CAREER: Flow, Failure, and Migration in Glassy Materials

职业：玻璃材料中的流动、失效和迁移

• 批准号: 1352184
• 负责人: Mary Lisa Manning
• 金额: $ 45万
• 依托单位: Syracuse University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-06-01 至 2020-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1352184&HistoricalAwards=false
• 关键词: CAREER; Flow; Failure; Migration; Glassy

Technical Summary:This CAREER award supports theoretical and computational research and education to investigate how disordered materials and biological tissues flow and fail. Understanding these flows is of immediate practical importance. For example, bulk metallic glasses show great promise as structural materials but have not been widely adopted because they fail via poorly understood localized shear bands. Similarly, rates of cell migration help govern embryogenesis and cancer tumorigenesis, yet it is unclear how these rates are influenced by single cell mechanical properties. Although non-biological disordered and glassy solids flow when forces are applied at a boundary, and biological tissues flow when individual cells apply forces to their neighbors, there is a surprising universality in the way that these "materials" flow and deform. The PI will use tools from statistical and soft matter physics to exploit this universality and make verifiable predictions about flow, failure, and cell migration. To achieve this goal, the PI will focus on three approaches: (1) Exploit a new universality class of random matrix ensembles to make first-principles predictions about the vibrational modes and localized defects that govern plasticity in jammed solids. (2) Identify flow defects, or soft spots, in disordered solids and test the assumptions made by three well-known continuum models for plastic flow. This will determine which model, if any, correctly describes the defects. This will allow testing the behavior of defects under shear reversal, their statistics as a function of the degree of structural disorder, and their evolution inside the shear bands leading to catastrophic failure. The continuum model will then be parameterized using only microscopic information from simulations. (3) Develop a new theory that makes predictions for the rates of cell migration in confluent tissues, addressing how packing topology, boundaries between two tissue types, and abnormal cell mechanics affect migration rates; predictions will be directly tested in experiments.This research will be integrated with several education initiatives that focus on students in the last years of high school and the first years of college. Specifically, the PI will partner with a high school program to develop and deploy modules in high schools that (a) "tune-up" the math skills of marginal students, and (b) connect introductory physics concepts to research at the frontier of materials science. At the introductory college level, the PI will (c) work with an economics education professor to implement a weekly self-assessment for students to help them internalize class expectations and social norms, and (d) collaborate with physics education and science teaching professors to improve training for graduate assistants in a newly developed "Teaching Fellows" program. The PI will also (e) use online and classroom technologies to develop social networking and discussion platforms that help students build a sense of community.Nontechnical Summary: This CAREER award supports theoretical research and education with the aim of understanding how disordered solids deform and fail. Making predictions about these materials is challenging because they respond like a solid when a small force is applied, and yet the atoms, particles, or cells that comprise them are arranged like those in a liquid. When larger forces are applied, these materials exhibit interesting flow patterns that are important in both nature and industry. For example, bulk metallic glasses show great promise as structural materials but have not been widely adopted because they fail via poorly understood localized shear bands. Recently, researchers have also discovered that biological tissues behave like a disordered solid, and therefore cell migration in embryonic development and cancer metastasis can also be thought of as flow within these "materials". The goal of the proposed work is to develop predictive, verifiable theories for flow in disordered solids. To achieve this goal, the PI proposes to analyze the dynamics of the defects that govern flow, and characterize their properties. Although identifying a "defect" in these solids is non-trivial because the systems are disordered, the PI has developed several tools based on ideas from statistical and soft matter physics to do so. Armed with these new techniques, the PI aims to answer questions such as: how do defects self-organize to cause catastrophic failure? How many defects should one expect in a given material? Is it possible for a mechanically abnormal cell, such as a cancer cell, to act as a defect inside a biological tissue and thereby migrate more quickly?A second part of the proposal aims to increase retention in Science, Technology, Engineering and Math (STEM) disciplines. It focuses on students in the last years of high school and the first years of college, because many students leave the science fields during this time period. The PI will partner with a high school program in Syracuse, NY to deploy teaching modules, made freely available online, that connect introductory physics concepts to research at the frontier of materials science, highlighting their relevance in the real world. Additional modules will "tune-up" the math skills of marginal students, giving them a chance to succeed in physics classes. The PI will also implement several initiatives in an introductory college course, including a weekly self-assessment, training and fellowships for graduate teaching assistants, and online and social networking technologies to help students build a sense of community.

