Three-Dimensional Printing of Bottlebrush Block Copolymer for Structural Color with Dynamic Control

Materials with structural color can reflect light of different wavelengths depending on their nanostructures, creating various colors without the use of chemical pigments. This eco-friendly alternative to traditional synthetic dyes helps prevent environmental pollution from industrial waste. Structural color also exhibits high brightness and dynamic photonic properties that are difficult to achieve with synthetical dyes. Advanced additive techniques can utilize controlled self-assembly to create 3D objects with multiple structural colors from materials such as liquid crystals, nanoparticles, and block copolymers. Among these materials, bottlebrush block copolymers (BBCPs) are particularly promising for mimicking biological structural color due to their ability to self-assemble into diverse nanoscale morphologies with tunable domain sizes. However, printing complex 3D structures with dynamic properties remains a challenge due to the trade-off between controlling assembly kinetics and maintaining mechanical stability. In this study, we demonstrate an evaporation-driven direct-ink-writing method to construct 3D structures with high-density BBCPs. By controlling printing parameters such as speed and ink concentration, we can adjust the aspect ratio of the liquid bridge at the nozzle opening, thereby controlling the evaporation rate during printing. This allows us to kinetically trap different non-equilibrium states of self-assembly. The tunable reflective spectrum of the printed objects is achieved through varying domain sizes confirmed by spectrometry and scanning electron microscopy. This mechanism enables 3D freeform printing with dynamically controlled structural color from a single ink.