Trivedi Rahul P, Tasinkevych Mykola, Smalyukh Ivan I
Department of Physics and Department of Electrical, Computer and Energy Engineering, University of Colorado, Boulder, Colorado 80309, USA.
Max-Planck-Institut für Intelligente Systeme, Heisenbergstrasse 3, D-70569 Stuttgart, Germany.
Phys Rev E. 2016 Dec;94(6-1):062703. doi: 10.1103/PhysRevE.94.062703. Epub 2016 Dec 14.
Cholesteric liquid crystals can potentially provide a means for tunable self-organization of colloidal particles. However, the structures of particle-induced defects and the ensuing elasticity-mediated colloidal interactions in these media remain much less explored and understood as compared to their nematic liquid crystal counterparts. Here we demonstrate how colloidal microspheres of varying diameter relative to the helicoidal pitch can induce dipolelike director field configurations in cholesteric liquid crystals, where these particles are accompanied by point defects and a diverse variety of nonsingular line defects forming closed loops. Using laser tweezers and nonlinear optical microscopy, we characterize the ensuing medium-mediated elastic interactions and three-dimensional colloidal assemblies. Experimental findings show a good agreement with numerical modeling based on minimization of the Landau-de Gennes free energy and promise both practical applications in the realization of colloidal composite materials and a means of controlling nonsingular topological defects that attract a great deal of fundamental interest.
胆甾相液晶有可能为胶体颗粒的可调谐自组装提供一种手段。然而，与向列相液晶相比，在这些介质中由颗粒诱导的缺陷结构以及随之而来的弹性介导的胶体相互作用仍有待深入探索和理解。在这里，我们展示了相对于螺旋节距具有不同直径的胶体微球如何在胆甾相液晶中诱导偶极状指向矢场构型，其中这些颗粒伴随着点缺陷和形成闭环的各种非奇异线缺陷。使用激光镊子和非线性光学显微镜，我们表征了随之而来的介质介导的弹性相互作用和三维胶体组装。实验结果与基于朗道 - 德热纳自由能最小化的数值模拟结果吻合良好，并有望在胶体复合材料的实现中得到实际应用，同时也为控制引起大量基础研究兴趣的非奇异拓扑缺陷提供了一种方法。
