Understanding microscopic dynamics in sheared highly polydisperse soft materials

了解剪切高度多分散软材料的微观动力学

• 批准号: 2306371
• 负责人: Eric Weeks
• 金额: $ 35.93万
• 依托单位: Emory University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-07-01 至 2026-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2306371&HistoricalAwards=false
• 关键词: Understanding; microscopic; dynamics; sheared; highly

This award is an experimental and computational study of how soft materials flow. The flow of materials like mud, cement, foam, and dirt in landslides is quite different from the flow of liquids. These materials have been studied before but their complexity makes it difficult to determine general principles about how these interesting substances flow. Some past studies used simple systems to try to mimic these complicated materials: a standard simple system is a liquid full of round particles with a specific size. It is clear that these simple systems fail to reproduce many of the interesting flow behaviors of the real materials. This work studies the flow of materials with intermediate complexity: liquids with particles with a mixture of sizes in the same sample. Microscopy is used to view the trajectories of particles in a flowing sample. These observations will be used to develop basic ideas about the flow of disordered materials, which will lead to better understanding of how to move, mix, and process complex materials of industrial relevance. The researchers will regularly host field trips of visiting students (first grade through high school) to teach them about soft squishy materials and how scientists study these materials.The objective of this award is to understand how amorphous solids flow, in particular to connect particle-scale rearrangements to macroscopic flow profiles and rheological behavior. The main samples to be studied are highly polydisperse emulsions, where the largest droplets are ten times the radius of the smallest droplets; and computational models that mimic these emulsions. Flowing and sheared samples are studied with video and confocal microscopy with a goal of simultaneous tracking of individual droplets for long times. These trajectories will be characterized in terms of magnitudes of displacements, relative motions of neighboring droplets, and cascading rearrangements that might be triggered as the sample flows. Similar analysis will be done for the computational data. These microscopic observations will be connected to macroscopic rheological properties. The overall motivation is to bridge the gap between prior model systems that studied mixtures of particles of fairly similar sizes, and complex real-world materials such as mud and cement. The research team will also host field trips each year to demonstrate to visiting students that cutting edge science can be done with simple materials which they can literally get their hands on.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

这个奖项是关于软材料如何流动的实验和计算研究。在山体滑坡中，泥浆、水泥、泡沫和泥土等物质的流动与液体的流动大不相同。这些物质以前曾被研究过，但它们的复杂性使得很难确定这些有趣物质流动的一般原理。过去的一些研究使用简单的系统来试图模拟这些复杂的材料：一个标准的简单系统是一个充满特定大小的圆形颗粒的液体。很明显，这些简单的系统不能再现真实材料的许多有趣的流动行为。这项工作研究了具有中等复杂性的材料流动：在同一样品中具有不同大小混合颗粒的液体。显微镜用于观察流动样品中粒子的运动轨迹。这些观察结果将用于发展关于无序材料流动的基本思想，这将有助于更好地理解如何移动、混合和处理与工业相关的复杂材料。研究人员将定期组织来访的学生（一年级到高中）进行实地考察，教他们关于软黏糊糊的材料以及科学家如何研究这些材料。该奖项的目的是了解非晶固体如何流动，特别是将颗粒尺度的重排与宏观流动曲线和流变行为联系起来。研究的主要样品是高度分散的乳液，其中最大的液滴是最小液滴半径的十倍；以及模拟这些乳剂的计算模型。用视频和共聚焦显微镜研究流动和剪切样品，目的是长时间同时跟踪单个液滴。这些轨迹将根据位移的大小、邻近液滴的相对运动以及可能在样品流动时触发的级联重排来表征。将对计算数据进行类似的分析。这些微观观察将与宏观流变特性联系起来。总的动机是为了弥合先前模型系统之间的差距，这些模型系统研究的是相当相似大小的颗粒混合物，以及复杂的现实世界材料，如泥浆和水泥。研究小组每年还将组织实地考察，向来访的学生展示，他们可以用简单的材料来完成尖端科学，而且他们真的可以得到这些材料。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。