Researchers at the University of South Dakota and the South Dakota School of Mines and Technology have developed a technology to print invisible quick-response codes that could be used to combat counterfeiting. The quick-response codes, which can hold up to 100 times more information than a traditional bar code, have become more popular because they can be scanned with smartphones. For example, the invisible codes could be used to verify documents or monitor remote equipment.
he inks contain nanoparticles that are invisible outside the presence of infrared lasers. The nanoparticles absorb photons in the invisible, near-infrared part of the light spectrum and then emit light from the visible spectrum.The use of a nanoparticle solvent in the inks allows molecules to be modified and used on plastic, wood, metal and other surfaces.