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Abstracts: ASAIO Bioengineering/tissue Engineering Abstracts

MICROSCOPIC FLOW VISUALIZATION OF RED BLOOD CELL TRAJECTORY IN THE BLADE TIP AND BACK CLEARANCE OF A MINI BLOOD PUMP

Antaki, James F1; Diao, Chenguang1; Wu, Jingchun2; Borovetz, Harvey S3; Wagner, William3; Snyder, Trevor3

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A persistent challenge to quantitative design of rotating blood pumps is the great disparity of spatial scales between the primary flow paths and microscopic clearance regions. Flow gaps within journals and blade tips are often on the order of a few cells, confounding the application of macroscopic continuum models. Yet, precisely in these regions exist the highest shear most likely to cause cellular trauma. This study is to determine the kinematics of cellular deformation and screening within small clearances of a small VAD. A transparent model of a centrifugal pump (46mm dia.) with an adjustable tip clearance (0∼200 μm) was developed. Microscopic imaging of the blood cells in the tip and back clearances was achieved with a custom designed visualization system, consisting of inverted microscope fitted with 40x objective, Nd:YAG laser and high resolution CCD camera. The acquisition of the blood cell image in the tip clearance was synchronized to the impeller rotation. The cellular deformation vs. gap dimension was thus determined. Experiments with 6μm fluorescent particles were generally in agreement with the corresponding CFD simulation. However, studies with diluted porcine blood revealed the unique features of the cellular deformation, screening, and trajectory that occur in small clearances. As the gap reduces to zero, virtually all cells are excluded from the gap, suggesting a mechanism by which hydrodynamic film bearings may avoid catastrophic hemolysis.

Copyright © 2005 by the American Society for Artificial Internal Organs