Flow of red blood cells through microchannel with a confluence
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abstract
Micro-visualization techniques have been used to investigate the in vitro blood flow through straight glass capillaries. Although the glass microchannels present certain similarities to in vivo microcirculation, it is also clear that these kind of in vitro experiments differ from microvessels in several respects, such as: elasticity of microvessels, effect of the endothelial surface layer and microvascular networks composed with short irregular vessel segments which are linked by numerous bifurcations and convergences. Thus it was not surprising that several studies on blood flow in glass microtubes and in microvessels have yielded conflicting results with respect to blood viscosity and flow resistance. The main purpose of this work is to improve our understanding about the effect of a confluence on the rheological properties of in vitro blood. The flow behaviour of both pure water (PW) and dextran 40 (Dx40) containing about 14% (14Hct) of human red blood cells (RBCs) will be investigated by means of a confocal micro-PTV system. The experimental measurements obtained will be compared numerically by using the commercial finite element software package POLYFLOW® and different constitutive models to describe the rheology of the blood, namely: constant viscosity, power-law model and Carreau model.
Over the years micro-visualization techniques have been used to investigate in vitro blood flow through straight microchannels with dimensions close to in vivo capillaries. However, a few detailed studies have been performed in complex in vitro microvascular networks composed by diverging and converging bifurcations. The main purpose of present work is to show the application of a confocal micro-PTV system to track both flourescent particles and red blood cells (RBCs) through a rectangular polydimethysiloxane (PDMS) microchannel with a confluence. The measurements of the flow behaviour of trace particles suspended in pure water and RBCs in concentrated suspensions were performed in the surroundings of a confluence. After performing simulations with the commercial finite element software package POLYFLOW®, some experimental results were compared with the numerical ones. Experimental results for pure water were in a good agreement with numerical results. Overall, the RBCs velocities were higher than those for fluorescent particles which suggest that RBC deformability and cell-free layer formation around the apex of the confluence may play an important role on the observed deviations
