8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

P5.182Wed 711:10-14:00A low-density network-forming phase in dipolar colloids:equilibrium structures and templated 3D patternsAnand Yethiraj, 1 Andrew Bartlett, 2 and Amit Agarwal 31 Memorial University, Dept. of Physics Physical Oceanography, A1C 2L2, St. John’s,Canada2 Memorial University, St. John’s, Canada3 Instruments Research and Development Establishment, Dehradun, IndiaColloids in an external electric field interact via an effective dipolar inter-particle interaction. Inthe presence of the dipolar interaction, Brownian colloidal spheres are known to aggregate toform chains and clusters of chains along the field direction. At high densities, these chain clusterspercolate through the sample. At intermediate densities the chains cluster into islands [1]. In ourwork, we find a re-entrant percolation at low densities [2]. The clusters become less compact andform a stable network-like particle-rich structure with large particle-free regions (voids), likelyarising due to the simultaneous presence of long-range repulsions and shorter-range attractions inthe electric-field induced interactions. Analysis of the nature of this void phase leads us to considerthe role of corrections to the dipolar approximation, e. g. weak dielectrophoretic attractionscaused by field non-uniformities induced by the particles themselves. We find additionally that wecan template-order 3-dimensional colloidal patterns using dielectrophoretic attractions [3].[1]. J. E. Martin, J. Odinek, T. C. Halsey, Phys. Rev. Lett. 69, 1524-1527 (1992) ; U.Dassanayake, S. Fraden, A. van Blaaderen, J. Chem. Phys. 112, 3851-3858 (2000).[2]. A. Agarwal, A. Yethiraj, Phys. Rev. Lett. 102, 198301 (2009).[3]. A. P. Bartlett, A. Agarwal, A. Yethiraj, Langmuir, 27, 4313-4318 (2011).182