Flow patterns in a platelet adhesion test cell - Implications for adhesion measurement

Flow patterns in a test cell used by Lyman et al. (1) to study adhesion of platelets to polymer surfaces were determined using a tracer particle technique. Flow was found to be characterized by low average shear rate of the order of 3 to 4 sec−1 and by vortex formation at the entrance to the cell. The vortices, however, would not have impinged on the surface regions where platelet adhesion was measured. The implications of these results for the platelet adhesion data obtained with this cell are that flow conditions were mild, rouleaux were present and red cell motions were minimal. Insofar as these motions can be critical for platelet transport and the provision of energy for surface reaction, the adhesion process was probably dominated by the platelet-surface forces. By contrast the data of Friedman et al. (2,16), obtained at higher shear rates could have been dominated by red cell motions leading to independence of adhesion on surface properties.