Electric field generation of Skyrmion-like structures in a nematic liquid crystal

Cattaneo, Laura; Kos, Žiga; Savoini, Matteo; Kouwer, Paul H. J.; Rowan, Alan E.; Ravnik, Miha; Muševič, Igor; Rasing, T.H.M.

doi:10.1039/c5sm01726b

Cited by 12 publications

(9 citation statements)

References 28 publications

(32 reference statements)

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“…The preferred orientation of the BP is thus mediated by the strain imposed by a patterned surface, and the generality of this concept is established by designing different patterns that stabilize different orientations along the BPII (100) , BPII (110) and BPII (111) crystallographic lattice planes. In this context, we hasten to point out that Cattaneo et al 41. have shown that square-like patchy patterns can be used to induce formation of Skyrmion-like phases in non-chiral liquid crystals—the molecules of this phases form chiral twists but the entire phase does not possess a crystalline symmetry.…”

Section: Discussionmentioning

confidence: 99%

“…In this context, we hasten to point out that Cattaneo et al . 41 have shown that square-like patchy patterns can be used to induce formation of Skyrmion-like phases in non-chiral liquid crystals—the molecules of this phases form chiral twists but the entire phase does not possess a crystalline symmetry. A closer inspection of the LC texture in the proximity of our BPII (111) and BPII (110) interfaces, also reveals the formation of Skyrmion structures reminiscent of those observed by these authors (see Supplementary Fig.…”

Section: Discussionmentioning

confidence: 99%

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Directed self-assembly of liquid crystalline blue-phases into ideal single-crystals

et al. 2017

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Chiral nematic liquid crystals are known to form blue phases—liquid states of matter that exhibit ordered cubic arrangements of topological defects. Blue-phase specimens, however, are generally polycrystalline, consisting of randomly oriented domains that limit their performance in applications. A strategy that relies on nano-patterned substrates is presented here for preparation of stable, macroscopic single-crystal blue-phase materials. Different template designs are conceived to exert control over different planes of the blue-phase lattice orientation with respect to the underlying substrate. Experiments are then used to demonstrate that it is indeed possible to create stable single-crystal blue-phase domains with the desired orientation over large regions. These results provide a potential avenue to fully exploit the electro-optical properties of blue phases, which have been hindered by the existence of grain boundaries.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Directed self-assembly of liquid crystalline blue-phases into ideal single-crystals

et al. 2017

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“…Such behaviour is also reported to be observed experimentally. 72 The free energy of these induced boojum states is several 10% higher than the free energy of the HAN configuration.…”

Section: Boojum Nematic Configurationmentioning

confidence: 95%

Relevance of saddle-splay elasticity in complex nematic geometries

Kos

Ravnik

2016

Soft Matter

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We demonstrate the relevance of saddle-splay elasticity in nematic liquid crystalline fluids in the context of complex surface anchoring conditions and the complex geometrical confinement. Specifically, nematic cells with patterns of surface anchoring and colloidal knots are shown as examples where saddle-splay free energy contribution can have a notable role which originates from nonhomogeneous surface anchoring and the varying surface curvature. Patterned nematic cells are shown to exhibit various (meta)stable configurations of nematic field, with relative (meta)stability depending on the saddle-splay. We show that for high enough values of saddle-splay elastic constant K24 a previously unstable conformation can be stabilised, more generally indicating that the saddle-splay can reverse or change the (meta)stability of various nematic structures affecting their phase diagrams. Furthermore, we investigate saddle-splay elasticity in the geometry of highly curved boundaries - the colloidal particle knots in nematic - where the local curvature of the particles induces complex spatial variations of the saddle-splay contributions. Finally, a nematic order parameter tensor based saddle-splay invariant is shown, which allows for the direct calculation of saddle-splay free energy from the Q-tensor, a possibility very relevant for multiple mesoscopic modelling approaches, such as Landau-de Gennes free energy modelling.

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“…9,10,[21][22][23][24][25] It has been shown that the classification of such topological systems is given by topological conservation laws and depends on topological invariants, such as knot polynomials and the crossing number of the knots. 26,27 Complex nematic fluids are shown to stabilise a variety of topological structures spanning from solitonic structures like skyrmions, merons, torons and hopfions [28][29][30][31][32][33][34][35] to different forms of defect points and lines. [36][37][38] These topological structures can form either spontaneously or by localized inclusions, such as with colloidal particles.…”

Section: Introductionmentioning

confidence: 99%

Nematic colloidal knots in topological environments

Hashemi

Ravnik

2018

Soft Matter

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The role of environment in shaping material properties is of great significance, but less is known about how non-trivial topology of the environment couples to material states, which can be of non-trivial topology themselves. In this paper, we demonstrate the role of the topology of the environment on the formation of complex nematic fields and defect structures, specifically in the system of nematic colloidal knots. The topological environments around knotted colloidal particles are suggested to exist as spherical surface-patterned nematic cavities imposing radial, uniform or hyperbolic nematic profiles. We show that topologically different nematic environments significantly affect and create differences in the colloidal field structure created within the environment, such as the location, profile and number of topological defects. Specifically, we demonstrate that topological environments in combination with knotted colloidal particles of non-trivial topology lead to the formation of diverse nematic knotted and linked fields. These fields are different adaptations of the knotted shape of the colloidal particles, creating knots and links of topological defects as well as escaped-core defect-like solitonic structures. These are observed in chiral nematic media but here are stabilised in achiral nematic media as a result of the distinct shape of the knotted colloidal particle, with a double helix segment and nematic environmental patterns. More generally, this paper is a contribution towards understanding the role of environment, especially its topology, on the response and defect formation in elastic fields, such as in nematic liquid crystal colloids.

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Electric field generation of Skyrmion-like structures in a nematic liquid crystal

Abstract: We report the generation of stable Skyrmion-like structures in a thin nematic liquid crystal film on chemically patterned patchy surfaces.

Cited by 12 publications

References 28 publications

Directed self-assembly of liquid crystalline blue-phases into ideal single-crystals

Directed self-assembly of liquid crystalline blue-phases into ideal single-crystals

Relevance of saddle-splay elasticity in complex nematic geometries

Nematic colloidal knots in topological environments

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