Transcript Document

The Dynamics of Electrolytes at Large Voltages
Thursday, March 29, 2007
Time
Place
Martin Z. Bazant
Associate Professor of Applied Mathematics
Department of Mathematics
Massachusetts Institute of Technology
Cambridge, Massachusetts
The dynamics of electrolytes is usually described by circuit models, where the double layer
is an impedance in series with a bulk resistance. When diffuse-charge dynamics has been
considered, the classical theory (Poisson-Nernst-Planck equations, Smoluchowski slip
formula,...) has been almost invariably used, which assumes a dilute solution of point-like
ions interacting through a mean field in a uniform dielectric continuum. In many situations of
current technological interest, however, such as induced-charge electro-osmotic flows in
microfluidics, charging of supercapacitors, or impedance measurements in micro-biosensors,
electrolytes are subject to "large" voltages (>> kT/e = 25 mV) where the classical theory
breaks down, due to crowding of ions near a surface. This talk presents some general
consequences of steric and viscoelectric effects in double-layer charging and ICEO flow,
compared to experimental data in microfluidic devices. .
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