The role of random nanostructures for the omnidirectional anti-reflection properties of the glasswing butterfly

Abstract

The glasswing butterfly (Greta oto) has, as its name suggests, transparent wings with remarkable low haze and reflectance over the whole visible spectral range even for large view angles of 80°. This omnidirectional anti-reflection behaviour is caused by small nanopillars covering the transparent regions of its wings. In difference to other anti-reflection coatings found in nature, these pillars are irregularly arranged and feature a random height and width distribution. Here we simulate the optical properties with the effective medium theory and transfer matrix method and show that the random height distribution of pillars significantly reduces the reflection not only for normal incidence but also for high view angles.

Multifunctional biophotonic nanostructures inspired by the longtail glasswing butterfly for medical devices

“…1a) belongs to the Riodinidae family found in South America. We have discovered that the C. faunus wings are distinct from most other transparent wings in nature 9,11,22 . They have a rare combination of two transparent regions that transmit light differently: (1) the basal transparent areas close to thorax (indicated by a blue arrow in Fig.…”

Surface Modification of Sol-Gel Silica Antireflective Coatings by F-PMHS: A Simple Method for Improvement of Amphiphobicity

“…It can be found from the top view that the unmodified sol-gel silica ARC is porous. This is benefit for sol-gel silica ARCs because the nano-pores lower the refractive index of ARCs to the square root of that of substrate and, therefore, nearly 100% transmittance can be realized [29,30]. Suppose that, during F-PMHS modification of ARCs, most of the nano-pores in …”

It's Not a Bug, It's a Feature: Functional Materials in Insects

“…While most wings are relatively unstructured thin films of chitin, [311] some dragonflies, cicadas, and butterflies have optimized the transparency of their wings by employing a local nanostructure (Figure 15A). [337][338][339][340][341] In the wings of these insects, the thin film of chitin that forms the wing membrane is covered on both sides by small conical or nipple-shaped nanopillars that provide impedance matching ( Figure 15B). It is crucial for the pillars to be smaller than the wavelength of light to prevent interference effects, resulting in a maximum size of about ≈250 nm.…”

“…Furthermore, height and positional disorder of the nanopillars facilitate broadband omnidirectionality of the transparency effect, resulting in a reflectance below 0.05% for viewing angles below 50° and reaching a maximal value of 5% at an angle of incidence of ≈80°. [338] Optical-impedance-matching mechanisms are useful not only for transparency but also to optimize light transport into a structure. This phenomenon is critical for ensuring optimal light transmission to optical sensors in insect eyes.…”

“…Biphasic secretion True bugs, [469,470] tenebrionid beetles, [638] fire ants [639] Built structures Green lacewings [640] Froths and foams Pyrgomorphid grasshoppers, [641] lubber grasshoppers, [642] froghopper nymphs [474] Hemolymph defense Sawflies, [643,644] katydids, [450,645] stoneflies, [645] stonefly nymphs [646] Projectile dispersal Stick insects, [451,459] termites [647] Material motif General functionality System of interest Insect and reference Thermoregulation Cooling Honeybees, [410] mosquitos, [411] sawflies [412] Water active properties Surface excretion Leafhoppers [166,167,648] Layering Collective materials Built structures Social wasps [649,650] Raft building to survive flooding Fire ants [580] Bivouac assemblies Army ants [512] Color vision and color manipulation Impedance matching Dragonflies, [337] cicadas, [339] butterflies, [338,341,342] moths, [342,343] beetles [342] Water active properties Desiccation resistance Antarctic midges, [651] African lake flies [652] Regular repeated patterns…”