Chinese Journal of Liquid Crystals and Displays, Volume. 39, Issue 5, 569(2024)

Photoalignment guided order evolution of liquid crystals

Daoxing LUO, Jinbing WU, Zhenghao GUO, and Wei HU*
Author Affiliations
  • College of Engineering and Applied Sciences,Nanjing University,Nanjing 210023,China
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    Figures & Tables(14)
    Different liquid crystal phases. Schemes of director distributions and typical microscopic textures of(a)nematic phase,(b)cholesteric phase and(c)smectic phase liquid crystals[30].
    Different deformation types of directors of liquid crystals. Three basic deformations:(a)splay,(b)twist and(c)bend deformations;(d)Splay,layer compression [31] and(e)saddle-splay[32] deformations in smectic A phase liquid crystals.
    Topological defects in nematic liquid crystals.(a)Schematics of point defects with different topological charges in two-dimensional liquid crystal systems[33];(b)Schematics of disclination lines formed by different combinations in three-dimensional liquid crystal systems[34];(c)Schematics of splay-bend,twist and mixed wall defects[35].
    Topological defects in smectic A phase.(a)Schematic of FCD with characteristic defect pairs as confocal ellipses and hyperbolas,and its polarized microscope image[31];(b)Schematic of TFCD with characteristic defect pairs as circular defects in confocal and linear defects over the center of a circle,and its polarized microscope image[38-39];(c)Schematic of SFCD with characteristic defect pairs as the two asymptotes of the characteristic hyperbolic defects parallel and perpendicular to the substrate,and its polarized microscope image[40];(d)Schematic of FCDs closely alternating to form the Zigzag-FCD and its polarized microscope image[41];(e)Schematic of PFCD with characteristic defects as the two parabolic defect pairs in confocal andits polarized microscope image[42-43];(f)Schematic of OS with one-dimensional lattice periodic distribution of characteristic defects in thin layer liquid crystal system and its polarized microscope image[44].
    Basic types of FCDs[36].(a)Schematic of FCD-I with negative Gaussian curvature;(b)Schematic of FCD-‍Ⅱ with positive Gaussian curvature;(c)Schematic of FCD-Ⅲ with both positive and negative positive Gaussian curvature.
    Evolutionsof topological defects across the N-S phase transition.(a)Schematics of ±1 point defects and their evolutions during the N-S phase transition;(b)Orientation patterns with periodic distribution of+1 and -1 singularities enabled by photoalignment technology and the evolutions of ±1 point defects during the N-S phase transition under slow cooling;(c)Evolutions of disclination lines during the N-S phase transition under rapid cooling,and the formation of wall defects in the N phase;(d)Relationship between system energy F and temperature T during the N-S phase transition,topological analysis of three different N textures and the coexistence of point defects and wall defects[5].
    Controlled evolutions of topological defects across the N-S phase transitions.(a)Structural evolutions of disclination lines and wall defects when the initial azimuthal angles of the radial orientational alignment lattices are 0°,30°,60°,and 90°,respectively[11];(b)Periodic and quasiperiodic topological defects with Ci(i=2~6)symmetries guided by alignment lattices with different symmetries,and their topological analysis. The lattice types and symmetries are rectangular lattice(C2),diamond lattice(C2),triangular lattice(C3),square lattice(C4),quasiperiodic lattice(C5),and hexagonal lattice(C6),respectively[12].
    Controlled generation of TFCDs,SFCDs and d-TFCDs.(a)Polarized microscopy images and SEM images of TFCDs with one-dimensional periodicity under microchannel confinement[51];(b)Realization of TFCDs array with controllable unit domain size enabled by photoalignment technology[8];(c)Formation of SCFDs array guided by periodic alternating ± 45° orientation pattern and its structural dependence on orientational angle[6];(d)Generations of d-TFCDs array supported by complex alignment designs[7].
    Microlens functions of TFCDs and d-TFCDs.(a)Schematic of imaging for TFCDs microlens array[52];(b)Continuous tuning of focal length of polymer stabilized TFCDs microlens array enabled by external electric fields[8];(c)Imaging characterization of FCDs microlens array with continuous variation in unit size[54];(d)Four-dimensional imaging characterization of d-TFCDs microlens arrays[7].
    Other advanced applications of TFCDs.(a)Optical diffraction characteristics of SFCDs array[6];(b)Diffraction characterization of periodic and quasiperiodic TFCDs array with Ci(i=2~6)symmetries[31];(c)Fluorescent silicaparticles captured by TFCDs array to achieve particles array assembly[51];(d)Generation of vortex optical arrays with topological charge s=2 using TFCDs array[55].
    Controllable generation of OSs.(a)Three-dimensional schematic of OSs[58];(b)Programmable arbitrary patterned OSs enabled by photoalignment technology[29];(c)Switching state and structural rotation of the OSs under the external electric fields[29];(d)Realization of reversible rotation of chiral OSs under light stimulations[9].
    Functional applications of OSs.(a)Diffraction characterization of patterned OSs gratings[65];(b)Characterization of chiral OSs gratings with reversible rotation stimulated by light[9];(c)Self-assembly of gold nanoparticle arrays using OSs and characterization of surface enhanced Raman scattering effect[66-67];(d)Superhydrophobic surface achieved by OSs[68];(e)Cell culture enabled by OSs[69].
    Investigation of transformation from FCDs to OSs.(a)Schematic of one-dimensional periodic OSs and two-dimensional periodic FCDs,and the structural transformations observed when film thickness varies[59];(b)Evolution of OSs to FCDs under different film thicknesses based on photoalignment technology[10];(c)Polarization micrograph of liquid crystal system in critical phase transition state with gradient changes in film thickness,phase diagram of critical temperature T and film thickness derivative 1/h[71];(d)Transformation from FCDs to OSs achieved by applying external electric fields[72].
    Simulations of topological defects in the SmA phase.(a)Simulations of topological defects in the two-dimensional SmA phase[25];(b)Simulations of TFCDs and OSs[27].
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    Daoxing LUO, Jinbing WU, Zhenghao GUO, Wei HU. Photoalignment guided order evolution of liquid crystals[J]. Chinese Journal of Liquid Crystals and Displays, 2024, 39(5): 569

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    Paper Information

    Category: Research Articles

    Received: Feb. 2, 2024

    Accepted: --

    Published Online: Jul. 8, 2024

    The Author Email: Wei HU (huwei@nju.edu.cn)

    DOI:10.37188/CJLCD.2024-0043

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