Highly Invisible Photonic Crystal Patterns Encrypted in an Inverse Opaline Macroporous Polyurethane Film for Anti-Counterfeiting Applications

• DOI: 10.1021/acsami.9b18995
• Publication Date: 2019-11-11T14:54:12Z
• Authors: Ke Chen; Yixin Zhang; Jianping Ge
• Keywords: 02 engineering and technology; 0210 nano-technology

Invisible photonic crystal (PC) pattern with encrypted and discoverable information is potentially useful for anti-counterfeiting labels, but it still a big challenge to realize strict invisibility, fast response, convenient triggering. Here, new kind of soaking-revealed invisible PC fabricated by the regional coating "ethylene glycol-ethanol" ink on collapsed inverse opaline macroporous polyurethane (IOM-PU) film, followed quick thermal treatment. During above process, wet heating retains recoverable IOM structure, dry disables recovery ordered structure due adhesion macropore walls, which render "pattern" "background" different optical responses solvent. In state, was because both IOM-PU film adhesive PU are colorless transparent. Once sample soaked in ethanol-water mixtures, appears immediately only "wet-heated" region recovers shows color, forms significant contrast color "dry-heated" region. Compared previously pattern, current material has many superior properties, such as high large showing, excellent recyclability, good toughness bending stretching.