Biomedical Engineering Reference
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Fig. 9.8 Labelled RBC trajectory at diluted suspensions of cells (3 % Hct) obtained by the
proposed confocal micro-PTV system (adapted from [ 26 ])
The ability of the confocal system to generate thin in-focus planes has allowed
both qualitative and quantitative measurements in flowing blood at concentrated
suspensions (up to 35% Hct) of: cell-cell hydrodynamic interaction, RBC orienta-
tion and RBC radial dispersion at different depths. Hence, to evaluate the capability
of the confocal micro-PTV system to track RBCs, motions of labelled RBCs were
followed at several Hcts (3-37%). The measurements of complex micro-
rheological events in flowing blood (such as interaction and orientation of blood
cells) were performed near the wall of the micro-channel ( z
ΒΌ 20
m m) with
Hct ~ 20% and Re ~0.007.
9.4.3.1 RBC-RBC Interactions in Flowing Blood
The effect of hemodynamic interactions on the motion of RBCs depend on
multi-physics factors, such as shear rate, deformability, plasma layer and wall
constriction. Figure 9.11 shows the trajectories of two-RBC interactions close to
the cell-free layer. This figure shows clearly the radial disturbance effect enhanced
by the collision of a neighbouring RBC. The radial displacement (
R ) of the RBCs
increases from two to six times of its initial radial displacement. For the case
of RBC1,
D
R continues to increase, due not only to the interaction above but also
to others which may occur with neighbouring cells.
D
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