技术摘要：该职业奖支持理论和计算研究及教育，以研究无序材料和生物组织如何流动和失效。 了解这些流动具有直接的实际意义。例如，大块金属玻璃作为结构材料显示出巨大的前景，但尚未得到广泛采用，因为它们会因人们对局部剪切带知之甚少而失效。同样，细胞迁移速率有助于控制胚胎发生和癌症肿瘤发生，但尚不清楚单细胞机械特性如何影响这些速率。 尽管当在边界施加力时非生物无序和玻璃状固体会流动，并且当单个细胞向其邻居施加力时生物组织会流动，但这些“材料”流动和变形的方式存在令人惊讶的普遍性。 PI 将使用统计和软物质物理学的工具来利用这种普遍性，并对流动、失效和细胞迁移做出可验证的预测。 为了实现这一目标，PI 将重点关注三种方法：（1）利用随机矩阵系综的新通用类，对控制堵塞固体塑性的振动模式和局部缺陷进行第一性原理预测。 (2) 识别无序固体中的流动缺陷或软点，并测试三个著名的塑性流动连续介质模型所做的假设。这将确定哪个模型（如果有）正确描述了缺陷。这将允许测试缺陷在剪切反转下的行为、它们作为结构紊乱程度函数的统计数据，以及它们在剪切带内导致灾难性失效的演变。然后，仅使用模拟中的微观信息对连续体模型进行参数化。 (3) 发展一种新理论，预测汇合组织中的细胞迁移率，解决堆积拓扑、两种组织类型之间的边界以及异常细胞力学如何影响迁移率；预测将直接在实验中进行检验。这项研究将与几项针对高中最后几年和大学第一年学生的教育计划相结合。具体来说，PI 将与高中项目合作，在高中开发和部署模块，以 (a) “调整”边缘学生的数学技能，以及 (b) 将入门物理概念与材料科学前沿的研究联系起来。在大学入门级，PI将(c)与经济学教育教授合作，对学生进行每周自我评估，以帮助他们内化课堂期望和社会规范，(d)与物理教育和科学教学教授合作，在新开发的“助教”计划中改进对研究生助理的培训。 PI 还将 (e) 使用在线和课堂技术开发社交网络和讨论平台，帮助学生建立社区意识。非技术摘要：该职业奖支持理论研究和教育，旨在了解无序固体如何变形和失效。 对这些材料进行预测具有挑战性，因为当施加很小的力时，它们会像固体一样做出反应，而组成它们的原子、粒子或细胞的排列却像液体中的一样。当施加较大的力时，这些材料会表现出有趣的流动模式，这在自然和工业中都很重要。 例如，大块金属玻璃作为结构材料显示出巨大的前景，但尚未得到广泛采用，因为它们会因人们对局部剪切带知之甚少而失效。 最近，研究人员还发现生物组织的行为就像无序的固体，因此胚胎发育和癌症转移中的细胞迁移也可以被认为是在这些“材料”内流动。拟议工作的目标是开发无序固体流动的预测性、可验证的理论。 为了实现这一目标，PI 建议分析控制流动的缺陷的动态，并表征其属性。 尽管识别这些固体中的“缺陷”并非易事，因为系统是无序的，但 PI 已经根据统计和软物质物理学的思想开发了多种工具来实现这一点。 借助这些新技术，PI 旨在回答以下问题：缺陷如何自组织导致灾难性故障？给定材料中应该预期有多少缺陷？ 机械异常细胞（例如癌细胞）是否有可能充当生物组织内的缺陷，从而更快地迁移？该提案的第二部分旨在提高科学、技术、工程和数学 (STEM) 学科的保留率。 它主要针对高中最后几年和大学第一年的学生，因为许多学生在这段时间离开科学领域。 该 PI 将与纽约州锡拉丘兹的一个高中项目合作，部署在线免费提供的教学模块，将介绍性物理概念与材料科学前沿的研究联系起来，强调它们在现实世界中的相关性。额外的模块将“调整”边缘学生的数学技能，让他们有机会在物理课上取得成功。 PI 还将在大学入门课程中实施多项举措，包括每周自我评估、研究生助教培训和奖学金，以及帮助学生建立社区意识的在线和社交网络技术。