Structural color palettes from colloidal color mixing

Abstract

Mixing chemical pigments of basic colors to create a broad spectrum of hues is fundamental to the modern ink and coating industries. Colloidal-assembled photonic crystals offer a promising, sustainable alternative for color applications. However, due to the distinct mechanisms by which they produce color, achieving the same flexibility and consistency as pigments in commercial production has been a significant challenge. Combining colloidal particles of different sizes presents a potential solution, but the underlying mechanisms and applicability across various colloidal systems remain largely unexplored. In this study, we explore the color mixing effects of particles of different sizes in a low-viscosity matrix. Our findings show that, while the reflection colors of mixed particles depend on their average size, the brightness is influenced by both effective polydispersity and the composition of the mixtures. For particle mixtures with the same average size and polydispersity, the brightness of reflection colors varies significantly based on the number of components and their relative proportions. Remarkably, a mixture of two distinct particle sizes can achieve 3–4 times higher reflectance than a mixture of five distinct sizes, even with the same size polydispersity. Our results demonstrate how a wide range of colors can be produced using particles of several basic sizes and how their brightness and saturation can be controlled by adjusting the composition. These insights provide new strategies for color mixing in photonic crystals and may facilitate their industrial application.