Design of liquid crystal superstructures: geometry, topology, flow, and mesophase

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• Ravnik, M (University of Oxford/Ljubljana)
• Thursday 21 March 2013, 09:00-09:50
• Seminar Room 1, Newton Institute.

If you have a question about this talk, please contact Mustapha Amrani.

The Mathematics of Liquid Crystals

Structuring of liquid crystalline fluids allows for various exciting material mechanisms such as self-assembly [1], memory effects [2], entanglement [3], nonlinear electrophoresis [4], nonlinear rotary dynamics [5], and nanoscopic surface shape changing [6]. Here, we present strategies for creating colloidal and bulk liquid crystal superstructures, in 2D and 3D, using nematic, twisted nematic, and cholesteric blue phases. Our work is based on the numerical minimization of the phenomenological Landau-de Gennes free energy and solving hybrid Lattice Boltzmann algorithm for Beris-Edwards nematodynamics model, with full link to experiments. We show that 3D colloidal crystals can be assembled from elastic dipoles of spherical beads in nematic liquid crystals or via inherently inhomogeneous order profiles in cholesteric blue phases [7]. By using colloidal platelets, we show that crystalline [8] and quasi-crystalline symmetry can be imprinted into the structures. Topological defects are manipulated into structures of knots and links using various colloidal arrays [9]. Finally, passive and active material flow is used to produce distinct backflow generated complex nematic profiles in microfluidic channels.

[1] P. Poulin, H. Stark, T. C. Lubensky, D. A. Weitz, Science 275, 1770 (1997). [2] T. Araki, M. Buscaglia, T. Bellini, and H. Tanaka, Nature Materials 10, 303 (2011). [3] M. Ravnik, et al, Phys. Rev. Lett. 99, 247801 (2007). [4] O. D. Lavrentovich, I. Lazo and O. P. Pishnyak, Nature 467, 947 (2010). [5] J. S. Lintuvuori, K. Stratford, M. E. Cates, D. Marenduzzo, Phys. Rev. Lett. 107, 267802 (2012). [6] D. Vanzo, M. Ricci, R. Berardi and C. Zannoni, Soft Matter 8, 11790 (2012). [7] M. Ravnik, G. P. Alexander, J. M. Yeomans, and S. Zumer, Proc. Natl. Acad. Sci. USA 108 , 5188 (2011). [8] J. Dontabhaktuni, M. Ravnik and S. Zumer, Soft Matter 8, 1657 (2012). [9] U. Tkalec, M. Ravnik, S. Copar, S. Zumer and I. Musevic, Science 333, 62 (2011).

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