CAREER: Dynamics and Pattern Formation in Active Fluids

技术概述该奖项支持软物质和生物学界面的理论研究、教育和推广活动。这项研究计划的目标是发展关于活性流体中紧急行为的定量理论。活性流体是由于每个颗粒的内部活动而被驱使失去平衡的“颗粒”的集合。它们与传统的非平衡流体系统不同，因为维持系统远离平衡的能量是在单个单位的尺度上产生的，而不是在边界上产生的。活性流体的特殊实现包括悬浮中的细菌、底物上的可移动细胞、由细胞骨架细丝和马达蛋白组成的体外系统以及催化推动的纳米棒。对这些系统的研究对细胞骨架动力学、细菌生物膜形成、伤口愈合和形态发生等现象具有重要意义。在活性流体中，由于物理相互作用产生的非平衡动力学和控制系统物理性质的生化调节之间的复杂相互作用，出现了紧急行为。活性流体在空间和时间上缺乏经典流体微观动力学和观测到的宏观动力学的尺度分离。因此，详细考虑边界、波动和相关性的影响，对于建立真实系统的量化理论至关重要。该项目将以两种方式应对这些挑战：(1)将研究宏观和微观的最小模型，以明确地识别导致观察到的活动流体中的紧急动力学和图案形成的物理机制。(2)发展定量捕捉边界和涨落对非平衡系统动力学的影响的理论，并将其应用于研究推力。具体的计划研究包括：a)阐明集体运动和物理相互作用对图案形成和涌现动力学的影响；这与细胞骨架动力学以及伤口愈合和组织发育中发生的细胞集体运动有关。B)表征形状和可变运动性在这些系统的大规模行为中的作用，并着眼于通常由不同表型组成的细菌生物膜，这些表型在这两个性质上都表现出变异性。C)绘制由于流体动力相互作用和直接接触相互作用对可移动粒子集体动力学的影响，这与大多数活动流体的实验实现有关。该奖项还支持一项推广工作，该努力利用软材料物理的可及性及其通过日常材料和桌面演示与生物系统的关系。具体举措包括：a)一个多人参与的网站，将成为软材料物理热门文章的储存库和教师资源中心；b)针对中学生介绍流变学的概念及其与技术应用和生物学的相关性的讲座演示；以及c)为Waltham地区的高中教师和Brandeis的物理教员提供合作的教师发展计划，以互动地开发辅助工具和创新，在课堂上教授科学。非技术性总结：该奖项支持软物质和生物学界面的理论研究、教育和推广活动。活细胞的细胞骨架是由长长的线状分子组成的，这些分子在不同的地方相互连接，就像一个非常小的、做工很差的鱼网。从这个角度来看，它是一种类似于日常橡胶的材料。液体悬浮液中的游动细菌类似于构成现代显示技术基础的液晶。这些系统的主要特征，组织在术语活性材料，是它们被各种生化过程推到平衡之外，这些过程一起用于动态地重塑材料。这个项目将使用材料理论的工具来理解复杂的生物系统，如上面的例子，以了解在不同系统中观察到的现象所依据的共同机制。这项研究与目前正在进行的详细的生物和生化化学研究相结合，将成为对从伤口愈合和形态发生到细菌生物膜形成等生物现象的定量和预测性理解的踏脚石。该奖项还支持一项推广工作，通过日常材料和桌面演示，利用软材料物理及其与生物系统的关系。具体活动包括：a)一个多人参与的网站，它将是软材料物理热门文章的储存库和教师资源中心；b)一个讲座演示，将向中学生介绍流变学的概念及其与技术应用和生物学的相关性；以及c)一个面向Waltham地区的高中教师和Brandeis物理教员的合作教师发展计划，以互动地开发辅助工具和创新，在课堂上教授科学。

Technical SummaryThis award supports theoretical research, education, and outreach activities at the interface of soft matter and biology. The goal of this research program is to develop quantitative theories for emergent behavior in active fluids. Active fluids are a collection of "particles" that is driven out of equilibrium due to the internal activity of each particle. They differ from traditional nonequilibrium fluid systems because the energy that maintains the system far from equilibrium is generated at the scale of the individual units rather than at a boundary. Particular realizations of active fluids include bacteria in suspension, motile cells on substrates, in vitro systems made of cytoskeletal filaments and motor proteins and catalytically propelled nanorods. The study of these systems has implications for phenomena ranging from cytoskeletal dynamics, bacterial biofilm formation, wound healing, and morphogenesis.Emergent behavior arises in active fluids from a complex interplay between nonequilibrium dynamics arising from physical interactions and bio-chemical regulation that controls the physical properties of the system. Active fluids lack the scale separation between the microscopic dynamics and the observed macroscopic dynamics exhibited in classical fluids, in both space and time. As a consequence, detailed considerations of the effect of boundaries, fluctuations and correlations become critical for building quantitative theories of real systems. This project will address these challenges in two ways: (1) Minimal models, both macroscopic and microscopic, will be studied to unambiguously identify physical mechanisms that lead to observed emergent dynamics and pattern formation in active fluids. (2) Theory will be developed to quantitatively capture the effect of boundaries and fluctuations on the dynamics of out-of-equilibrium systems and applied in research thrusts. Specific planned investigations include: a) Elucidating the influence of collective motility