While most of us may not give much thought to the dyes used in color inks, they are in fact often quite toxic. That's why scientists at Russia's ITMO University have developed a more eco-friendly alternative – a non-toxic ink that produces different colors by altering the nanostructure of the material to which it's applied.

Such "nanostructure inks" work in a manner similar to certain surfaces found in nature, including butterfly wings – they reflect light in such a way that the light frequencies interfere with one another, causing the surface to appear to be a given color.

Previous attempts at creating these inks have required either a high-temperature fixing process, or they've had to be applied to specialized printing surfaces. In this latest case, however, both of those limitations were overcome.

Led by Aleksandr V. Yakovlev and Alexandr V. Vinogradov, the ITMO team developed a colorless titanium dioxide-based colloidal ink that doesn't require high-temperature fixing, and that can be applied to a wide variety of surfaces. It's applied using a regular inkjet printer, and its perceived color can be changed by varying the thickness of the deposited ink … although vibrant red is reportedly still a bit of a challenge.

A paper on the research was recently published in the journal ACS Nano.