Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, PA 19104, USA.
Proc Natl Acad Sci U S A. 2013 Jan 2;110(1):34-9. doi: 10.1073/pnas.1214708109. Epub 2012 Dec 3.
Controlling topological defects in 3D liquid crystal phases is a crucial element in the development of novel devices, from blue-phase displays to passive biochemical sensors. However, it remains challenging to realize the 3D topological conditions necessary to robustly and arbitrarily direct the formation of defects. Here, using a series of short pillar arrays as topological templates, we demonstrate the hierarchical assembly of focal conic domains (FCDs) in smectic-A liquid crystals that break the underlying symmetry of the pillar lattice, exhibit tunable eccentricity, and together develop a nontrivial yet organized array of defects. The key to our approach lies in the selection of the appropriate ratio of the size of focal domain to the dimension of pillars such that the system favors the "pinning" of FCD centers near pillar edges while avoiding the opposing effect of confinement. Our study unequivocally shows that the arrangement of FCDs is strongly influenced by the height and shape of the pillars, a feature that promotes both a variety of nontrivial self-assembled lattice types and the attraction of FCD centers to pillar edges, especially at regions of high curvature. Finally, we propose a geometric model to reconstruct the smectic layer structure in the gaps between neighboring FCDs to estimate the energetic effects of nonzero eccentricity and assess their thermodynamic stability.
控制 3D 液晶相中的拓扑缺陷是开发新型器件的关键要素，从蓝相显示器到被动生化传感器都有涉及。然而，要实现能够稳定且任意引导缺陷形成的必要的 3D 拓扑条件仍然具有挑战性。在这里，我们使用一系列短柱状物阵列作为拓扑模板，展示了在近晶 A 型液晶中焦锥畴（FCD）的分级组装，该组装打破了支柱晶格的基础对称性，表现出可调节的偏心度，并共同形成了一种非平凡但有序的缺陷阵列。我们方法的关键在于选择适当的焦域尺寸与支柱尺寸的比值，使得系统有利于 FCD 中心在支柱边缘附近“钉扎”，同时避免受限的反作用。我们的研究明确表明，FCD 的排列强烈受到支柱的高度和形状的影响，这一特征促进了多种非平凡的自组装晶格类型的形成，以及 FCD 中心对支柱边缘的吸引力，尤其是在曲率较高的区域。最后，我们提出了一个几何模型来重建相邻 FCD 之间的近晶层结构，以估计非零偏心度的能量效应，并评估它们的热力学稳定性。
