Butterfly Thin Films Serve as Solar Collectors

Thin film structures in butterfly wing and body scales cause optical interference that results in colorful iridescence. This reflected sunlight serves a variety of known functions, including coloration for camouflage and signaling for courtship. As a complementary function, our findings demonstrate that by absorbing the noniridescent wavelengths these film structures capture a significant amount of the total solar radiation. Butterflies can absorb as much as 96% of the incident solar radiation, or as little as 65%, depending on minute variations in film thicknesses. These results suggest that the specialization of these films includes the known reflective functions, as well as absorptive functions such as thermoregulation.