Confocal Micro-PIV/PTV Measurements of the Blood Flow in Micro-channels - Bioanalysis Advanced Materials Methods and Devices - page 142

Fig. 9.16 Effect of the microtube geometry on the RBC D yy (adapted from [ 29 ])
capillary tube. The results demonstrated significant enhancement of the particle diffu-
sion, due to a micron-scale flow-field generated by the RBC motions, whereas the
dispersion of tracer particles was about 0.7 times that of RBCs. The results also showed
that by increasing the flow rate particle dispersion tends to increase almost linearly
under constant Hct levels. Moreover, the particle dispersion showed near linear depen-
dency on Hct up to 20%.
9.4.3.5 Effect of Hct on the Cell-free Layer (CFL)
Recent studies have investigated the Hct effect on the cell-free layer (CFL) thick-
ness of both straight circular glass and PDMS micro-channels [ 8 , 10 , 33 ]. Labelled
RBCs flowing near the CFL were tracked manually by using the MtrackJ plugin
from Image J. Figure 9.17 gives an example of two trajectories of labelled RBCs
flowing at the edge of the CFL. By using MtrackJ, the positions of the tracked RBCs
are measured and the average thickness of the CFL is calculated [ 8 , 10 , 30 , 33 ].
Examination of Fig. 9.18 reveals an overall enhancement of the CFL thickness
as Hct decreases. For the case of the PDMS micro-channel, the CFL thickness
decreases almost four fold as Hct is increased from 3 to 37% [ 30 , 33 ]. The results are
clear evidence that the CFL thickness tends to reduce as the diameter of the micro-
channel decreases.