Boundary Geometry Effects on the Coalescence of Liquid Crystalline Tactoids and Formation of Topological Defects

2019 ◽  
Vol 10 (2) ◽  
pp. 278-282 ◽  
Author(s):  
Orla O’Keeffe ◽  
Pei-Xi Wang ◽  
Wadood Y. Hamad ◽  
Mark J. MacLachlan
Keyword(s):  
Liquid Crystalline ◽  
Topological Defects ◽  
Boundary Geometry ◽  
Geometry Effects

scholarly journals Introduction to Colloidal and Microfluidic Nematic Microstructures

Crystals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 956
Author(s):  
Simon Čopar ◽  
Miha Ravnik ◽  
Slobodan Žumer
Keyword(s):  
Soft Matter ◽  
Liquid Crystalline ◽  
Colloidal Particles ◽  
Topological Defects ◽  
Crystalline Materials ◽  
Inherent Anisotropy ◽  
Metastable Structures ◽  
Liquid Crystalline Materials ◽  
Mesoscopic Theory

In this brief review, we give an introduction to selected colloidal and microfluidic nematic microstructures, as enabled by the inherent anisotropy and microscopic orientational ordering in complex liquid crystalline materials. We give a brief overview of the mesoscopic theory, for equilibrium and dynamics, of nematic fluids, that provides the framework for understanding, characterization, and even prediction of such microstructures, with particular comment also on the role of topology and topological defects. Three types of nematic microstructures are highlighted: stable or metastable structures in nematic colloids based on spherical colloidal particles, stationary nematic microfluidic structures, and ferromagnetic liquid crystal structures based on magnetic colloidal particles. Finally, this paper is in honor of Noel A. Clark, as one of the world pioneers that helped to shape this field of complex and functional soft matter, contributing at different levels to works of various groups worldwide, including ours.

scholarly journals INTERPLAY BETWEEN ART AND SCIENCE IN EDUCATION: “MUSIC” BASED APPROACH IN NANOSCIENCES

2014 ◽  
Vol 61 (1) ◽  
pp. 67-76
Author(s):  
Samo Kralj ◽  
Boris Aberšek ◽  
Irena Kralj
Keyword(s):  
Physical Properties ◽  
Learning Strategies ◽  
Liquid Crystalline ◽  
Topological Defects ◽  
Physical Property ◽  
Soft Materials ◽  
Localized States ◽  
Basic Unit ◽  
Local Geometry ◽  
Rich Diversity

Music can be viewed as a structure formed by notes. Different structures in music have potential to yield enormously rich diversity of different melodies. Music is a typical example where a structure defines a property. Similar concepts could be also exploited in education, in presented case in nano-sciences, which are typical representatives of soft materials the structure of which can be strongly manipulated with local geometry and presence of appropriate nanoparticles. The objects of study, named also LC shells, will be exploited as basic unit elements for future soft colloidal crystals. A different arrangement of colloids within the crystal would result in different physical properties in a similar way as different packing of atoms results in different crystals made of real atoms. In presented research will be demonstrated, how relevant basic mechanisms in thin films of nematic liquid crystals could be explained in a classroom and used as a case study, also for explanation of many other physical properties. This research topic is still in its infancy. At this stage only various defect structures in relatively simple geometries (spherical and elliptical) will be analyzed. There is a need to find simple ways to control sensitively the valence of LC shells and in particular to develop strategies to assemble them in crystal structures of desired symmetry. This would allow tailoring specific optical dispersion relations or other physical property of interest and make new ways to teach different physical properties on the »music« based approach. Key words: teaching/learning strategies, »music« based approach, topological defects, localized states, nanoscience, soft materials, liquid crystalline shells.

