Zhou Ronghui, Chang Hsueh-Chia
Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN 46556, USA.
J Colloid Interface Sci. 2005 Jul 15;287(2):647-56. doi: 10.1016/j.jcis.2005.02.023.
Blood suspension fails to penetrate a capillary with radius R less than 50 microm even if the capillary is perfectly wettable. This invasion threshold is attributed to three red blood cells (RBCs) segregation mechanisms--corner deflection at the entrance, the intermediate deformation-induced radial migration and shear-induced diffusion within a packed slug at the meniscus. The shear-induced radial migration for deformable particles endows the blood cells with a higher velocity than the meniscus to form the concentrated slug behind the meniscus. This tightly packed slug has a higher resistance and arrests the flow. Rigid particles and rigidified blood cells result in wetting behavior similar to that seen for homogeneous liquids, with decreased RBC migration towards the capillary centerline and reduction of packing. Corner deflection with a radial drift velocity accelerates the radial migration for small capillaries. However, deformation-induced radial migration is the key mechanism responsible for penetration failure. This sequence of mechanisms is confirmed through videomicroscopy and scaling theories were applied to capture the dependence of the critical capillary radius as a function of RBC concentrations.
即使毛细血管具有完全可润湿性，血液悬浮液也无法穿透半径小于50微米的毛细血管。这种侵入阈值归因于三种红细胞（RBC）分离机制——入口处的角偏转、中间变形诱导的径向迁移以及弯月面处填充段塞内的剪切诱导扩散。可变形颗粒的剪切诱导径向迁移使血细胞具有比弯月面更高的速度，从而在弯月面后方形成浓缩段塞。这个紧密填充的段塞具有更高的阻力并阻止流动。刚性颗粒和僵化的血细胞导致的润湿行为类似于均匀液体，红细胞向毛细血管中心线的迁移减少且堆积减少。具有径向漂移速度的角偏转加速了小毛细血管中的径向迁移。然而，变形诱导的径向迁移是导致渗透失败的关键机制。通过视频显微镜证实了这一机制序列，并应用标度理论来捕捉临界毛细血管半径与红细胞浓度的函数关系。
