Image scanning ellipsometry for measuring the transient, film thickness profiles of draining liquids

Image Scanning Ellipsometry, a technique to measure the two‐dimensional thickness profile of a nonuniform, thin, liquid film, from several nanometers up to tens of microns, in the steady and transient states, was developed and tested. The ability of this full‐field imaging technique to map every point on the surface simultaneously was demonstrated by measuring the thickness profiles of very thin, draining, liquid films in the interfacial, transition, hydrodynamic, and capillary regions. Depending on the relative size of the intermolecular, gravitational, and capillary forces, four flow regions were identified. Using a simple model for the transient film thickness profiles of a completely wetting, draining film of FC‐70, the experimental results were successfully analyzed in the interfacial, transition, and hydrodynamic regions. A diffusion coefficient for the junction line between the interfacial and transition regions was theoretically and experimentally evaluated.