Connecting Glassy Dynamics to Micro-Scale Elasticity

1236378 PI：WyartParticulate materials，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。这些系统是复杂的存在的障碍，以及结构和动力学的异质性，往往在多个长度尺度。在高密度下，这种颗粒状流体经历堵塞或玻璃化转变，其中动力学停止。近年来，已经有相当大的努力来描述这种转变，它已经意识到，动力学的不均匀性发挥了关键作用。然而，对于是什么导致了这种异质性，还没有达成共识。本计画将发展一种新的方法来量测非晶材料的微尺度弹性。这种方法将被用于实验和数值表征的无序和非晶固体的异质性，并调查他们形成的干扰过渡。该方法包括引入受控形状和尺寸的探针颗粒。热噪声导致探针粒子在时间尺度上旋转，该时间尺度由其局部环境的弹性以及其形状和大小决定。通过共焦显微镜、光散射或模拟中的数值方法测量探针的旋转动力学将获得局部弹性性质。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整。该方法将用于胶体悬浮液的实验和数值计算，以测量随着胶体浓度的增加弹性及其空间不均匀性的变化，并验证玻璃化转变的基本理论。该项目将创建一种实验方法，以探测无序颗粒材料的微观特性，无序颗粒材料是除水之外最常用的工业材料。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的问题。从这项研究中获得的见解将有助于改善玻璃材料的设计和推进我们的理解堵塞或堵塞，这是重要的多相流相关的石油工业和潜在的致命血管闭塞eventt？堵塞？发生在镰状细胞病中。除了这些应用之外，该项目的主题还适用于教育和社区推广活动。

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.