Color plays an important role in daily life and modern industry. Generally, color is generated by dyes or pigments rather than the transparent materials, people have to use multiple inks to achieve different colors. However, a recent study from the Institute of Chemistry, Chinese Academy of Sciences (ICCAS), led by Prof. SONG Yanlin, broke this cognition. They achieved the full-color structural-color printing with a single transparent polymer ink.

This structural color is arisen from the domed microstructure (microdome), which can manipulate the total internal reflections (TIRs) and interference of light. To precisely construct the optical microstructure with well-controlled morphology, researchers developed a digitally controlled inkjet printing method named droplet by droplet printing. They directly printed the transparent polymer ink with accurate volume on a hydrophobic and transparent substrate. Under the surface-tension effect, the ink droplets would retract into perfect microdomes automatically. The inverted microdomes can induce the interference color from TIR and serve as independent pixels to create the structural color. By changing the ink volume, the microdome morphology and the optical path could be precisely controlled. Thus, full-color pixels across the whole visible regions were easily obtained with one printing nozzle and one transparent ink.

Besides the microscale pixel, full-color structural-color images were also prepared by the digital programmable printer. The gamut, lightness, saturation, and grayscale of the printed image could be systematically controlled with single-pixel precision. Furthermore, this color printing method could be fully compatible with the commercial printing technology and suitable for the large-area industrial production. The paper entitled “Facile full-color printing with a single transparent ink” was published in Science Advances (DOI: 10.1126/sciadv.eabh1992).

The research was financially supported by the National Natural Science Foundation of China, the National Key R&D Program of China, the Beijing Natural Science Foundation, the K. C. Wong Education Foundation, and the Beijing National Laboratory for Molecular Sciences.

Typical structural-color printing with a single transparent ink (Image by Prof. SONG’ group)

Contact:
Prof. SONG Yanlin
Institute of Chemistry, Chinese Academy of Sciences
Email: ylsong@iccas.ac.cn