fung’s bifurcation law, which stipulates that a particle (in Fung’s case, a red blood cell) enters the bifurcation branch with the highest flow rate. We also consider the same branched channels operating under constant pressure drop conditions and show that such systems are difficult to control due to the transient additional pressure drop caused by the capsule. The present results obtained for dilute systems open new perspectives on the design of microfluidic systems, with optimal channel geometries and flow conditions to enrich cell and particle suspensions.

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“…New experimental techniques have been developed to characterize elastic polymer membranes at liquid interfaces [14][15][16][17][18] . The rheology of such membranes has been studied in model geometries 15,17,[19][20][21][22][23] and also on real capsules in viscous flows to mimic real conditions of fabrication and use, through various experiments 16,[23][24][25][26] , theories [27][28][29] and simulations [30][31][32] . From this perspective, microfluidics is an ideal tool which allows to integrate measurement units directly in situ in the devices and to perform automated measurements on a large number of capsules.…”

Section: Introductionmentioning

confidence: 99%

Microfluidic probing of the complex interfacial rheology of multilayer capsules

et al. 2019

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Encapsulation of chemicals using polymer membranes enables to control their transport and delivery for applications such as agrochemistry or detergency. To rationalize the design of polymer capsules, it is necessary to understand how the membranes' mechanical properties control the transport and release of the cargo. In this article, we use microfluidics to produce model polymer capsules and study in situ their behavior in controlled elongational flows. Our model capsules are obtained by assembling polymer mono and hydrogen-bonded bilayers at the surface of an oil droplet in water. We also use microfluidics to probe in situ the mechanical properties of the membranes in a controlled elongational flow generated by introducing the capsules through a constriction and then in a larger chamber. The deformation and relaxation of the capsules depend on their composition and especially on the molecular interactions between the polymer chains that form the membranes and the anchoring energy of the first layer. We develop a model and perform numerical simulations to extract the main interfacial properties of the capsules from the measurement of their deformations in the microchannels.

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Characterizing the membrane properties of capsules flowing in a square-section microfluidic channel: Effects of the membrane constitutive law

Cited by 48 publications

References 21 publications

Deformation and sorting of capsules in a T-junction

Deformation and sorting of capsules in a T-junction

Path selection of a spherical capsule in a microfluidic branched channel: towards the design of an enrichment device

Microfluidic probing of the complex interfacial rheology of multilayer capsules

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