Photonic Structure for Anti-Counterfeiting

Opportunity  

Multiscale structures in nature impart brilliant structural colours, integrating properties of multiple optical elements. These natural structural colours arise from fundamental physical processes and have evolved over millions of years, resulting in hierarchical micro/nanostructures that provide adaptive colouration or functions. For example, iridescence, non-iridescence, mixed or dynamic colours, chirality, polarisation, ultra blackness are derived from these multi-scale nanomaterials. These optical effects are important for camouflaging, mating, warning, signalling or thermo-regulation in nature.  

Inspired by these photonic structures, significant efforts have been made to mimic these micro-/nano-architectures to achieve the corresponding optical properties. This has spurred the development of next-generation photonic sensors, displays and photovoltaics. Optical elements with delicate optical features, derived from collective optical functions and precisely engineered by nanoscale variations, hold significant potential for highly secure anti-counterfeiting applications. 

Technology  

Films with tuneable combined optical features are prepared by infiltration-driven rod coating, with control over film thickness and particles size. Using PDMS micro-imprinting methods, micro/millimetre patterns of particles are removed from the TFI films, manipulating the interplay between TFI and coherent scattering. Depending on the thicknesses of the TFI films, the imprinted regions display either coherent scattering-dominated or combined optical properties. By microprinting patterns on these TFI films, HDPS anti-counterfeiting labels with encoded hidden information or multiple optical properties are successfully demonstrated, providing high-security anti-counterfeiting with virtually infinite optical coding. 

Applications & Advantages  

Main application areas include the verification of currency notes and premium and luxury products. 

Advantages: 

• Ease of scaling up production. 
• Ink formulation is compatible with standard inkjet printers. 
• The ink can be functionalised to respond to specific gases or temperatures.