Structure and dynamics of flexible and active packings

柔性活性填料的结构和动力学

• 批准号: 1506750
• 负责人: Narayanan Menon
• 金额: $ 41.95万
• 依托单位: University of Massachusetts Amherst
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-01 至 2019-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1506750&HistoricalAwards=false
• 关键词: Structure; dynamics; flexible; active; packings

Non-technical AbstractThe properties of a material typically depend on how a fixed set of constituents are arranged and interact via intermolecular forces. In this research we study two types of materials that do not fit this paradigm. This first type of material is fibrous matter, made up of long, flexible filaments. The constraints of packing or weaving together can cause individual filaments to bend and twist thus modifying the way in which an individual filament interacts with other filaments. Fibrous materials are the main constituent of plant matter, as well as human products ranging from paper to fabrics and insulants, so a basic understanding of this ubiquitous class of materials is important. The second type of material is composed of assemblies of so-called active particles, which when energized have a tendency to move in some direction along their body. At one level, this is intended to illuminate behaviors seen in living systems such as flocking, swarming and group locomotion. On the other hand, we hope to use some of these behaviors to create materials with new functionalities. The proposed work gives graduate and undergraduate students exposure to a variety of techniques and the opportunity to work in emerging areas of physics. The PI is an organizer of an annual summer school hosted at UMass Amherst for early-career graduate students in soft matter and statistical physics. During the project, the PI will also create and disseminate lesson plans for introductory physics courses taught in a team-based format. Technical AbstractNonequilibrium systems made up of macroscopic entities that do not undergo thermal fluctuations are an important part of our technological, physical and biological world. The experiments proposed here study two broad classes of model nonthermal systems. (i) Systems of flexible filaments, where in addition to the rich physics of rigid nonthermal packing, we gain new geometrical elements, such as the possibility of entanglements between filaments. A particular focus will be the roles of friction and elasticity in determining the strength of a mat of fibres. (ii) Systems of active particles, driven by external noise that provide propulsion at the level of individual particles. The central scientific question will be to identify the separate roles of the symmetry of the particle mobility and interaction, which in previous studies have been chosen to coincide. The PI will study bulk packings, assembled either spontaneously, or templated. These will be studied in 2D by imaging directly and in 3D, by laser-sheet or x-ray imaging. The proposed work gives graduate and undergraduate students exposure to a variety of techniques and the opportunity to work in newly-emerging areas of physics. The PI is also an organizer of an annual summer school hosted at UMass Amherst for early-career graduate students in soft matter physics. During the project, the PI will also create and disseminate lesson plans for introductory physics courses taught in a team-based format.

摘要材料的性质通常取决于一组固定的组分如何排列并通过分子间力相互作用。在这项研究中，我们研究了两种不符合这种范式的材料。第一种材料是纤维物质，由长而柔韧的细丝组成。包装或编织在一起的约束可能导致单个长丝弯曲和扭曲，从而改变单个长丝与其他长丝相互作用的方式。纤维材料是植物物质的主要成分，也是从纸到织物和绝缘材料等人类产品的主要成分，因此对这种无处不在的材料有一个基本的了解是很重要的。第二种材料是由所谓的活性粒子组合而成的，当这些粒子被激发时，它们有沿着自身向某个方向运动的倾向。在一个层面上，这是为了阐明生命系统中的行为，如群集、蜂群和群体运动。另一方面，我们希望使用这些行为中的一些来创建具有新功能的材料。提议的工作使研究生和本科生接触到各种技术，并有机会在物理学的新兴领域工作。PI是在马萨诸塞大学阿默斯特分校为软物质和统计物理学的早期研究生举办的年度暑期学校的组织者。在项目期间，PI还将创建和传播以团队为基础的物理入门课程的教案。由不经历热波动的宏观实体组成的非平衡系统是我们技术、物理和生物世界的重要组成部分。本文提出的实验研究了两大类模型非热系统。(1)柔性细丝系统，其中除了刚性非热填料的丰富物理特性外，我们还获得了新的几何元素，例如细丝之间纠缠的可能性。一个特别的重点将是摩擦和弹性在确定纤维垫的强度方面的作用。（ii）主动粒子系统，由外部噪声驱动，提供单个粒子水平的推进力。核心的科学问题将是确定粒子迁移率和相互作用的对称性的不同作用，这在以前的研究中是一致的。PI将研究散装包装，自发组装或模板。这些将在2D中通过直接成像进行研究，在3D中通过激光片或x射线成像进行研究。提议的工作使研究生和本科生接触到各种技术，并有机会在新兴的物理领域工作。PI也是在马萨诸塞大学阿默斯特分校为软物质物理学的早期研究生举办的年度暑期学校的组织者。在项目期间，PI还将创建和传播以团队为基础的物理入门课程的教案。