A research group led by Yuki Tanaka, a graduate student at Kobe University Graduate School, has demonstrated that it is possible to create the world's lightest class of structural color coatings by using a uniquely developed structural color ink.
Recently, structural colors have been attracting attention as a coloring technology that does not fade. The microstructure of a material that itself does not have ``color'' is arranged periodically to produce color. Color is produced by the interference and diffraction of light due to the periodic structure, and the color changes to an iridescent color depending on the viewing angle. Conventional structures in which fine particles of several hundred nanometers are arranged in three dimensions require precise creation of periodic structures, and cannot be colored by coating or printing processes.
The research group has so far developed a coloring method that utilizes the "Mie resonance" phenomenon exhibited by silicon nanostructures and uses strong scattering of light of a specific wavelength, and has produced "structural color nanoparticle ink" that changes color depending on the particle size to the world. It was realized for the first time.
In this research, we used a structural color nanoparticle ink to form a monolayer film of silicon nanoparticles on a glass substrate, and investigated the coloring properties. As a result, the monolayer film showed a purple to orange structural color depending on the particle size, which hardly changed even when observed from a 45-degree angle, and unlike conventional structural colors, the angle dependence was very small. In addition, the peak reflectance was 30 to 50%, and a sufficiently bright structural color could be achieved with a single layer of silicon nanoparticles.
Furthermore, when we partially oxidized a silicon nanoparticle monolayer film to artificially increase the distance between the particles, we found that silicon nanoparticles were sparsely scattered on the substrate (less number of particles than in a monolayer film). But I was able to color it using structural colors.
As a result of this achievement, it is possible to paint with a much smaller amount than conventional paints, and it is possible that, for example, the weight of painting large aircraft, which would otherwise require several hundred kilograms, could be reduced to less than 100/1 of the weight.
Paper information:[ACS Applied Nano Materials] Monolayer of Mie-Resonant Silicon Nanospheres for Structural Coloration
