Now no one can say butterflies are all style and no substance.
This might look like a pretty lily pad but it is actually a wafer created with lasers to mimic the iridescent colours of a butterfly’s wings. For extra credit, Shu Yang at the University of Pennsylvania in Philadelphia, who led the project, also made the wafer water-repellent – another property of butterflies’ wings, which helps them fly through rain.
Yang used holographic lithography to recreate the wings’ reflective properties, using a laser to make a 3D cross-linked pattern in a kind of material called photoresist. A solvent then washes away all the photoresist untouched by the laser, creating the 3D structure that affects light to create the colour effects. Then a poorer solvent roughens the surface, creating the texture that makes butterfly wings water-resistant.
Why do this? As it turns out, we have plenty to gain from butterflies. Yang has a grant to develop butterfly-inspired hydrophobic coatings for drier, cleaner and hence more efficient solar panels.
But it doesn’t stop there – Yang has a vision of butterfly cities. She’s working with architects to create a low-cost version of her artificial butterfly wing material. “Specifically, we’re interested in putting this kind of material on the outside of buildings,” Yang said. “The structural colour we can produce is bright and highly decorative.”
The butterfly building would be connected to a chip that would let its owner change its colours and transparency at will. Because the material is water-resistant, it wouldn’t need to be cleaned as often. Yang plans on having her prototype hatch from its cocoon by June.