Dynamics and Mechanics of Active Matter

该奖项支持活性物质的理论研究和教育，包括自驱动实体的集合，如鸟群或活细胞，从环境中获取能量以产生协调运动。将注入分子尺度的能量转化为宏观尺度上有组织的运动和功能的能力是生命系统的一个决定性特性。人们可能会认为这种组织一定是由复杂的通讯途径或生化信号控制的。然而，近年来，研究人员已经设计了许多具有生命性质的合成类似物，从化学反应驱动的微型游泳者到能够自组织行为的纳米机器人群，证明了物理相互作用在控制集体行为中的关键作用。PI和她的团队研究的中心目标是量化条件，在这些条件下，基于最小交互集的物理模型可以捕获活体和工程系统中的复杂组织，并开发和测试这些模型。这项研究将提供一个新的强大的数学框架，用于描述自然界中大量涌现的现象，在这些现象中，大群体表现出与个体截然不同的协调行为。与锡拉丘兹大学和普林斯顿大学的实验人员合作，PI将采用活性物质范式来确定驱动土壤中细菌黏液球菌（Myxococcus xanthus）生命周期的物理机制，这种细菌的生命周期是由集体和个人行为之间的连续反馈循环控制的。PI和她的学生还将模拟合成微游泳者的集体行为，并检查这些活性粒子驱动惰性粒子的组装和组织所需的条件。这项工作将为能够主动组装、重新配置和自我修复的智能材料的工程铺平道路。该项目将在多个领域产生变革性影响，从物理学到生物学再到工程学，并在多个方面造福社会。例如，通过区分由物理机制而非遗传机制引发的转化，对黄分枝杆菌的研究将有助于减少常规遗传研究中必须调查的大量可能性。这项研究将包括本科生、研究生和博士后研究人员的机会。其高度跨学科的性质将在科学和生物工程之间的界面提供广泛的培训，开辟各种就业机会。该奖项支持有关活性物质的理论研究和教育。这个名字是指由许多相互作用的实体组成的扩展系统，这些实体被注入微观尺度的能量赶出平衡，打破了详细的平衡。例子包括许多生命系统，从鸟群到活细胞，以及工程系统，从由运动蛋白激活的体外生物聚合物网络到合成微游泳者。PI将使用多管齐下的方法，从基于主体的模型到连续统现象学，并通过与实验人员的合作来推进对活性物质的组织原理和力学的理解。所解决的问题围绕三个目标进行组织：(1)使用最小模型来制定活性物质的非平衡统计力学，特别关注由限制引起的空间非均匀行为；(2)通过检查拓扑缺陷的动力学和涌现行为，识别受限几何中活动流动的一般性质；(3)应用活性物质范式阐明驱动黄粘球菌复杂生命周期的物理机制。自推进粒子模型的研究将计算和理论相结合，以解决无微观时间反转对称性的主动系统的非平衡统计力学的基本问题。它将具体地考察在多大程度上用平衡概念进行有效的描述是可能的。拓扑缺陷在驱动和维持自我持续的主动流动中的作用的研究将为描述生物体液体内和体外流动模式之间的转变提供一个强大的框架，从细胞质到细菌悬浮液。通过对M. xanthus的研究，PI将证明活性物质范式为组织生物数据和分离控制生命系统复杂发育周期的物理机制提供了一种有用的方法。活性物质领域汇集了来自广泛学科和影响领域的社区，从生物学到材料设计。提出的自推进粒子模型和主动组装的工作将指导具有程序化功能的新材料的发展。对微生物发育的研究旨在区分由物理机制而非遗传机制引发的转化，这将有助于减少基因研究中必须调查的大量可能性。拟议的工作将为物理、工程和生物学领域的研究生和博士后提供广泛的培训，并促进多样化STEM劳动力的发展。PI将通过组织会议和为年轻科学家提供专业发展机会的学校，继续与科学界接触。

NON-TECHNICAL SUMMARYThis award supports theoretical research and education in active matter, consisting of assemblies of self-driven entities, such as bird flocks or living cells, that take energy from the environment to produce coordinated motion. The ability to turn energy injected at the molecular scale into organized motion and function at the macroscopic scale is a defining property of living systems. One may then think that such organization must be controlled by complex communication pathways or biochemical signaling. In recent years researchers have, however, engineered a number of synthetic analogues with life-like properties, from microswimmers powered by chemical reactions to swarms of nanobots capable of self-organized behavior, demonstrating the key role of physical interactions in controlling collective behavior. The central goal of the research by the PI and her team is to quantify the conditions under which physical models based on a minimal set of interactions can capture complex organization in both living and engineered systems, and to develop and test such models. The research will provide a new powerful mathematical framework for describing quantitatively emergent phenomena in nature, where large groups exhibit coordinated behaviors that are very different from those of the individuals. Working with experimentalists at Syracuse University and at Princeton University, the PI will employ the active matter paradigm to identify the physical mechanisms that drive the life cycle of the soil-dwelling bacterium Myxococcus xanthus, which is controlled by a continuous feedback loop between collective and individual behavior. The PI and her students will also model the collective behavior of synthetic microswimmers and examine the conditions required for such active particles to drive the assembly and organization of inert particles. This work will pave the way to the engineering of smart materials capable of active-assembly, reconfiguration, and self-healing.The project will have transformative impact across several fields, from physics