Polymers Make Pigment-Free Printing Possible

By exposing polymers to stress, scientists in Japan have developed a colour palette for printing which does not involve the use of pigments.

AsianScientist (Jun. 28, 2019) – Researchers in Japan have created a minuscule painting, measuring just one millimeter in width, without the use of pigments. They published their findings in the journal Nature.

The late Katsushika Hokusai is a titan of Japanese art, as revered in his homeland as Da Vinci, Van Gogh and Rembrandt Van Rijn are in the West. Of all his famed masterpieces, the ‘Great Wave off Kanazawa’ stands out as a testament to his artistic genius.

Now, a team of researchers led by Professor Easan Sivaniah at Kyoto University, Japan, has recreated the famous painting using nothing but stretched polymers.

“Polymers, when exposed to stress, undergo a process called ‘crazing’ in which they form tiny, slender fibers known as fibrils,” Sivaniah explained. “These fibers cause a powerful visual effect. Crazing is what the bored school kid sees when he repeatedly bends a transparent ruler until the stretched plastic starts to cloud into a kind of opaque white.”

Importantly, the researchers realized that by controlling a process called organized microfibrillation (OM)—the way the microscopic fibrils were formed and organized in a periodic pattern—they can also control the scattering of light to create colors across the whole visible spectrum, from blue to red. This allowed them to create a new color palette without using pigments.

Zoologists have long been familiar with this non-pigment-based color phenomenon, which they term ‘structural color.’ It is exactly how nature produces the vivid colors seen in butterfly wings, the spectacular plumage of male peacocks and other shimmering, iridescent birds. Some of the most spectacular wildlife on the planet is, in fact, devoid of pigmentation and depends upon light interacting with the surface structure for its mesmerizingly beautiful effect.

The OM technology can be used to generate images at resolutions of up to 14,000 dots per inch on a number of flexible and transparent formats. This has countless applications, for example, in anti-forgery technology for banknotes.

“OM allows us to print porous networks for gases and liquids, making it both breathable and wearable. So, for example, in the area of health and well-being, it is possible to incorporate it into a kind of flexible ‘fluid circuit board’ that could sit on your skin, or your contact lenses, to transmit essential biomedical information to the Cloud or directly to your health care professional,” said Sivaniah.

The article can be found at: Ito et al. (2019) Structural Color Using Organized Microfibrillation in Glassy Polymer Films.


Source: Kyoto University; Photo: Kyoto University iCeMS.
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