Adsorption in Confined Films

许多普通的产品是由悬浮在液体中的颗粒组成的。例子包括油漆、食品和化妆品。这些产品的一个重要特征是颗粒保持特定的排列，而不是聚集或从悬浮液中分离。保持颗粒的适当排列可能具有挑战性，特别是对于具有长保质期的产品。 保持颗粒的理想排列的关键方面是控制在颗粒几乎彼此接触的小间隙中发生的事情。 这个项目利用了我们最近的发展，使这些小差距的定义明确的例子。 该项目研究了分子如何吸附到间隙中，以及吸附如何受到差距大小的影响。 这种分子吸附对于控制间隙是随着时间的推移而缩小还是扩大，从而控制消费品是否保持最有用的排列至关重要。 该项目的研究将被整合到本科生和研究生的教学计划中，并将提供教育工具，以激励高中生，特别是那些在STEM领域代表性不足的学生，继续进行科学和工程研究。离子，表面活性剂，聚合物和颗粒的吸附是决定薄润湿膜中胶体分散体稳定性的关键因素，因此是许多工程过程的中心。 在单一界面上的吸附已被很好地研究，但胶体稳定化的直接相关量是在两个界面之间的薄膜中的吸附。这在以前的工作中很少被测量。一种新的技术已经发展到测量两个固体之间的纳米级薄膜中的物种的数量。 这种技术将被用来测量吸附在关键制度的基础上泊松-玻尔兹曼理论的简单建模预计失败，如在浓缩溶液，多价离子，表面活性剂和颗粒。该技术有三个要素：（1）制造一个强大的薄膜之间的两个固体与连续梯度的厚度在1？200 nm;（2）通过干涉测量法测量膜厚度;和（3）从荧光发射强度测量吸附分子的量。预期成果是：（1）精确测量薄膜中物质的量;（2）评估常用模型的有效性;（3）深入了解各种应用中薄膜的稳定性;（4）测量垂直于平面薄膜方向上荧光团浓度分布的方法的某些发展。我们将这项工作整合到“计算机和技术在弗吉尼亚理工大学”（C-Tech 2），这是一个为期两周的夏季计划，每年120名女高中参加动手活动，以帮助发展和保持对科学和工程的兴趣。这项工作还将为光学、微细加工、建模和显微镜领域的研究生提供跨学科培训。本科生将参与该项目，目的是激励他们继续攻读工程或科学研究生课程。该奖项反映了NSF的法定使命，并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，被认为值得支持。

Many commonplace products are composed of collections of particles suspended in liquid. Examples include paints, food products and cosmetics. An important feature of these products is that the particles remain in particular arrangements, rather than aggregating or separating from the suspending liquid. Maintaining the proper arrangement of the particles can be challenging, especially for products with long shelf lives. The key aspect of maintaining the desired arrangement of particles is to control what happens in the small gaps where the particles almost touch each other. This project takes advantage of a recent development in our ability to make well-defined examples of these small gaps. The project examines how molecules adsorb into the gaps, and how the adsorption is affected by the gap size. This molecular adsorption is critical to controlling whether the gaps close or widen with time, and thus whether consumer products maintain the most useful arrangement. The research in this project will be integrated into programs that teach undergraduate and graduate students, and will provide educational tools to inspire high school students, especially those underrepresented in STEM fields, to continue in science and engineering studies.Adsorption of ions, surfactants, polymers, and particles is a key factor in determining the stability of colloidal dispersions in thin wetting films, and thus is central to many engineering processes. Adsorption at single interfaces has been well studied, but the directly relevant quantity for colloid stabilization is adsorption in a thin film between two interfaces. This has only rarely been measured in prior work. A new technique has been developed to measure the amount of a species in nanometer-scale films between two solids. This technique will be used to measure adsorption in critical regimes where simple modeling based on Poisson-Boltzmann theory is expected to fail, such as in concentrated solutions, multivalent ions, surfactants, and particles. The technique has three elements: (1) fabrication of a robust thin film between two solids with a continuous gradient of thicknesses in the range of 1?200 nm; (2) measurement of film thickness by interferometry; and (3) measurement of the amount of adsorbed molecules from the intensity of fluorescence emission. The expected outcomes are: (1) accurate measurements of amounts of species in thin films; (2) assessment of the validity of common models; (3) insight into the stabilization of films in various applications; and (4) some development of the method to measure the profile of fluorophore concentration in the direction normal to a planar film. We will integrate this work into the "Computers and Technology at Virginia Tech" (C-Tech2), which is an annual two-week summer program for 120 female high school to participate in hands-on activities to help develop and sustain interest in science and engineering. The work will also provide interdisciplinary training for a graduate student in the fields of optics, microfabrication, modelling, and microscopy. Undergraduates will work on the project, with the aim of inspiring them to pursue graduate study in engineering or science.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.