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Full-Text Articles in Physics

Note: Automated Maskless Micro-Multidomain Photoalignment, Christopher Culbreath, Nikolaus Glazar, Hiroshi Yokoyama Dec 2011

Note: Automated Maskless Micro-Multidomain Photoalignment, Christopher Culbreath, Nikolaus Glazar, Hiroshi Yokoyama

Chemical Physics Publications

We present a fully automated maskless exposure system for the fabrication of microscopic orientational surface alignment patterns. The maskless system allows us to fabricate arbitrary surface patterns over a 2 mm × 2 mm area with a resolution of 2.2 μm. A confocal autofocus system insures accurate and repeatable focus. Microscopic orientational surface patterns have been demonstrated to exhibit a variety of novel functionalities, such as surface alignment multi-stability.


Orientational Coupling Amplification In Ferroelectric Nematic Colloids, Fenghua Li, Oleksandr Buchnev, Chae Il Cheon, Anatoliy Glushchenko, Victor Reshetnyak, Yuri Reznikov, Timothy J. Sluckin, John L. West Oct 2006

Orientational Coupling Amplification In Ferroelectric Nematic Colloids, Fenghua Li, Oleksandr Buchnev, Chae Il Cheon, Anatoliy Glushchenko, Victor Reshetnyak, Yuri Reznikov, Timothy J. Sluckin, John L. West

Chemistry & Biochemistry Publications

We investigated the physical properties of low concentration ferroelectric nematic colloids, using calorimetry, optical methods, infrared spectroscopy, and capacitance studies. The resulting homogeneous colloids possess a significantly amplified nematic orientational coupling. We find that the nematic orientation coupling increases by similar to 10% for particle concentrations of 0.2%. A manifestation of the increased orientational order is that the clearing temperature of a nematic colloid increases by up to 40 degrees C compared to the pure liquid crystal host. A theoretical model is proposed in which the ferroelectric particles induce local dipoles whose effective interaction is proportional to the square ...


Fluorine Containing Nonsymmetrical Five-Ring Achiral Banana-Shaped Compounds With Columnar And Synclinic Antiferroelectric Layered Phases, Channabasaveshwar V. Yelamaggad, Indudhara Swamy Shashikala, Uma S. Hiremath, Guangxun Liao, Antal Jakli, Doddamane S. Shankar Rao, Subbarao Krishna Prasad, Quan Li Jul 2006

Fluorine Containing Nonsymmetrical Five-Ring Achiral Banana-Shaped Compounds With Columnar And Synclinic Antiferroelectric Layered Phases, Channabasaveshwar V. Yelamaggad, Indudhara Swamy Shashikala, Uma S. Hiremath, Guangxun Liao, Antal Jakli, Doddamane S. Shankar Rao, Subbarao Krishna Prasad, Quan Li

Chemical Physics Publications

The phase transitional behavior of two homologous series of five-ring banana-shaped compounds comprising fluorine substituents synthesized through covalent linking of two chemically dissimilar rod-like anisometric cores (arms) to central 1,3-phenylene is reported. The novelty of these molecules originates from the fact that the molecules are highly nonsymmetrical. One of the arms, which is either salicylaldimine or Schiff base core, possesses two vicinal fluorine atoms at the terminal ring having a n-decyloxy tail; while the n-alkyl tail attached to the other arm was varied to realize a homologous series of compounds. The mesophases have been characterized by several complementary studies ...


Pattern Formation In Non-Newtonian Hele-Shaw Flow, P. Fast, L. Kondic, M. J. Shelley, Peter Palffy-Muhoray Jan 2001

Pattern Formation In Non-Newtonian Hele-Shaw Flow, P. Fast, L. Kondic, M. J. Shelley, Peter Palffy-Muhoray

Chemical Physics Publications

We study theoretically the Saffman-Taylor instability of an air bubble expanding into a non-Newtonian fluid in a Hele-Shaw cell, with the motivation of understanding suppression of tip-splitting and the formation of dendritic structures observed in the flow of complex fluids, such as polymeric liquids or liquid crystals. A standard visco-elastic flow model is simplified in the case of flow in a thin gap, and it is found that there is a distinguished limit where shear thinning and normal stress differences are apparent, but elastic response is negligible. This observation allows formulation of a generalized Darcy's law, where the pressure ...


Ericksen's Bar And Modeling Of The Smectic A-Nematic Phase Transition, M. Carme Calderer, Peter Palffy-Muhoray Mar 2000

Ericksen's Bar And Modeling Of The Smectic A-Nematic Phase Transition, M. Carme Calderer, Peter Palffy-Muhoray

Chemical Physics Publications

We consider free energy functionals to model equilibrium smectic A liquid crystal configurations in the neighborhood of the nematic phase transition. We begin with the functional proposed by de Gennes based on the Ginzburg Landau model for superconductivity and consider its covariant formulations. Exploring qualitative analogies with the nonlinear elastic bar of Ericksen, we motivate a revision of the liquid crystal energy so as to include a nonconvex constraint. We study boundary-value problems corresponding to Neumann and Dirichlet boundary conditions for smectic A liquid crystals conned between two parallel plates. We show that the nonconvex term of the free energy ...


Unipolar Electro-Optic Effect In A Nematic Cell, V. G. Nazarenko, R. Klouda, Oleg Lavrentovich Jan 1998

Unipolar Electro-Optic Effect In A Nematic Cell, V. G. Nazarenko, R. Klouda, Oleg Lavrentovich

Chemical Physics Publications

We report on a unipolar electro-optic effect in a nematic liquid crystal cell. The cell placed between two polarizers behaves as an "optical diode:" only one polarity of the applied voltage makes the cell transparent. The phenomenon is caused by a double symmetry breaking at the two plates that bound the nematic slab.


Monte Carlo Simulations Of Stable Point Defects In Hybrid Nematic Films, C. Chiccoli, Oleg Lavrentovich, P. Pasini, C. Zannoni Dec 1997

Monte Carlo Simulations Of Stable Point Defects In Hybrid Nematic Films, C. Chiccoli, Oleg Lavrentovich, P. Pasini, C. Zannoni

Chemical Physics Publications

Monte Carlo (MC) simulations based exclusively on nearest-neighbor intermolecular interactions reveal the existence of stable long-range deformations and topological defects in a thin nematic film confined between two surfaces with antagonistic (normal and tangential) molecular orientations. Thus the MC technique allows one to describe a delicate balance of bulk elasticity and surface energy usually treated only with macroscopic theories.


Stripe Domain Phase Of A Thin Nematic Film And The K13 Divergence Term, Oleg Lavrentovich, V. M. Pergamenshchik Aug 1994

Stripe Domain Phase Of A Thin Nematic Film And The K13 Divergence Term, Oleg Lavrentovich, V. M. Pergamenshchik

Chemical Physics Publications

To verify the status of the divergence K13 term in the elastic theory of liquid crystals we study submicron films placed onto an isotropic fluid substrate in the Langmuir trough (Langmuir liquid crystal, LLC). The upper and lower surfaces favor normal and tangential molecular orientation, respectively. The periodic domain phase is observed in a nematic LLC. The dependence of the periodicity L of the domains vs film thickness h can be explained only if the elastic energy is accompanied by divergence terms with nonzero constants K13 and K24. It is found that for 5CB K13 almost-equal-to -0.2K11.