We’re surrounded by iridescence. It graces butterfly wings, adorns certain minerals, and shines bright from the water droplets on a petri dish lid. When researchers at Pennsylvania State University and the Massachusetts Institute of Technology spotted iridescence in the two-component oil droplets they were studying, though, they weren’t sure where it was coming from. When they investigated, they found that light entering the droplets bounces repeatedly off the curved interface between the two types of oils making up the droplet, a phenomenon called total internal reflection (Nature 2019, DOI: 10.1038/s41586-019-0946-4). The researchers can control how the light bounces by tuning the curvature of that interface with surfactants. They developed a model to describe the technique and hope it could one day be used to create vibrant color-shifting inks and displays.
“Kitty in the Window” by Podington Bear is licensed under CC BY-NC 4.0.