Dynamic Properties of Confined Complex Fluids

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。这个项目将是一个实验研究，重点是推进我们对复杂流体（即含有分散纳米胶体的流体）在约束条件下的动态行为的理解。虽然这些薄膜的振荡平衡结构是由纳米胶体的有序结构引起的，但人们对薄膜的减薄率、结构形成和粘滞阻力之间的动态关系却很少关注，也很少了解。了解这些关系对于预测泡沫稳定性和产品储存寿命等基本特性非常重要。这项工作将建立在PI获得的重要初步测量的基础上，并将解决以下问题：在多大程度上，薄膜对排水的粘性阻力可以用纯流体的润滑方程来预测？2. 变薄的速度如何影响纳米胶体的有序能力？这些特殊的研究也将集中于验证PI先前得出的佩莱特数分析。3. 薄膜的粘性阻力和纳米颗粒的有序能力如何受到纳米颗粒形状的影响？这是一个尚未探索的问题，将使用模型棒状纳米颗粒进行研究。这些研究将使用胶体探针原子力显微镜进行，这已经被发现是测量这种类型的理想工具。该项目的第四个任务将是开发一个实验试验台，演示如何利用有吸引力的耗竭力分离流过固定收集器珠填充床的胶体颗粒。这项任务将再次建立在PI的初步工作基础上，该工作证明了该应用程序的可行性。含有分散相的液体薄膜在许多普通产品和工业过程中都可以找到。例子包括食品、肥皂和洗涤剂，以及利用泡沫浮选回收矿物。了解这些电影的稳定性是至关重要的，从这个项目中获得的知识显然将有助于实现这一目标。排水动力学在预测颗粒聚集、沉积和运输速率方面也很重要。除了作为一种有用的应用之外，耗尽相互作用作为粒子分离工具的提议还可以刺激对利用这种力的独特性质的新应用的进一步研究。虽然耗竭力已被广泛研究了60多年，但利用其能力的实际应用很少。本项目将资助一名全日制博士研究生3年，一名博士后1年，并为本科生提供研究机会。作为弗吉尼亚理工大学化学工程系的负责人，PI完全致力于维护多元化的教育环境，并不断努力为代表性不足的群体提供机会。该项目还将为开发夏季课程的培训模块提供所需的支持，该课程旨在鼓励高中生和中学生考虑从事科学和工程方面的职业。最后，提议的颗粒分离装置将被纳入PI正在开发的胶体和界面的实验课程中。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).0932937Walz This project will be an experimental investigation focused on advancing our understanding of the dynamic behavior of complex fluids (i.e., fluids containing dispersed nanocolloids) in confinement. While the oscillatory equilibrium structure of these films, resulting from ordering of the nanocolloids, has been well studied, the dynamic relationship between thinning rate, structure formation, and viscous resistance of the film has received far less attention and is poorly understood. Understanding these relationships is important for predicting such basic properties as froth stability and product storage life. The work will build upon significant preliminary measurements obtained by the PI and will address the following issues: 1. To what extent can the viscous resistance of the film to drainage be predicted using lubrication equations developed for pure fluids? 2. How does the rate of thinning affect the ability of the nanocolloids to order? These particular studies will also be focused on validating a a Peclet number analysis previously derived by the PI. 3. How are the viscous resistance of the film and ability of the nanoparticles to order affected by nanoparticles shape? This is an unexplored issue and will be studied using model rod like nanoparticles. The studies will be conducted using colloidal probe atomic force microscopy, which has been found to be an ideal tool for measurements of this type. A fourth task of the project will be to develop an experimental test bed demonstrating the use of attractive depletion forces to separate colloidal particles flowing through a packed bed of stationary collector beads. This task will again build upon preliminary work by the PI which demonstrated the feasibility of this application. Intellectual Merit Thin liquid films containing a dispersed phase are found in many common products and industrial processes. Examples include food products, soaps and detergents, and recovery of minerals using froth flotation. Understanding the stability of these films is of critical importance, and the knowledge gained from this project will clearly be useful toward this goal. Drainage dynamics can also be important in predicting the rate of particle aggregation, deposition, and transport. In addition to being a useful application, the proposed use of depletion interactions as a particle separation tool could spur additional research into new applications that capitalize on the unique properties of this force. While the depletion force has been extensively studied for more than 60 years, there are very few actual applications utilizing its capabilities. Broader Impacts This project will support a full time Ph.D. graduate student for three years, a post doctoral researcher for one year, and provide research opportunities to undergraduate researchers. As Head of the Department of Chemical Engineering at Virginia Tech, the PI is fully committed to maintaining a diverse educational environment and continually strives to provide opportunities to underrepresented groups. The project will also provide support needed to develop a training module for summer programs at the University aimed at encouraging high school and middle school students to consider a career in science and engineering. Finally, the proposed particle separation apparatus will be incorporated into a laboratory course in colloids and interfaces that the PI is developing.