Mechanics Seminar, Department of Mechanical Engineering, MIT
Monday, May 13, 2002
Room 5-234  Time: 4:00-5:00 p.m.


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

Professor Martin Bazant
Department of Mathematics, MIT

Abstract: When a background electric field is applied in a liquid
electrolyte across a conducting object, 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, a metal sphere in a DC field field sucks in fluid along the
field axis and ejects it radially, and various broken symmetries can
cause the object to swim (or, if it is fixed, to pump fluid).  Similar
time-averaged flows occur with AC fields in a certain range of
frequencies. In this talk, a simple physical theory of these
intruiging phenomena will be presented, and a variety of potential
microfluidic applications will be discussed, such as micro-pumps and
mixers driven by AC fields. [Joint work with Todd Squires (Department
of Physics, Harvard University).]