and physical interactions on pattern formation and emergent dynamics; this is relevant at the scale of cytoskeletal dynamics and for collective motility of cells that occurs in wound healing and tissue development. b) Characterizing the role of shape and variable motility in the large scale behavior of these systems with an eye toward bacterial biofilms that are typically made of different phenotypes that show variability in both properties. c) Charting the influence of hard walls on the collective dynamics of motile particles due to both hydrodynamic interactions and direct contact interactions which is relevant for most experimental realizations of active fluids.This award also supports an outreach effort that capitalizes on the accessibility of soft materials physics and its relationship to biological systems through everyday materials and table top demonstrations. Specific initiatives include: a) a multiple contributor website that will be a repository of popular articles on soft materials physics and a teacher's resource center, b) a lecture-demonstration that will introduce the concepts of rheology and its relevance to technological applications and biology targeted at middle school and high school students, and c) a collaborative teacher development program for high school teachers in the Waltham area and the physics faculty at Brandeis to interactively develop aids and innovations to teach science in the class room.Nontechnical Summary:This award supports theoretical research, education, and outreach activities at the interface of soft matter and biology. The cytoskeleton of a living cell is made of long string-like molecules that are interconnected in various places rather like a very tiny poorly made fish net. Viewed this way, it is a material analogous to everyday rubber. Swimming bacteria in a fluid suspension resemble the liquid crystals that form the basis of modern display technology. The key features of these systems, organized under the term active materials, is that they are pushed out of the balance of equilibrium by various biochemical processes that together serve to dynamically remodel the material. This project will use the tools of materials theory to understand complex biological systems such as the examples above in order to understand common mechanisms that underlie observed phenomena in diverse systems. Such a study when coupled to detailed biological and biochemical chemical investigations being undertaken today will serve as a stepping stone towards approaching a quantitative and predictive understanding of biological phenomena ranging from wound healing and morphogenesis to bacterial biofilm formation. This award also supports an outreach effort that capitalizes on the accessibility of soft materials physics and its relationship to biological systems through everyday materials and table top demonstrations. Specific initiatives include: a) a multiple contributor website that will be a repository of popular articles on soft materials physics and a teacher's resource center, b) a lecture-demonstration that will introduce the concepts of rheology and its relevance to technological applications and biology targeted at middle school and high school students, and c) a collaborative teacher development program for high school teachers in the Waltham area and the physics faculty at Brandeis to interactively develop aids and innovations to teach science in the class room.