Inkjet printers create hidden symbols

December 12, 2016

New technology can conceal secret information in images that could prevent counterfeiting and protect genuine products.

New Atlas reported that the University of Utah has developed a method to “create images only visible using polarized sub-millimetre electromagnetic waves” using inkjet printers and inks created from artificial materials (metamaterials). The new technique could be used to “secretly conceal information in images that look normal to the naked eye”, researchers believe, and this would be “useful in anti-counterfeiting or product authentication”.

Experimenting with different methods, researchers printed images with “varying conductivities”, which is very difficult because of the different types of metal required, but Professor Ajay Nahata explained: “We used silver and carbon ink to print an image consisting of small rods that are about a millimetre long and a couple of hundred microns wide. We found that changing the fraction of silver and carbon in each rod changes the conductivity in each rod just slightly, but visually, you can’t see this modification.

“Passing terahertz radiation at the correct frequency and polarisation through the array allows extraction of information encoded into the conductivity.”The process encodes data in printed symbols and “researchers produced three 72-by-72 pixel QR codes of different types” which all had varied conductivities that corresponded to “different grayscales and colours”. Nahata added: “We have created the capability to fabricate structures that can have adjacent cells, or pixels, with very different conductivities and shown that the conductivity can be read with high fidelity. That means that when we print a QR code, we see the QR code and not any blurring or bleeding of colours.”

The article noted that the “current printing resolution achievable with the cheap (less than $60 (€56)) printers used is around 100 microns” and researchers said that this could be improved, with “higher-quality, off-the-shelf printers could get down to about a 20-micron resolution”. Researchers also believe that despite the simplicity “QR codes are somewhat simple in the information they carry, the process could be employed to encode information within much more detailed images on larger scales”.

The researchers concluded that “though terahertz electromagnetic radiation is used to reveal the information embedded in the images due to the compatibility of the wavelength with images produced by inkjet printers”, they are aiming to “develop ways to use the technique at visible wavelengths”, and that this will require “bespoke new printers to be developed” that can print “smaller rods to create images with greater resolutions”.

 

Categories : Products and Technology

Tags : Inkjet Printers Technology