Understanding microscopic dynamics in sheared highly polydisperse soft materials

该奖项是一个实验和计算研究如何软材料流动。滑坡中的泥浆、水泥、泡沫和泥土等物质的流动与液体的流动大不相同。这些材料以前已经被研究过，但它们的复杂性使得很难确定这些有趣物质如何流动的一般原理。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：标准的简单系统是充满特定尺寸的圆形颗粒的液体。很明显，这些简单的系统不能再现真实的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的流动：在同一样品中具有混合尺寸的颗粒的液体。显微镜用于观察流动样品中颗粒的轨迹。 这些观察结果将用于发展有关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访问学生（一年级到高中）进行实地考察，向他们介绍软质糊状材料以及科学家如何研究这些材料。该奖项的目的是了解无定形固体如何流动，特别是将颗粒尺度的重排与宏观流动剖面和流变行为联系起来。 要研究的主要样品是高度多分散的乳液，其中最大的液滴是最小液滴半径的十倍;以及模拟这些乳液的计算模型。 流动和剪切的样品进行了研究，视频和共聚焦显微镜的目标是同时跟踪单个液滴很长一段时间。 这些轨迹的特征在于位移的幅度，相邻液滴的相对运动，以及可能被触发的样品流动的级联重排。 将对计算数据进行类似的分析。 这些微观观察结果将与宏观流变特性相联系。 总体动机是弥合先前模型系统之间的差距，这些模型系统研究了相当相似尺寸的颗粒混合物和复杂的现实世界材料，如泥浆和水泥。该研究团队每年还将举办实地考察，向来访的学生展示尖端科学可以用简单的材料完成，他们可以从字面上得到他们的手。这个奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

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.