Collaborative Research: Concentration Polarization Induced Electrokinetic Flows around Dielectric Surfaces

微流控系统中的精确控制流动在临床诊断、药物发现、化学和生物病原体检测、免疫测定、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绕带电介质表面流动。这些流动被假设为是由电介质表面周围的浓度极化效应引起的。这种浓度极化引起的流动可以通过调节介电结构和流体的性质来容易地控制。这一特性为微流体流动控制提供了一种通用技术，包括泵送和混合，以及颗粒的操纵。本计画的主要目的是阐明介质表面浓度极化诱导流动的机制。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。该项目将为本科生、研究生和高中生提供微流体方面的教育和实践培训。该项目的目标是通过实验和理论相结合的方法，全面了解浓差极化诱导电动流的各种控制参数。具体而言，将直接测量流速，并与电场频率、盐浓度、表面zeta电位和介电常数方面的理论预测进行比较。此外，固定电介质柱的对称性破缺以及因此非对称浓度极化诱导的动电流将被用于微流体泵送。最后，介电粒子周围的浓差极化诱导的电动流将被证明和利用粒子操纵。所提出的实验可以定量地验证所提出的理论预测，以加深对这种流动的基本理解。数学模型所需的所有参数都可以从补充实验中准确地获得。理论和实验之间的这种严格比较表明了这项研究对该领域的独特贡献：它不仅将为揭示潜在的物理学提供重要的见解，该奖项反映了NSF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。

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.