Levich Institute Seminar Announcement, 02/07/2012
Tuesday, 02/07/2012
2:00 PM
Steinman Hall, Room #312
(Chemical Engineering Conference Room)

Professor Todd Squires
University of California, Santa Barbara
Department of Chemical Engineering

"Nonlinear Electrokinetics in Microfluidics"


ABSTRACT


I will discuss nonlinear, or induced-charge, electrokinetic flows, in which an applied electric field induces an ionic double-layer around a polarizable surface, then forces that induced ionic cloud (and the fluid around it) into motion. Such flows have seen increasing interest in the last decade for microfluidic systems -- for both fundamental and applied reasons -- but date back to Levich's pioneering work. From the standpoint of fundamental science, they are appealing because, in principle, all aspects (including the zeta potential) of these flows can be predicted from the standard theories of ion transport and fluid mechanics. Subsequent measurements, then, can be used to directly test the standard electrokinetic models. Measurements in our and other laboratories have shown significant discrepancies between theoretical predictions and experimental measurements. We will describe an experimental system we have developed that enables high-throughput measurements of ICEK flows over a wide variety of surfaces, and experiments we have developed with an eye to low-voltage, high-pressure microfluidic pumps. Our experimental motivated a series of theoretical problems to identify mechanisms that contribute to these discrepancies, which then motivated new experiments.

ACADEMIC/EMPLOYMENT BACKGROUND:
  • Ph.D. in Physics from Harvard University in 2005 under the supervision of Michael Brenner and Howard Stone, on problems in colloidal hydrodynamics and electrokinetics
  • Then spent three years as a Lee A. Dubridge Prize Postdoctoral Fellow and NSF Mathematical Sciences Postdoctoral Fellow at Caltech, where he continued theoretical work in electrokinetics and microfluidics, and initiated new studies of nonlinear microrheology with John Brady.
  • Currently associate professor of Chemical Engineering at the University of California, Santa Barbara, where he started his faculty career in 2005. His group focuses on micro-scale fluid mechanics and transport, both experimentally and theoretically. Specific areas of interest include linear, nonlinear and interfacial microrheology, and theoretical, experimental and computational studies of electrokinetics and ion transport for flow manipulation and energy storage.

CURRENT RESEARCH INTERESTS:

Physicochemical Hydrodynamics, with a specific emphasis on electrokinetic effects in microfluidics; rheology of soft matter: active, nonlinear and interfacial