Investigating the Origins of Structural Color and Iridescence in Blue Morpho Butterflies

Color in nature comes mostly from inherent colors of pigmented materials, though it sometimes has a purely physical origin that is produced by light reflecting, diffracting, and interfering with structures. The goal of my Capstone project was to explore this phenomenon, known as structural coloration, that gives the wings of the Blue Morpho Butterfly its beautiful iridescent blue color. Essentially, the structural color and iridescence is a product of visible light interacting with rows of Christmas tree-shaped nanostructures on the scales of these butterfly wings. These Christmas trees have anywhere from 6-10 alternating branches, which cause light to constructively interfere between 400-500nm in wavelength (blue and purple) when you factor in the following variables: phase shift, branch thickness, air’s refractive index, branch’s refractive index, diffraction integer, and observation angle. The Blue Morpho is just one example of a biologically induced structural color but scientists have begun studying other similar nanostructures with the goal of manipulating light to create anti-counterfeit currency, biometric
fabrics, multilayer solar innovations, and thermal detecting mechanisms.

In many ways, this Capstone project challenged my ability to learn quickly and adapt to the unforeseen circumstances that often wreak havoc on our structured lives. My favorite part of this project was learning to use the Keck Lab’s Scanning Electron Microscope to capture some amazing images of the butterfly wings. I’m sure that I share the same thoughts as many of my fellow graduates regarding the timing of this global pandemic, but I’m currently helping out at my family’s aerospace manufacturing business with the goal of one day running the business. I also would like to give a quick shout out to Dr. James Lee for all his help!