The role of boundaries in 2D active nematics

第1部分：非技术概述活性物质试图描述在纳米尺度上消耗化学能导致在宏观尺度上运动的材料。活细胞的运动就是一个例子。最近的理论表明，活细胞的运动受到某些特定行为的物理定律的限制，这些相同的理论提出了一种有趣的可能性，即有可能设计出具有迄今为止仅在活体中发现的功能的新材料。目前，缺乏验证理论的定量实验阻碍了这一进程。这一建议试图通过在受限的二维活性液晶中提供理论和实验之间的定量比较来纠正这种不平衡。这些理论测试和新现象的发现将推动该领域向前发展，导致新材料的创造，如自组织发动机和自泵流体。第二部分：技术综述：活性物质研究处于软物质领域的前沿，但缺乏定量的实验来检验理论是阻碍进展的因素。这项建议旨在纠正这种不平衡。为了阐明边界条件对结构和动力学的影响，我们将对受限二维活性向列相液晶进行实验研究。由于其相对简单和高度的可控性，将采用可伸展微管束的模型系统。其中一个推动力将是建立微管束延伸和产生流动的微观机制。这将通过结合使用荧光显微镜和二次谐波显微镜来完成。第二个推力将是通过创建各种各样的受限结构来研究边界条件对活动向列学的作用，并定量测量比较理论和实验所需的量。这将使用光刻和微流控制造方法以及定量光学显微镜来实现。第三个推动力将是使用有限元计算将实验与理论进行比较，第四个推力将是设计基于受限主动向列学的软机器，这些向列学自组织执行工作，例如抽出流体。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。

PART 1: NON-TECHNICAL SUMMARY Active matter seeks to describe materials in which chemical energy is consumed at the nanoscale resulting in motion at the macro scale. Examples include the motion of living cells. Recent theories suggest that the motions of living cells are constrained by physical laws to certain characteristic behaviors, and these same theories raise the intriguing possibility that it is possible to engineer new materials with functionalities that heretofore are only found in living organisms. Currently, a lack of quantitative experiments to test theory is hampering progress. This proposal seeks to rectify this imbalance by providing quantitative comparison between theory and experiment in confined two-dimensional active liquid crystals. These tests of theory and discovery of new phenomena will propel the field forward leading to the creation of novel materials, such as self-organizing engines and self-pumping fluids. PART 2: TECHNICAL SUMMARY Active matter research is at the forefront of the field of soft matter, but a lack of quantitative experiments to test theory is hampering progress. This proposal seeks to rectify this imbalance. Experimental studies of confined 2D active nematic liquid crystals will be performed with the goal to elucidate the role of boundary conditions in influencing structure and dynamics. A model system, extensile microtubule bundles, will be employed because of their relative simplicity and high degree of controllability. One thrust will be to establish the microscopic mechanism by which microtubule bundles extend and produce flow. This will be accomplished using combined fluorescence and second harmonic generation microscopy. A second thrust will be to investigate the function of boundary conditions on active nematics by creating a wide variety of confined structures and quantitatively measure the quantities necessary to compare theory and experiment. This will be accomplished using photolithographic and microfluidic manufacturing methods and quantitative light microscopy. A third thrust will be to compare experiment to theory using finite element computation and a fourth thrust will be to engineer soft machines based on confined active nematics that self-organize to perform work, such as pumping of 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.