A team of scientists from Russia’s ITMO University has developed a colorless, non-toxic ink for inkjet printing by modifying the ink’s nanostructure so as to create colors on paper.
Current technologies which blend dyes to print in color are known to be harmful to the environment. Some dyes are toxic to marine life and can react with disinfectants like chlorine to form harmful byproducts.
An alternative to dyes involves changing the nanostructure of materials so that they reflect light in particular ways. An example of this kind of coloring by light interference is found in squids. They can modify the nanostructure of their skin to mirror back their surrounding environment, creating a natural camouflage.
Though previous researches have investigated printing color by light interference, these attempts have required high-temperature fixing or specialized printing surfaces. Aleksandr V. Yakovlev, Alexandr V. Vinogradov and colleagues at ITMO University wanted to develop a nanostructure color printing technology that is “greener” and can be printed on a wide variety of surfaces.
The team found that a colorless titanium dioxide-based colloidal ink was best suited for the job. It does not require high temperature fixing and can be deposited on many surfaces. The researchers can control the color produced on surfaces by varying the thickness of ink deposition from a normal inkjet printer.
The paper published by the researchers in ACS Nano explains in detail the principle of producing interference images by the classical inkjet method and shows the advantages of this technique in depositing coatings with uniform thickness, which is required for large-scale interference color imaging even on unprepared polymer films.
Creating a vibrant color red and a very narrow angle of coloring with this method remains a challenge. However the team has reported ‘green’ ink that is both safe for the ecosystem and does not fade from UV exposure.
Image credits: ACS