3D Printing of Multi-Layer Diffraction Gratings for Additive Mixing of Structural Colors.

Structural coloration by diffraction grating offers a robust alternative to pigment-based color generation, yet producing extra-spectral colors such as magenta remains a challenge. Additive color mixing from multiple diffraction gratings can achieve such coloration, but often at the cost of reduced spatial resolution. Here, we demonstrate 3D printing of multi-layer diffraction gratings for additive mixing of structural colors from a single pixel. A direct ink writing process involving a non-contact lateral printing technique allowed for the fabrication of double-layer diffraction gratings composed of orthogonally aligned nanowire arrays. Subsequent thermal annealing was introduced to rearrange the nanowires to produce distinct structural colors from each layer. The multi-layer gratings facilitate additive color mixing, successfully generating magenta from the superposition of red and blue diffraction light. The demonstration of additive color mixing from a single pixel suggests potential applications in high-resolution color displays, filters, and sensors.