Fundamental studies of liquid crystal nanodroplets

液晶由细长的分子组成，这些分子可以排列成有序的结构，让人想起固体晶体中的原子，同时保持流体状态。这种有序结构可以用来操纵光——这是液晶显示器所利用的一种特性。液晶的一个有趣的特点是，它们的结构可以通过界面上的微小扰动而改变；因此，液晶可以用作放大器，能够在相对较远的距离上传输分子事件。这种特性已被用于开发针对特定分子（包括毒素）的传感器，这些分子在液体界面上的吸附会触发一系列分子转化，从而导致宏观颜色变化，这种变化可以可靠且廉价地检测到。在这个项目中，PI将使用理论和计算来推进对一系列事件的理解，从分子或纳米级粒子被吸附在液晶-水或液晶-蒸汽界面的那一刻起，到随后导致可测量光学响应的结构变化。从该项目中获得的知识将有助于液晶传感技术的发展，特别是在生物毒素领域，可以增强或超越现有的液晶传感技术，从而带来重要的社会效益。PI的目标是将该项目的科学和计算方面部分整合到高中生的暑期研讨会和旨在向芝加哥内城公立学校的少数民族学生介绍计算的推广活动中。该奖项支持理论和计算研究和教育，以促进对液晶界面的基本理解。PI旨在开发能够描述原子尺度、中尺度和宏观长度尺度的预测分子模型。这里考虑的主要物理几何将由液晶液滴组成，其界面将与水或空气接触。在原子水平上，分子模拟将用于预测材料的性质，如界面上的分子构象，这些性质很难通过实验测量，而且通常是不可用的。在稍长的长度尺度上，粗粒度的分子模型将用于预测和检查纳米颗粒负载LC系统中出现的缺陷，从而提供不同形态如何对异物和外部刺激作出反应的直接描述。在更长的长度尺度上，连续统模型将用于理解液滴及其界面不同区域中表面活性分子或纳米级颗粒的排列或分离，以及这些系统中有序结构的形成。这样的模型将依赖于基于更精细的、原子的和粗粒度的描述级别生成的材料属性和见解。从这个项目中产生的LC系统研究的理论和计算形式将提供许多有吸引力的特征，包括描述感兴趣的非均匀材料及其结构和热力学性质的大型、全三维实现的能力。这种形式主义将有助于识别由三维LC系统与二维装饰界面耦合控制的新物理现象，并将作为有前途的材料组合的筛选工具，并用于演示本提案中提出的概念。PI的目标是将该项目的科学和计算方面部分整合到高中生的暑期研讨会和旨在向芝加哥内城公立学校的少数民族学生介绍计算的推广活动中。

NONTECHNICAL SUMMARYLiquid crystals consist of elongated molecules that can pack into ordered structures, reminiscent of those assumed by atoms in solid crystals, while remaining fluid. Such ordered structures can be used to manipulate light - a property that is exploited in liquid crystal displays. An interesting feature of liquid crystals is that their structure can be altered through small perturbations at an interface; the liquid crystal can therefore serve as an amplifier, capable of transmitting molecular events over relatively long distances. This property has been used to develop sensors for specific molecules, including toxins, in which adsorption at a liquid interface triggers a series of molecular transformations that result in macroscopic color changes, which can be detected reliably and inexpensively. In this project, the PI will use theory and computation to advance understanding of the series of events, from the moment a molecule or a nanoscopic particle is adsorbed at a liquid crystal-water or at a liquid crystal-vapor interface, to the ensuing structural changes that lead to measurable optical responses. The knowledge gained from this project will contribute to the development of liquid crystal sensing technologies that could augment or surpass those available today, particularly in the realm of biological toxins, thereby leading to important societal benefits.The PI aims to integrate science and computational aspects of this project in part into a summer workshop for high school students and an outreach activity aimed to introduce computation to minority students in inner city Chicago public schools.TECHNICAL SUMMARYThis award supports theoretical and computational research and education to advance the fundamental understanding of liquid crystal interfaces. The PI aims to develop predictive molecular models capable of describing atomistic, mesoscale, and macroscopic length scales. The primary physical geometry considered here will consist of liquid crystal droplets, whose interfaces will be in contact with water or air. At the atomistic level, molecular simulations will be used to predict material properties, such as molecular conformation at an interface, that are difficult to measure experimentally and are often unavailable. At slightly longer length scales, coarse-grained models of the molecules will be used to predict and examine the defects that arise in nanoparticle-laden LC systems, thereby providing a direct description of how different morphologies respond to foreign bodies and external stimuli. At even longer length scales, continuum models will be used to understand the arrangement or segregation of surface-active molecules or nanoscopic particles in distinct regions of the droplets and their interfaces, and the formation of ordered structures within such systems. Such models will rely on the material properties and insights generated on the basis of finer, atomistic and coarse-grained levels of description. The theoretical and computational formalism for study of LC systems that will emerge from this project will offer a number of attractive features, including the ability to describe large, fully three-dimensional realizations of the inhomogeneous materials of interest and their structural and thermodynamic properties. That formalism will serve to identify new physical phenomena governed by the coupling of a three-dimensional LC system to a two-dimensional, decorated interface, and will serve as a screening tool for promising materials combinations and for demonstration of the concepts put forth in this proposal.The PI aims to integrate science and computational aspects of this project in part into a summer workshop for high school students and an outreach activity aimed to introduce computation to minority students in inner city Chicago public schools.