Hybrid GA-PSO-Optimized Bio-Inspired Structural Colors With Ultra-High Saturation, High Brightness, And Wide Viewing Angles

ABSTRACT A bio-inspired photonic multilayer coating was fabricated that addresses ultra-high saturation, high brightness, and wide viewing angles through a computationally guided design compatible with standard thin-film fabrication. Drawing from the wing-scale architecture of Chrysiridia rhipheus (Madagascan sunset moth), the structure alternates high-index TiO₂ layers with low-index SiO₂ layers atop a diffuse scattering substrate. Randomized height variations at the substrate expand angular tolerance, while the precisely tuned multilayer preserves the steep, narrowband spectral response required for vivid hues. A hybrid Genetic Algorithm–Particle Swarm Optimization (GA-PSO) method navigates the high-dimensional thickness space, enabling simultaneous optimization of the reflection band position, bandwidth, and angular response for blue, green, and red primaries. The optimized designs exceed the sRGB gamut for all three colors. Samples fabricated by electron-beam evaporation exhibit reflectance peaks above 90% at target wavelengths and maintain ΔE₀₀ < 2 for incidence angles up to 30°, corresponding to color shift within the acceptable tolerance for display applications. The color gamut area reaches 117.5% of sRGB, with perceptual brightness values (HSB B ≥ 0.80) suitable for display and signage applications. The samples also demonstrate excellent illuminance stability (ΔE₀₀ < 2) from 2400 to 7200 lux. This work establishes a practical, computationally guided route to ultra-saturated, angle-insensitive structural colors using mature thin-film processes, enabling energy-efficient, high-fidelity color systems for passive displays and optical information encoding.