Karl Gaff

Thin Film Cosmicscape, 2018

Photomicrograph
Olympus BX51 DIC microscope; capture magnification ~x150; the image displays thin film interference

Dublin, Ireland

When two fluids of different surface tensions are mixed, a complex interplay of fluid dynamics unfolds. In this case, the fluid is a mixture of dishwashing liquid and water. By introducing some sugar into the mixture, the lifetime of the soap film can be extended, while the continuous film breaks up into islands, as seen here. The islands are lipid globules floating on a thin film; because the film is too thin to support the interference of light, it appears as black as space. The islands and continuous lipid film produce dazzling interference colors because their film thickness is on the same order of magnitude as the wavelength of light. Variations in color are a result of the modulations in the thickness of the film. The film is thickest in the lower right of the image and gradually thins out diagonally toward the upper left, before decreasing to only several nanometers, where it becomes jet black.