Formation of grid patterns in an ac-driven electroconvection system

Jong-Hoon Huh and Haruki Osoguchi
Phys. Rev. E 101, 062701 – Published 1 June 2020
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Abstract

We report the formation mechanism of a unique pattern observed in ac-driven electroconvection of nematic liquid crystals (NLCs), in which many well-organized grid cells are very regularly aggregated in a two-dimensional plane, globally forming a nearly perfect grid pattern (GP). Intuitively, the formation of such a pattern is unpredictable; usually, the perfectly regular normal roll (NR) showing a preferred roll direction is observed in this system by imposing a fixed initial direction of an NLC. The GP was investigated by varying the ac voltage and frequency. To characterize the GP, the density ρGP, the width a and length b of the grids, and the oscillation period TGP of an inner optical pattern of the grids were measured; moreover, the lengths L¯x and L¯y characterizing phase-jump lines (PJLs) in the GP were examined. By taking into account the process of evolution from a fluctuating NR with defects to the GP, the velocity and director fields of the GP are estimated. Furthermore, in comparison with the bimodal mechanism proposed in the earlier study, a possible mechanism for the GP formed by the PJLs is discussed; various routes to GPs depending on the ac frequency are proposed.

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  • Received 19 January 2020
  • Revised 17 March 2020
  • Accepted 8 May 2020

DOI:https://doi.org/10.1103/PhysRevE.101.062701

©2020 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Jong-Hoon Huh and Haruki Osoguchi

  • Department of Physics and Information Technology, Faculty of Computer Science and Systems Engineering, Kyushu Institute of Technology, Fukuoka 820-8502, Japan

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Issue

Vol. 101, Iss. 6 — June 2020

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