Structural Colour Images Inkjet Printed on Polymer Substrates Patterned with Nanostructural Pixels

This work demonstrates a novel means of manufacturing nano-optical devices, functioning according to the principle of structural colouration, by inkjet printing silver nanoparticle ink on nanostructured surfaces. The structural colouration is created by a surface containing micro- or nano- features interacting with light. In this study, we use a polymer substrate patterned with different types of nanostructure arrays as structural pixels that give red, green, and blue primary colours. We utilize nanoimprint lithography to replicate the nanostructured substrate from a prefabricated stamp. These days, inkjet printing has become a scalable micropatterning technology due to its precise, flexible control and cost-effective additive process. In this current work, inkjet printing technology is employed to selectively activate pixels by printing silver nanoparticle ink on the nanosubstrate surface to gain colour mixing. In the experiments performed, a nanostructured substrate patterned with diffractive nanostructure arrays was implemented to print full-colour images. The effect of surface wettability, different concentrations of silver nanoparticle ink, drop and line spacing, and polymer nanostructures on the optical properties of the subpixels of dried silver printed dots, are investigated to achieve high printing resolution. This method is a key to achieving full-colour, scalable, high-throughput, flexible and cost-effective printing of structural colour images. The printed pictures demonstrate unique optically variable effects that distinguish from security products using pigments or printing inks in their manufacturing processes. Therefore, this technique is an ideal candidate for security and authentication applications that require customizable anti-counterfeiting features.