Electrically triggered photonic crystal anti-counterfeiting tags with multi-level response fabricated by regioselective modification of ITO electrode surface.

Anticounterfeiting materials based on the photonic crystal (PC) have attracted great interest due to their unique visual effects originating from the changeable structural colors under various external stimuli. However, there still are challenges to improving the anticounterfeiting performance by enhancing the complexity and diversity of the color changes. Here, we fabricated an electrically triggered anticounterfeiting tag by encapsulating the responsive PC with the surface-modified and patterned ITO electrode. The degree of Au deposition or chemical etching in different regions of the ITO was precisely controlled to achieve multi-level differentiated electrical responses, which made the invisible pattern of the tag at 0 V be "revealed in multicolor form" or "gradually revealed" under increasing voltages. The tag possessed two working modes, more diversified visual effects, good usability, and reversibility, which let it become a potentially useful material for anti-counterfeiting applications in the future.