Researchers in the US have come up with an invisible quick response (QR) code comprised of tiny nanoparticles in an effort to add an extra layer of security over existing methods to tackle counterfeit goods, such as fake bank notes.
The researchers from the University of South Dakota and South Dakota School of Mines and Technology have published their findings in the journal Nanotechnology today.
According to the scientists, their new style of QR code also has the potential to authenticate almost any solid object. Traditionally used in advertising and marketing, QR codes can hold 100 times more information than conventional barcodes.
The QR code pioneered by the US researchers combined tiny nanoparticles with blue and green fluorescence ink, so that it remains invisible until illuminated via laser light.
They created the QR code using computer-aided design (CAD) before printing it onto a surface using an aerosol jet printer, a production process that’s apparently difficult to replicate.
When it is illuminated by near infra-red light, during a process known as upconversion, the QR code can then be scanned by a smartphone.
"The QR code is tough to counterfeit. We can also change our parameters to make it even more difficult to counterfeit, such as controlling the intensity of the upconverting light or using inks with a higher weight percentage of nanoparticles," said Jeevan Meruga, the lead author of the study.
"We can take the level of security from covert to forensic by simply adding a microscopic message in the QR code, in a different coloured upconverting ink, which then requires a microscope to read the upconverted QR code," he added.
And to determine if the QR code could survive being placed on paper such as bank notes, the researchers printed the QR code onto a piece of paper and then randomly folded it 50 times. The code was still readable at the end of this experiment.
The researchers also printed the QR code on glass and a plastic film to show how it has the potential to be used on a variety of commercial goods.
Check out this video explaining the procedure to create the invisible QR code: