ChEMS Seminar: Colloids near Electrodes - Complex Behavior via Microscale Electrohydrodynamic Flows
Department of Chemical Engineering
University of California, Davis
Abstract: In this talk, we review recent advances in our understanding of the behavior of colloids and emulsions near electrodes, with an emphasis on the implications for new techniques to arrange colloids in desired locations. Application of a 1 V, 100 Hz electric field causes micron-scale colloids or droplets adjacent to the electrode to aggregate laterally, a behavior believed to be caused at least in part by electrohydrodynamic fluid flows generated along the electrode surface. We discuss the experimental and theoretical evidence for this interpretation, and we demonstrate how the electric field frequency can be used to modulate the aggregation rate and packing density. Furthermore, we show that under some conditions the average height of the particles over the electrode undergoes a tremendous bifurcation, with a high fraction of the particles “trapped” at heights as large as 30 μm away from the electrode. The results point a path toward a low-energy, non-fouling approach for recovering dilute colloids and oils from wastewater or other aqueous streams where improved sustainability is desired.
Bio: William D. Ristenpart is the Joe & Essie Smith Endowed Professor of Chemical Engineering at UC Davis. He received his doctorate from Princeton University and completed his postdoctoral work at Harvard University. His research focuses on complex transport phenomena in a variety of applications including electrocoalescence of charged droplets, shear-induced deformation of red blood cells and electrically induced aggregation of food colloids. Most recently he became the founding director of the UC Davis Coffee Center, the mission of which is to advance the state of research and education focused on the world’s most popular complex fluid.
Host: Professor Regina Ragan