While it sounds counterintuitive, it is possible. Ultimately achieving one color or another is a matter of filtering light rays in one way or another. New research has shown that it is possible obtain colors using a transparent ink. Transparent and special, because because of how it is composed, it allows modifying the light without the need for pigments.
The Institute of Chemistry of the Chinese Academy of Sciences is the one behind this new advance. The idea to make a transparent ink starts from the fact that current pigments and dyes can be harmful to the environment (as well as very expensive!). After all, they are chemical compounds that do not always end up being recycled correctly. The researchers wondered: Why not use an ink that does not use pigments?
The idea is inspired by some living beings in nature that already do this. Some animals such as the peacock have microstructures in their feathers that allow them to retain or reflect light at specific angles to change the wavelength and consequently the color that is reflected. This, with the right tools, humans can also do.
Microscopic Polymer Ink Domes
According to the researchers, they have created a water-based polymer ink that appears transparent to the human eye. And the truth is that theoretically it is, because there is no polymer in it. This ink can be printed on a glass with a hydrophobic surface. The hydrophobic surface makes the ink droplets form a microscopic domed structure.
By how these domes are organized when light hits it is reflected in such a way that it produces colors. By changing the size of the domes or the organization that they have, the light is reflected in a different way, thus allowing the creation of different colors when the human eye perceives the reflected light.
The interesting thing about this is that being on a glass and the domes oriented towards one of the faces, only seen from one side of the glass. That is, if they were placed in a window, for example, we could see a color image from the outside but a completely transparent glass from the inside.
One last detail is the useful life of this ink. As it is not pigment, it does not degrade over time since it is simply a structure that will always reflect the light in the same way if nothing alternates the painting. That is, unless the laws of physics change and as long as nothing touches the ink, it will reflect the colors in the same conditions forever.
The researchers believe that with enough analysis and manipulation of the dome structure, they could fully control saturation, brightness and hue of colors among other things. At the moment there is much to advance in this, as well as in demonstrating the viability that it has to produce it on a large scale.
Vía | Phys
More information | ScienceAdvances