scholarly journals Prolate and oblate chiral liquid crystal spheroids

2020 ◽  
Vol 6 (28) ◽  
pp. eaba6728
Author(s):  
Monirosadat Sadati ◽  
Jose A. Martinez-Gonzalez ◽  
Ye Zhou ◽  
Nader Taheri Qazvini ◽  
Khia Kurtenbach ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystalline ◽  
Wearable Sensors ◽  
Mechanical Strain ◽  
Orientational Order ◽  
Topological Defects ◽  
Smart Fabrics ◽  
Chiral Liquid Crystal ◽  
Smart Coatings ◽  
Optical Appearance

Liquid crystals are known to exhibit intriguing textures and color patterns, with applications in display and optical technologies. This work focuses on chiral materials and examines the palette of morphologies that arises when microdroplets are deformed into nonspherical shapes in a controllable manner. Specifically, geometrical confinement and mechanical strain are used to manipulate orientational order, phase transitions, and topological defects that arise in chiral liquid crystal droplets. Inspired by processes encountered in nature, where insects and animals often rely on strain and temperature to alter the optical appearance of dispersed liquid crystalline elements, chiral droplets are dispersed in polymer films and deformation induced by uniaxial or biaxial stretching. Our measurements are interpreted by resorting to simulations of the corresponding systems, thereby providing an in-depth understanding of the morphologies that arise in these materials. The reported structures and assemblies offer potential for applications in smart coatings, smart fabrics, and wearable sensors.

scholarly journals Experimental Advances in Nanoparticle-Driven Stabilization of Liquid-Crystalline Blue Phases and Twist-Grain Boundary Phases

Nanomaterials ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 2968
Author(s):  
George Cordoyiannis ◽  
Marta Lavrič ◽  
Vasileios Tzitzios ◽  
Maja Trček ◽  
Ioannis Lelidis ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Liquid Crystalline ◽  
Experimental Studies ◽  
Topological Defects ◽  
Optical Measurements ◽  
Core Composition ◽  
Liquid Crystalline Phases ◽  
Blue Phases ◽  
Underlying Mechanisms ◽  
Chiral Liquid Crystals

Recent advances in experimental studies of nanoparticle-driven stabilization of chiral liquid-crystalline phases are highlighted. The stabilization is achieved via the nanoparticles’ assembly in the defect lattices of the soft liquid-crystalline hosts. This is of significant importance for understanding the interactions of nanoparticles with topological defects and for envisioned technological applications. We demonstrate that blue phases are stabilized and twist-grain boundary phases are induced by dispersing surface-functionalized CdSSe quantum dots, spherical Au nanoparticles, as well as MoS2 nanoplatelets and reduced-graphene oxide nanosheets in chiral liquid crystals. Phase diagrams are shown based on calorimetric and optical measurements. Our findings related to the role of the nanoparticle core composition, size, shape, and surface coating on the stabilization effect are presented, followed by an overview of and comparison with other related studies in the literature. Moreover, the key points of the underlying mechanisms are summarized and prospects in the field are briefly discussed.

scholarly journals Controlled deformation of vesicles by flexible structured media

2016 ◽  
Vol 2 (8) ◽  
pp. e1600978 ◽  
Author(s):  
Rui Zhang ◽  
Ye Zhou ◽  
José A. Martínez-González ◽  
Juan P. Hernández-Ortiz ◽  
Nicholas L. Abbott ◽  
...  
Keyword(s):  
Free Energy ◽  
Equatorial Plane ◽  
Liquid Crystalline ◽  
Topological Defects ◽  
Energy Functional ◽  
Surface Forces ◽  
Free Energy Functional ◽  
Structured Media ◽  
Spheroidal Shape ◽  
Anchoring Strength

