Flow-Induced Structures in Lyotropic Chromonic Liquid Crystals

非技术描述：液晶对外部影响高度敏感，包括电场、磁场或机械应力。这种灵敏度带来的液晶可调特性引发了显示技术和光学传感器的革命。在过去的十年中，一类新型液晶受到越来越多的关注，即所谓的溶致发色液晶。这些是水基生物相容性材料，因此为生物传感和微流体应用提供了新的机会。为了充分利用它们尚未开发的潜力，需要了解这些液晶如何响应流动。然而，目前还缺乏这样的认识。值得注意的是，流动可以产生大规模的有序结构。该项目探讨了这些结构如何自发出现，以及如何通过调整流动和材料特性来控制它们。该研究纳入了一项全面的推广计划，包括为高中生和教师举办讲座、为本科生提供研究实习以及为高中女生举办实验室讲习班。该项目将呈现现场科学和艺术表演，将视觉、音频和舞蹈元素融为一体，让广大观众参与真正的科学对话。技术描述：该研究探讨了在流动的向列溶致发色液晶溶液中实现自组织结构的条件。该项目结合了先进的显微镜技术、稳定性分析和数值模拟，解决了导向场的不稳定性如何触发流动结构以及这些不稳定的配置如何松弛到宏观域。特别是，研究了两种稳态流动引起的纹理：当排列平行于流动方向时在平面表面锚定条件下出现的周期性条纹图案和在垂直于流动方向的平面排列时出现的带状纹理。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像上。这是值得注意的，因为液晶单元本身是非手性的，并且非手性向列液体通常预期形成非手性结构。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、流动和材料特性对于选择特征长度尺度和宏观纹理的作用，这项工作将为利用流动作为一种简单且非侵入性的途径来实现复杂流体的复杂有序结构开辟道路。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值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.