An invisible quick response (QR) code has been created by researchers in an attempt to increase security on printed documents and reduce the possibility of counterfeiting, a problem which costs governments and private industries billions of pounds each year.
The researchers from the University of South Dakota and South Dakota School of Mines and Technology believe the new style of QR code could also be used to authenticate virtually any solid object.
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The research by the experts has been published in IOP Publishing’s journal Nanotechnology,
The QR code is made of tiny nanoparticles that have been combined with blue and green fluorescence ink, which is invisible until illuminated with laser light.
It is generated using computer-aided design (CAD) and printed onto a surface using an aerosol jet printer.
According to the researchers, the QR code will add an increased level of security over existing counterfeiting methods as the complexity of the production process makes it very difficult to replicate.
The combination of the blue and green inks also enabled the researchers to experiment with a variety of characters and symbols in different colours and sizes, varying from microscopic to macroscopic.
Under normal lighting conditions the QR code is invisible, but becomes visible when near infra-red light is passed over it.
QR codes can hold one hundred times more information than conventional barcodes and have traditionally been used in advertising and marketing.
For example, simply scanning a QR code on a commercial product with a smartphone will take the user to a company''s website, giving them more information about the product they are scanning.
"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,” lead author of the study, Jeevan Meruga, said.
"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.u00a0
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