Viscous dissipation in molecularly thin liquid films

在这个项目中，我们想研究在原子光滑表面之间的液体薄膜的粘度和流动特性，在几个分子直径的间隔数量级。与各向同性的散装液体不同，这种受限液体层中的分子排列成与界面平行的层。通常，这种层状结构延伸几个分子直径进入液相。本项目的目标是确定在固液界面的几纳米内，这种结构重排是如何影响液体的粘度的。为了研究这些现象，我们使用了所谓的表面力仪（SFA）的两种不同的扩展。第一个是最近在我们实验室开发的，它允许在分子水平上对流体动力过程进行直接视频成像。第二种是SFA与荧光显微技术的结合，特别是光漂白后荧光恢复（FRAP）。在这种情况下，荧光分子被用来修饰受限液体层内的流动模式。

In this project, we want to study the viscosity and the flow properties in thin liquid films confined between atomically smooth surfaces at a separation of the order of a few molecular diameters. In contrast to bulk liquids, which are isotropic, the molecules in such confined liquid layers are arranged in layers parallel to the interfaces. Typically, this layer structure extends a few molecular diameters into the liquid phase. The goal of the present project is to determine how the viscosity of liquids is affected by this structural rearrangement within a few nanometers of the solid-liquid interface. In order to study these phenomena, we use two different extensions of the so-called Surface Forces Apparatus (SFA). The first one, which was developed recently in our laboratory, allows for direct video imaging of hydrodynamic processes at the molecular level. The second one is a combination of the SFA with fluorescence microscopy techniques, in particular fluorescence recovery after photobleaching (FRAP). In this case, fluorescent molecules are used to decorate flow patterns within the confined liquid layers.