Direct Laser Writing of Polymer Nanocomposites for Tunable Structural Color.

Self-assembled colloidal particles offer a means of manipulating light, giving rise to some of the most brilliant structural colors. Conventionally, changing the reflection band of colloidal crystal assemblies has required the synthesis of different-sized nanoparticles or multiple fabrication steps. This is not a means conducive to fine-tuning structural color. Herein, it is shown that, by combining nanocomposite photoresists, self-assembly, and direct laser writing, it is possible to achieve high-resolution fabrication and precise placement of nanoparticles, combined with highly tunable structural color using one composition and one particle size. Confinement of polymerization brought by direct laser writing allows for fine control over a series of fabrication parameters, such as slicing and hatching distances, thereby enabling control of the inter-particle distance in a nanocomposite. This is key to generating microstructures that exhibit a wide gamut of color that traverses the visible spectrum. Finite-difference time-domain simulations are further used as a means of understanding the structural modifications that control color variation. The method described herein is suitable for fine-tuning of structural color in self-assembled systems, and is applicable to a wide range of materials.