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). A virtual mask scheme is specially developed in the elemental image construction, allowing for eliminating the crosstalk between neighboring units and containing more information in one unit without the necessity for ultra-high-resolution fabrication process and sophisticated operation. The proposed QR code device, capable of being read by an unmodified smart phone, is inexpensive, mass-producible, nondestructive, unclonable and convenient for authentication. This new solution should take a place among the existing solutions to fight counterfeiting and QR code attacks.