A full-color reflective display using polymer-stabilized blue phase liquid crystal

Yan, Jin; Wu, Shin‐Tson; Cheng, Kung‐Lung; Shiu, Jyh‐Wen

doi:10.1063/1.4793750

Cited by 84 publications

(83 citation statements)

References 26 publications

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“…The growth time for formation of single crystals is much shorter than that reported for monodomains in earlier studies; on rubbed polymer substrates, for example, several hours were necessary (24)(25)(26)(27)(28). The timescale for single-crystal growth is approximately 2 min for the BPII, and it is 1 h for the BPI when it is nucleated from a cholesteric phase (heating).…”

Section: Discussionmentioning

confidence: 73%

“…Recent efforts have sought to develop strategies to significantly increase the thermal stability of BPs (14,(16)(17)(18)(19)(20)(21)(22)(23). Control of the lattice orientations of BPs, however, has been difficult to achieve; unlike nematic LCs, the molecular alignment of BPs is not uniform, and multiple nucleation seeds occur simultaneously during the course of a BP phase transition (24)(25)(26)(27)(28).…”

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confidence: 99%

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Mesoscale martensitic transformation in single crystals of topological defects

Martínez‐González

Hernández-Ortíz

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Liquid-crystal blue phases (BPs) are highly ordered at two levels. Molecules exhibit orientational order at nanometer length scales, while chirality leads to ordered arrays of double-twisted cylinders over micrometer scales. Past studies of polycrystalline BPs were challenged by the existence of grain boundaries between randomly oriented crystalline nanodomains. Here, the nucleation of BPs is controlled with precision by relying on chemically nanopatterned surfaces, leading to macroscopic single-crystal BP specimens where the dynamics of mesocrystal formation can be directly observed. Theory and experiments show that transitions between two BPs having a different network structure proceed through local reorganization of the crystalline array, without diffusion of the doubletwisted cylinders. In solid crystals, martensitic transformations between crystal structures involve the concerted motion of a few atoms, without diffusion. The transformation between BPs, where crystal features arise in the submicron regime, is found to be martensitic in nature when one considers the collective behavior of the double-twist cylinders. Single-crystal BPs are shown to offer fertile grounds for the study of directed crystal nucleation and the controlled growth of soft matter.T here is considerable interest in understanding at a fundamental level the processes through which crystals are nucleated, and how they grow and transform between different lattice symmetries. Among crystal-crystal transformations, martensitic transitions are of particular interest, as they involve a collective and diffusionless atomic rearrangement that occurs at velocities comparable to the speed of sound in the material (1). Here, we use liquid crystals (LCs) that exhibit long-range order and crystalline symmetries with lattice constants in the submicron regime, the socalled blue phases (BPs), to study a liquid analog of a crystalcrystal transformation. BPs are thermodynamically stable liquid crystalline states that occur in a narrow range of temperatures between the cholesteric (Chol) and isotropic (I) phases of chiral LCs. In BPs, the molecules are locally oriented and organized in such a way as to form structures known as double-twist cylinders. These cylinders, which arise from a balance of long-range elastic distortions and short-range enthalpic contributions to the free energy, adopt a cubic lattice structure, which is interdispersed by an ordered network of topological defects (disclination lines). Depending on the thermodynamic conditions, the double-twist cylinders adopt a body-centered cubic structure (BCC), which produces the so-called blue phase I (or BPI), or they adopt a simple cubic structure (SC), which corresponds to the so-called blue phase II (or BPII). In both cases, the lattice parameters are on the order of a few hundred nanometers (2-4). BPs exhibit selective light reflections; they have fast electro-optical switching characteristics, with submillisecond response times, and their viscosity is relatively large (3,(5)(6)(7)(8). This c...

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Section: Discussionmentioning

confidence: 73%

mentioning

confidence: 99%

Mesoscale martensitic transformation in single crystals of topological defects

Martínez‐González

Hernández-Ortíz

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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“…Alignment layers have previously been reported to induce uniform domains of BPs; 13,14 however, to the best of our knowledge, their preferential influence on one of two cubic BPs has never been documented. It is also worth noting that we did not observe the previously reported pinning effect where alignment layers substantially suppress the change in photonic bandgap in response to changes in temperature.…”

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confidence: 82%

On the effect of alignment layers on blue phase liquid crystals

Joshi

Shang

Smet

et al. 2015

Applied Physics Letters

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In the present work, the effect of alignment layers on blue phase liquid crystals was investigated. It was found that homogeneous alignment layers have profound selective influence on blue phase II (BPII). In the absence of alignment layers, BPII domains were randomly oriented and showed weak Bragg reflection in the UV, whereas with assistance of anchoring uniform domains with sharp Bragg reflection in the visible range appeared. On the other hand, the magnitude of Bragg shift in response to alignment layers in BPI is negligible. Domains of BP with alignment layers exhibit sharp Bragg reflection peaks (with FWHM < 15 nm), with very vivid colors and possessing fast switching speeds (<5 ×10−4 s). This simple method of selectively assisting one of the cubic phases is expected to be advantageous in the comparative studies of the two phases.

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“…[11] Based on the electro-optical properties of the BPs, the concept of a full-colour-reflective BP display was proposed and demonstrated in a recent paper. [12] The red, blue and green subpixels are made by BP with different chiral concentrations, and then, by applying the voltage the reflected intensities of those subpixels are tuned due to the lattice distortion and LC director reorientation. The key point to reproduce their idea is that one should know the relationship between the reflection colour and the chiral dopant concentration (or pitch lengths) in BPI.…”

Section: Introductionmentioning

confidence: 99%

Lattice structure in liquid-crystal blue phase with various chiral concentrations

Chen

Hsieh

2015

Liquid Crystals

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Lattice structures, including reflection lattice planes and lattice constant, of liquid-crystal blue phase I (BPI) are studied via the measurements on reflection spectrum and Kossel diagram as concentration of a chiral dopant is changed. Peaks of the reflection wavelength in BPI are mainly dominated by the lattice plane and the lattice constant, which are affected by the chiral concentration. In the chiral nematic state, as decreasing the chiral concentration the reflection peak will shift to a longer wavelength because the helical pitch linearly depends on the chiral concentration and becomes longer. However, this dependence of the chiral concentration and reflection wavelength is broken in the BPI. The reflection peak of BPI moves to a short wavelength when the chiral concentration is less due to the contraction of the lattice constant as well as helical pitch. Moreover, when the concentration of the chiral dopant increases over a certain value, a discontinuous shift in reflection peak occurs due to the production of the different lattice planes. It means that the relationship between the chiral concentration and the helical pitch in BPI is not the same as it in the chiral nematic phase and should be reconsidered.

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A full-color reflective display using polymer-stabilized blue phase liquid crystal

Cited by 84 publications

References 26 publications

Mesoscale martensitic transformation in single crystals of topological defects

Mesoscale martensitic transformation in single crystals of topological defects

On the effect of alignment layers on blue phase liquid crystals

Lattice structure in liquid-crystal blue phase with various chiral concentrations

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