Collaborative Research: Concentration Polarization Induced Electrokinetic Flows around dielectric Surfaces

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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.