RED BLOOD CELL GHOSTS FLOW IN MICRO CHANNEL

International audienceOptical characterization of high hematocrit whole blood flows in small to medium size vessels are of particular interest in many patho-physiological conditions. However, such characterizations remain challenging because of the optical properties of blood. Blood is a complex multiphasic fluid and its optical and rheological properties are governed by interactions between red blood cells (RBC) and plasma. In particular the transmission characteristics of such a suspension is ruled by the combined effect of absorption from some molecules and scattering from the cells. These combined effects make it globally difficult to image RBC at high hematocrit in depth larger than a few 10th of micrometers limiting therefore the studies to small size vessels or to wall regions . Major rheological and fluid mechanical behaviors are therefore not accessible with traditional laboratory instrumentation. As an example, the blunting of the velocity profile is a known effect in physiological high hematocrit flow conditions. Such a deviation from the traditionally accepted Poiseuille theory has a major consequence on the local flow conditions (shear rate/stress) and can hardly be observed because of the aforementioned limitations. To overcome such problems, transparent suspensions can be prepared by using RBC ghosts (i.e. hemoglobin free RBC) [1]. By such a technique one can obtain a transparent high hematocrit mixture that can be imaged over large depth of flow (Figure 1, right) in which high precision microscopic particle image velocimetry flow field measurements (microPIV) can be performed. To demonstrate this capacity and to have a close insight in the flow of a blood mimicking fluid in vessels larger than previously reported in the literature are the goals of this work