Structural colors with angle-insensitive optical properties generated by Morpho-inspired 2PP structures

Abstract

This paper describes how two-photon polymerization was used to generate biomimetic nanostructures with angle-insensitive coloration inspired by the blue butterflies of Morpho. Less angle dependence was achieved by engineering the structures with a certain degree of disorder, which delimited them from classical photonic crystals. Variations in the processing parameters enabled the color hue to be controlled. In this context, blue, green, yellow, and brown structures were demonstrated. Reflection spectra of the structures were simulated and studied experimentally in a broad range of incident angles. Additionally, a molding technique was performed as a potential scale-up strategy. The application of such biomimetic structures is discussed.

Tailored Disorder in Photonics: Learning from Nature

“…This approach enables adjusting of structural colors with a distinct hue such as blue, green, yellow and brown via modifications of the process parameters. [11] For mimicking this complex natural photonic multilayer architecture, the interference-assisted polymerization method is applied, [108] since the resolution of the conventional two-photon polymerization process is too low. This allows an adjustment of the structural features in the range of approximately 20 nm by varying solely the average laser power during the direct laser writing process.…”

“…[10] Various animals and plants use them for warning signals, to attract mating partners or sophisticated camouflage to increase the chance for survival of the species. [11,12] These structural colors are based on a highly complex morphology of the epidermis of the organisms. Such natural photonic systems often exhibit a specific disorder which manifests itself by irregularities in the arrangement of the spatial distribution of the architectured materials.…”

“…Such natural photonic systems often exhibit a specific disorder which manifests itself by irregularities in the arrangement of the spatial distribution of the architectured materials. [11,13] Thus, stunning displays of coloration, which are highly intense and, in contrast to pigments, do not fade, are generated by the interaction between the visible light and nanoscaled intricate structures that affect polarization, reflection, or absorption. [9,14,15] Some examples of structural coloration in nature are presented in Figure 1.…”

“…h,i) The optical properties of the biomimetic architectures in reflection and transmission depend on the tilt direction of the sample or the illumination position. g-i) Adapted under the terms of a Creative Commons Attribution CC BY license [11]. Copyright 2020, The Authors, published by Springer Nature.…”

Direct laser writing of vapour-responsive photonic arrays

“…It allows for imitation of naturally occurring photonic arrays, such as periodic microspheres, lunulae, and multilayer lamellae, among others. [15][16][17] More recently, the group of J. Yang exploited such highresolution 3D fabrication combined with high temperatureinduced irreversible shrinkage (at 450 1C) of a commercially available photoresist (IP-Dip) to generate 12 repeat-layer scaffolds. 18 Upon heating, different degrees of shrinking resulted in a range of different lattice constants, which correspond to a wide variation of reflected colours.…”