Rapid fabrication of cephalopod-inspired fluorophore-integrated waterborne polyurethane films for customizable patterns and cryptographic encryption

Traditional encryption technologies using single-fluorescent materials are increasingly vulnerable to attacks due to their predictable responses to stimuli. Furthermore, conventional waterborne polyurethane (WPU) film fabrication methods, such as casting, suffer from long drying times and inconsistent thickness, limiting scalability for advanced applications. To address these issues, we developed cephalopod-inspired WPU composite films that integrate 6,7-dihydroxy coumarin (6,7-CU) and perylene tetracarboxylic acid (PTCA) as fluorophores in segregated layers. This colloidal system achieves good emulsion stability and interfacial interactions, which play a crucial role in the films' complex functionality. The dyes’ hydroxy and carboxylic acid groups strengthen both optical properties and mechanical strength of WPU, achieving a tensile strength of 24 MPa in a 100 μm thin film. Using the electrochemical demulsification-induced fast solidification (DIFS) method, we achieved rapid drying and uniform film formation, overcoming the limitations of traditional casting. This method leverages controlled interfacial dynamics to produce films with sophisticated multicolor responses and improved encryption complexity. Density functional theory (DFT) calculations further reveal the films' stimuli-responsiveness, providing insights into the influence of interfacial mechanisms on their reversible color transformations under UV light and pH changes. Applications in data engraving and QR code labeling demonstrate the films' potential in secure information encryption and anti-counterfeiting technologies.