Mapping Forces and Elasticity in Random Solids

映射随机固体中的力和弹性

• 批准号: 0305395
• 负责人: Anthony Dinsmore
• 金额: $ 30万
• 依托单位: University of Massachusetts Amherst
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-08-01 至 2006-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0305395&HistoricalAwards=false
• 关键词: Mapping; Forces; Elasticity; Random; Solids

This soft condensed matter physics project deals with disordered solids, which include glassy materials, polymer gels, particle gels, and sand piles. Although the microscopic details differ tremendously, there is increasing evidence that these materials are examples of a more general class known as jammed solids. From a fundamental point of view, the great challenge of these materials is that they are far from thermal equilibrium and continuum elasticity might not apply at microscopic or mesoscopic length scales. This project will use optical methods to obtain direct and quantitative imaging of forces, their spatial correlations, and the topology of inter-particle connections in three dimensional samples. Results are to be compared to recent theories, simulations and measurements on surfaces or on two-dimensional materials. This focus is on confocal optical microscopy of monodisperse liquid droplets with fluorescent surfaces, a model system that allows imaging of forces in the interior of three-dimensional samples. By varying the sizes of the droplets used, the systems studied will be varied between those solidified by attractive inter-particle forces and subject to strong thermal fluctuations, to those solidified by gravitational stresses at, effectively, zero temperature. The project also investigates how these force maps are changed by external stresses or by point forces applied inside the material. The project provides in-depth training of students for research in applied or fundamental programs.Disordered solids are very common in everyday life, with examples including window glass, yogurt, soot, and sand piles. Although the microscopic details of these examples differ tremendously - molecules in one case and millimeter-sized rough sand grains in another - there is compelling evidence that they may be understandable within a single theoretical framework. From a fundamental point of view, the great challenge of these materials is that they never approach thermal equilibrium and do not form ordered (crystalline) structures. Moreover, continuum elasticity theory might be incorrect at length scales comparable to several times the size of the basic particle. This work will provide the first experimental maps of forces, structure, and connectivity inside these materials. The major experimental challenge is, somehow, to peer inside a sand pile and measure forces between adjacent particles. Here this is accomplished using liquid droplets (instead of sand grains) whose deformation is quantified in three dimensions using optical microscopy. In addition to allowing investigation of a number of new questions, the measurements will provide the first tests of theoretical predictions and computer simulations, and will connect with earlier experiments on two-dimensional materials or on the surface of three-dimensional materials. The project also provides training for students at all levels in soft condensed matter physics and advanced research techniques suitable for academic or industrial research positions.

这个软凝聚态物理项目涉及无序固体，包括玻璃质材料，聚合物凝胶，颗粒凝胶和沙堆。 虽然微观细节差异巨大，但越来越多的证据表明，这些材料是一个更一般的类别，称为堵塞固体的例子。 从基本的角度来看，这些材料的巨大挑战是它们远离热平衡，连续弹性可能不适用于微观或介观长度尺度。 该项目将使用光学方法来获得三维样品中力的直接和定量成像，它们的空间相关性以及颗粒间连接的拓扑结构。 将结果与表面或二维材料上的最新理论、模拟和测量进行比较。 这一重点是单分散液滴与荧光表面，模型系统，允许在三维样品的内部力的成像的共聚焦光学显微镜。 通过改变所使用的液滴的尺寸，所研究的系统将在通过颗粒间吸引力固化并受到强烈热波动的那些系统与通过重力应力在有效的零温度下固化的那些系统之间变化。 该项目还研究了这些力图如何被外部应力或材料内部施加的点力改变。 该项目为学生提供深入的应用或基础课程研究培训。无序固体在日常生活中非常常见，例如窗户玻璃，酸奶，烟灰和沙堆。 虽然这些例子的微观细节差别很大--一个例子是分子，另一个例子是毫米大小的粗糙沙粒--但有令人信服的证据表明，在一个单一的理论框架内，它们是可以理解的。 从基本的角度来看，这些材料的巨大挑战是它们永远不会接近热平衡，也不会形成有序的（晶体）结构。 此外，连续介质弹性理论在长度尺度相当于基本粒子尺寸的几倍时可能是不正确的。 这项工作将提供这些材料内部的力，结构和连接性的第一个实验图。 主要的实验挑战是，以某种方式，窥视沙堆内部并测量相邻颗粒之间的力。 在这里，这是使用液滴（而不是沙粒）来实现的，其变形使用光学显微镜在三维空间中进行量化。 除了允许调查一些新的问题，测量将提供理论预测和计算机模拟的第一次测试，并将与二维材料或三维材料表面上的早期实验相联系。 该项目还为各级学生提供软凝聚态物理和适合学术或工业研究职位的先进研究技术方面的培训。