Liquid crystalline (LC) materials, such as actin or tubulin networks, are known to be capable of deforming the shape of cells. Here, elements of that behavior are reproduced in a synthetic system, namely, a giant vesicle suspended in a LC, which we view as a first step toward the preparation of active, anisotropic hybrid systems that mimic some of the functionality encountered in biological systems. To that end, we rely on a coupled particle-continuum representation of deformable networks in a nematic LC represented at the level of a Landau–de Gennes free energy functional. Our results indicate that, depending on its elastic properties, the LC is indeed able to deform the vesicle until it reaches an equilibrium, anisotropic shape. The magnitude of the deformation is determined by a balance of elastic and surface forces. For perpendicular anchoring at the vesicle, a Saturn ring defect forms along the equatorial plane, and the vesicle adopts a pancake-like, oblate shape. For degenerate planar anchoring at the vesicle, two boojum defects are formed at the poles of the vesicle, which adopts an elongated, spheroidal shape. During the deformation, the volume of the topological defects in the LC shrinks considerably as the curvature of the vesicle increases. These predictions are confirmed by our experimental observations of spindle-like shapes in experiments with giant unilamellar vesicles with planar anchoring. We find that the tension of the vesicle suppresses vesicle deformation, whereas anchoring strength and large elastic constants promote shape anisotropy.

scholarly journals Tuning the defect configurations in nematic and smectic liquid crystalline shells

2013 ◽  
Vol 371 (1988) ◽  
pp. 20120258 ◽  
Author(s):  
Hsin-Ling Liang ◽  
JungHyun Noh ◽  
Rudolf Zentel ◽  
Per Rudquist ◽  
Jan P.F. Lagerwall
Keyword(s):  
Boundary Conditions ◽  
Self Assembly ◽  
Liquid Crystalline ◽  
Topological Defects ◽  
Microfluidic System ◽  
Director Field ◽  
Smectic Phases ◽  
Anchor Points ◽  
External Forces ◽  
Linker Molecules

Thin liquid crystalline shells surrounding and surrounded by aqueous phases can be conveniently produced using a nested capillary microfluidic system, as was first demonstrated by Fernandez-Nieves et al. in 2007. By choosing particular combinations of stabilizers in the internal and external phases, different types of alignment, uniform or hybrid, can be ensured within the shell. Here, we investigate shells in the nematic and smectic phases under varying boundary conditions, focusing in particular on textural transformations during phase transitions, on the interaction between topological defects in the director field and inclusions in the liquid crystal (LC), and on the possibility to relocate defects within the shell by rotating the shell in the gravitational field. We demonstrate that inclusions in a shell can seed defects that cannot form in a pristine shell, adding a further means of tuning the defect configuration, and that shells in which the internal aqueous phase is not density matched with the LC will gently rearrange the internal structure upon a rotation that changes the influence of gravity. Because the defects can act as anchor points for added linker molecules, allowing self-assembly of adjacent shells, the various arrangements of defects developing in these shells and the possibility of tuning the result by modifying boundary conditions, LC phase, thickness and diameter of the shell or applying external forces make this new LC configuration very attractive.

scholarly journals Chiral Liquid Crystal Lenses Confined in Microchannels

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3761
Author(s):  
Sean M. Hare ◽  
Beatrice Lunsford-Poe ◽  
MinSu Kim ◽  
Francesca Serra
Keyword(s):  
Phase Transition ◽  
Liquid Crystalline ◽  
Focal Length ◽  
Topological Defects ◽  
Experimental Conditions ◽  
Smectic A ◽  
Heating And Cooling ◽  
Chiral Nematic ◽  
Nematic Phases ◽  
Tunable Lenses

It is known that the liquid crystalline smectic-A phase has geometric defects, called focal conic domains, which can be used as gradient-index microlenses. Cholesteric (chiral nematic) phases also have topological defects with a central symmetry and a singularity at their center. We explore a weakly chiral system in which both types of defects can be present in the same material at different temperatures, and with this strategy we create lenses whose focal length is tunable with temperature. We measure the focal length of the tunable lenses, and we investigate the behavior of the defects near the phase transition. We identify the experimental conditions that make the simultaneous presence of the smectic focal conic domains and the circular cholesteric domains possible, such as the concentration of chiral dopant and the rate of heating and cooling. The transformation of focal conic domains into circular cholesteric domains is a new example of memory at the phase transition between smectic-A and nematic liquid crystals.

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