Structural Color Spectral Response of Dense Structures of Discoidal Particles Generated by Evaporative Assembly

Traditional coloration methods rely on pigments or dyes, which can degrade or pollute. Structural color offers an alternative by using physical structures to interact with light. While spherical colloidal particles have been studied for structural color, their optical properties are limited by symmetry and order. Recent work has explored anisotropic particles, such as rods or discs, to expand design possibilities. However, the relationship between particle shape and resulting color remains unclear. This gap motivated the exploration of discoidal particles. Prior research has shown that particle shape affects scattering and reflection patterns. But no prior work had resolved how discoidal anisotropy influences structural color tuning. This paper addresses that uncertainty by investigating how discoid shape and size affect optical response. The study builds on established methods in colloidal assembly and optical simulation. It aims to clarify how discoid geometry can be leveraged for practical coloration applications.

The study aims to explore how discoidal particle geometry influences structural color. Specifically, it seeks to determine how shape anisotropy and particle size affect optical properties. The researchers propose that discoids can produce noniridescent structural color. They hypothesize that discoid shape and size can act as independent design parameters. The motivation comes from the need for sustainable and tunable coloration methods. Structural color from discoids could offer advantages over traditional dyes. The study also aims to validate experimental results with simulations. By comparing real and simulated data, the researchers hope to confirm their findings and guide future design.

The researchers prepared discoidal particles by uniaxial compression of spheres. They varied the shape anisotropy and particle size of the discoids. Thin films of discoids were assembled using evaporation. The assembled structures were analyzed for optical properties. Reflection spectra were measured to assess structural color. Microstructures were compared with Monte Carlo simulations. Finite-difference time-domain simulations were used to model light interaction. The combination of experimental and computational methods allowed the researchers to verify their findings. This approach enabled them to isolate the effects of particle geometry on optical response.

Discoidal particles with higher anisotropy produced more disordered assemblies. The resulting structural color was dominated by diffuse backscattering. Multilayer reflection was suppressed in anisotropic discoids. Peak height in reflection spectra decreased with increasing anisotropy. Peak width became broader as discoids became more anisotropic. Structural color was found to be tunable by particle size. The color showed low dependence on viewing angle. Simulations confirmed the experimental observations. These results suggest that discoid geometry can be independently adjusted to control coloration.

The study demonstrates that discoid shape and size can be used to tune structural color. Discoidal anisotropy reduces multilayer reflection and increases diffuse backscattering. Particle size affects the spectral response independently of shape. The low dependence on viewing angle makes discoid coloration practical for applications. The researchers propose that discoids offer a design advantage over spheres. Their findings suggest that discoid geometry can expand the range of structural color options. The combination of experimental and simulation methods supports these conclusions. These results may inform future work on sustainable and tunable coloration materials.