Abstract

Since their inception, liquid crystals (LCs) have been a topic of great interest among researchers around the globe. The alignment of LC molecules remains pivotal to explore the basic and applied aspects of LCs. Various alignment techniques such as rubbing of polyimides, coating of surfactants, magnetic field, oblique evaporation of SiOx, photoalignment, etc. have been widely explored to obtain the uniform alignment of LCs, eventually required in the fabrication of LC based displays and other photonic devices. One has to judiciously select the alignment technique to produce LC displays at industrial scale. However, certain issues have always remained which further stimulated the researchers to explore new sustainable ways of aligning LCs. Under this framework, the nanoparticles-controlled alignment could be one of new methods to align LCs. In this review, we have focused on the nanoparticles (isotropic and anisotropic) controlled alignment of LCs. The alignment of LCs could be achieved by: (i) doping of nanoparticles in the bulk LCs and (ii) patterning or growth of nanostructures on the substrates. Interestingly, the nanostructures grown on the non-conducting substrate are found to work as LC aligning agent and transparent conducting electrode. The nanoparticles doped polyimide alignment layers are also found to significantly improve the alignment of LCs. The quality of LC alignment obtained by using nanoparticles is more or less same as in conventional alignment techniques but less time consuming and cost-effective. Besides the induced or improved alignment of LCs due to nanoparticles, the electro-optical properties of LC devices are also found to be greatly improved as compared to devices using conventional alignment techniques. Moreover, we have discussed the pros and cons and future perspectives of nanoparticles tuned alignment of LCs.

摘要

自问世以来，液晶 (LC) 一直是全球研究人员非常感兴趣的话题。LC 分子的排列仍然是探索 LC 的基础和应用方面的关键。聚酰亚胺摩擦、表面活性剂涂层、磁场、SiOx 倾斜蒸发、光对准等各种对准技术已被广泛探索以获得 LC 的均匀对准，最终在基于 LC 的显示器和其他光子器件的制造中需要. 必须明智地选择对准技术以生产工业规模的 LC 显示器。然而，某些问题始终存在，这进一步激发了研究人员探索对齐 LC 的新的可持续方法。在此框架下，纳米粒子控制的排列可能成为排列 LC 的新方法之一。在这篇综述中，我们重点关注了 LC 的纳米粒子（各向同性和各向异性）控制排列。LC 的对齐可以通过以下方式实现：(i) 在块状 LC 中掺杂纳米粒子和 (ii) 在基板上形成纳米结构的图案或生长。有趣的是，发现在非导电基板上生长的纳米结构可用作 LC 取向剂和透明导电电极。还发现纳米粒子掺杂的聚酰亚胺排列层显着改善了 LC 的排列。通过使用纳米粒子获得的 LC 排列质量与传统排列技术大致相同，但耗时更少且具有成本效益。除了由于纳米粒子引起的或改进的 LC 排列外，与使用传统对准技术的器件相比，还发现 LC 器件的电光特性得到了极大的改善。此外，我们还讨论了 LC 的纳米粒子调谐排列的优缺点和未来前景。