Resistance to the Brownian movement of red blood cells on flat horizontal surfaces.

The movements of red blood cells (RBC), suspended in plasma, on plastic, glass, rhodium metal plate, siliconized glass, and siliconized rhodium were recorded on ciné-film and analyzed. Values for the drag coefficient were calculated, using Einstein's theory on Brownian movement, and compared with the theoretical Stokes' hydrodynamic drag. The difference between the computed and Stokes' values gave the frictional coefficient or resistance resulting from the interaction of the cells with the test surface. Of the three uncoated test surfaces, plastic was found to have the least interaction with the RBC. The frictional coefficient for plastic was found to be 1.75 X 10(-7) N s m-1 compared with a value of 2.82 X 10(-7) N s m-1 for rhodium metal, which had the largest interaction. Upon siliconization of the test surfaces, the interaction decreased by 40%. Reduction in the pH of the suspending plasma increased the interaction between the cells and the uncoated test surfaces, but the pH effect diminished when the surfaces were siliconized.