A team of researchers from the ITMO ChemBio Cluster has developed a unique nanoparticle-based ink, to print invisible images. This technology could be the next important step in preventing counterfeiting.
With digitalization, software and game developers were able to protect their products through online verifications and online registrations. Manufacturers of physical products on the other hand still suffer from the problem, that their products can be forged and there is almost no way to protect them. Therefore the market for polygraphic materials and technologies is exponentially growing.
Researchers from the ITMO ChemBio Cluster took this chance and developed a unique printing technology to print invisible images.
It’s All About The Ink
The team at the ITMO ChemBio Cluster worked for five years to get the desired application of organized high resolution nanostructure. To achieve this, the researchers had to create a unique colloidal ink based on cellulose nanoparticles. These nanorod-like crystals can be programmed in such a way, that they orient themselves along a defined axis. Once the ink drops dry, the surface becomes optically active.
“We had to find a way to apply an anisotropic optical structure to a transparent substrate using an inkjet printer,”
says Alexander Vinogradov, head of the team.
“In an anisotropic optical structure, cellulose nanoparticles spin around one of the axes comprising the so-called chiral nematic structure. Put simply, it means that nanoparticles in a multilayer system have a specific order instead of distributing themselves at random. The thickness of such covers created by ink settling is chosen to allow for interference in polarized light. Thus, colored optical feedback of a printed image that is unseen in daylight can be easily detected when subjected to light from any LCD screen, including that of a smartphone.”
The new ink has a base of 10nm wide and around 20nm long particles, which are chaotic under regular conditions. But when settled with an inkjet printer, the particles are forced to organize themselves. This effect is created by modifying the nanoparticles in a solution of charge, iconic force and solution characteristic, keeping in mind what these parameters have to be during the printing.
A Revolutionary Technology
With the new technology the team is able to print any image – numbers, letters, drawings or logos – which is only visible in polarized light. These images could be used on banknotes, tickets and directly on products. Various QR codes and special signals are now used for these purposes, but the new protection method doesn’t require attracting substantial investments. At the same time such common methods have to be constantly updated, however, as sooner or later they are reproduced by opportunistic manufacturers. Using inkjet printing to counter forgery could make the production of protected packaging products significantly easier.
