Shear-induced gradient diffusivity of a red blood cell suspension: effects of cell dynamics from tumbling to tank-treading
Shear-induced gradient diffusivity of a red blood cell suspension: effects of cell dynamics from tumbling to tank-treading
复制标题
红细胞悬浮液的剪切诱导梯度扩散：细胞动力学从翻滚到踩罐的影响
DOI：
10.1039/d1sm00938a
复制
发表时间：
2021
期刊：
影响因子：
3.4
通讯作者：
Sarkar, Kausik
中科院分区：
文献类型：
--
作者：
Malipeddi, Abhilash Reddy;Sarkar, Kausik
流体动力相互作用在剪切流中产生颗粒的扩散运动，这在整体颗粒流变学及其微观结构中发挥着重要作用。在这里，我们使用数值模拟来研究红细胞 (RBC) 悬浮液中剪切诱导的扩散，解决红细胞的个体运动和变形。红细胞的非球形静止形状在剪切流中产生性质不同的细胞动力学状态，例如坦克踩踏、呼吸、翻滚和摆动，具体取决于由弹性毛细血管数决定的细胞灵活性。我们表明，从翻滚到坦克踩踏的转变会导致梯度扩散率降低。扩散率是使用连续体方法根据随机堆积的细胞层宽度随时间的演变以及悬浮液的动态结构因子来计算的。两种方法虽然操作上不同，但匹配并表明，对于中间毛细管数量，红细胞停止翻滚，并伴随着梯度扩散系数的下降。毛细管数量的进一步增加由于变形的增加而增加了扩散率。还简要研究了弯曲模量和粘度比变化的影响。将计算出的剪切诱导扩散率与文献中的值进行比较。除了对血流中的细胞边缘化和在医学诊断中的使用产生影响外，这种现象还为具有非球形平衡形状的可变形颗粒的悬浮液提供了重要的见解，这也可以在利用颗粒灵活性进行无标记分离或材料加工等应用中发挥关键作用。
Hydrodynamic interactions generate a diffusive motion in particulates in a shear flow, which plays seminal roles in overall particulate rheology and its microstructure. Here we investigate the shear induced diffusion in a red-blood cell (RBC) suspension using a numerical simulation resolving individual motion and deformation of RBCs. The non-spherical resting shape of RBCs gives rise to qualitatively different regimes of cell dynamics in a shear flow such as tank-treading, breathing, tumbling and swinging, depending on the cell flexibility determined by the elastic capillary number. We show that the transition from tumbling to tank-treading causes a reduction in the gradient diffusivity. The diffusivity is computed using a continuum approach from the evolution of a randomly packed cell-layer width with time as well as by the dynamic structure factor of the suspension. Both approaches, although operationally different, match and show that for intermediate capillary numbers RBCs cease tumbling accompanied by a drop in the coefficient of gradient diffusivity. A further increase of capillary number increases the diffusivity due to increased deformation. The effects of bending modulus and viscosity ratio variations are also briefly investigated. The computed shear induced diffusivity was compared with values in the literature. Apart from its effects in margination of cells in blood flow and use in medical diagnostics, the phenomenon broadly offers important insights into suspensions of deformable particles with non-spherical equilibrium shapes, which also could play a critical role in using particle flexibility for applications such as label free separation or material processing.