Using Confinement to Study the Colloidal Glass Transition

*非技术摘要*纳米技术的最新进展发现，一些材料在非常小的范围内表现出不同的行为。例如，较小的物体比较大的物体更容易破碎；但厚度小于100纳米的小塑料片甚至比我们从较厚的塑料片推断出来的更容易破碎。塑料是无定形材料，类似于窗户玻璃，现在人们知道，许多玻璃材料在足够小的样品中表现不同。然而，有些人变得更强，有些人变得更弱。这一个人研究人员奖支持研究液体中微小塑料颗粒的模型系统的实验，当颗粒浓度增加时，该系统的行为类似于玻璃。这些实验将使用显微镜来观察颗粒的运动，并观察当样品被限制在两个间隔很近的平行玻璃板之间时，这种运动是如何变化的。这样，系统如何依赖于板之间的间距将被直接观察到。这项研究对未来纳米技术的应用非常重要，这些应用依赖于由塑料等玻璃材料建造的微小结构。该项目为本科生和研究生提供培训和教育。此外，该实验室每年将至少为高中生群体进行一次实地考察。这些实地考察给了学生实际的实验室体验，而显微镜的视觉特性使学生很容易对他们的参观感到兴奋。*技术摘要*聚合物玻璃和分子玻璃的玻璃化转变通常是在宏观大系统的背景下研究的。然而，限制样品以使一个或多个维度是微观的通常会改变样品的行为，例如改变样品成为玻璃的温度。这一个人研究人员奖支持一个项目，该项目研究限制在薄样室内的胶体悬浮液，作为受限几何图形中玻璃化转变的模型系统。胶体悬浮液是由液体中微观尺寸的固体颗粒组成的；如果颗粒浓度足够高，这种体系的行为类似于玻璃。实验将使用共焦显微镜直接观察胶体颗粒的运动，以及这种运动在限制条件下的变化。随着越来越多的技术建立在纳米尺度上，理解限制对材料的物理影响在今天变得越来越重要。该项目为本科生和研究生提供培训和教育。该实验室每年至少为高中生群体进行一次实地考察。这些实地考察为学生提供了亲身实践的实验室体验，研究的可视化性质使学生很容易对他们的访问感到兴奋。

****NON-TECHNICAL ABSTRACT****Recent advances in nanotechnology have discovered that some materials behave differently on a very small scale. For example, smaller objects are easier to break than larger objects; but small pieces of plastic less than 100 nanometers thick are even easier to break than would be expected by extrapolating from what we know about thicker pieces of plastic. Plastics are amorphous materials, similar to window glass, and now it is known that many glassy materials behave differently in small enough samples. However, some become stronger and some become weaker. This individual investigator award supports experiments to study a model system of small plastic particles in a liquid, which behaves analogously to a glass when the particle concentration is increased. The experiments will use a microscope to view the motion of the particles and see how this motion changes when the sample is confined between two closely spaced parallel glass plates. In this way, how the system depends on the spacing between the plates will be directly observed. This research is important for future nanotechnology applications that rely on tiny structures built out of glassy materials such as plastic. This project provides training and education for both undergraduate and graduate students. Additionally, the laboratory will conduct at least one field trip each year for groups of high school school students. These field trips give students hands-on laboratory experiences, and the visual nature of microscopy makes it easy to get students excited about their visit.****TECHNICAL ABSTRACT****The glass transitions of polymer glasses and molecular glasses are usually studied in the context of macroscopically large systems. However, confining samples so that one or more dimensions are microscopic typically changes the behavior of the sample, for example changing the temperature at which the sample becomes a glass. This individual investigator award supports a project to study a colloidal suspension confined in thin sample chambers as a model system for glass transitions in confined geometries. Colloidal suspensions are composed of microscopic-sized solid particles in a liquid; this system behaves analogous to a glass if the particle concentration is sufficiently high. Experiments will use confocal microscopy to directly observe the motion of colloidal particles and how this motion changes in confinement. Understanding the physical effects of confinement on materials is increasingly important today as more and more technology is built at the scale of nanometers. This project provides training and education for both undergraduate and graduate students. The laboratory will conduct at least one field trip each year for groups of high school school students. These field trips give students hands-on laboratory experiences, and the visual nature of the research makes it easy to get students excited about their visit.