Michael Hill, M. Hill & Associates, PO Box 622, Wyckoff, NJ 07481 and Edward F. Leonard, Chemical Engineering, Columbia University, 500 W. 120th St., 801 Mudd Dept of Chemical Engineering, New York, NY 10027.
Nanoporous membranes with precise, short pores and high void fractions are becoming available. Their use in blood filtration strains assumptions inherent in existing theories, introduces design challenges because of the very low hydraulic resistance of the membrane-proper, and provides new insights into several aspects of blood flow in narrow spaces. These aspects include the balance among shear-induced motion away from the filtering surface, convection toward the surface, and shear-enhanced diffusion, as well as the role of erythrocyte motion on the transverse motion of leukocytes and thrombocytes. Different pore sizes in the range 450 to 1200 nm (1.2 um) elicit different behavior of cells adjacent to the filtering surface. Direct observation of cell behavior is accomplished at low hematocrits and is augmented by measurement of transmembrane electrical resistance, allowing extension of measurements to suspensions with higher hematocrits.