The deformation of red blood cells (RBCs) in Poiseuille flows of capillary vessels is fundamental for hemodynamics in cellular scale for various physiological or pathological scenarios. However, the mechanical criterion for membrane buckling and the impact of the asymmetric deformations of cells on the hemodynamics are currently unclear. In this study, a microfluidic system with narrow tubular channels was set up for experimental observations, and numerical simulations using the immersed boundary method were performed to illustrate the deformation of RBCs and their surrounding flow fields in detail. The dependence of the buckling on the capillary number (a dimensionless parameter measuring the ratio of viscous fluid force with elastic force of membrane) was discovered. Then we derived the criterion of buckling of cell membrane under local circumferential pressure by considering the buckling of an elastic ring with neglecting thickness. Results also show that the extra pressure drop and the wall shear stress associated with the appearance of membrane buckling increase nonlinearly. This work provides biomechanical fundamentals for mechanobiological studies of microvascular disease associated with the change of mechanical properties of RBCs.

中文翻译：

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狭窄毛细血管中红细胞膜的屈曲会引起过大的壁剪切应力


毛细血管泊沙叶流中红细胞 （RBC） 的变形是各种生理或病理情况下细胞尺度血流动力学的基础。然而，膜屈曲的力学标准和细胞不对称变形对血流动力学的影响目前尚不清楚。在本研究中，建立了一个具有窄管状通道的微流控系统进行实验观察，并使用浸没边界法进行数值模拟，以详细说明 RBC 及其周围流场的变形。发现了屈曲对毛细管数（测量粘性流体力与膜弹性力之比的无量纲参数）的依赖性。然后，我们通过考虑忽略厚度的弹性环的屈曲，推导出了细胞膜在局部圆周压力下屈曲的准则。结果还表明，与膜屈曲外观相关的额外压降和壁面剪切应力呈非线性增加。这项工作为与红细胞机械性能变化相关的微血管疾病的机械生物学研究提供了生物力学基础。