Soft suspensions: inertia cooperates with flexibility

Abstract

Cross-streamline migration of soft particles in suspensions is essential for cell and DNA sorting, blood flow, polymer processing and so on. Pioneering work by Poiseuille on blood flow in vivo revealed an erythrocyte-free layer close to blood vessel walls. The formation of this layer is related to a viscous lift force caused by cell deformation that pushes cells towards the centre of blood capillaries. This lift force has in this case a strong impact on blood flow. In contrast, rigid spherical particles migrate from the centre towards the periphery, owing to inertia (the Segré-Silberberg effect). An important open issue is to elucidate the interplay between particle deformation and inertia. By using a capsule suspension model, Krueger, Kaoui & Harting (J. Fluid Mech., 2014, vol. 751, pp. 725-745) discovered that capsule flexibility can suppress the Segré-Silberberg effect and inertia promotes overall flow efficiency thanks to a strong inertial flow focusing effect.

Emerging Attractor in Wavy Poiseuille Flows Triggers Sorting of Biological Cells

“…The field includes important physics-based strategies to understand the dynamics of particles in microflows and the mechanics of (deformable) cells with a great variety of applications in life science and technology. For example, studies of soft particles in suspension and their cross-streamline migration (CSM) in low Reynolds-number linear shear and Poiseuille flows provide important insights about blood flow, cell dynamics, DNA sorting, and polymer processing, among others [8][9][10][11][12][13]. Furthermore, a surprising splitting of streams of wormlike colloids in shear-thinning fluids through modulated channels was found [14].…”

Migration reversal of soft particles in vertical flows

“…-Microfluidics is a rapidly evolving cross-disciplinary field, ranging from basic physics to a great variety of applications in life science and technology [1][2][3][4][5][6][7][8][9]. The blooming subfield of the dynamics of neutrally buoyant soft particles in suspension and their crossstreamline migration (CSM) in rectilinear shear flows, plays a central role for cell and DNA sorting, blood flow, polymer processing and so on [6,[10][11][12][13]. In contrast, little is known about the dynamics of non-neutrally buoyant soft particles in rectilinear flows, but we show in this work for such particles a novel migration reversal.…”