Monolithic Micro-/Nanoarchitectonic Multi-Level Pixel Arrays Via a Two-Step Photo-Cross-Linking Process for Multi-Modal and Transformative Structural Coloration

Abstract

Thin film-based structural coloration predominantly uses an elastomeric substrate and active materials, which exhibit uniform color changes under external stimuli such as bending, heat, and chemical environments. However, generating distinctive structural colors in a single stimulation is challenging, especially for microscale pixel arrays, which interact in more spectral and structural ways than bare thin films or static color pixels. This study presents a two-step photo-cross-linking fabrication approach for monolithic pixel arrays. The pixelated structure is devised using ultraviolet-curable chitosan (UVCC) on polydimethylsiloxane with controlled thickness at the nanoscales. The pixelated device can generate bending-based reversible wrinkles with different sizes according to the thickness of the UVCC. Subsequently, each pixel exhibits thickness-specific structural color covering the entire visible spectrum when bent. By coupling four microscale pixels with different colors, it is demonstrated that a unit of pixels can be seen as a combined color of each pixel color with the bare eyes. To demonstrate the micropixel approach, a traditional Korean Dancheong pattern is adopted and categorized its colors into three different ones. The proposed method generates distinguishable structural colors between the pixels, which makes this approach a strong contender for pixel-based structural color applications such as anti-counterfeiting, camouflage, and security printing.