Asymmetry of red blood cell motions in a microchannel with a diverging and converging bifurcation

Abstract

In microcirculation, red blood cells (RBCs) flowing through bifurcations may deform considerably due to combination of different phenomena that happen at the micro-scale level, such as: attraction effect, high shear, and extensional stress, all of which may influence the rheological properties and flow behavior of blood. Thus, it is important to investigate in detail the behavior of blood flow occurring at both bifurcations and confluences. In the present paper, by using a micro-PTV system, we investigated the variations of velocity profiles of two working fluids flowing through diverging and converging bifurcations, human red blood cells suspended in dextran 40 with about 14% of hematocrit level (14 Hct) and pure water seeded with fluorescent trace particles. All the measurements were performed in the center plane of rectangular microchannels using a constant flow rate of about 3.0 Â 10 À12 m 3 /s. Moreover, the experimental data was compared with numerical results obtained for Newtonian incompressible fluid. The behavior of RBCs was asymmetric at the divergent and convergent side of the geometry, whereas the velocities of tracer particles suspended in pure water were symmetric and well described by numerical simulation. The formation of a red cell-depleted zone immediately downstream of the apex of the converging bifurcation was observed and its effect on velocity profiles of RBCs flow has been investigated. Conversely, a cell-depleted region was not formed around the apex of the diverging bifurcation and as a result the adhesion of RBCs to the wall surface was enhanced in this region.

Microbubble moving in blood flow in microchannels: effect on the cell-free layer and cell local concentration

“…In microfluidic systems and in capillary vessels, the RBCs have a size that is a significant fraction of the size of the channel. Effects due to the discrete size of the cells, such as the formation of a plasma layer (Leble et al 2011, Garcia et al 2012, Pinho et al 2013, plasma skimming (Faivre et al 2006), the Zweifach-Fung effect (Svanes and Zweifach 1968, Fung 1973, Doyeux et al 2011, the Fahraeus effect (Fåhraeus 1929) and the Fahraeus-Lindqvist effect (Fåhraeus and Lindqvist 1931) are relevant. A plasma layer or cell-free layer (CFL) is usually formed near the wall of small vessels due to the migration of red blood cells to the center of the microchannel.…”

A microfluidic device for partial cell separation and deformability assessment

“…This phenomenon is due to the existence of a CFL in both inner walls and a consequent formation of a triangular CFL in the region of the confluence apex [10,11]. Faivre et al [12] and Sollier et al [13] have demonstrated that the CFL could be enhanced by using a microchannel containing a constriction followed by sudden expansion to separate plasma from the whole in vitro blood.…”

“…Recently, Ishikawa et al [10] and Leble et al [11] have shown the existence of thin CFL in the centre of the microchannel, just downstream of a confluence. This phenomenon is due to the existence of a CFL in both inner walls and a consequent formation of a triangular CFL in the region of the confluence apex [10,11].…”

Visualization and Measurement of the Cell-Free Layer (CFL) in a Microchannel Network

“…6 and 7). The existence of these new CFLs is derived from the confluence geometries that influence the RBCs distribution and trajectories, as was shown by a past study performed in a simple microchannel composed by a single bifurcation followed by a confluence [14].…”

“…Past studies made in in vitro in microchannels with a simple divergent and convergent bifurcation that showed a pronounced CFL immediately downstream of the apex of the convergent bifurcation [14]. This interesting result led us to the present work, where the CFL in a microchannel network is investigated by using a high-speed video microscopy system in order to further understand the blood flow behaviour in microvessel networks.…”