You can draw without a drop of ink, and this “pen and paper” is so magical

The team of Qiu Min of Westlake University used a composite film composed of titanium nitride and aluminum nitride titanium as a special “paper”, and used ultrafast laser for micro-nano processing on its surface to achieve “femtosecond laser inkless color playing”, which provided a new idea for the industrial application of laser ink-free color printing technology. Recently, the results of the study were published in Nature Communications.

It is reported that Dr. Geng Jiao of Westlake University is the first author, Dr. Shi Liping and Guoqiang Chair Professor Qiu Min are the corresponding authors of the paper, and the co-authors also include Xu Liye, a doctoral student of Westlake University, and Dr. Yan Wei.

Schematic diagram of the principle of ultrafast laser coloring on the surface of composite ceramic film Courtesy of Qiu Min Laboratory

Printers are one of the important sources of environmental pollution, because the widely used inkjet or laser color printers require a large amount of ink or toner, and these pigments will cause non-negligible pollution to the environment and cause harm to the human body. How to get rid of “ink”?

At the heart of this technology lies first in their invention of a novel “paper” – no more than about 110 nanometers thick and only one-thousandth of a hair. This “paper” is divided into three layers: the researchers plated 50 nm of titanium nitride and then 60 nm of titanium aluminum nitride on a single crystal silicon substrate. Due to the hardness of titanium nitride and aluminum nitride titanium, they are called ceramic materials, and the feather-like light “paper” composed of this layer of “ceramics” will become a “coat” attached to the item to be printed.

At the same time, Qiu Min’s laboratory developed another use of “pen” – “engraving” on ceramic film paper. The laser will be projected on the film, and by controlling the energy or scanning speed of the incident laser, the thickness of the oxide film (alumina) and the aluminum nitride titanium film can be changed at the same time; After the thickness changes, the incident natural light will pass through a complex interference effect between the three-layer film structures to form a specific reflected color. As a result, a variety of colors take shape.

They found that the use of titanium nitride and aluminum titanium nitride, two superhard ceramic materials, made of “special paper”, can fully achieve high-speed, high-resolution, wide color gamut, large size, insensitive observation angle, anti-aging full-color ink-free laser printing.

At present, the “femtosecond laser inkless color playing” technology invented by Qiu Min Laboratory has achieved nearly 90% of the RGB standard color system, far exceeding the current mainstream laser coloring technology. Their laser-induced oxidation of the composite film will simultaneously change the thickness of the oxide film (alumina) and the aluminum nitride titanium film, adding one more degree of freedom, resulting in a wider color gamut.

This technology enables simultaneous high-speed and high-resolution, full-color, ink-free printing. In terms of print speed, the technology reached a record 10 cm2/s. This means that a sheet of A4 paper can be printed in full color in less than 1 minute. In terms of printing resolution, it exceeds the maximum resolution of traditional ink printing by more than 10 times.

The high absorption characteristics of titanium aluminum nitride result in considerable additional phase differences at its interface, which counteract the change in color caused by film thickness differences with viewing angle. Simply understood, it is precisely because this “feather coat” is so light and thin, so in the range of 0-80°, no matter which angle is observed, the color will basically not change, which is another problem in the field of laser coloring.

The researchers conducted a series of destructive experiments, but the work of “femtosecond laser inkless coloring” is still “timeless”. After a series of national standard anti-aging tests, the researchers further confirmed that the color difference induced by the laser on aluminum nitride titanium is still <7, which fully meets the needs of industrial applications. And the last step of the experiment is the most "colorful". Can you believe that this is all an "artistic masterpiece" from a group of engineering students?

The work of “femtosecond laser inkless color playing” – Picasso’s famous painting “Weeping Woman” Photo courtesy of Qiu Min Laboratory

The work of “femtosecond laser inkless color playing” – “Spring Xiaotu of the Han Palace” by Ming dynasty painter Qiu Ying Courtesy of Qiu Min Laboratory

The work of “femtosecond laser inkless color playing” – Wang Xizhi’s calligraphy “Lanting Collection Preface” Photo courtesy of Qiu Min Laboratory(Source: Wen Caifei, China Science News)

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