CAREER: Topological dynamics of three-dimensional active fluids

非技术摘要自然界中可以在不同的尺度上观察到自发的集体运动：成群的鸟类、迁徙的蚂蚁，甚至我们体内的细胞集体运动以闭合伤口。这个研究项目的目标是通过使用简单的三维仿生材料来更好地理解这些集体运动是如何出现的。这些活性物质由蛋白质组成，这些蛋白质可以通过从环境中获取能量来自我推进。我们将研究两种类型的3D液晶，其中推进是由分子马达驱动的，或者是由从一端生长而从另一端收缩的生物丝驱动的，这概括了活细胞迁移所使用的两种基本机制。这项研究项目将解决如何将微观尺度上产生的力与3D中出现的集体性质联系起来，这是朝着机器人或生物工程应用的新型活性材料的预测性设计迈出的关键一步。在教育方面，该项目将改善从幼儿园到中学后教育的每一个学术级别的代表性不足的少数群体的多样性和留住他们。首席研究员将利用活性物质的有形性质来i)创建一本双语科学儿童书籍，ii)每月科学/披萨讲座和iii)在当地学校进行互动演示，以及iv)为REU学生举办一年一度的活性物质训练营。技术摘要由生物聚合物组成的简单仿生材料已经成为研究自发流动的活性流体的范例。在宏观尺度上，这些流动经常驱动运动奇点的成核，例如拓扑缺陷。在3D中研究这种拓扑动力学提出了新的概念和实验挑战。此外，需要将这些系统大小的拓扑特征与微观驱动力联系起来，以严格测试活动流体的流体动力学理论。这一职业奖旨在阐明介观活动应力的大小和对称性如何驱动具有取向顺序的3D活动流体的紧急拓扑动力学，特别关注3D活动向列学和3D极性流体。这两个相辅相成的研究项目共同提供了三维动态拓扑缺陷的非平衡流体动力学的全面描述。他们将为构建具有仿生特性的先进仿生材料奠定基础。这一奖项反映了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 AbstractSpontaneous collective motion can be witnessed at different scales in nature: flocks of birds, migrating ants, and even cells within our own body moving collectively to close a wound. The goal of this research project is to better understand how these collective motions appear by employing simple three-dimensional biomimetic materials. These active materials are composed of proteins that can self-propel by harvesting energy from their environment. Two types of 3D liquid crystals will be investigated where the propulsion is driven by either molecular motors or by biofilaments that grow from one end and shrink from the other, recapitulating two fundamental mechanisms employed by living cells to migrate. This research project will address how to relate the forces generated at the microscopic scale to the emergent collective properties in 3D, a critical step towards the predictive design of novel active materials for robotic or bioengineering applications. On the educational side, this project will improve diversity and retainment of underrepresented minorities at each academic level, from Kindergarten through postsecondary education. The principal investigator will leverage the tangible nature of active matter to i) create a bilingual science children’s book, ii) monthly Science/Pizza talks and iii) interactive demonstrations in local schools, and iv) an annual active matter bootcamp for REU students.Technical abstractSimple biomimetic materials composed of biopolymers have become a paradigm for studying active fluids that spontaneously flow. At the macroscale, these flows often drive the nucleation of motile singularities such as topological defects. Investigating such topological dynamics in 3D presents novel conceptual and experimental challenges. In addition, connecting these system-sized topological features to the microscopic driving forces is required to rigorously test hydrodynamic theories of active fluids. This CAREER award aims to elucidate how the magnitude and the symmetry of mesoscopic active stresses drive the emergent topological dynamics of 3D active fluids with orientational order, with a particular focus on 3D active nematics and 3D polar fluids. Together, these two complementary research projects provide a comprehensive description of the out-of-equilibrium hydrodynamics of motile topological defects in 3D. They will set the foundations for building advanced biomimetic materials endowed with life-like properties.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.