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Electrohydrodynamic Flow and Colloidal Patterning near Inhomogeneities on Electrodes

Summary: Electrohydrodynamic Flow and Colloidal Patterning near
Inhomogeneities on Electrodes
W. D. Ristenpart,
P. Jiang, M. A. Slowik, C. Punckt, D. A. Saville,
and I. A. Aksay*
Department of Chemical Engineering, Princeton UniVersity, Princeton, New Jersey 08544
ReceiVed May 7, 2008. ReVised Manuscript ReceiVed July 15, 2008
Current density inhomogeneities on electrodes (of physical, chemical, or optical origin) induce long-range
electrohydrodynamic fluid motion directed toward the regions of higher current density. Here, we analyze the flow
and its implications for the orderly arrangement of colloidal particles as effected by this flow on patterned electrodes.
A scaling analysis indicates that the flow velocity is proportional to the product of the applied voltage and the difference
in current density between adjacent regions on the electrode. Exact analytical solutions for the streamlines are derived
for the case of a spatially periodic perturbation in current density along the electrode. Particularly simple asymptotic
of the streamlines are in good agreement with particle velocimetry experiments near a mechanically generated
inhomogeneity (a "scratch") that generates a current density larger than that of the unmodified electrode. We demonstrate
that proper placement of scratches on an electrode yields desired patterns of colloidal particles.
Guided patterning of surfaces with colloidal particles is of
interest for use in applications ranging from biosensors,1


Source: Aksay, Ilhan A. - Department of Chemical Engineering, Princeton University


Collections: Materials Science