In this paper, we describe a new way of producing digital prints with high reflectivity and dichroic or metallic appearance. The special visual effect is achieved using conventional office class inkjet printers and jetting inks containing metal oxide nano-particles onto surface of
nanoporous substrates, such as inkjet photo papers. A thin metal oxide layer of uniform thickness in ~10-1000μm range may be produced almost instantly by ambient drying of the print. The formation of metal oxide layer of highly uniform thickness is a result of interaction of metal oxide
ink with surface of inkjet media of certain pore structure and high volume porosity. Capillary forces drain liquid phase of the ink into the substrate, while retaining the nanoparticles on the surface. These forces also help to flatten jetted metal oxide particles into optically uniform and
continuous layer with high optical reflectivity.
The appearance of the films produced is highly dependent on refractive index, native coloration and printed layer thickness of the metal oxide used. Inks based on magnetite (Fe3O4, refractive index ~2.5) printed
into layers with ~ 50-100-nm thickness produce prints with visual appearance of metallic gold. Inkjet printing may also be used for stacking high refractive index metal oxide films with layers of conventional colorants (organic pigment particles) and produce prints with metallic color appearance.