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Colloquium
Thursday, November 05, 2009, 12:15 p.m., SCIC 126
Nematic liquid crystal shells
Dr. Alberto Fernandez-Nieves
School of Physics
Georgia Institute of Technology
Abstract:
When nematic liquid crystals are confined to
spherical shells, complex defects structures emerge [1]. These structures
are characterized by a varying number of point defects and disclination lines, depending on the elastic energy of
the liquid crystal, the thickness of the shell, and the boundary conditions
for the director at the confining spheres. Topology establishes
restrictions that must be fulfilled, but it is the energy landscape what
ultimately determines the final state of the system. By using double
emulsion drops, we can experimentally address this fascinating interplay
between topology and energy. We find a wealth of defect structures in our
shells and propose that the shell thickness inhomogeneity
is the key parameter that enables the broad range of possibilities we
observe; this allows observation of long-time predicted configurations [2],
as well as new structures and transitions between them that where never
considered before. Control of these different arrangements can provide a
starting point for the generation of colloids with a valence, which could
serve as building blocks for unconventional colloidal assemblies [3].
[1]
A. Fernadez-Nieves, V. Vitelli,
A.S. Utada, D.R. Link, M. Marquez, D.R. Nelson,
D.A. Weitz, Phys. Rev. Lett.
99, 57801 (2007).
[2]
T.C. Lubensky, J. Prost, J. Phys. II France 2,
371 (1992).
[3] D. R. Nelson, NanoLetters 2, 1125
(2002).
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