Topology Driven Flows in Chromonic Liquid Crystals

非技术性总结该奖项支持理论和计算研究，以及液晶缺陷的教育。液晶是由棒状分子组成的，显示复杂的空间排列，尽管介于完美有序的晶体和完全无序的液体之间。 它们具有像流体一样流动的综合能力，同时传递定向力并具有像晶体一样的方向依赖性，使它们适用于广泛的应用。然而，由于它们的弱结晶度，缺陷在实验室样品中是丰富的。尽管这种性质长期以来被认为对应用有害，但最近的研究发现了这些材料的许多新的和意想不到的性质，这些性质正是由于缺陷的存在及其操纵而产生的。例子包括其他分子种类或生物制剂的引导运输，由光或电场激活的机械开关的发展，甚至涉及生物反应的类比。该项目旨在改进现有的描述缺陷液晶的理论模型，以及任何伴随的传输。将开发详细描述缺陷结构和运动的新模型，包括它们与质量或流体流动的相互作用。其目的是开发一个预测框架，描述液晶的操作条件或外部影响的响应。研究的具体重点是溶致变色液晶，其中液晶行为是通过使用适当的稀释溶剂来改变棒状分子的浓度而诱导的物质。它们作为染料（包括食品染料）已经被知道很长时间了，并且是肺表面活性剂的类似物。它们也是生物相容的液晶，目前正在开发用于活细胞转向或分选。这类液晶具有异常大的缺陷特征，使它们适合光学分析，并与理论进行比较。这项研究将用于进一步发展和加强物理科学中计算的跨学科课程。参与该项目的学生将受益于明尼苏达超级计算研究所的大量培训和合作机会。技术总结该奖项支持理论和计算研究，以及专注于系统研究拓扑缺陷，平衡形态和溶致变色液晶中向列-各向同性界面的动态演化的教育。所考虑的两相包括纯单相，或单相和各向同性相共存的两相区。这项研究的动机是正在进行的实验表明，有色化合物的特征微观尺度是微米的数量级，远远大于传统的热致液晶中的10 nm尺寸。如此大的尺度允许现代光学成像技术来解决缺陷核心和两相界面，从而提取介观自由能模型的参数下降到前所未有的空间尺度。这一信息打开了大门，目前的非线性，梯度理论的非平衡向列相的关键和定量测试。此外，不寻常的形态结构域（tactoids），和他们的非平衡演化，预计将导致新的行为，由于在这个规模的相互作用的复杂性，包括强各向异性，非局部弹性相互作用，由于拓扑缺陷，和介观双轴性。 缺陷驱动的流动和悬浮在有色物质中的生物物质的动力学是计划中的调查。这些都在积极审查，因为在微流体和光生物器件的流动控制，在生物医学领域的细胞分选和生物传感的潜在应用。这项研究将用于进一步开发和加强在物理科学计算的跨学科课程。参与该项目的学生将受益于明尼苏达州超级计算研究所的大量培训和合作机会。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

NONTECHNICAL SUMMARYThis award supports theoretical and computational research, and education on defects in liquid crystals.Liquid crystals are made of rod like molecules that display complex spatial arrangements, though intermediate between perfectly ordered crystals and completely disordered liquids. Their combined ability to flow like a fluid, while transmitting directional forces and possessing direction dependent properties like a crystal, make them suitable for a wide range of applications. However, because of their weak crystallinity, defects are abundant in laboratory samples. Although this property has long been considered deleterious for applications, recent research has uncovered a host of new and unexpected properties of these materials that follow precisely from the existence of defects, and from their manipulation. Examples include guided transport of other molecular species or biological agents, the development of mechanical switches activated by light or electric fields, and even analogies involving biological response. This project is aimed to improve existing theoretical models that describe defected liquid crystals, and any accompanying transport. New models detailing the structure and motion of defects will be developed, including their interaction with transport of mass or fluid flow. The aim is to develop a predictive framework that describes the response of the liquid crystal to operating conditions or external influences. The specific focus of the research is on lyotropic chromonic liquid crystals, substances in which the liquid crystalline behavior is induced by using an appropriate dilution solvent to change the concentration of the rod like molecules. They have been known for a long time as dyes (including food dyes), and are analogs of lung surfactant agents. They are also bio-compatible liquid crystals, and are currently being developed for live cell steering or sorting. This class of liquid crystals features unusually large defect features that make them amenable to optical analysis, and comparison to theory.The research will be used to further develop and enhance an interdisciplinary course on computation in the physical sciences. Students participating in the project will benefit from substantial training and collaboration opportunities at the Minnesota Supercomputing Institute.TECHNICAL SUMMARYThis award supports theoretical and computational research, and education focused on the systematic study of topological defects, equilibrium morphologies, and dynamical evolution of nematic-isotropic interfaces in lyotropic chromonic liquid crystals. Configurations considered include a pure nematic phase, or the biphasic region of coexistence between nematic and isotropic phases. This study is motivated by ongoing experiments that show that the characteristic microscopic scale of chromonics is on the order of microns, much larger than the 10 nm size in conventional thermotropic liquid crystals. Such large scales allow modern optical imaging techniques to resolve defect cores and two-phase interfaces, and hence to extract the parameters of mesoscopic free energy models down to an unprecedented spatial scale. This information opens the door to critical and quantitative tests of current nonlinear, gradient theories of nonequilibrium for nematics. In addition, the unusual morphology of nematic domains (tactoids), and their nonequilibrium evolution, are expected to lead to novel behavior due to the complexity of interactions at this scale, including strong anisotropy, nonlocal elastic interactions due to topological defects, and mesocale biaxiality. Defect driven flows and the dynamics of biological matter suspended in the chromonic are among planned investigations. These are under active scrutiny because of potential applications in flow control in microfluidics and optobiological devices, in the biomedical field for cell sorting and bio sensing.The research will be used to further develop and enhance an interdisciplinary course on computation in the physical sciences. Students participating in the project will benefit from substantial training and collaboration opportunities at the Minnesota Supercomputing Institute.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.