In nature, when light shines on a large number of ordered structures at a small place, reactions such as refraction, diffuse reflection, diffraction or interference will occur. The resulting color is called structural color, such as the colorful wings of insects and birds. This process does not use "pigment". Inspired by this phenomenon, Professor Qiu Min and his team members from West Lake University tried to use ultrafast laser to create micro-nano structures on the surface of materials to produce structural colors. Recently, the international journal Nature · Communication published the research results of the team. The researchers take the composite film composed of titanium nitride and aluminum titanium nitride as a special "paper", and use ultrafast laser to carry out micro-nano processing on its surface to realize "femtosecond laser inkless color printing", which provides a new idea for the industrial application of laser inkless color printing technology. Worldwide, the annual sales volume of printers can reach hundreds of millions. At present, the widely used inkjet or laser color printers need to use a large amount of ink or toner. The ink contains certain concentrations of volatile harmful substances such as lead, cadmium, mercury, polybrominated biphenyls, etc. The toner will also release micro-particles that can be absorbed by the human body, causing harm to the environment and human body. Compared with ink pigments, structural colors have the advantages of fastness, high resolution and environmental protection. In the ultra-fast laser printing technology, the laser is not only a "pen", but also responsible for making ceramic materials with special structures. "For example, all kinds of traditional anti-counterfeiting code paper can produce rainbow color by using laser-induced paper surface microstructure grating, which has certain application value in anti-counterfeiting, but can not produce the pattern of specified color." The researchers said that this kind of technology is also used for the printing of commemorative coins, but the printing color gamut is narrow, can only be produced on the surface of precious metal, and the finished product is easy to fade. The reporter of Science and Technology Daily learned that the core of this technological breakthrough was, first of all, the team invented a novel "paper" - a composite ceramic film with a thickness of only about 110 nanometers and only one thousandth of the hair. This "paper" is divided into three layers: the bottom layer is metallic titanium nitride, which is used as the reflection layer of light to block light penetration and increase brightness; The middle layer is a high-loss aluminum nitride titanium dielectric, which can regulate the absorption of natural light; The top layer is aluminum oxide. When the ultra-fast laser acts on the surface of aluminum titanium nitride, an additional layer of transparent film dominated by aluminum oxide will be formed. Together with aluminum titanium nitride, it will regulate the natural light absorbed. At the same time, the team used a laser to "carve" on the ceramic film: after the laser is cast on the film, the thickness of the oxide film (alumina) and aluminum nitride titanium film can be changed simultaneously by controlling the energy or scanning speed of the incident laser; After the thickness changes, the incident natural light will form a specific reflection color through the complex interference effect between the three layers of film structure, and the rich and colorful colors will be formed accordingly. The researchers used a variety of technical means, such as energy dispersive X-ray, X-ray photoelectron spectroscopy, X-ray diffraction, focused ion beam etching, to conduct material analysis of the laser colored area, and confirmed that the observed color was indeed from the oxide layer formed by the laser. At present, the "femtosecond laser inkless color printing" technology invented by Qiu Min's team can simultaneously achieve high-speed and high-resolution full-color inkless printing