Soap Film Hurricane
Steffen Berg and Sandra Troian
Department of Chemical Engineering
The image shows white-light reflection from a flat soap film formed from an aqueous solution of the anionic surfactant sodium dodecyl sulfate and the hydrosoluble polymer poly-(ethylene oxide). The planar film was formed in a 10 mm wide, vertical frame. The very dark upper region of the film, the so-called “black film” region, is less than 100 nanometers thick and has low optical reflectivity. A step-wise thinning front in the black film region progresses from right to left and causes a swirl in the yellow soap film band. The peacock feather patterns in the yellow and green parts of the film arise from inhomogeneous distributions of the surfactant causing gradients in the surface tension.