Connecting Glassy Dynamics to Micro-Scale Elasticity

1236378PI: wyart颗粒状材料，如悬浮液或颗粒状物质，是工业中除水之外最常用的材料。然而，解释它们的流变特性仍然是一个挑战。这些系统由于无序以及结构和动力异质性的存在而变得复杂，通常在多个长度尺度上。在高密度下，这种颗粒状流体会发生堵塞或玻璃化转变，此时动力学停止。近年来，已经有相当多的努力来描述这种转变，并且已经认识到动态异质性起着关键作用。然而，对于是什么原因导致了这种异质性，并没有达成共识。本项目将开发一种新的方法来测量非晶材料的微观弹性。这种方法将在实验和数值上用于表征非晶固体的无序性和非均质性，并研究它们形成的干扰转变。该方法包括引入形状和大小可控的探针粒子。热噪声导致探针粒子在一个时间尺度上旋转，这个时间尺度是由它们所在环境的弹性、它们的形状和大小决定的。通过共聚焦显微镜、光散射或数值模拟来测量探针的旋转动力学，可以获得局部弹性特性。时间尺度和长度尺度的范围可以通过控制探针的形状和大小来调节。该方法将被用于胶体悬浮液，实验和数值，以测量弹性的演变及其空间异质性随着胶体浓度的增加，并测试玻璃化转变的基本理论。该项目将创建一种实验方法来探索无序颗粒材料的微观特性，无序颗粒材料是工业上仅次于水的最常用材料。这种方法将解决粒子流、生物物理学、土壤力学和材料科学领域的基本和实际重要性问题。从这项研究中获得的见解将有助于改进玻璃材料的设计，并提高我们对堵塞或堵塞的理解，这对于与石油工业相关的多相流以及潜在的致命血管阻塞事件（堵塞）非常重要。发生于镰状细胞病的除了这些应用之外，这个项目的主题也适用于教育和社区外展活动。

1236378PI: WyartParticulate materials, such as suspensions or granular matter, are the most commonly used materials in industry after water. However, explaining their rheological properties remains a challenge. These systems are complicated by the presence of disorder as well as by structural and dynamical heterogeneities, often on multiple length scales. At high densities, such a granular fluid undergoes a jamming or glass transition where the dynamics stop. In recent years there has been a considerable effort to characterize this transition, and it has been realized that dynamical heterogeneities play a key role. However, there is no consensus concerning what causes such heterogeneities. This project will develop a novel method to measure the micro-scale elasticity of amorphous materials. This approach will be used both experimentally and numerically to characterize the disorder and heterogeneities of amorphous solids, and to investigate the jamming transition by which they are formed. The method consists of introducing probe particles of controlled shapes and sizes. Thermal noise causes the probe particles to rotate on a time scale governed by the elasticity of their local environment, and by their shape and size. Measuring the rotational dynamics of the probe by means of confocal microscopy, light scattering, or numerically in simulations will give access to local elastic properties. The range of time scales and length scales can be tuned by controlling the shape and size of the probes. This method will be employed in colloidal suspensions, both experimentally and numerically, to measure the evolution of elasticity and its spatial heterogeneities as the concentration of colloids is increased, and to test fundamental theories of the glass transition.This project will create an experimental method to probe the microscopic properties of disordered granular materials, the most commonly used materials in industry after water. This method will address questions of fundamental and practical importance in the fields of particle flow, biophysics, soil mechanics, and material science. Insights gained from this study will help improve the design of glassy materials and advance our understanding of clogging or jamming, which are of important for multi-phase flows relevant to the oil industry and potentially for the lethal vaso-occlusive eventt?clogging?occurring in sickle cell disease. In addition to these applications, the subject matter of this project lends itself to educational and community outreach activities.