Wide-Gamut Biomimetic Structural Colors from Interference-Assisted Two-Photon Polymerization

Two-photon
polymerization (TPP) is an emerging direct laser writing
technique for the fabrication of structural colors. However, its coloration
ability is suppressed as the vertical resolution is up to several
microns. To solve this issue, an interference-assisted TPP technique
was employed. Laser interference at a highly reflective interface
produced the periodic energy redistribution along the vertical direction,
turning the laser voxel into multilayer structures and confirming
this technology as a facile and robust method for precise control
of its vertical feature size. Biomimetic structural colors (BSCs)
inspired from the ridge-lamella configurations in the Morph butterflies
were fabricated using this improved TPP technique. The coloration
mechanisms of the multilayer interference from the lamella layers,
the thin-film interference from the fusion of multilayers, and the
hybrid situations were systematically studied. These BSC colors were
grouped as pixel palettes with various TPP parameters corresponding
to each other, and they spanned almost the entire standard red–green–blue
color space. Moreover, under optimized conditions, it was possible
to fabricate a 1 cm2 area within 2.5 h. These features
make interference-assisted TPP an ideal coloration method for practical
applications, such as display, decoration, sensing, and so on.