Collaborative Research: Concentration Polarization Induced Electrokinetic Flows around Dielectric Surfaces

微流控系统在临床诊断、药物开发、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绕过带电介质表面的流动。假设这些流动是由电介质表面周围的浓差极化效应造成的。通过调节介质结构和流体的性质，可以容易地控制这种由浓差极化引起的流动。这一特性为微流体流量控制提供了一种通用技术，包括泵送和混合，以及对颗粒的操纵。本项目的主要目的是阐明介质表面浓差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，并为他们提供通向与研究有关的职业的桥梁。它将为本科生、研究生和高中生提供微流体学方面的教育和动手培训。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势流的各种控制参数。具体来说，将直接测量流速，并将其与理论预测的电场频率、盐浓度、表面Zeta电位和介电常数进行比较。此外，静止电介质柱的对称性被破坏，因此不对称的浓差极化电动流将被用于微流控泵送。最后，我们将演示浓差极化诱导的电动势绕过介质颗粒的流动，并将其用于颗粒操纵。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。该数学模型所需的所有参数均可通过互补性实验得到准确的结果。理论和实验之间的严格比较体现了这项拟议研究对该领域的独特贡献：它不仅将为揭示潜在物理提供关键的见解，还将为开发各种微流体应用的浓差极化诱导电动流动提供指导。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.