Flow of red blood cells in microchannel networks: in vitro studies
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abstract
Human blood is a multiphase biofluid primarily composed by the deformable red blood cells (RBCs) suspended in plasma. Because the complex structure of RBCs, blood exhibits unique flow characteristics on micro-scale level, due to their complex biochemical mechanisms and their response to both shear and extensional flow, which influence the rheological properties and flow behaviour of blood [1,2].
In the past years in vitro blood studies have been extensively performed and some important physiological phenomena, such as Fahraeus and Fahraeus-Lindqvist effect, were revealed [1,3]. This pioneer studies performed by Fahraeus and Fahraeus-Lindqvist in straight glass microchannels [4] revealed that for narrow tubes (diameter<300 μm), the apparent viscosity of blood declines with decreasing diameter. More recently, due to the developments in microscopy, computers and image analysis techniques, several researchers have used new measuring methods to obtain deeper quantitative understanding of the blood flow dynamics, in vitro [5-8] and in vivo experiments [9-10]. The increasing interest by the microfluidic and biomedical communities has also played a key role in several recent developments of lab-on-chip devices for blood sampling, analysis and cell culturing, aimed in a near future, the development of blood diagnostic devices, as an alternative tool to the traditional diagnostic strategies.
However, the blood flow in microvascular networks phenomena remains incompletely understood. Thus, it is important to investigate in detail the behaviour of RBCs flow occurring in a microchannel network, such as, with divergent and convergent bifurcations, which mimics the irregular vessel segments linked by numerous diverging and converging bifurcations.
Previously, we made in vitro studies in microchannels with a simple divergent and convergent bifurcation, that showed a pronounced cell-free layer (CFL) immediately downstream of the apex of the convergent bifurcation [1,4]. 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 microvessels networks.
