Collaborative Research: Concentration Polarization Induced Electrokinetic Flows around dielectric Surfaces

微流控系统在临床诊断、药物发现、化学和生物病原体检测、免疫分析、快速化学分析、生物防御等领域有着广泛的应用。最近的实验发现了一种新型的流体在电场作用下围绕带电介质表面流动。假设这些流动是由介电表面周围的浓度极化效应引起的。这种浓度极化诱导流可以很容易地通过调整介质结构和流体的性质来控制。这一特点保证了微流体流动控制的通用技术，包括泵送和混合，以及颗粒的操纵。本项目的主要目的是阐明介电介质表面的浓度极化诱导流动的机理。该项目还将侧重于扩大妇女和代表性不足的少数群体的参与，并为他们提供通往研究相关职业的桥梁。它将为本科生、研究生和高中生提供微流体方面的教育和实践培训。本项目旨在通过实验与理论相结合的方法，全面了解浓度极化诱导的电动流动的各种控制参数。具体而言，将直接测量流速，并在电场频率、盐浓度、表面zeta电位和介电常数方面与理论预测进行比较。此外，在微流体抽运中，将利用固定介电柱的不对称破坏和不对称浓度极化诱导的电动力学流动。最后，我们将展示介电粒子周围的浓度极化诱导的电动力学流动，并将其用于粒子操纵。所提出的实验可以定量地验证所提出的理论预测，从而加深对这一流动的基本理解。数学模型所需的所有参数都可以通过补充实验准确地得到。这种理论和实验之间的严格比较是本研究对该领域的独特贡献：它不仅将为揭示潜在的物理原理提供重要的见解，而且还将为开发各种微流体应用的浓度极化诱导的电动流动提供指导。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Precise control flow in microfluidic systems has many applications in areas such as clinical diagnosis, drug discovery, detection of chemical and biological pathogen, immunoassays, rapid chemical analysis, biodefense, etc. Recent experiments have discovered a new type of fluid flow around charged dielectric surfaces under the action of electric fields. These flows are hypothesized to result from an effect known as concentration polarization around the dielectric surfaces. Such concentration polarization-induced flows can be readily controlled by tuning the properties of the dielectric structure and the fluid. This feature promises a versatile technique for microfluidic flow control, including pumping and mixing, as well as manipulation of particles. The principal aim of this project is to elucidate the mechanism of the concentration polarization-induced flow around dielectric surfaces. This project will also focus on broadening participation from women and underrepresented minority groups and provide them with a bridge toward research-related careers. It will provide education and hands-on training in microfluidics to undergraduate, graduate, and high school students.The goal of this project is to develop a comprehensive understanding of the various control parameters for the concentration polarization induced electrokinetic flow via a combined experimental and theoretical approach. Specifically, the flow velocity will be directly measured and compared with the theoretical prediction in terms of the electric field frequency, salt concentration, surface zeta potential, and dielectric permittivity. Furthermore, the broken symmetry of stationary dielectric posts and hence the asymmetric concentration polarization induced electrokinetic flow will be exploited for microfluidic pumping. Finally, the concentration polarization induced electrokinetic flow around dielectric particles will be demonstrated and exploited for particle manipulation. The proposed experiments can quantitatively verify the proposed theoretical predictions to deepen the fundamental understanding of this flow. All parameters needed for the mathematical model can be obtained accurately from the complementary experiments. Such a rigorous comparison between theory and experiment features the unique contribution of this proposed research to the field: it will not only provide crucial insights for revealing the underlying physics, but also provide the guidance to exploit concentration polarization induced electrokinetic flows for various microfluidic applications.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.