Fluorescence microscope to observe dynamical processes in monomolecular layers at the air/water interface

An experimental setup is described to microscopically observe surfactant monolayers at the air/water interface. It basically consists of a film balance, incorporated into a fluorescence microscope, detecting the emission of dye probes. The apparatus is stable enough to observe dynamical processes over more than 5 h, with a spatial resolution of less than 2 μm and is sensitive enough to use probe concentrations as low as 0.1 mol%. Examples of surface textures appearing during lipid phase transitions demonstrate the good performance characteristics.