The motion of close-packed red blood cells in shear flow

Experimental and theoretical results are presented concerning the motion of close-packed red blood cell suspensions subjected to steady simple shear flow. The behavior of the suspension was observed microscopically using a cone-and-plate rheoscope. At moderate and high shear rates the cells show a fairly orderly arrangement, each appearing polygonal in the field of view. An idealized theoretical model for the suspension is developed, in which each cell is a 14-sided polyhedron of varying shape, but with constant surface area and volume. Tank-treading motion of the membrane is predicted, and an approximation to the motion is calculated which is consistent with the known mechanical properties of the membrane. It is shown that considerably more energy is dissipated in the membrane than in the cytoplasm during tank-treading.