Invisible QR Codes Printed With Nano-Engineered Ink to Secure Next-Gen Currencies, Authenticate Documents
The researchers started with ink made with nanometer-sized particles that glow under a laser light.
But the way the ink fluoresces is different than expected. Normally, fluorescent ink emits light of a longer wavelength. For example, shine ultraviolet light onto one of those blacklight posters and visible light colors are produced. But in this case, the nanoparticle ink produces wavelengths that are shorter. Near-infrared light shined onto the ink produces bright blue or green colors.
These types of fluorescent inks are a lot harder for forgers to reproduce. A smartphone can read it and know if the document is authentic or not. The laser light reader doesn’t have to be a part of the phone either, but can be a separate device that’s linked wirelessly to a smartphone’s camera.
A third element in this QR code enhances its security. The team devised a way to embed microscopic image into the code, something forger would have to produce. Without the microscopic image, a close examination would show that the QR code was a fake.
(via Invisible QR Codes Could Stop Counterfeiters : Discovery News)