to biology to engineering, and benefit society in several ways. For instance, by differentiating transformations that are triggered by physical mechanisms as opposed to genetics, the work on M. xanthus will help cut down the vast number of possibilities that must be investigated in routine genetic studies. The research will include opportunities for undergraduates, graduate students and postdoctoral researchers. Its highly interdisciplinary nature will provide broad training at the interface between science and bioengineering, opening up a variety of employment opportunities.TECHNICAL SUMMARYThis award supports theoretical research and education on active matter. This name refers to extended systems composed of many interacting entities that are driven out of equilibrium by energy injected at the microscopic scale, breaking detailed balance. Examples include many living systems, from bird flocks to living cells, and engineered ones, from in vitro biopolymer networks activated by motor proteins to synthetic microswimmers. The PI will use a multipronged approach ranging from agent-based models to continuum phenomenology, and informed by collaborations with experimenters to advance understanding of the organizational principles and mechanics of active matter. The problems addressed are organized around three objectives: (1) using minimal models to formulate the nonequilibrium statistical mechanics of active matter, with specific attention to spatially inhomogeneous behavior induced by confinement; (2) identifying generic properties of active flows in confined geometry by examining the dynamics and emergent behavior of topological defects; and (3) applying the active matter paradigm to elucidate the physical mechanisms that drive the complex life cycle of Myxococcus xanthus. The work on self-propelled particle models combines computation and theory to address fundamental questions on the nonequilibrium statistical mechanics of active systems with no microscopic time reversal symmetry. It will specifically examine the extent to which effective descriptions in terms of equilibrium concepts may be possible. The study of the role of topological defects in driving and maintaining self-sustained active flows will provide a powerful framework for characterizing transitions between flow patterns in biofluids in vivo and in vitro, from the cytoplasm to bacterial suspensions. Through the work on M. xanthus, the PI will demonstrate that the active matter paradigm provides a useful way for organizing biological data and isolate the physical mechanisms at play in controlling complex developmental cycles of living systems. The field of active matter brings together communities from a broad range of disciplines and impacts areas ranging from biology to materials design. The proposed work on self-propelled particle models and active assembly will guide the development of new materials with programmed functions. The research on microbial development aims at differentiating transformations that are triggered by physical mechanisms as opposed to genetics and will help cut down the vast number of possibilities that must be investigated in genetic studies. The proposed work will provide broad training for graduate students and postdocs at the interface of physics, engineering and biology and promote the development of a diverse STEM workforce. The PI will continue her engagement with the scientific community by organizing conferences and school that will provide professional development opportunities for young scientists.