University of Chicago
MRSEC Seminar
January 21, 2002


Title: 		Induced-charge Electro-osmosis: 
		Theory and Microfluidic Applications

Speaker:	Martin Bazant
		Department of Mathematics
		Massachusetts Institute of Technology

Abstract:

When a background electric field is applied to a conductor immersed in
a liquid electrolyte, its surface charge evolves to produce a
nonuniform zeta potential, and the resulting ``induced-charge
electro-osmotic flow" is very different from the familiar case of an
insulator (with a fixed zeta potential). For example, as the electric
field increases, a charged, conducting sphere reaches a limiting
electrophoretic velocity (i.e. its mobility vanishes), and a secondary
flow develops, which sucks in fluid along the field axis and ejects it
radially.  In this talk, a simple physical theory of such intriguing
phenomena will be presented, and a variety of microfluidic
applications will be discussed, such as micro-pumps and mixers driven
by AC electric fields. [Joint work with Todd Squires (Department of
Physics, Harvard University).]