Flow-Induced Structures in Lyotropic Chromonic Liquid Crystals

非技术描述：液晶对外界影响高度敏感，包括电场、磁场或机械应力。由这种灵敏度产生的液晶的可调特性使显示技术和光学传感器发生了革命。在过去的十年里，一类新的液晶得到了越来越多的关注，即所谓的溶致变色液晶。这些都是水基生物兼容材料，因此在生物传感和微流控应用中提供了新的机会。为了充分利用它们巨大的未开发潜力，需要了解这些液晶对流动的反应。然而，目前还缺乏这样的理解。值得注意的是，流动可以诱导大规模的有序结构。这个项目探索了这些结构是如何自发出现的，以及如何通过调节流动和材料属性来控制它们。这项研究纳入了一项全面的推广计划，其中包括为高中生和教师授课，为本科生提供研究实习机会，以及为女高中生举办实验室研讨会。该项目将呈现现场科学和艺术表演，将视觉、音频和舞蹈元素结合在一起，让广大观众参与真正的科学对话。技术描述：该研究探索在流动的向列相溶致变色液晶溶液中实现自组织结构的条件。结合使用先进的显微技术、稳定性分析和数值模拟，该项目研究了指向矢场的不稳定性如何触发流动结构，以及这些不稳定的构型如何松弛到宏观区域。特别是，研究了两种稳态流动诱导的织构：当排列平行于流动方向时，平面表面锚定条件下出现的周期性条纹图案，以及垂直于流动方向的平面排列时出现的带状织构。令人兴奋的是，周期性条纹图案是手性的：它的镜像不能叠加在原始图案上。这是值得注意的，因为液晶单元本身是非手性的，并且非手性向列相液体通常被期望形成非手性结构。该项目旨在揭示镜像对称性破缺的机制。通过确定表面锚定条件、流动和材料属性在选择特征长度尺度和宏观纹理方面的作用，这项工作将开辟一条途径，将流动作为一种简单和非侵入性的途径来开发复杂流体的有序结构。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Non-technical Description:Liquid crystals are highly sensitive to external influences, including electric fields, magnetic fields, or mechanical stresses. The tunable properties of liquid crystals that result from this sensitivity have enabled revolutions in display technology and optical sensors. Over the past decade, a new class of liquid crystals has gained increasing attention, so-called lyotropic chromonic liquid crystals. These are water-based bio-compatible materials that therefore offer novel opportunities in biosensing and microfluidic applications. To fully harness their vastly unexplored potential, it needs to be understood how these liquid crystals respond to flow. Such an understanding, however, is currently lacking. Remarkably, flow can induce large-scale ordered structures. This project explores how these structures spontaneously emerge and how they can be controlled by tuning the flow and material properties. Integrated into the research is a comprehensive outreach plan that includes lectures for high-school students and teachers, research internships for undergraduates, and laboratory workshops for women high-school students. The project will present live science and art performances that will integrate visual, audio and dance elements to engage a broad audience in genuine scientific dialogue.Technical Description:The research probes the conditions under which self-organized structuring can be achieved in flowing nematic lyotropic chromonic liquid crystal solutions. Using a combination of advanced microscopy techniques, stability analyses, and numerical simulations, the project addresses how instabilities of the director field can trigger flow structuring and how these unstable configurations relax into macroscopic domains. In particular, two steady-state flow-induced textures are investigated: a periodic stripe pattern that occurs for planar surface anchoring conditions when the alignment is parallel to the flow direction and a band texture that emerges for a planar alignment perpendicular to the flow direction. Excitingly, the periodic stripe pattern is chiral: its mirror image cannot be superimposed on the original. This is remarkable, as the liquid crystalline units themselves are achiral, and achiral nematic liquids are generally expected to form achiral structures. The project aims to reveal the mechanism for the mirror symmetry breaking. By establishing the role of the surface anchoring conditions, the flow, and the material properties for the selection of characteristic length scales and macroscopic textures, the work will open the path to exploit flow as a simple and non-invasive pathway to intricate ordered structuring of complex fluids.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.