The ingenious engineering of the brilliant blue wings of the mountain swallowtail (Papilio ulysses) have inspired engineers to design a new water-repellent surface.
The wings of the butterfly easily shed water because of the way ultra-tiny structures in its wings trap air and create a cushion between water and wing.
Engineers have been trying to create similarly water repellent surfaces, but past attempts at artificial air traps tended to lose their contents over time due to external perturbations.
Now, an international team of researchers from Sweden, the United States, and Korea, taking the butterfly wing as model, has found a way to create a multilayered silicon structure that traps air and holds it for longer than one year.
The researchers used an etching process to carve out micro-scale pores and sculpt tiny cones from the silicon.
The team found that features of the resulting structure that might usually be considered defects, such as undercuts beneath the etching mask and scalloped surfaces, actually improved the water repellent properties of the silicon by creating a multilayered hierarchy of air traps.
The intricate structure of pores, cones, bumps, and grooves also succeeded in trapping light, almost perfectly absorbing wavelengths just above the visible range.
The biologically inspired surface could find uses in electro-optical devices, infrared imaging detectors, or chemical sensors.
The study has been described in the AIP’s journal Applied Physics Letters.