Hydrodynamics and rheology of a vesicle doublet suspension

Abstract

The dynamics of an adhesive two-dimensional vesicle doublet under various flow conditions is investigated numerically using a high-order, adaptive-in-time boundary integral method. In a quiescent flow, two nearby vesicles move slowly towards each other under the adhesive potential, pushing out fluid between them to form a vesicle doublet at equilibrium. A lubrication analysis on such draining of a thin film gives the dependencies of draining time on adhesion strength and separation distance that are in good agreement with numerical results. In a planar extensional flow we find a stable vesicle doublet forms only when two vesicles collide head-on around the stagnation point. In a microfluid trap where the stagnation of an extensional flow is dynamically placed in the middle of a vesicle doublet through an active control loop, novel dynamics of a vesicle doublet are observed. Numerical simulations show that there exists a critical extensional flow rate above which adhesive interaction is overcome by the diverging stream, thus providing a simple method to measure the adhesion strength between two vesicle membranes. In a planar shear flow, numerical simulations reveal that a vesicle doublet may form provided that the adhesion strength is sufficiently large at a given vesicle reduced area. Once a doublet is formed, its oscillatory dynamics is found to depend on the adhesion strength and their reduced area. Furthermore the effective shear viscosity of a dilute suspension of vesicle doublets is found to be a function of the reduced area. Results from these numerical studies and analysis shed light on the hydrodynamic and rheological consequences of adhesive interactions between vesicles in a viscous fluid.Keywords: Vesicle hydrodynamics, membrane adhesion, drop and bubble phenomena/drop interactions, interfacial flows/thin fluid films, rheology/flow confinement, biological fluid dynamics/collective behavior/clustering, emergence of patterns

Two-dimensional hydrodynamics of a Janus particle vesicle

“…We also observe an adhesive effect between the two JP vesicles that is set up by the hydrophobic attraction (figure 10c). Similar dynamics have been observed between a pair of adhering vesicles in a shear flow (Quaife et al 2019;Abbasi et al 2021). This adhesive behaviour is absent when two JP vesicles are well-separated.…”

“…The two overlapping trajectories of the JP vesicles' centroids in a shear flow evolve as expected when the two centroids are initialized on the same horizontal level. We also observe a rotating behaviour that is present in models involving vesicle adhesion (Quaife et al 2019). The hydrophobic attraction led to this adhesive effect when two JP bilayers are sufficiently close.…”

“…Internal pressure is initially zero, but then grows as the vesicles come close to contact (see panel c). The insets are generated from simulations of a continuum model of the vesicles(Quaife et al 2019). The streamlines of the two models are in agreement.…”

Non-equilibrium dynamics of initially spherical vesicles in general flow

“…There have been many theoretical and numerical investigations of vesicles with zero sub- optical area [14][15][16][17][18][19]. Fewer investigations starting with the assumption of a spherical vesicle and sub-optical area exist.…”

Erythrocyte-erythrocyte aggregation dynamics under shear flow

“…More recently Quaife et al [27] studied dynamics of a doublet under extensional and shear flows by using a 2D vesicle model. Under a linear shear flow (which is of interest to our study) they observed that the doublet undergoes a tumbling regime, that we shall refer to as rolling (for the sake of distinction with the classical single cell tumbling).…”