QR codes, those pixelated looking squares that appear on almost everything, can link to digital content on the web; activate a number of phone functions including email, IM and SMS using any smartphone. Now, thanks to the combined efforts of researchers from the South Dakota School of Mines & Technology and the University of South Dakota, invisible QR codes may be the new defense against counterfeiting. Combining nanoparticles with blue and green fluorescent ink, the team has developed a process that can spray this upconverting nano-ink onto surfaces such as glass, plastic film, and paper. The nano-code remains invisible until placed under a near-infrared laser, where it glows. This method holds great promise for routine security printing, especially on banknotes. Kellar, the South Dakota School of Mines engineer who led the development of the glowing code, stated, "It could be used with other legal documents, or protection against counterfeiting of any solid object." For example, this could be applied to an expensive piece of art without affecting the appearance in anyway. It has been suggested that these covert QR codes could be used economically and efficiently for mass security printing. The inks are produced from inexpensive starting materials, and very small amounts of ink are required to produce readable images. Multi-colored QR codes can be produced using various ink combinations.
New inks are currently being optimized in order to improve the security features of the QR codes. Lead author of the study, Jeevan Meruga of SDSM&T said: "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. We can take the level of security from covert to forensic by simply adding a microscopic message in the QR code, in a different colored upconverting ink, which then requires a microscope to read the upconverted QR code." Extensive testing has revealed the ink holds up to significant wear making it of great interest for printing on money. Since publication in the British journal Nanotechnology, it has been highlighted by Science Daily, MSNBC and The Huffington Post, to name a few. Joseph Wright, Associate Vice President for Research-Economic Development, stated that the commercial interest shown by various industry leaders is extremely promising. Soon, this could be the new standard in security printing using technology created from the research conducted here at SDSM&T.