Dielectrophoretic manipulation of the mixture of isotropic and nematic liquid.

Soo-Dong Kim,Bomi Lee,Shin-Woong Kang,Jang-Kun Song

doi:10.1038/ncomms8936

Soo-Dong Kim, Bomi Lee + Show 2 more

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https://doi.org/10.1038/ncomms8936

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Abstract

In various applications involving liquid crystals, the manipulation of the nanoscale molecular assembly and microscale director alignment is highly useful. Here we show that a nematic–isotropic mixture, a unique bi-liquid system, has potential for the fabrication of microstructures having an ordered phase within a disordered phase, or vice versa. The volume expansion and shrinkage, migration, splitting, mergence and elongation of one phase within the other are easily accomplished via thermal treatment and dielectrophoretic manipulation. This is particularly achievable when one phase is suspended in the middle. In that case, a highly biased ordered-phase preference of surfaces, that is, the nematic-philic nature of a polyimide layer and the nematic-phobic nature of a self-assembled monolayer of chlorosilane derivatives, is used. Further, by combining this approach with photopolymerization, the patterned microstructure is solidified as a patterned polymer film having both isotropic and anisotropic molecular arrangements simultaneously, or as a template with a morphological variation.

Highlights

In various applications involving liquid crystals, the manipulation of the nanoscale molecular assembly and microscale director alignment is highly useful
The extremely uneven surface roughness at the molecular scale disturbs the ordering of liquid crystal (LC) molecules and induces isotropic molecular arrangement near the surface, in contrast to the polymer alignment layer
Using the nematic-philic nature of polyimide (PI) and the nematic-phobic nature of self-assembled monolayer (SAM), we can produce a suspended isotropic phase surrounded by a nematic medium or vice versa, in the nematic–isotropic coexisting state, as explained below

Summary

Introduction

In various applications involving liquid crystals, the manipulation of the nanoscale molecular assembly and microscale director alignment is highly useful. A highly biased ordered-phase preference of surfaces, that is, the nematic-philic nature of a polyimide layer and the nematic-phobic nature of a self-assembled monolayer of chlorosilane derivatives, is used. By combining this approach with photopolymerization, the patterned microstructure is solidified as a patterned polymer film having both isotropic and anisotropic molecular arrangements simultaneously, or as a template with a morphological variation. According to the Landau-de Gennes theory, which elucidates the first-order transition between nematic and isotropic phases in calamitic LCs, nematic and isotropic phases can metastably coexist within a certain temperature range in a single-component LC because of the double-well-shaped free energy with respect to the order parameter[1,2]. This methodology provides a novel method utilizing two-phase LC mixtures

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