24th January 2019

NEW PROCESS PRINTS ON NANOMATERIALS

Researchers at Missouri University of Science & Technology have developed a method to print high-resolution images on nanoscale materials. The process uses a ‘no-ink’ method that reproduces very fine detail.

The print features are visible only with the aid of a high-powered electron microscope. The researchers illustrated their ‘no-ink’ printing method by reproducing the Missouri S&T athletic logo on a nanometer-scale surface.

The technique involves the use of thin sandwiches of nanometer-scale metal-dielectric materials known as metamaterials that interact with light in ways not seen in nature. Experimenting with the interplay of white light on sandwich-like structures, or plasmonic interfaces, the researchers developed what they call “a simple but efficient structural color printing platform” at the nanometer-scale level. They believe the process holds promise for future applications, including nanoscale visual arts, security marking and information storage.

The researchers’ printing surface consists of a sandwich-like structure made up of two thin films of silver separated by a ‘spacer’ film of silica. The top layer of silver film is 25 nanometers thick and is punctured with tiny holes created by a microfabrication process known as focused ion beam milling.

The bottom layer of silver is four times thicker than the top layer but still minuscule at 100 nanometers. Between the top and bottom films lies a 45-nanometer silica dielectric spacer. The researchers created a scaled-down template of the university’s athletic logo and drilled out tiny perforations on the top layer of the metamaterial structure.

Under a scanning electron microscope, the template looks like a needlepoint pattern of the logo. The researchers then beamed light through the holes to create the logo using no ink – only the interaction of the materials and light.

By adjusting the hole size of the top layer, light at the desired frequency was beamed into the material with a perfect absorption. This allowed researchers to create different colors in the reflected light and thereby accurately reproduce the S&T athletic logo with nanoscale color palettes. The researchers further adjusted the holes to alter the logo’s official green and gold color scheme to introduce four new colors (an orange ampersand, magenta S and T, cyan pickaxe symbol and navy blue ‘Missouri’).

“To reproduce a colourful artwork with our nanoscale color palettes, we replaced different areas in the original image with different nanostructures with specified hole sizes to represent various visible colors,” says Dr. Xiaodong Yang, an assistant professor at Missouri S&T. “We chose the athletic logo to fill that need.”

www.mst.edu