Figure 6. Soap-film coating setup.

A substrate is fixed on a sample holder that can be moved forward or backward by controlling the compressed air at the two terminals of the cylinder. A speed monitor is placed between the sample holder and the soap-particle film to detect the speed of the moving substrate. The soap-particle film is held by a frame constructed from nylon wires, which is hanging in front of the sample holder. A “control wire” (see text) is placed on the soap film to increase the lifetime of the film. Above the frame, a funnel filled with suspensions that continuously refill the soap-particle film is mounted, as shown in the schematic drawing.