Regularity through randomness: Bioinspired quasi-amorphous photonic structures for multilevel information encryption

The biological world has produced a wealth of complex photonic materials offering abundant design inspirations. However, creating these intricate photonic structures intertwining order, disorder, and hierarchical arrangements remains challenging. Achieving this necessitates nano-fabrication technologies capable of integrating intended macroscopic properties while accommodating microscopic variability or randomness, akin to the operational principles observed in biological organisms. Here, we present quasi-amorphous photonic structure (QAPS) patterns with regulated sophisticated visual effects through hierarchically distributions of photonic elements with engineered randomness. Enabled by an infiltration-assisted (IFAST) inkjet printing method, the visual appearances of QAPS patterns are precisely controlled by collective harnessing of nanoscale resonant scattering of colloids, mesoscale interferences, and macroscale light transporting. The QAPS patterns exhibit isotropic diffuse colors, unprecedented iridescence and enable multichannel encrypted information that can be selectively identified using specific filters at particular specular illumination angles. Additionally, the intricate infiltration fields confer high adjustability in colloidal assembly, offering sophisticated packing geometries and color distributions at the microscale, which can serve as physical unclonable security features. The exceptional structural complexity and optical versatility of QAPSs enable the integration of multilevel security features within a single system, providing a promising roadmap to achieve larger information capacity, multichannel cryptography, and enhanced encryption levels.