Journal of Colloid and Interface Science ( IF 9.4 ) Pub Date : 2023-04-25 , DOI: 10.1016/j.jcis.2023.04.100 Hee Seong Yun 1 , Zazo Cazimir Meijs 2 , Geonhyeong Park 1 , Yutong Fu 2 , Lucio Isa 2 , Dong Ki Yoon 3
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Hypothesis
Colloidal particles in nematic liquid crystals (LCs) are of high interest for self-assembly of soft matter systems. When two free particles approach within a uniaxially-oriented nematic LC, an elastic force is generated due to the distorted nematic director configuration around them, allowing particles to self-assemble by an attractive force. We hypothesize that if particles are immobilized, repulsive forces emerge instead, causing the deflection of the interacting defects to compensate for the energy increase.
Experiments
We fabricated tailored arrays of spherical silica microparticles via capillarity-assisted particle assembly (CAPA) to investigate the interactions of defects as a function of particle separation. By transferring the particle arrays from the CAPA templates to a glass substrate, we studied interacting boojum defect textures within thin LC films sandwiched between two substrates using polarized optical microscopy (POM).
Findings
We observed deflected boojum defects on arrays of fixed silica particles, confirming our hypothesis that the elastic repulsive force between the particles affects the defect orientation. The nematic director configuration is reconstructed by Landau-de Gennes q-tensor modeling, and simulated POM images are obtained by the Jones-Matrix method. Our results provide a new platform for controlling defect interactions and pave the way for future work to study topology and implement new defect based applications in LC films.
中文翻译：
通过毛细管辅助粒子组装控制固定微粒阵列上的液晶 boojum 缺陷
假设
向列液晶 (LC) 中的胶体颗粒对于软物质系统的自组装具有很高的兴趣。当两个自由粒子在单轴取向的向列 LC 内接近时，由于它们周围扭曲的向列导向器配置，会产生弹力，从而使粒子通过吸引力自组装。我们假设，如果粒子被固定，排斥力反而会出现，导致相互作用缺陷的偏转以补偿能量增加。
实验
我们通过毛细管辅助粒子组装 (CAPA) 制造了定制的球形二氧化硅微粒阵列，以研究作为粒子分离函数的缺陷相互作用。通过将粒子阵列从 CAPA 模板转移到玻璃基板，我们使用偏振光学显微镜 (POM) 研究了夹在两个基板之间的薄 LC 薄膜内的相互作用 boojum 缺陷纹理。
发现
我们在固定二氧化硅颗粒阵列上观察到偏转的 boojum 缺陷，证实了我们的假设，即颗粒之间的弹性排斥力影响缺陷方向。通过 Landau-de Gennes q-tensor 建模重建向列导向器配置，并通过 Jones-Matrix 方法获得模拟的 POM 图像。我们的结果为控制缺陷相互作用提供了一个新平台，并为未来研究拓扑结构和在 LC 薄膜中实施新的基于缺陷的应用铺平了道路。
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