Ultrafast Laser Inkless Full‐Color Printing on Flexible and Thermolabile Substrates

Abstract Laser‐induced structural color technology holds great promise for the mass‐production of structural colors of wide color gamut, high stability, and low cost. However, its application to flexible and thermolabile substrates (such as plastics and paper) is currently hindered by the reliance on high‐temperature processes or metal substrates. Here, an ultrafast laser inkless printing technology is proposed to address this challenge. By optimizing the magnetron sputtering process with a pre‐sintered TiN target, the reflective TiN layer can be prepared at room temperature, on which coated an absorptive TiN layer to produce the TiN hybrid film. Under laser irradiation, this hybrid film is transformed into an “oxide‐absorptive‐reflective” tri‐layer film structure when the upper absorptive TiN layer is oxidized. In this case, the thicknesses of the oxide and absorptive layers can be adjusted by modifying the total accumulated laser fluence. This enables the tuning of the double‐absorption wavelength, thereby obtaining basic structural colors for printing. The high durability of the obtained structural colors is verified through various aging tests. Notably, this technology is successfully applied to flexible and thermolabile substrates, including plastics and cardboard paper, which may further promote the practical application of laser‐induced structural color technology.