Invisible QR codes could secure banknotes

[Nipuna]

Jacob Aron, reporter

(Image: roccomontoya/Getty Images)

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Quick response (QR) codes have been springing up everywhere in the past few years - you've probably seen them adorning adverts on posters and in magazines.These black-and-white graphics are designed to be scanned by smartphones for rapid access to web links and other information.

Now researchers in South Dakota have worked out how to create QR codes that are invisible to the naked eye. These could then be used to authenticate objects such as banknotes.

The new QR codes are made from nanoparticles of blue and green fluorescent ink which are invisible to the naked eye but reveal themselves under near-infrared laser light. A smartphone can then snap a picture as normal to scan the code.

Jeevan Meruga and colleagues at the South Dakota School of Mines and Technology in Rapid City, South Dakota, used an online QR code generator to create a normal QR code but then converted it into a file suitable for printing using an aerosol jet printer. This took a total of one-and-a-half hours, though the process could be reduced to 15 minutes if commercialised. Meruga says the technique makes it difficult to counterfeit the codes, as they can add additional security features such as using a particular concentration of nanoparticles.

Because the codes are invisible they can be added to objects without spoiling their physical appearance. Such security may prove useful if 3D printer piracy ever takes off, as manufacturers will want to protect their products from being scanned and duplicated.