Session Q8: Colloidal Phase Behavior
11:15 AM–2:15 PM, Wednesday, March 12, 2008
Morial Convention Center Room: RO6
Sponsoring Unit:
DFD
Chair: Jerzy Blawzdziewicz, Yale University
Abstract ID: BAPS.2008.MAR.Q8.4
Abstract: Q8.00004 : Low-electric-field phase behaviour of Brownian colloidal suspensions in sedimentation equilibrium
11:51 AM–12:03 PM
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Abstract 
Authors:
Amit Agarwal
(Department of Physics and Physical Oceanography, Memorial University of Newfoundland)
Ning Li
(Department of Physics and Physical Oceanography, Memorial University of Newfoundland)
Anand Yethiraj
(Department of Physics and Physical Oceanography, Memorial University of Newfoundland)
We study the phase diagram of the suspension of micron-scale fluorescent labeled silica colloids in aqueous suspension as a function of concentration in the presence of a moderate (less than 1 volt per $\mu m$) AC electric field. Confocal microscopy was used to track three-dimensional structure and dynamics of colloidal suspensions in sedimentation equilibrium. We characterize thresholds for field-induced organization in monodisperse colloidal suspensions of two particle diameters using orientational order parameters. We then study structure formation at moderate fields above the field threshold. At concentrations greater than $10\%$, and electric fields much larger than the field threshold measured, the colloidal suspension crystallizes to form a body centered tetragonal structure as has been previously reported. At lower concentrations and moderate fields, we uncover complex structure formation phenomena that include equilibrium cellular structures.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2008.MAR.Q8.4