Non-Newtonian Fluids in Squeeze Films

挤压薄膜中的非牛顿流体

• 批准号: 0828163
• 负责人: William Ducker
• 金额: $ 30万
• 依托单位: Virginia Polytechnic Institute and State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-08-15 至 2012-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0828163&HistoricalAwards=false
• 关键词: Non; Newtonian; Fluids; Squeeze; Films

CBET-0828163DuckerThe flow of fluid in narrow channels is receiving increased attention because of the growing importance of both microfluidics and nanoparticle science and engineering. Reduction to smaller length scales raises interesting questions, including: what is the boundary condition at the solid-liquid interface? How can the flow of fluid be enhanced in narrow channels? How is the flow of complex fluids affected by confinement into a thin film? Here we propose to address these questions by using colloidal probe microscopy to study the flow of fluids in the squeeze film between a sphere and a plate. This method has recently been successful in confirming the no-slip boundary condition at the solid-liquid interface for simple liquids, and is now ready for the study of more complex fluids. The outcomes of this work have implications in two fields. First, the forces acting on small particles as they approach plates are important for in their own right because of the widespread use of particles and the presence of particle contamination on membranes, semiconductor wafers etc. Second, these measurements open a window on fundamental questions such as the fluid boundary conditions and the importance of confinement on fluid flow. The proposal is to use force microscopy to measure the force, velocity and displacement of a colloidal particle as it approaches the plate. The particle will be immersed in a fluid. The measured parameters will be compared to theoretical values to validate theories. The first order theory will be Brenner's lubrication result for simple liquids under creeping flow. Comparison to this theory allows us to determine the effective slip-length and the effective viscosity. Measurements will be made on a variety of non-Newtonian fluids, including polymer melts, surfactant solutions, nanoparticle dispersions, and rarefied gases. Some development of theory will be necessary to interpret these measurements. Attempts will be made to enhance flow through the adsorption of low viscosity fluids or films at the interface. The proposal is also to improve the colloidal force measurement by increasing the range of frequencies and shear rates that are accessible. Greater shear rates will be accessed by incorporating a high velocity drive, and greater frequencies will be accessed by development of an oscillatory drive. This oscillatory drive will enable the simultaneous measurement of elastic and dissipative responses over a small range of separations. The advantage of colloidal probe microscopy is the very high resolution in displacement and force that is achieved. For example, colloidal probe microscopy can determine the slip-length with only a few nanometers of uncertainty. The educational component of this proposal will be to train a post-doctoral researcher, a graduate student and undergraduate students.

CBET-0828163Ducker 由于微流体学和纳米粒子科学与工程的重要性日益增加，狭窄通道中的流体流动受到越来越多的关注。 减小到更小的长度尺度引发了有趣的问题，包括：固液界面的边界条件是什么？如何增强狭窄通道中的流体流动？复杂流体的流动如何受到薄膜限制的影响？在这里，我们建议通过使用胶体探针显微镜研究球体和板之间的挤压膜中的流体流动来解决这些问题。 该方法最近成功地证实了简单液体固液界面的无滑移边界条件，现在可以用于研究更复杂的流体。这项工作的成果对两个领域有影响。首先，由于颗粒的广泛使用以及膜、半导体晶片等上存在颗粒污染，当小颗粒接近板时作用在它们上的力本身就很重要。其次，这些测量为了解基本问题打开了一个窗口，例如作为流体边界条件和限制对流体流动的重要性。 该提议是使用力显微镜来测量胶体颗粒接近板时的力、速度和位移。颗粒将浸入液体中。测量的参数将与理论值进行比较以验证理论。一阶理论将是布伦纳对蠕动流下简单液体的润滑结果。与该理论的比较使我们能够确定有效滑移长度和有效粘度。将对各种非牛顿流体进行测量，包括聚合物熔体、表面活性剂溶液、纳米颗粒分散体和稀薄气体。解释这些测量结果需要一些理论的发展。将尝试通过在界面处吸附低粘度流体或薄膜来增强流动。 该提案还旨在通过增加可用的频率和剪切速率范围来改进胶体力测量。通过合并高速驱动器将获得更大的剪切速率，并且通过开发振荡驱动器将获得更高的频率。这种振荡驱动将能够同时测量小范围分离内的弹性和耗散响应。胶体探针显微镜的优点是可以实现非常高分辨率的位移和力。例如，胶体探针显微镜可以确定滑移长度，不确定性只有几纳米。 该提案的教育部分将是培训一名博士后研究员、一名研究生和本科生。