Role of Stimuli on Liquid Crystalline Defects: From Defect Engineering to Switchable Functional Materials

Abstract

Achieving tunable physical properties is currently one of the most exciting research topics. In order to realize this goal, a medium that is responsive to external stimuli and can undergo a change in its physical property is required. Liquid crystal (LC) is a prominent candidate, as its physical and optical properties can be easily manipulated with various stimuli, such as surface anchoring, rubbing, geometric confinement, and external fields. Having broken away from the past devotion to obtaining a uniform domain of LCs, people are now putting significant efforts toward forming and manipulating ordered and oriented defect structures with a unique arrangement within. The complicated molecular order with tunability would benefit the interdisciplinary research fields of optics, physics, photonics, and materials science. In this review, the recent progress toward defect engineering in the nematic and smectic phases by controlling the surface environment and electric field and their combinational methods is introduced. We close the review with a discussion of the possible applications enabled using LC defect structures as switchable materials.

Visualization of nonsingular defect enabling rapid control of structural color

“…The detailed nature of the screw dislocation core structure plays a critical role on the efficient interlayer diffusion in various 1D periodic materials including smectic liquid crystals (28,29), 2D layered crystals (39), and nanoporous materials (40). Thus, engineering of such valuable defects via substrate patterning (41)(42)(43) suggests future designs for purposeful defect-containing layered materials to enhance the dynamics of SC suitable for emerging stimuli-interactive SC sensors and displays. A hexagon with flat surface of an as-fabricated pattern was obtained in the step ① of (A).…”

Synergistic Effect of Fluorination and Molecular Orientational Order on the Dielectric Properties of Low-κ Liquid Crystal Polymer Films

“…Furthermore, another approach to modulating dielectric properties is the manipulation of molecular orientational order. , Previously, many reports have used surface treatments to generate nanotopography to guide various anisotropic materials such as LCs, block copolymers, cells, and metal gold nanoparticles. − The underlying principle lies in the deformation of a surface to induce a nanotopography that enables orientations of various LC and polymer materials . Particularly, rubbing has proved to be a mild and reproducible method to orient molecules and, at the same time, avoid chain entanglement.…”

The fate of liquid crystal topological defects on chemically patterned surfaces during phase transitions

“…Both FCDs and TFCDs have been studied during the fabrication of highly ordered LC defect arrays through different methods, such as self-assembly [5][6][7][8][9] or external stimuli driven transformations. 6,10,11 Well-organized arrays of topological defects have been successfully employed in applications, such as particle manipulation, 12,13 micro lenses, 14,15 micropatterns, 16,17 and vortex beam generators. 18,19 So far, most studies on SmA LCs focused on manipulating and utilizing these SmA LC defects.…”