Cell Exclusion in Couette Flow: Evaluation Through Flow Visualization and Mechanical Forces
Cell Exclusion in Couette Flow: Evaluation Through Flow Visualization and Mechanical Forces
复制标题
DOI：
10.1111/j.1525-1594.2012.01561.x
复制
发表时间：
2013-03-01
影响因子：
2.4
通讯作者：
Tansley, Geoff D.
中科院分区：
文献类型：
--
作者：
Leslie, Laura J.;Marshall, Lindsay J.;Tansley, Geoff D.
细胞排斥是一种现象，即红细胞比容和血液粘度在高应激区域下降。虽然这在人体内自然发生的泊泽维尔流中是众所周知的，但以前从未在库埃特流中发现过，库埃特流发生在包括血泵在内的植入式设备中。高剪切应力发生在边界之间的间隙在库埃特流是已知的导致红细胞溶血。我们建议通过使用螺旋槽轴承（SGB）启动细胞排斥来减轻这种损害，该轴承将提供逃逸路线，使细胞可以从等离子体和间隙中的高应力中分离出来。测量了Couette流中两个轴承（其中一个为SGB）之间的力。在不同间隙高度的透明SGB上可见染色的红细胞，以及与红细胞直径相似的银球。研究发现，与粘度相当的液体相比，人体血液在轴承上的作用力有所降低。这表明由于细胞排斥导致红细胞压积降低，导致流体在轴承上的粘度降低。相应的图像清楚地显示细胞和球体通过进入凹槽而被排除在间隙之外。这是第一次在库埃特流中发现细胞排斥现象。它不仅进一步加深了我们对血液对不同流量的反应的理解，而且还可能导致未来医疗设备设计的改进。
Cell exclusion is the phenomenon whereby the hematocrit and viscosity of blood decrease in areas of high stress. While this is well known in naturally occurring Poiseuille flow in the human body, it has never previously been shown in Couette flow, which occurs in implantable devices including blood pumps. The high-shear stresses that occur in the gap between the boundaries in Couette flow are known to cause hemolysis in erythrocytes. We propose to mitigate this damage by initiating cell exclusion through the use of a spiral-groove bearing (SGB) that will provide escape routes by which the cells may separate themselves from the plasma and the high stresses in the gap. The force between two bearings (one being the SGB) in Couette flow was measured. Stained erythrocytes, along with silver spheres of similar diameter to erythrocytes, were visualized across a transparent SGB at various gap heights. A reduction in the force across the bearing for human blood, compared with fluids of comparable viscosity, was found. This indicates a reduction in the viscosity of the fluid across the bearing due to a lowered hematocrit because of cell exclusion. The corresponding images clearly show both cells and spheres being excluded from the gap by entering the grooves. This is the first time the phenomenon of cell exclusion has been shown in Couette flow. It not only furthers our understanding of how blood responds to different flows but could also lead to improvements in the future design of medical devices.