Shape control of surface-stabilized disclination loops in nematic liquid crystals

Sunami, Kanta; Imamura, Koki; Ouchi, Tomohiro; Yoshida, Hiroyuki

doi:10.1103/physreve.97.020701

Cited by 17 publications

(19 citation statements)

References 31 publications

(36 reference statements)

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“…[23][24][25] The resulting topological structures with or without disclinations, identified as torons or hopfions, can be stable, although homeotropic alignment in the bulk has a lower elastic energy. The structures studied by the Ozaki group 22,26 can also be considered as solitons.…”

Section: Introductionmentioning

confidence: 99%

“…In their experiments Sunami et al use a similar circular photo-alignment pattern, but with only a 180°rotation of the azimuthal angle and therefore they find only one structure with a single disclination ring. 26 In the following we discuss the technology for the fabrication process, the patterned alignment and the cell assembly, show polarization optical microscopy (POM) images of the structures, present finite-element Q-tensor simulations for the director configuration and corresponding transmission simulations based on a beam propagation method (BPM).…”

Section: Introductionmentioning

confidence: 99%

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Ring-shaped liquid crystal structures through patterned planar photo-alignment

et al. 2020

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Ring-shaped liquid crystal structures through patterned planar photo-alignment

et al. 2020

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“…This ability was exploited in recent years to create an artificial web of disclination lines (in non-equilibrium conditions) [21], and to stabilize 2D diffractive structures with intricate bulk director configurations demonstrating symmetry breaking and regions with pronounced non-planar director orientation in the bulk [22][23][24][25]. In general, patterned planar photo-alignment offers valuable possibilities to study the formation of (twist) disclination lines, their interaction and their annihilation when the alignment patterns are well designed [21][22][23][24][25][26][27][28][29][30]. When a different azimuthal angle is imposed at corresponding locations at the top and bottom substrate, a position dependent twist in the bulk can occur.…”

Section: Introductionmentioning

confidence: 99%

“…When a different azimuthal angle is imposed at corresponding locations at the top and bottom substrate, a position dependent twist in the bulk can occur. However, for some combinations of alignment patterns at the substrates, the topology at the interfaces requires either the creation of disclinations in the bulk or regions with vertical director orientation [15,[23][24][25][26][27][28][29][30]. We recently demonstrated for different alignment configurations that surface induced twist conflicts are often elegantly resolved, without the need for singular disclination lines, by introducing a region with vertical director orientation in the bulk of the device [15,[23][24][25].…”

Section: Introductionmentioning

confidence: 99%

Surface Stabilized Topological Solitons in Nematic Liquid Crystals

2020

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Photo-alignment is a versatile tool to pattern the alignment at the confining substrates in a liquid crystal (LC) cell. Arbitrary alignment patterns can be created by using projection with a spatial light modulator (SLM) for the illumination. We demonstrate that a careful design of the alignment patterns allows the stabilization of topological solitons in nematic liquid crystal (NLC) cells, without the need for chirality or strong confinement. The created LC configurations are stabilized by the anchoring conditions imposed at the substrates. The photo-aligned background at both substrates is uniformly planar aligned, and ring-shaped regions with a 180° azimuthal rotation are patterned with an opposite sense of rotation at the top and bottom substrate. A disclination-free structure containing a closed ring of vertically oriented directors is formed when the patterned rings at the top and bottom substrate overlap. Thanks to the topological stability, a vertical director orientation in the bulk is observed even when the centra of both patterned rings are shifted over relatively large distances. The combination of numerical simulations with experimental measurements allows identification of the 3D director configuration in the bulk. A finite element (FE) Q-tensor simulation model is applied to find the equilibrium director configuration and optical simulations are used to confirm the correspondence with experimental microscopy measurements. The created LC configurations offer opportunities in the field of optical devices, light guiding and switching, particle trapping and studies of topological LC structures.

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“…[36][37][38] Therefore, significant efforts have recently been dedicated to developing techniques for generating topological defects with designable structures. [39][40][41][42][43][44][45][46] For example, Yoshida and co-workers demonstrated suspended disclination loops by designing twist angle distribution [40,41] and 3D disclination networks by shifting defect patterns at the top and bottom surfaces. [42] Yokoyama et al demonstrated stable webs of freestanding disclinations by using designed alignment patterns on two confining surfaces.…”

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confidence: 99%

Photopatterned Designer Disclination Networks in Nematic Liquid Crystals

Guo

Afghah

Peng

et al. 2021

Advanced Optical Materials

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between the boundary conditions and the long range orientational ordering in the bulk or long range distortions of the director field. [7,9,11] A spherical particle, immersed in an otherwise uniformly aligned nematic LC, introduces a hyperbolic point defect-hedgehog or a disclination loop when bearing vertical surface alignment of the director. [12][13][14] Arrays of spherical particles can generate disclination loops with knots and links, such as the Hopf link, the star of David, and the Borromean rings. [15][16][17][18][19] The topology of the generated disclinations can be further enriched by immersing particles with complex topologies into LCs, leading, for example, to two disclination loops around a torus particle or knotted disclination loops around a trefoil particle. [20][21][22][23][24] LCs with topological defects represent a promising medium for photonic applications, [25][26][27] for directing the self-assembly of particles with sizes from micrometers to nanometers, [15,[28][29][30][31][32][33] for programmable origami, [34,35] and for command of active matter. [36][37][38] Therefore, significant efforts have recently been dedicated to developing techniques for generating topological defects with designable structures. [39][40][41][42][43][44][45][46] For example, Yoshida and co-workers demonstrated suspended disclination loops by designing twist angle distribution [40,41] and 3D disclination networks by shifting defect patterns at the top and bottom surfaces. [42] Yokoyama et al. demonstrated stable webs of freestanding disclinations by using designed alignment patterns on two confining surfaces. [43] These studies demonstrate many appealing features of topological defects while triggering a question whether the approach can be further developed to enable more complex geometries of disclinations with preprogrammed features.In this work, we demonstrate the capability to precisely design and create complex 3D disclination networks, by using a recently developed plasmonic photopatterning technique to inscribe arbitrary 2D director patterns of LCs at two flat confining surfaces. [47,48] We present examples of precisely designed networks in which singular disclinations are either anchored to the substrates or remain freely suspended in bulk, forming polygonal loops or wavy curves. The type of the network is entirely determined by the designed director patterns at two confining surfaces of a flat nematic slab. We further demonstrate that the radius of curvature, size, and shape of these Linear defect-disclinations are of fundamental interest in understanding complex structures explored by soft matter physics, elementary particles physics, cosmology, and various branches of mathematics. These defects are also of practical importance in materials applications, such as programmable origami, directed colloidal assembly, and command of active matter. Here an effective engineering approach is demonstrated to pattern molecular orientations at two flat confining surfaces that produce complex yet designable network...

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Shape control of surface-stabilized disclination loops in nematic liquid crystals

Cited by 17 publications

References 31 publications

Ring-shaped liquid crystal structures through patterned planar photo-alignment

Ring-shaped liquid crystal structures through patterned planar photo-alignment

Surface Stabilized Topological Solitons in Nematic Liquid Crystals

Photopatterned Designer Disclination Networks in Nematic Liquid Crystals

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