Q-tensor model for electrokinetics in nematic liquid crystals

O. M. Tovkach, Christopher Conklin, M. Carme Calderer, Dmitry Golovaty, Oleg D. Lavrentovich, Jorge Viñals, Noel J. Walkington

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

We use a variational principle to derive a mathematical model for a nematic electrolyte in which the liquid crystalline component is described in terms of a second-rank order parameter tensor. The model extends the previously developed director-based theory and accounts for the presence of disclinations and possible biaxiality. We verify the model by considering a simple but illustrative example of liquid crystal-enabled electro-osmotic flow around a stationary dielectric spherical particle placed at the center of a large cylindrical container filled with a nematic electrolyte. Assuming homeotropic anchoring of the nematic on the surface of the particle and uniform distribution of the director on the surface of the container, we consider two configurations with a disclination equatorial ring and with a hyperbolic hedgehog, respectively. The computed electro-osmotic flows show a strong dependence on the director configurations and on the anisotropies of dielectric permittivity and electric conductivity of the nematic, characteristic of liquid crystal-enabled electrokinetics. Further, the simulations demonstrate space charge separation around the dielectric sphere, even in the case of isotropic permittivity and conductivity. This is in agreement with the induced-charge electroosmotic effect that occurs in an isotropic electrolyte when an applied field acts on the ionic charge it induces near a polarizable surface.

Original languageEnglish (US)
Article number053302
JournalPhysical Review Fluids
Volume2
Issue number5
DOIs
StatePublished - May 2017

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Nematic liquid crystals
Nematic Liquid Crystal
Electrolytes
Tensors
Liquid Crystals
Electrolyte
Tensor
Electroosmotic Flow
Liquid crystals
Containers
Charge
Permittivity
Container
Liquid Crystal
Conductivity
Electric space charge
Rank order
Configuration
Anisotropy
Uniform distribution

Cite this

Tovkach, O. M., Conklin, C., Calderer, M. C., Golovaty, D., Lavrentovich, O. D., Viñals, J., & Walkington, N. J. (2017). Q-tensor model for electrokinetics in nematic liquid crystals. Physical Review Fluids, 2(5), [053302]. https://doi.org/10.1103/PhysRevFluids.2.053302

Q-tensor model for electrokinetics in nematic liquid crystals. / Tovkach, O. M.; Conklin, Christopher; Calderer, M. Carme; Golovaty, Dmitry; Lavrentovich, Oleg D.; Viñals, Jorge; Walkington, Noel J.

In: Physical Review Fluids, Vol. 2, No. 5, 053302, 05.2017.

Research output: Contribution to journalArticle

Tovkach, OM, Conklin, C, Calderer, MC, Golovaty, D, Lavrentovich, OD, Viñals, J & Walkington, NJ 2017, 'Q-tensor model for electrokinetics in nematic liquid crystals', Physical Review Fluids, vol. 2, no. 5, 053302. https://doi.org/10.1103/PhysRevFluids.2.053302
Tovkach, O. M. ; Conklin, Christopher ; Calderer, M. Carme ; Golovaty, Dmitry ; Lavrentovich, Oleg D. ; Viñals, Jorge ; Walkington, Noel J. / Q-tensor model for electrokinetics in nematic liquid crystals. In: Physical Review Fluids. 2017 ; Vol. 2, No. 5.
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