Levich Institute Seminar Announcement, 10/24/2006
Steinman Hall, Room #312
(Chemical Engineering Conference Room)
Professor Hsueh-Chia Chang
University of Notre Dame
Center for Micro-Fluidics and Medical Diagnostics
"Understanding AC Electrokinetics"
High-frequency AC electrokinetic devices such as micro-pumps, micro-mixers, cell sorters etc offer very precise particle and fluid manipulation capabilities because they can be micro-fabricated and embedded in diagnostic chips without generating bubbles or other Faradaic ionic products. However, their design is complicated by the fact that the AC polarization of electrode and particle double layers by electrolyte ions is far from Poisson-Boltzmann equilibrium. Non-equilibrium AC electrokinetics hence requires detailed analyses of the multi-time/spatial scale charging and discharging phenomena. We focus on the classical dielectrophoretic phenomenon of a charged sphere in this talk and show by asymptotic analysis that double layer polarization fundamentally alters its DEP direction and velocity from dielectric polarization. These dramatic effects of double layer polarization are confirmed experimentally.
BRIEF ACADEMIC/EMPLOYMENT BACKGROUND: