Fluidics of micro-capsules in shear flow: Dynamical shape transformations and role of membrane roughness

本文对外剪切流中微胶囊的流体学进行了理论分析。微胶囊是一种薄的中空弹性胶囊，可以是人工制备的聚酰胺胶囊和聚电解质壳体，也可以是自然界中存在的红细胞等。这些胶囊在流体动力流动中变形取决于它们的粘弹性性质。对于无限剪切流中的微胶囊，我们将重点讨论非零弯曲刚度对实验观察到的剪切诱导皱缩的作用。对于在纳米尺度上与基质相互作用的微胶囊，将研究限制几何的作用。引起弹性变形的引力相互作用和流动诱导的流体动力升力之间的竞争，既取决于这种变形，也取决于衬底和胶囊之间的薄润滑层，可以导致动态解结合转变。作为方法，我们将使用球形小偏差的分析方法和数值边界积分技术，该技术将全部流体动力学结合到胶囊形状的非局部运动方程中，对于该胶囊形状，膜的分子结构进入边界条件。

This proposal deals with a theoretical analysis of the fluidics of micro-capsules in external shear flow. Micro-capsules are thin hollow elastic capsules either prepared artificially such as polyamid capsules and polyelectrolyte shells or occuring in nature such as red-blood-cells. These capsules deform in hydrodynamic flow depending on their visco-elastic properties. For micro-capsules in unbounded shear flow, we will focus on the role of a non-zero bending rigidity for the experimentally observed shear-induced crumpling. The role of a confining geometry will be studied for micro-capsules interacting on nano-scales with a substrate. The competition between attractive interactions causing elastic deformations and the flow-induced hydrodynamic lift, which depends both on this deformation and the thin lubricating layer between substrate and capsule, can lead to a dynamical unbinding transition. As methods, we will use both an analytical approach for small deviations from a spherical shape and a numerical boundary-integral technique which incorporates the full hydrodynamics into a non-local equation of motion for the capsule shape for which the molecular architecture of the membrane enters the boundary conditions.