Machine-Vision-Authenticated Hue-Programmable Bilayer Heterostructures for Anticounterfeiting

Conventional anticounterfeiting based on structural color relies on human vision for authentication, which introduces subjective bias and ambiguity, particularly for individuals with color vision deficiencies. Here, we propose a strategy that overcomes this limitation by integrating hue-programmable bilayer heterostructures with machine-vision authentication, wherein optical information is encrypted by structural color and objectively decrypted via a smartphone-based pattern recognition system. To realize this strategy, we design bilayer heterogeneous photonic crystals (BHPCs) comprising monolayers of polystyrene nanospheres with diameters of 400 nm and 500 nm, fabricated by gas-liquid interface self-assembly and tape-assisted transfer. The BHPCs uniquely access a magenta hue sector unattainable by either monolayer, offer a large angular extension, and enable dual-region authentication. We elucidate its diffraction mechanism as incoherent spectral superposition, validated by experiment and simulation. This approach eliminates subjective color perception bias, avoids expensive spectrometers, and allows user-defined encryption levels. The work provides a new paradigm for high-security, machine-readable anticounterfeiting and offers design insights for PC-based displays and sensors.