Self-assembly of Topologically Distinct Colloid Particles in Partially Ordered Fluids

非技术性质的液体晶体无疑是凝聚态物质最重要的商业形式之一。它们被广泛应用于显示器、电光和光子器件以及能量转换。这种有用性源于利用电场和磁场控制这些雪茄形状分子的取向的能力。新材料允许设计更复杂的结构，并增加液晶材料的功能。首席研究员(PI)和他的团队将开发由分散在液晶介质中的微小胶体颗粒组成的新型液晶。胶体颗粒将具有不同的形状(拓扑)，这将决定液晶在受到电场和磁场作用时将形成的结构类型。他们将研究这些“拓扑胶体”的行为，以了解纳米粒子和液晶分子之间的相互作用如何决定结构，目标是开发一本“配方书”，将粒子组织成精确受控的结构。了解这种“拓扑引导”自组装的基本原理，可以开发出具有独特性能的新型电控和光控材料，用于对社会具有重要意义的实用设备，如柔性显示器和数据存储设备。该协会将把这项研究与广泛的协同教育和推广活动结合起来，包括在小学和中学举行的“光、颜色和物质”精灵表演，为高中生提供科学之旅，为专业社团的学生分会提供建议，并为少数族裔服务机构的学生和教职员工提供研究经验。该协会致力于开发一种名为“拓扑胶体”的新软物质系统，并确定液晶(LCS)中胶体粒子由拓扑决定的自组装背后的基本组织原理。这项研究将包括可伸缩制备不同大小的不同拓扑结构的胶体粒子及其在液晶中的分散的方法的设计，粒子拓扑结构、指向矢场和拓扑缺陷之间相互作用的实验研究和模拟，以及利用电场和磁场和光控制的可切换胶体自组装和取向的探索。新兴的跨学科科学前沿是纳米科学、凝聚态物理和拓扑学/数学的结合点。从亚原子粒子到宇宙学，许多现象都是由场、表面和单极或弦状缺陷的拓扑相互作用引起的。这种拓扑相互作用受到拓扑学中的定理的约束，但很难通过实验来探讨。拓扑胶体的模型系统可以直接对这种拓扑相互作用进行实验研究，从而影响到许多科学领域，远远超出了拟议研究活动的具体目标。这一研究活动本质上是变革性的，有望为从拓扑约束自组装到低维拓扑的实验研究等新的研究方向奠定基础。除了对物理基础的探索外，Pi和他的学生正在开发的实验领域可能会实现纳米颗粒的支架，可重构拓扑存储设备的自组装，以及基于不同多稳定指向矢场和粒子取向之间切换的新电光效应。这些基本现象将在基于自组装的新型纳米结构复合材料的制造环境中进行研究，并可能导致对社会具有重要意义的实用LC器件，如新型显示器。这项研究与广泛的协同推广和教育活动相结合，范围从中小学的巫师表演到液晶行业的短期课程教学，以及组织国际会议和暑期学校。

NON-TECHNICAL ABSTRACTLiquid crystals are unquestionably one of the most commercially important forms of condensed matter. They are widely used in displays, electro-optic and photonic devices and for energy conversion. This usefulness arises from the ability to control the orientation of these cigar shaped molecules with electric and magnetic fields. New materials allow ever more complex structures to be engineered and increase the functionality of liquid crystalline materials. The Principal Investigator (PI) and his team will develop new types of liquid crystals consisting of tiny colloidal particles dispersed in a liquid crystal medium. The colloidal particles will have different shapes (topologies) which will determine the types of structures that the liquid crystals will develop when subjected to electric and magnetic fields. They will study the behavior of these 'topological colloids' to learn how the interactions between the nanoparticles and the liquid crystal molecules determine the structure with the goal of developing a "recipe book" to organize the particles into precisely controlled structures. Understanding of fundamental underpinnings of this 'topology-guided' self-assembly may enable development of new electrically- and optically-controlled materials with unique properties needed for practical devices of importance to society, such as flexible displays and data storage devices. The PI will integrate this research with a broad range of synergistic educational and outreach activities, including 'Light, Color, & Matter' Wizard Shows in elementary and secondary schools, Science Tours for high school students, advising student chapters of professional societies and providing research experiences for students and faculty from minority-serving institutions.TECHNICAL ABSTRACTThe PI seeks to develop a new soft matter system dubbed 'topological colloids' and identify the fundamental organizing principles behind topology-dictated self-assembly of colloidal particles in liquid crystals (LCs). This research will involve the design of methods for scalable fabrication of topologically distinct colloidal particles of different sizes and their dispersions in LCs, experimental study and modeling of the interplay between the topology of particles, director fields, and topological defects, as well as explorations of switchable colloidal self-assembly and alignment controlled by electric and magnetic fields and light. The emerging interdisciplinary scientific frontiers are at the nexus of nanoscience, condensed matter physics, and topology/mathematics. From subatomic particles to cosmology, many phenomena arise from the topological interaction of fields, surfaces, and monopole or string-like defects. This topological interplay is constrained by theorems from topology but is hard to be probed experimentally. The model system of topological colloids may enable direct experimental studies of such topological interactions, thus impinging on many scientific fields, well beyond the specific goals of the proposed research activity. The research activity is transformative in nature and expected to lay the groundwork for new research directions ranging from topology-constrained self-assembly to experimental studies of low-dimensional topology. Beyond the exploration of physical underpinnings, the experimental arena PI and his students are developing may enable scaffolding of nanoparticles, self-assembly of reconfigurable topological memory devices, as well as new electro-optic effects based on switching between different multi-stable director fields and orientations of particles. The fundamental phenomena will be examined in contexts of self-assembly-based fabrication of novel nanostructured composites and may lead to practical LC devices of importance to society, such as novel displays. The research is integrated with a broad range of synergistic outreach and educational activities ranging from Wizard Shows in elementary and secondary schools to teaching short courses for liquid crystal industry and to organizing international conferences and summer schools.