Biofluid Simulation and Modeling, Theoretische Physik, Universität Bayreuth, Germany.
Soft Matter. 2018 Mar 14;14(11):2032-2043. doi: 10.1039/c7sm02272g.
Red blood cells flowing through capillaries assume a wide variety of different shapes owing to their high deformability. Predicting the realized shapes is a complex field as they are determined by the intricate interplay between the flow conditions and the membrane mechanics. In this work we construct the shape phase diagram of a single red blood cell with a physiological viscosity ratio flowing in a microchannel. We use both experimental in vitro measurements as well as 3D numerical simulations to complement the respective other one. Numerically, we have easy control over the initial starting configuration and natural access to the full 3D shape. With this information we obtain the phase diagram as a function of initial position, starting shape and cell velocity. Experimentally, we measure the occurrence frequency of the different shapes as a function of the cell velocity to construct the experimental diagram which is in good agreement with the numerical observations. Two different major shapes are found, namely croissants and slippers. Notably, both shapes show coexistence at low (<1 mm s) and high velocities (>3 mm s) while in-between only croissants are stable. This pronounced bistability indicates that RBC shapes are not only determined by system parameters such as flow velocity or channel size, but also strongly depend on the initial conditions.
由于其高变形能力，流经毛细血管的红细胞呈现出多种多样的不同形状。预测实际形状是一个复杂的领域，因为它们是由流动条件和膜力学之间的复杂相互作用决定的。在这项工作中，我们构建了具有生理粘度比的单个红细胞在微通道中流动的形状相图。我们使用实验体外测量和 3D 数值模拟来相互补充。在数值上，我们可以轻松控制初始起始配置并自然访问完整的 3D 形状。有了这些信息，我们可以获得作为初始位置、起始形状和细胞速度函数的相图。在实验上，我们测量不同形状的出现频率作为细胞速度的函数，以构建实验相图，该相图与数值观察结果非常吻合。发现了两种主要的形状，即羊角面包和拖鞋。值得注意的是，两种形状都在低（<1mm/s）和高速度（>3mm/s）下共存，而在中间只有羊角面包是稳定的。这种明显的双稳定性表明，RBC 形状不仅由流速或通道尺寸等系统参数决定，而且还强烈依赖于初始条件。
