Bioinspired Nanofluidic-Assisted Printing Cellulose Nanocrystal Photonic Patterns

Cellulose nanocrystal (CNC) photonic films have emerged as sustainable alternatives to traditional pigments by harnessing cholesteric nanostructures for vivid, fade-resistant colors. However, scalable fabrication of continuously functionalized structural color patterns directly from CNC dispersion remains a grand challenge due to limitations in conventional printing techniques and coassembly approaches. Here, we present a bioinspired sequential nanofluidic-assisted photonic patterning (SNAPP) technique that leverages preformed cholesteric CNC films with three-dimensional helical nanochannels as self-regulated pathways for spontaneous ink diffusion. Mimicking nature's helical Venturi effect, this technique enables universal integration of diverse functional components (molecules, polymers, and nanoparticles) to manipulate photonic band gaps or impart stimuli-responsive functionalities while preserving long-range chiral order. By combining mask-guided patterning with capillary-driven transport, we achieve full visible-spectrum structural colors, humidity/thermal-responsive patterns, and fluorescent carbon dot integration with 4-fold enhanced emission intensity and circularly polarized luminescence. The resulting films retain angle-dependent iridescence and polarization selectivity, while exhibiting exceptional environmental stability, biocompatibility, and degradability. This multifunctional platform enables dual-channel optical encryption with orthogonal authentication modes (structural color, fluorescence, thermochromism, and circular polarization), positioning it as a high-security anticounterfeiting solution for pharmaceutical applications. The SNAPP technique overcomes the fundamental limitations of traditional methods, offering a scalable, versatile route to functional photonic materials with programmable dynamic responses.