Printing In Color, Through Plasmons

Metal nanostructures can produce color as light interacts with oscillating electrons on their surfaces. Scientists have tried to harness this phenomenon to print images that won’t fade and have higher resolution than is possible with dyes and inks. A team now reports a simple, fast technique to print such plasmonic colors using lasers (Nat. Nanotechnol. 2015, DOI: 10.1038/nnano.2015.285). Anders Kristensen of the Technical University of Denmark and colleagues start with a piece of plastic that they imprint to create a forest of nanoscale cylindrical pillars spaced 200 nm apart. They then deposit a 20-nm-thick aluminum film that lands just on the top of the pillars and the plastic forest floor. Each pillar acts like a pixelin a programmed image. A laser pulse alters the pillar’s metal in nanoseconds, changing the pixel’s color from blue to red to yellow depending on the laser energy. Kristensen and coworkers have printed images with resolutions up to 127,000 dots per inch and have started working with automobile companies on applications. Because the method produces color elements without expensive lithography, “it’s a step in the right direction to bring plasmonic color printing to mass adoption,” comments Joel K. W. Yang of Singapore University of Technology & Design.