Stimuli‐Responsive 3D‐Printed Structurally Colored Materials Based on Core–Shell Particle Architectures

ABSTRACT In additive manufacturing via fused deposition modeling (FDM), no easily scalable process for producing intelligent, e.g., pH‐responsive, structurally colored filaments is known yet. This work presents the preparation of a structurally colored and pH‐responsive filament for 3D printing via fused deposition modeling (FDM). The filament consists of tailored core–shell particles exhibiting an inherent pH‐responsive behavior due to the incorporation of poly(methacrylic acid) in the particle shell. The filament and 3D‐printed objects exhibit distinct structural coloring, exerting a clear color change when exposed to alkaline environments. The core–shell particles used are accessible via scalable stepwise emulsion polymerization in starved‐feed mode, followed by freeze‐drying. Through the targeted incorporation of additives and the extrusion of core–shell particles, a filament is produced, which is then utilized for 3D FDM printing. The particle design was adjusted, and the obtained materials were investigated with respect to their thermal, optical, and mechanical properties to gain a deeper understanding of the material's behavior. To gain additional insights, the obtained core–shell particles are also melt‐sheared to produce 2D pH‐responsive opal films. The material presented herein is a promising platform for smart sensing, secret information encoding, and anti‐counterfeiting applications in complex 3D‐printed objects.