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 引用本文: 蔡文莱, 黄亚军, 刘伟阳, 彭浩宇, 黄志刚. 柔性微粒介电泳分离过程的多尺度模拟[J]. 力学学报, 2019, 51(2): 405-414.
Wenlai Cai, Yajun Huang, Weiyang Liu, Haoyu Peng, Zhigang Huang. MULTISCALE SIMULATION OF THE DIELECTROPHORESIS SEPARATION PROCESS OF FLEXIBLE MICROPARTICLE[J]. Chinese Journal of Theoretical and Applied Mechanics, 2019, 51(2): 405-414.
 Citation: Wenlai Cai, Yajun Huang, Weiyang Liu, Haoyu Peng, Zhigang Huang. MULTISCALE SIMULATION OF THE DIELECTROPHORESIS SEPARATION PROCESS OF FLEXIBLE MICROPARTICLE[J]. Chinese Journal of Theoretical and Applied Mechanics, 2019, 51(2): 405-414.

## MULTISCALE SIMULATION OF THE DIELECTROPHORESIS SEPARATION PROCESS OF FLEXIBLE MICROPARTICLE

• 摘要: 介电泳分离是一种高效的微细颗粒分离技术,利用非均匀电场极化并操纵分离微流道中的颗粒. 柔性微粒在介电泳分离过程中同时受多种物理场、多相流和微粒变形等复杂因素的影响,仅用单一的计算方法对其进行模拟存在一定的难度,本文采用有限单元——格子玻尔兹曼耦合计算的方法处理这一难题.介观尺度的格子玻尔兹曼方法将流体看成由大量微小粒子组成,在离散格子上求解玻尔兹曼输运方程,易于处理多相流及大变形问题,特别适合模拟柔性颗粒在介电泳分离过程中的变形情况.另一方面,介电泳分离过程的模拟需求解流体、电场和微粒运动方程,计算量相当庞大,通过有限单元法求解介电泳力,提高计算效率.利用这种多尺度耦合计算方法,对一款现有的介电泳芯片分离过程进行了模拟.分析了微粒在电场作用下产生的介电泳力,揭示了介电泳力与电场变化率等因素之间的关系.对微粒运动轨迹及其变形的情况进行了研究,发现微粒的变形主要与流体剪切作用有关.这种多尺度耦合计算方法,为复杂微流体的计算提供了一种有效的解决方案.

Abstract: Dielectrophoresis field flow fraction (DEP-FFF) is an efficient method for the separation of micro particles, in which the particles in micro channels are polarized and controlled to separate via a non-uniform electric field. The separation of flexible particles in DEP-FFF are influenced by many complex factors including multiphysics effects, multiphase flows and particle deformation. It is difficult to simulate the process with a single calculation method. In this paper, a finite element-lattice Boltzmann coupling method is introduced to solve this problem. The lattice Boltzmann is a mesoscopic method, in which the micro volumes of a fluid are represented with small particles. The Boltzmann transport equation for fluid dynamics is solved on discrete lattice, such that the multiphase flows and large deformation problems can be easily handled. Due to these advantages, the particle deformation in the DEP-FFF process can be readily handled by the lattice Boltzmann method. On the other hand, the simulation of the total DEP-FFF process requires the solution of the Navier-Stokes equation, dielectrophoresis force equation and particle trajectory equation. The computational burden will be very severe if only the lattice Boltzmann method is employed. By computing the dielectrophoresis force with finite element method, the computational efficiency is significantly improved. The finite element-lattice Boltzmann coupling method is applied in the simulation of the particle separation process within a typical DEP-FFF chip. Analyzing the dielectrophoresis force on the particles produced by the non-uniform electric field, the relationship between the dielectrophoresis force and the change rate of electric field is revealed. The trajectories of the particles under different electric conditions are traced to validate the efficiency of the DEP-FFF method. Most importantly, the deformations of the particle under the non-uniform electric filed are analyzed. It is found that the change of the particle trajectory is controlled by the dielectrophoresis force and thus the non-uniform electric field, while the deformation of the particle is mainly related to the shearing effect of the flows. The finite element-lattice Boltzmann multiscale coupling method introduced in this paper provides an effective solution for the calculation of complex micro flows.

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