颗粒在确定性侧向迁移装置中的流动和分离

Separation of cells and particles plays an important role in microfluidic systems. The Deterministic Lateral Displacement (DLD) device, introduced by Sturm's group in Princeton University as a continuous separation method, is quite impressive in terms of speed and resolution despite the extreme concentration difference. This method is based on inherent properties of the particles and device, and no treatment is required before the test. Separation occurs if, under careful design, the larger particles are travelled diagonally through the device, which is called "direction rocking mode", while the small particles are followed the streamline and so called "zig-zag mode". To the deformable particles, several flow patterns have been found in the laboratory. Also, significant separation between red blood cell and parasitic protozoa of the Trypanosoma brucei has been found by optimizing the depth of the channel of DLD device. In this proposal, first, the rigid particle flow and separation in the DLD device will be studied by the Distributed Lagrange Multiplier based Fictitious Domain method (DLM/FD). The empirical equation for the critical diameter of the particle from fitting of the experiment results by Davis will be examined and be generalized. Secondly, separation in the triangular or rectangular obstacles will be investigated. Thirdly, for the deformable particles, we will focus on the flow patterns of non-spherical particles, such as erythrocytes and parasites. The wall effect to the separation will also be studied. The results achieved by this proposal can be used to enhance the design of the DLD device.

粒子分离是微流控芯片中的关键技术。确定性侧向迁移装置作为一种不需要预处理的连续分离方法，具有速度快，精度高，不受粒子组分浓度差异的影响等优点，具有广泛的应用前景。然而目前实验装置的设计主要依靠经验，尚缺乏理论指导。本项目的研究内容包括: 1）通过研究刚性球形颗粒在圆柱阵列中的运动特性，得到临界直径跟槽道参数之间的定量关系，推广Davis等人从实验中得到的拟合公式；2）研究三角形，长方形等非轴对称障碍物阵列对颗粒分离的影响；3）研究红细胞，布氏锥虫等柔性粒子在侧向迁移装置中的运动特性，并分析壁面对分离效果的影响。本项目的研究成果将为更有效地设计侧向迁移装置提供支持。

确定性侧向迁移分离技术（Deterministic lateral displacement , DLD）是近几年出现的一种基于颗粒不同尺寸，来连续、高效分离微纳米尺度颗粒的新技术，该技术对于分离浓度差比例悬殊的颗粒（比如血液中的白细胞和红细胞，寄生虫和红细胞等），与传统的方法相比具有很大的优势。目前关于该技术国外已经开展了很多的实验研究和少量的数值研究，但是目前关于颗粒的变形、形状和取向等对颗粒在DLD中运动有着重要影响的因素研究较少。本项目采用高精度直接数值模拟的方法（DLM/FD：任意拉格朗日乘子/虚拟区域法），对刚性颗粒、柔性颗粒在确定性侧向迁移装置内的流动和分离进行了较为系统的研究，分析了颗粒属性对DLD分离性能的影响，包括：颗粒变形特性、颗粒形状、颗粒取向。并研究了柱列参数:几何布置参数和柱列形状对颗粒运动的影响，为大浓度比生物颗粒的高效分离装置的优化设计提供有力的技术支撑，具有较大的学术价值和应用前景。