Color metasurfaces in industrial perspective

This doctoral thesis describes the utilization of color metasurfaces in an industrial perspective, where nano-scale textures and contingent post processing replace inks, dyes and pigments in plastic production. The concept of colors by structure arguably reduces the number of raw materials and eliminates mechanical color sorting in the recycling stage.

First, the development of experimental processes, techniques and equipment is described. A single-spot electron beam lithography scheme for master pattern definition is developed, and optical characterization equipment for both laboratory and production environments is developed. Second, the fundamental optical surface properties of dielectric materials are investigated within the framework of mass production applicability.

Different colors can be realized using a single-step etching process by altering the nano-texture in high-index materials, exemplified in silicon. However, only corresponding faint colors appear in polymeric materials. The concept of all-polymer pigment-free coloration seems somewhat restricted in relation to widespread industrial employment.

Finally, a novel plasmon color technology for structural coloration in plastics is developed based on metal-coated polymer nano-textures and a protective coating system. The technology utilizes a hybrid disk-hole plasmonic mode for resonances in the visible spectrum, based on aluminum as a cheap and abundant plasmonic material.

Angle-insensitive scratch-resistant colors are demonstrated, and it is shown that the dependence on polarization can be controlled. In collaboration with industry, polymer-based colored metasurfaces of square-centimeter size are demonstrated by embossing, injection molding, roll-to-roll printing, and film insert molding with full compatibility.

Furthermore, post production color modification by laser ablation is briefly described. The environmental benefits are analyzed by life cycle analysis, where the high recyclability leads to reduced environmental impact compared to conventional plastic production. In summary, a promising future is anticipated for plasmonic colors as a decoration element for everyday use.