CAREER: Dynamics and Pattern Formation in Active Fluids

职业：活性流体的动力学和模式形成

• 批准号: 1149266
• 负责人: Aparna Baskaran
• 金额: $ 45万
• 依托单位: Brandeis University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-07-01 至 2018-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1149266&HistoricalAwards=false
• 关键词: CAREER; Dynamics; Pattern; Formation; Active

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.

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。本研究计划的目标是为活性流体中的紧急行为发展定量理论。活动流体是“粒子”的集合，由于每个粒子的内部活动而被赶出平衡。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状态的能量是在单个单元的尺度上产生的，而不是在边界上产生的。活性流体的具体实现包括悬浮液中的细菌，底物上的运动细胞，由细胞骨架细丝和运动蛋白以及催化推进的纳米棒组成的体外系统。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，紧急行为是由物理相互作用引起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产生的。活动流体在空间和时间上都缺乏经典流体所表现出的微观动力学与观测到的宏观动力学之间的尺度分离。因此，对边界、波动和相关性影响的详细考虑对于建立真实系统的定量理论至关重要。本项目将以两种方式解决这些挑战：(1)将研究宏观和微观的最小模型，以明确识别导致观察到的活跃流体中出现的动态和模式形成的物理机制。(2)将发展理论，定量地捕捉边界和波动对非平衡系统动力学的影响，并应用于研究重点。具体的计划调查包括：a)阐明集体运动性和物理相互作用对模式形成和涌现动力学的影响；这与细胞骨架动力学和在伤口愈合和组织发育中发生的细胞集体运动的规模有关。b)描述形状和可变运动在这些系统的大规模行为中的作用，着眼于细菌生物膜，这些生物膜通常由不同的表型组成，在这两种特性上都表现出可变性。c)由于流体动力相互作用和直接接触相互作用，绘制了硬壁对运动粒子集体动力学的影响，这与大多数活性流体的实验实现有关。该奖项还支持通过日常材料和桌面演示利用软材料物理学的可及性及其与生物系统的关系的推广工作。具体举措包括：A)一个多贡献者网站，将成为软材料物理学和教师资源中心的热门文章的存储库；b)一个讲座演示，将介绍流变学的概念及其与技术应用和生物学的相关性，目标是初高中学生；c)为沃尔瑟姆地区的高中教师和布兰代斯大学的物理教师提供合作教师发展计划，以互动的方式开发辅助工具和创新方法，在课堂上教授科学。非技术总结：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串状的分子组成的，这些分子在不同的地方相互连接，就像一个做工拙劣的小渔网。从这个角度来看，它是一种类似于日常橡胶的材料。在液体悬浮液中游动的细菌类似于构成现代显示技术基础的液晶。这些被称为活性物质的系统的主要特征是，它们被各种生物化学过程推出平衡，这些过程共同作用于动态重塑物质。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，以便理解在不同系统中观察到的现象背后的共同机制。这样的研究如果与目前正在进行的详细的生物学和生化化学调查相结合，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进行定量和预测性理解的垫脚石。该奖项还支持通过日常材料和桌面演示利用软材料物理学的可及性及其与生物系统的关系的推广工作。具体举措包括：A)一个多贡献者网站，将成为软材料物理学和教师资源中心的热门文章的存储库；b)一个讲座演示，将介绍流变学的概念及其与技术应用和生物学的相关性，目标是初高中学生；c)为沃尔瑟姆地区的高中教师和布兰代斯大学的物理教师提供合作教师发展计划，以互动的方式开发辅助工具和创新方法，在课堂上教授科学。