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Electrically Guided Assembly of Planar Superlattices in Binary Colloidal Suspensions W. D. Ristenpart, I. A. Aksay, and D. A. Saville
 

Summary: Electrically Guided Assembly of Planar Superlattices in Binary Colloidal Suspensions
W. D. Ristenpart, I. A. Aksay, and D. A. Saville
Department of Chemical Engineering, Princeton University, Princeton, New Jersey 08544
(Received 15 October 2002; published 27 March 2003)
Binary colloidal suspensions are assembled into planar superlattices using ac electric fields. Either
triangular or square-packed arrays form, depending on the frequency and relative particle concen-
trations. The frequency dependence is striking since superlattices develop at low and high frequencies
but not at intermediate frequencies. We explain the low frequency behavior <3 kHz in terms of
induced-dipole repulsion balanced by attraction resulting from electrohydrodynamic (EHD) flow. At
high frequencies (20200 kHz), EHD flow is negligible but aggregation occurs since dipole-dipole
interactions become attractive.
DOI: 10.1103/PhysRevLett.90.128303 PACS numbers: 82.70.Dd, 47.65.+a
Monodisperse colloidal particles exhibit a wide range
of behavior in electric fields near electrodes [19].
Application of dc or low frequency f < 1 kHz ac fields
causes particles to move laterally across an electrode,
yielding planar close-packed clusters [1,2]. Electro-
hydrodynamic (EHD) fluid flow has been invoked to ex-
plain this behavior [35]. In high frequency > 1 kHz,
high amplitude fields, dipole-dipole interactions produce

  

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

 

Collections: Materials Science