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Flow of colloids and emulsions: Microscopic details of rearrangements and stresses

胶体和乳液的流动：重排和应力的微观细节

基本信息

批准号：
1336401
负责人：
Eric Weeks
金额：
$ 21.02万
依托单位：
Emory University
依托单位国家：
美国
项目类别：
Continuing Grant
财政年份：
2013
资助国家：
美国
起止时间：
2013-09-01 至 2016-08-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1336401&HistoricalAwards=false
关键词：
Flow colloids emulsions Microscopic details

项目摘要

1336401 PI: WeeksIn this project, the PI and his lab group will study the flow of soft materials, in particular emulsions (oil droplets in water). The goal is to connect the microscopic details of the flowing emulsions to their macroscopic properties. The project has two thrusts: first, to study the shear of dense three-dimensional emulsions; and second, to investigate the flow properties of dense two-dimensional emulsions. The 3D samples will be viewed using confocal microscopy. For these 3D samples, the importance of polydispersity will be examined using samples with droplet sizes that vary by as much as an order of magnitude. Flow of these highly polydisperse samples is qualitatively distinct from less polydisperse cases, and the data from this project will be a foundation to understand jammed materials that are highly polydisperse. For the 2D samples, the oil droplets will be confined between two parallel glass plates, so that the droplets are deformed into round quasi-two-dimensional disks. From the outlines of the droplets and knowledge of their surface tension, forces between droplet pairs will be measured and related to the rearrangements as the droplets flow. These measurements enable testing of theories of flowing amorphous materials. Microfluidic techniques will be used to create the oil droplets, allowing careful control over droplet sizes, viscosities, and surface tension. Soft jammed materials are common, and include colloidal pastes (such as toothpaste), gels (such as gelatin), foams (such as shaving cream), and emulsions (such as mayonnaise). In contrast to regular liquids like water, the flow properties of these materials are less well understood. For example, the flow of an emulsion composed of oil droplets in water must involve rearrangements of individual droplets; additionally, the droplets can be stretched and even break up, making the flow even more complicated. The projects funded by this award will use microscopes to take movies of flowing emulsions, to see how the oil droplets move and how these motions are related to the forces required to flow them. This will lead to better understanding of how to create emulsions with specific flow properties, and how to better process emulsions in industry. Additionally, Professor Weeks will conduct at least one field trip each year to his laboratory for groups of primary school students. These students will investigate the properties of "squishy" materials such as the oil-and-water emulsions used in this project. While such materials are common and safe, they are also counterintuitive and get students curious. For example, consider shaving cream, which can sit in a pile on a table, in contrast to a puddle of soapy water which must lie flat. Such materials challenge the ideas students have that materials only come as solids, liquids, or gases.

1336401 PI：Weeks在这个项目中，PI和他的实验室小组将研究软材料的流动，特别是乳液（水中的油滴）。我们的目标是将流动乳液的微观细节与其宏观性质联系起来。该项目有两个重点：第一，研究致密三维乳液的剪切;第二，研究致密二维乳液的流动特性。将使用共聚焦显微镜观察3D样品。对于这些3D样品，多分散性的重要性将使用液滴尺寸变化多达一个数量级的样品进行检查。这些高度多分散的样品的流动在性质上与较少多分散的情况不同，并且来自该项目的数据将是理解高度多分散的堵塞材料的基础。对于2D样品，油滴将被限制在两个平行的玻璃板之间，使得油滴变形为圆形准二维盘。从液滴的轮廓和它们的表面张力的知识，液滴对之间的力将被测量并且与液滴流动时的重排相关。这些测量使流动的非晶材料的理论测试。微流控技术将被用来创建油滴，允许仔细控制液滴大小，粘度和表面张力。软堵塞材料是常见的，并且包括胶体糊状物（诸如牙膏）、凝胶（诸如明胶）、泡沫（诸如剃须膏）和乳液（诸如蛋黄酱）。与水等常规液体相比，这些材料的流动特性不太清楚。例如，由水中的油滴组成的乳液的流动必须涉及单个液滴的重排;此外，液滴可以被拉伸甚至破裂，使流动更加复杂。该奖项资助的项目将使用显微镜拍摄流动乳液的电影，以观察油滴如何移动以及这些运动如何与流动它们所需的力相关。这将使人们更好地了解如何制造具有特定流动特性的乳液，以及如何在工业中更好地加工乳液。此外，Weeks教授每年将为小学生团体进行至少一次实地考察。这些学生将研究“粘稠”材料的特性，例如本项目中使用的油-水乳液。虽然这些材料是常见和安全的，但它们也违反直觉，让学生感到好奇。例如，考虑剃须膏，它可以坐在一堆在桌子上，而不是一个水坑的肥皂水，必须躺平。这些材料挑战了学生们认为材料只能以固体、液体或气体的形式出现的想法。