Fundamental Study of Nonlinear Electrokinetic Phenomena in Insulator-based Dielectrophoretic Microdevices

介电泳（DEP）在操纵微米/纳米尺寸的颗粒（例如，细胞、珠子、病毒、DNA和蛋白质分子）。基于绝缘体的介电电泳（iDEP）利用绝缘结构，如障碍物，柱子和脊，来捕获，浓缩，分离和分选颗粒。与传统的基于电极的介电电泳（eDEP）相比，iDEP微器件具有制作简单、性能稳定等优点。然而，通道内绝缘结构的存在导致两种现象，这两种现象可能强烈地干扰流动并且抑制或增强iDEP微器件中的颗粒操纵。这些现象是：由于绝缘体周围的流体中的放大焦耳加热而产生的电渗流，以及由于绝缘体的电极化而产生的感应电荷电渗（ICEO）流。由于整个器件中发生的热扩散或电场泄漏，对这两种现象的准确理解变得非常复杂。该项目旨在开发一种广义深度平均模型，用于iDEP微器件中非线性电动现象的基础研究。所提出的模型将大大减少预测iDEP设备中的粒子操纵性能的计算成本。它也将作为一个有效的和准确的工具，优化设计和控制的广泛类电动微流体装置与浅通道的几何形状。这项研究将密切编织到本科和研究生教育在克莱姆森大学和高中外展在南卡罗来纳州。本科生和高中生将积极参与部门，大学和国家提供的各种方案，重点是纳入妇女和代表性不足的少数民族。该项目将是iDEP微器件中非线性电动现象的第一个全面的基础研究。据推测，非线性ICEO和CO2流分别在低和高离子浓度流体中占主导地位，并且在中间离子浓度流体中可以相互抑制。本文将对浅微通道中的电动流动进行温度耦合的热、流体和电荷输运方程的渐近分析。深度平均模型将开发的渐近分析的基础上，模拟典型的iDEP微器件的温度，流场和电场的发展，同时考虑焦耳加热和感应电荷效应。将在绝热结构附近测量流体温度场和速度场。深度平均模型的有效性将通过将其预测与三维全尺寸数值模拟和实验数据进行比较来评估。所获得的非线性电动现象的基础知识将建立一个传热和流体力学框架的iDEP微器件。

Dielectrophoresis (DEP) is very useful in manipulating micro/nano-sized particles (e.g., cells, beads, viruses, DNA and protein molecules). Insulator-based dielectrophoresis (iDEP) exploits insulating structures, such as hurdles, posts and ridges, to trap, concentrate, separate and sort particles. Compared to the traditional electrode-based dielectrophoresis (eDEP), iDEP microdevices have the advantages of easy fabrication and robust performance. However, the presence of in-channel insulating structures cause two phenomena that may strongly disturb the flow and either suppress or enhance the particle manipulation in iDEP microdevices. These phenomena are: the electrothermal flow due to the amplified Joule heating in the fluid around the insulators, and the induced charge electroosmotic (ICEO) flow due to the electrical polarization of the insulators. An accurate understanding of either phenomenon is significantly complicated by the thermal diffusion or electric field leakage that occurs in the entire device. This project seeks to develop a generalized depth-averaged model for the fundamental study of nonlinear electrokinetic phenomena in iDEP microdevices. The proposed model will substantially reduce the computational cost for predicting the particle manipulation performance in iDEP devices. It will also serve as an efficient and accurate tool for the optimal design and control of a wide class of electrokinetic microfluidic devices with shallow-channel geometries. This research will be intimately weaved into the undergraduate and graduate educations at Clemson University and the high school outreach in South Carolina. Undergraduate and high school students will be actively involved through various programs available in the department, university, and state with emphasis on the inclusion of women and underrepresented minorities. This project will be the first comprehensive fundamental study of nonlinear electrokinetic phenomena in iDEP microdevices. It is hypothesized that the nonlinear ICEO and electrothermal flows are dominant in low and high ionic concentration fluids, respectively, and can suppress each other in an intermediate ionic concentration fluid. An asymptotic analysis of the temperature-coupled heat, fluid and charge transport equations will be performed for electrokinetic flow in shallow microchannels. A depth-averaged model will be developed based on the asymptotic analysis to simulate the development of temperature, flow and electric fields in typical iDEP microdevices with consideration of both Joule heating and induced charge effects. The fluid temperature and velocity fields will be measured near the insulating structures. The validity of the developed depth-averaged model will be assessed by comparing its predictions with both 3D full-scale numerical simulations and experimental data. The acquired fundamental knowledge of nonlinear electrokinetic phenomena will establish a heat transfer and fluid mechanics framework for iDEP microdevices.