Floating quick response code based on structural black color with the characteristic of privacy protection.

Since the printing quick response (QR) code can be easily produced and duplicated as a potential tool for cybercriminals, QR code security has been a hotly debated issue across globe. Here we demonstrate a floating QR code device based on the moiré principle which has the advantage of displaying an appealing three-dimensional (3D) effect and privacy protection. In the imaging system, the microlens array (MLA) contributes to efficiently sampling the multiple elemental images and the metal-coated nanostructure yields patterned structural black color with a high pattern resolution (>12, 500 dpi).