Spontaneous formation and dynamics of half-skyrmions in a chiral liquid-crystal film

Nych, A.; Fukuda, Jun Ichi; Ognysta, U.; Žumer, S.; Muševič, Igor

doi:10.1038/nphys4245

Cited by 111 publications

(118 citation statements)

References 53 publications

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“…Fabrication technologies that enable the control of multifunctional patterns in materials have emerged as key drivers in the interdisciplinary research fields at the interface of material science, bioscience, optics, photonics, and physics. [1][2][3][4] Arrays of topological defects in liquid crystals (LCs) are promising candidates for the creation of such patterns, with the additional benefit of their tunability. [5][6][7] In nature, topological defects exist in a variety of physical systems such as magnets and superconductors, and they are crucial to determining materials' physical properties.…”

Section: Introductionmentioning

confidence: 99%

Tunable Dynamic Topological Defect Pattern Formation in Nematic Liquid Crystals

Kim

Serra

2019

Advanced Optical Materials

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Soft materials are ideal candidates for the creation of tunable, self‐assembled structures. Herein, reconfigurable and switchable dynamic patterns are created using topological defects in nematic liquid crystals. The elastic properties of liquid crystals combined with their responsiveness to electric field are used to control the periodicity and the symmetry of an array of topological defects, assisted by polymeric micropillars. The switching between stable configurations is perfectly reversible and repeatable, and there is no limitation on the length scale of the regular array of defects. The array is used to create 2D diffraction patterns that can be tuned both in the azimuthal and in the polar directions. In addition, the refractive index of the liquid crystal mixture is controlled to optimize the diffraction efficiency. This system, with its flexibility and controllability, offers a promising route for the design of patters with arbitrary symmetry that can be employed in optics and reversible self‐assembly.

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Section: Introductionmentioning

confidence: 99%

Tunable Dynamic Topological Defect Pattern Formation in Nematic Liquid Crystals

Kim

Serra

2019

Advanced Optical Materials

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“…The decreased number of adsorbed nanoparticles may allow disclination lines to anneal and become points of high twist, such as skyrmions. We believe these defects are skyrmions and not, for instance, torons because the stabilizing nanoparticles formerly followed planar anchoring, while torons do not have regions of planar anchoring surrounding them [31,32,33]. Other types of cholesteric structures are also stabilized under conditions of reduced nanoparticle concentration, where cholesteric fingers form alongside disclinations ( Fig.…”

Section: Mapping Out and Stabilizing Topological Defectsmentioning

confidence: 97%

Swelling Cholesteric Liquid Crystal Shells to Direct the Assembly of Particles at the Interface

Tran

Bishop

2020

ACS Nano

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Cholesteric liquid crystals can exhibit spatial patterns in molecular alignment at interfaces that can be exploited for particle assembly. These patterns emerge from the competition between bulk and surface energies, tunable with the system geometry. In this work, we use the osmotic swelling of cholesteric double emulsions to assemble colloidal particles through a pathway-dependent process. Particles can be repositioned from a surface-mediated to an elasticity-mediated state through dynamically thinning the cholesteric shell at a rate comparable to that of colloidal adsorption. By tuning the balance between surface and bulk energies with the system geometry, colloidal assemblies on the cholesteric interface can be molded by the underlying elastic field to form linear aggregates. The transition of adsorbed particles from surface regions with homeotropic anchoring to defect regions is accompanied by a reduction in particle mobility. The arrested assemblies subsequently map out and stabilize topological defects. These results demonstrate the kinetic arrest of interfacial particles within definable patterns by regulating the energetic frustration within cholesterics. This work highlights the importance of kinetic pathways for particle assembly in liquid crystals, of relevance to optical and energy applications.

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“…We model a two-dimensional velocity field, but in order to allow for twist the director is free to point in three dimensions. For sufficiently high chirality, the ground state of the system is a hexagonal lattice of doubletwist cylinders surrounded by negative disclinations 30,32,38 . These double-twist cylinders are structures with a topological skyrmion number N = 1 4π dxdyn · ∂ n ∂ x × ∂ n ∂ y = 1 2 , and they are therefore termed half-skyrmions (see Fig.…”

Section: A Dynamic Blue Phasesmentioning

confidence: 99%

Topological states in chiral active matter: Dynamic blue phases and active half-skyrmions

Metselaar¹,

Doostmohammadi²,

Yeomans³

2019

The Journal of Chemical Physics

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We numerically study the dynamics of two-dimensional blue phases in active chiral liquid crystals. We show that introducing contractile activity results in stabilised blue phases, while small extensile activity generates ordered but dynamic blue phases characterised by coherently moving half-skyrmions and disclinations. Increasing extensile activity above a threshold leads to the dissociation of the half-skyrmions and active turbulence. We further analyse isolated active half-skyrmions in an isotropic background and compare the activity-induced velocity fields in simulations to an analytical prediction of the flow. Finally, we show that confining an active blue phase can give rise to a system-wide circulation, in which half-skyrmions and disclinations rotate together.

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Spontaneous formation and dynamics of half-skyrmions in a chiral liquid-crystal film

Cited by 111 publications

References 53 publications

Tunable Dynamic Topological Defect Pattern Formation in Nematic Liquid Crystals

Tunable Dynamic Topological Defect Pattern Formation in Nematic Liquid Crystals

Swelling Cholesteric Liquid Crystal Shells to Direct the Assembly of Particles at the Interface

Topological states in chiral active matter: Dynamic blue phases and active half-skyrmions

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