Focal Conic Flower Textures at Curved Interfaces

Abstract

Focal conic domains (FCDs) in smectic-A liquid crystals have drawn much attention both for their exquisitely structured internal form and for their ability to direct the assembly of micro- and nanomaterials in a variety of patterns. A key to directing FCD assembly is control over the eccentricity of the domain. Here, we demonstrate a new paradigm for creating spatially varying FCD eccentricity by confining a hybrid-aligned smectic with curved interfaces. In particular, we manipulate interface behavior with colloidal particles in order to experimentally produce two examples of what has recently been dubbed the flower texture, where the focal hyperbolae diverge radially outward from the center of the texture, rather than inward as in the canonical eventail or fan texture. We explain how this unconventional assembly can arise from appropriately curved interfaces. Finally, we present a model for this system that applies the law of corresponding cones, showing how FCDs may be embedded smoothly within a "background texture" of large FCDs and concentric spherical layers, in a manner consistent with the qualitative features of the smectic flower. Such understanding could potentially lead to disruptive liquid crystal technologies beyond displays, including patterning, smart surfaces, microlens arrays, sensors and nanomanufacturing

Inhomogeneous relaxation dynamics and phase behaviour of a liquid crystal confined in a nanoporous solid

“…Both the collective orientational (isotropic-to-nematic) and the translational (smectic-toliquid or smectic-to-nematic) transitions have turned out to be significantly affected by finite size and interfacial (solid-liquid or liquid-liquid) interactions introduced by confining walls [1][2][3][4][5][6] or the geometrical constraints in nanoporous media [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24].…”

Synergistic assembly of nanoparticles in smectic liquid crystals

“…33 The POM images suggested that domains of vertically aligned smectic layers constituted the hybrid F-SiO 2 NPs/F-LC structures, where the average field director lay parallel to the planes of the air/LC and LC/substrate interfaces, respectively (see schematic in Fig. 28. This is only possible if there is planar alignment of the LC director at the upper interface.…”

“…[11][12][13][14][15][16][17][18][19][20] From a technological standpoint, the ability to tailor the topological defects will offer new tools to design, fabricate, and dynamically tune the advanced materials and devices. 28 These defect domains arise from a balance of the elastic energy cost of layer bending and the anchoring energies on bounding surfaces, typically planar anchoring on the substrate and homeotropic anchoring (i.e., in perpendicular orientation) at the LC/air interface. Compared with nematic LCs, which have only orientational order wherein molecules self-align along their common long axis, smectic LCs have both orientational and translational long-range ordering, and thus can arrange into layers or planes with the long molecular axis parallel to the layer normal.…”

Nano-imaging enabled via self-assembly

“…The fabrication of this lens array is particularly interesting because regular arrays of bundles of carbon nanotubes were used as seeds to direct the formation of the liquid-crystal nano-lenses under an applied voltage [91]. In another use of liquid-crystals, self-assembled focal conic domains exhibit nano-lens-like properties over large arrays, however they have not yet been applied to any practical devices [92]. The ability to dynamically control the shape of liquid crystal structures is likely to enable advanced imaging and/or sensing applications.…”