Shape-mediated margination and demargination in flowing multicomponent suspensions of deformable capsules

Abstract

We present detailed simulations and theory for flow-induced segregation in suspensions of deformable fluid-filled capsules with different shapes during simple shear flow in a planar slit. This system is an idealized model for transport for blood cells and/or drug carriers in the microcirculation or in microfluidic devices. For the simulations, an accelerated implementation of the boundary integral method was employed. We studied the binary mixtures of spherical and ellipsoidal capsules, varying the aspect ratio κ of the ellipsoid while keeping constant either (a) equatorial radius or (b) volume. Effects of a variety of parameters was studied, including κ, volume fraction and number fraction of the spherical capsules in the mixture. In suspensions where the ellipsoids have the same equatorial radius as the spheres, capsules with lower κ marginate. In suspension where the ellipsoids have the same volume as the spheres, ellipsoidal (both oblate and prolate) capsules are seen to demarginate in a mixture of primarily spherical capsules. To understand these results, a mechanistic framework based on the competition between wall-induced migration and shear-induced collisions is presented. A simplified drift-diffusion theory based on this framework shows excellent qualitative agreement with simulation results.

Manipulating nanoparticle transport within blood flow through external forces: an exemplar of mechanics in nanomedicine

“…Thus, particle-particle collision is inevitable when they move close to each other, especially for blood flows with high haematocrit Ht (volume fraction of RBCs in blood flow). Owing to the complexity of collision between multiple particles, previous studies mainly focus on the pair collision, which can explain the collision-relevant phenomena in blood flow [23,[54][55][56][56][57][58]. Figure 2a shows a simplified collision model including three processes: pre-collision, collision and post-collision.…”

“…For the heterogeneous collision (collision between particles with different stiffness), simulation results showed stiff particles migrated faster than floppy particle (Y sf > Y fs ), except that stiff particles had larger velocity than that in homogeneous collision (Y sf > Y ss ), and at the same time, floppy particles possessed less migration velocity compared to that in homogeneous collision (Y fs < Y ff ). 10 -2 10 -1 particle size (mm) Recently, Sinha & Graham [57] investigated the margination and demargination behaviours of deformable capsules, which were modelled as blood cells and/or drug carriers in the microcirculation or in micro-fluidic devices. Again, pair collision was recognized as a critical factor in the movement of capsules.…”

“…(b) Essential forces for particle transport in blood flow Particles (platelets, WBCs, RBCs and NPs) experience different kinds of forces [52,53]. Particleparticle collision force happens between the same or different kinds of particles when they move close to each other [23,[54][55][56][56][57][58]. If particles are soft, they can deform under the shear stress of blood flow, and a lift force will be induced, which is perpendicular to the flow direction in the vicinity of the vessel wall [52,[59][60][61][62].…”

A parallel fluid–solid coupling model using LAMMPS and Palabos based on the immersed boundary method

“…Fluid flows containing solid particles are common in engineering and medicine, e.g., suspension flows [1], sedimentation[2], cell transport in blood flow [3, 4, 5, 6, 7], and platelet deposition on blood vessel walls [8, 9, 10]. The dynamic behavior in such phenomena is complex due to interactions between individual particles as well as interactions between the particles and the surrounding fluid and bounding walls.…”

Size-Dependence of Rotation Rates of Spheres and Disks in Turbulence

“…In stars, they are bubbles of the very plasma that is turbulently churning. In our blood vessels, they are blood cells whose shapes and deformabilities change with the type of cell and where it needs to be within the vessel [7]. In planetary nebulae, the particles are planetesimals that bump and crash together, gravitationally and electrostatically influencing everything around them as they build up into rocks big enough that we would call them planets.…”