分叉微流管中多微胶囊流动与分离规律的三维数值研究

Liquid-filled microcapsule (or called microcapsule) consists of a micro droplet enclosed by a very thin elastic membrane. Red blood cells are typical microcapsules. This specific structure provides potential protection of internal effective medium, and the ability of large deformations allows it to flow fluently through a microfluidic channel and to realize targeted delivery. It has been widely applied in many areas, e.g., in the design of controlled release drug and in the development of functional materials. The complex flow of microcapsules through a bifurcating channel is a fundamental phenomenon in human's microcirculation, and it is also highly associated with the design of microfluidc channel system for cells sorting or size classification of artificial microcapsules. Thus, this project focuses on the dynamical mechanism in the motion and separation of liquid-filled microcapsules through a bifurcating channel. We firstly develop a three-dimensional numerical model (coupled by boundary integral method and finite element method) to simulate the motion and deformation of this sophisticated system involving fluid-structure and multi-body interactions under complex boundary conditions. Thereafter, numerical simulations are carried out on the flow of multi microcapsules inside a cylindrical channel (part of a bifurcating one), with the aim of seeking rational explanations for slipper-shape puzzle and zipper-type flow which are frequently observed in experiments. And then, numerical simulations are also implemented on the motion and separation of microcapsules through a bifurcating channel, the dynamical mechanism will be summarized based on the numerical results. The achievement of this project would promote the numerical study of microcapsule flow, enrich the theories in blood rheology, and provide more theoretical support for the design of functional microfluidic systems.

充液微胶囊(简称微胶囊)是由一层极薄的固体弹性薄膜包裹微液滴而形成的微米级细容器。红细胞是典型的天然微胶囊。该柔性结构能有效隔离外界环境，在狭窄微流管中顺畅变形与流动，被广泛用于内容物可控释放、新材料研制等方面。分叉微流管中微胶囊的大变形流动，不仅与血液微循环密切相关，而且是构建细胞分选、微胶囊分类等功能化微流管系统的基础。本项目拟采用边界积分结合有限元的耦合方法建立三维数值模型，展开数值模拟，探索分叉微流管中多微胶囊流动与分离规律。首先建立复杂边界条件下大变形流固耦合系统运动的三维数值模型；然后模拟微流直管段中多微胶囊流动现象，揭示流动形式的形成机理，解释“拖鞋状谜题”和拉链式流动等实验难解现象；然后模拟分叉微流管中多微胶囊流动和分离现象，揭示分离机理并总结规律。本项目的完成，能促进本领域内三维数值模型的发展，丰富血液流变学基础理论，为构建用于微胶囊分类的功能化微流管系统提供理论支撑。

本项目以微流管中微胶囊流动和分离现象为研究对象，对复杂边界条件下单(多)相流的三维数值建模展开系统研究，对微流道中微胶囊的流动变形展开数值模拟。研究结果在一定程度上解释了拖鞋状形变的形成机理，为微胶囊流动分析技术提供了坚实的理论基础；项目建立的计算流体力学数值模型，被成功地用于分析酶膜反应器、燃料电池、液压机械等工程设备内的多相流动现象，具备一定实际应用价值。