Plasma and platelet skimming at T-junctions.

Separation of plasma, erythrocytes, and platelets was studied in T-shaped bifurcations prepared by a casting technique. The diameters of the side and main channel were 100 microns and 200 microns, respectively. Small blood samples (about 20 microliters) were collected from the side channel for determination of erythrocyte and platelet concentrations which were compared to the corresponding values in the reservoir. Conversely to the well-known erythrocyte reduction due to plasma skimming a relative enrichment of platelets in the side branch was observed. The thickness of the plasma layer in the main channel was found to depend on the aggregation tendency of the erythrocytes for Reynolds numbers around 0.3.