Controlled Fabrication and Photonic Structure of Cholesteric Liquid Crystalline Shells

Uchida, Yoshiyuki; Takanishi, Yoichi; Yamamoto, Jun

doi:10.1002/adma.201300776

Cited by 110 publications

(103 citation statements)

References 23 publications

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“…Experiments were performed for spherical Ch droplets, in which disclinations correspond to the equilibrium state, thus ensuring reproducible templating conditions (16,17). Droplets of thermotropic Ch liquid crystals were proposed for applications as omnidirectional lasers, microresonators, Bragg-Berry optical elements, and photonic crystals (18)(19)(20)(21)(22)(23). Here, we focus on the lyotropic droplets formed by an aqueous Ch suspension of cellulose nanocrystals (CNCs) and refer to this Ch phase as the Ch-CNC phase.…”

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confidence: 99%

Periodic assembly of nanoparticle arrays in disclinations of cholesteric liquid crystals

Prince

Cho

et al. 2017

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

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An important goal of the modern soft matter science is to discover new self-assembly modalities to precisely control the placement of small particles in space. Spatial inhomogeneity of liquid crystals offers the capability to organize colloids in certain regions such as the cores of the topological defects. Here we report two selfassembly modes of nanoparticles in linear defects-disclinations in a lyotropic colloidal cholesteric liquid crystal: a continuous helicoidal thread and a periodic array of discrete beads. The beads form one-dimensional arrays with a periodicity that matches half a pitch of the cholesteric phase. The periodic assembly is governed by the anisotropic surface tension and elasticity at the interface of beads with the liquid crystal. This mode of self-assembly of nanoparticles in disclinations expands our ability to use topological defects in liquid crystals as templates for the organization of nanocolloids. colloidal liquid crystals | nanoparticle self-assembly | liquid crystal droplets | topological defects | anisotropic surface tension T he most extensively studied liquid crystalline phase, the socalled nematic, has been so named after the linear defectdisclinations that appear as flexible threads in optical microscopy textures; "thread" is "ν«μα" in Greek (1, 2). The disclinations represent singularities of the director that describes the local orientation of molecules. As one approaches the "core" of the defect, director deformation becomes so strong that the degree of orientational order varies in space. Disclinations can attract additives, e.g., colloidal particles (3-8) and even small molecules (9, 10). Such an attraction is energetically favored, as the strongly distorted disclination core region is replaced with the additive (4). The unique templating ability of disclinations has stimulated the exploration of their applications, such as the fabrication of optical materials (11), conductive microwires (12), soft magnets (13), and electrooptical devices (5,14,15).Disclinations in nematic liquid crystals are generally onedimensional structures, as the director pattern repeats itself along the line. When an additive is attracted to the disclination core, two possible morphologies are expected: (i) continuous thread-like assembly, or (ii) a linear array of discrete beads. The disclination-templated assemblies reported so far had a threadlike shape, as observed for polymers in the so-called blue phases (15) and for molecular amphiphiles at the cores of nematic disclinations (9, 10).Here, we report the templating behavior of disclinations in the chiral version of the nematic liquid crystal, the so-called cholesteric (Ch) phase. The local directorn in this phase undergoes helicoid twisting around a helical axisv while being perpendicular to this axis (1, 2). Continuous twist leads to a pseudolayered structure, with a well-defined pitch but no modulation of density. Experiments were performed for spherical Ch droplets, in which disclinations correspond to the equilibrium state, thus ensuring...

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confidence: 99%

Periodic assembly of nanoparticle arrays in disclinations of cholesteric liquid crystals

Prince

Cho

et al. 2017

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

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“…More complex control over the laser properties and processes can be offered by creating a double emulsion with an outside layer of CLC material encapsulating an aqueous phase holding the laser dye [124]. Altering the type and combination of CLC and dye materials enables a switch between different modes of laser operation (between Bragg and MDR based lasers), due to the differing alignment of the crystal helical axes in each case.…”

Section: Liquid Crystalsmentioning

confidence: 99%

Droplet lasers: a review of current progress

McGloin

2017

Rep. Prog. Phys.

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Abstract. It is perhaps surprising that something as fragile as a microscopic droplet could possibly form a laser. In this article we will review some of the underpinning physics as to how this might be possible, and then examine the state of the art in the field. The technology to create and manipulate droplets will be examined, as will the different classes of droplet lasers. We discuss the rapidly developing fields of droplet biolasers, liquid crystal laser droplets and explore how droplet lasers could give rise to new bio and chemical sensing and analysis. The challenges that droplet lasers face in becoming robust devices, either as sensors or as photonic components in lab on a chip devices is assessed.

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“…We have recently reported an omnidirectional laser action based on CLC core-shell microspheres, which are waterin-oil-in-water (W/O/W) double emulsion droplets containing a CLC phase as the middle phase. [4] The CLC core-shell microspheres hold great promise for the optical application because both hydrophilic and hydrophobic dyes are utilizable as the laser dye. Since colors of the CLC core-shell microspheres should depend on temperature, they could also work as temperature sensors.…”

Section: Introductionmentioning

confidence: 99%

Temperature-dependent Color Change of Cholesteric Liquid Crystalline Core-shell Microspheres

Iwai

Kaji

Uchida

et al. 2015

Molecular Crystals and Liquid Crystals

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We have fabricated water-in-oil-in-water (W/O/W) double emulsion droplets with a cholesteric liquid crystalline (CLC) material, which is a mixture of a nematic liquid crystalline compound, 4-cyano-4 -pentylbiphenyl (5CB), and a chiral dopant, cholesteryl oleyl carbonate (COC), as the middle phase and an aqueous poly(vinylalcohol) (PVA) solution as the inner and outer phases (CLC core-shell microspheres).Here we report the strongly temperature-dependent color change of CLC core-shell microsphere.

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Controlled Fabrication and Photonic Structure of Cholesteric Liquid Crystalline Shells

Cited by 110 publications

References 23 publications

Periodic assembly of nanoparticle arrays in disclinations of cholesteric liquid crystals

Periodic assembly of nanoparticle arrays in disclinations of cholesteric liquid crystals

Droplet lasers: a review of current progress

Temperature-dependent Color Change of Cholesteric Liquid Crystalline Core-shell Microspheres

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