Fluorescence imaging of multi-component wetting

Fluorescence imaging methods are explored as tools to study multi-component wetting of liquids. A novel approach was employed using polymer labeled with contrasting fluorescent dyes, which allow optical recognition and also caused differences in surface tension between blend components. Total internal reflection-fluorescence microscopy probes a thin surface layer to the order of 100 nm to investigate the structure of the spreading drop next to the substrate. Dye segregation out of solution and phase separation of polymer blends were observed. Confocal microscopy can visualize the larger three-dimensional structure of sessile drops. Component segregation was observed and quantified using relative fluorescence intensities.