Mass printing of colored natural patterns on Al plate by roll imprinting and thin film deposition

Metal surfaces finished in color patterns are useful and attractive for both practical and artistic purposes. Although the surface of metals can be patterned by diverse methods including computerized-numerical-control machining, laser-direct surface structuring, and droplet printing, these serial processes are not suitable for the massive manufacturing of complex patterns with variant feature sizes. In this work, we present a continuous roll-imprinting process as a large-area, high-throughput method for producing arbitrary surface patterns on Al. The surface patterns of natural objects such as silk, leather, and paper are replicated via Ni electroplating, and the electroplated Ni replica mold is used as the imprinting roller to transfer the original natural pattern onto an Al plate. The conformity of the imprinted pattern to the original pattern is 80―85 %. Surface-patterned Al plates are also colorized by coating a metal-dielectric double layer, where the top metal layer adjusts the amount of light incident into the underlying dielectric film, strengthening the interference effect. Diverse colors are generated by varying the thicknesses of the coating layers. The colors obtained via experiments agree well with the results predicted using finite-difference time-domain simulation. This study provides a fast and scalable route for producing colored surface patterns on metals and may find various applications ranging from surface decoration and visual arts to product identification and anti-counterfeiting.