CAREER: Fundamental and Applied Studies of Novel Electrokinetic Effects

University Of California-Santa Barbara, Santa Barbara CA

Investigators

Abstract

Abstract CBET-0645097 T. Squires, UC-Santa Barbara Microfabricated fluidic devices have the potential to revolutionize chemistry, biology, and medicine, much as the integrated circuit did for computing, science and technology. Sophisticated devices have already been developed to perform tasks that would be vastly more expensive, more difficult, or even impossible with macro-scale techniques. If microfluidic flows can be driven in a self-contained, portable fashion, such devices could be taken out of the lab and into the field (or under the skin). Electrokinetic flows present many advantages towards microfluidic portability; however, fundamental issues have thus far precluded their use in practical systems. This CAREER proposal describes a theoretical and experimental program with two central goals: 1) a fundamental understanding of electro-osmotic flow over liquid/liquid interfaces, and 2) the exploitation of these and related phenomena to develop truly portable microfludic manipulation systems. To achieve the first goal, the PI will develop and employ a microfluidic system that will enable, for the first time, direct measurements of electro-osmotic flow over liquid/liquid interfaces, while providing a control over the input 'variables' that is unprecedented (even impossible) in colloidal studies. As such, this will allow the first direct and stringent test of electrokinetic theories. To achieve the second goal, the PI will develop a low-voltage, high-pressure microfluidic pump that employs transverse induced-charge electrokinetic phenomena within a novel anisotropic porous bed. Intellectual Merit: The microfluidic platform proposed will allow groundbreaking, fundamental studies in a field that is nearly two centuries old. Previous colloidal studies probed electrokinetic flows only indirectly, and allowed little or no control over surface charge density, geometry, or double-layer dynamics. The proposed system allows direct control over all of these quantities, and directly measures the consequent flows. A variety of physical regimes will thus be available for study: linear and nonlinear electrokinetics, transient double-layer effects, and surface conductivity. The direct application of the resulting new knowledge to microfluidic manipulation systems will significantly broaden our understanding of induced-charge electrokinetics, both in testing theories for asymmetric bodies and in developing statistical theories for concentrated collections. In all cases, the PI will emphasize the simplest, most intuitive systems to elucidate key phenomena. Broader Impacts: The proposed electrokinetic pump may be immediately integrated into existing elastomeric microfluidic devices for rapid and broad impact. This will enable an entirely portable, robust, and versatile fluidic manipulation system and make possible hand-held hazard sensors and medical diagnostic tools, as well as implantable biomedical devices. The PI will continue his efforts to bridge the divide between the "application" and "fundamental" communities in microfluidics, and has designed this CAREER program to demonstrate the value of fundamental understanding in engineering solutions to real-world challenges, and the impact one can have by seriously considering real-world challenges in designing fundamental research. He will promote this view in his role as the "fundamentals expert" on the editorial board of the new American Institute of Physics journal Biomicrofluidics. He will continue to leverage existing, successful programs at UCSB (such as the California Alliance for Minority Participation) to integrate undergraduates and under-represented minorities into his research, and will include high-school students and teachers. Education: The PI seeks to re-invigorate student interest in fluid and transport phenomena by using microfluidics as an exciting motivational framework, by emphasizing physically intuitive understanding, and by addressing the variety of disciplines and applications that depend on such phenomena. He will use his review article on microfluidic physical phenomena as the basis for a multidisciplinary special-topics course and as the foundation for a textbook. He will develop and web-publish a freshman seminar course in microfluidics for non-scientists/engineers to broaden the impact of the research, and to more generally cultivate an appreciation for the variety of interesting, exciting, surprising and beautiful phenomena that occur in microfluidics.