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Related Experiment Video

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Novel Techniques for Observing Structural Dynamics of Photoresponsive Liquid Crystals

Novel Techniques for Observing Structural Dynamics of Photoresponsive Liquid Crystals

Published on: May 29, 2018

Defect structures in nematic liquid crystals around charged particles.

K Tojo¹, A Furukawa, T Araki

¹Department of Physics, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.

The European Physical Journal. E, Soft Matter

|September 17, 2009

Summary

This study numerically investigates liquid crystal defects around charged particles. Novel "ansa" defects form when dielectric anisotropy is negative, influencing particle pair alignment.

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Area of Science:

Materials Science
Condensed Matter Physics
Soft Matter Physics

Background:

Nematic liquid crystals exhibit complex behavior around impurities.
Charged particles introduce electrostatic interactions that can deform the director field.
Understanding defect formation is crucial for liquid crystal display technology and advanced materials.

Purpose of the Study:

To numerically investigate orientation deformations in nematic liquid crystals induced by charged particles.
To characterize novel defect structures, such as "ansa" defects.
To analyze the influence of dielectric anisotropy and particle charge on defect formation and particle alignment.

Main Methods:

Utilizing a Ginzburg-Landau theory framework.
Implementing numerical simulations with an inhomogeneous electric field.
Analyzing director orientation and free energy minimization.

Main Results:

Saturn-ring defects are observed for positive dielectric anisotropy (ε₁ > 0).
Novel "ansa" defects (disclination lines) appear for negative dielectric anisotropy (ε₁ < 0).
Oppositely charged particle pairs align parallel (ε₁ > 0) or perpendicular (ε₁ < 0) to the background director; identically charged pairs show reversed preferences.
Competition between charge-induced and short-range anchoring is examined, with long-range electrostatics dominating far from the surface.

Conclusions:

Charged particles induce distinct defect structures in nematic liquid crystals based on dielectric anisotropy.
The alignment of charged particle pairs is dictated by electrostatic interactions and dielectric properties.
Electrostatic interactions play a significant role in director orientation, especially in competition with surface anchoring effects.