First Full-Color Micro Images Produced with a 100,000-dpi ResolutionAugust 13, 2012
This breakthrough allows coloring to be treated not as an inking process, but as a lithographic matter, which can potentially revolutionize the way images are printed and be further developed for use in high-resolution reflective color displays and high-density optical data storage.
The inspiration for the research was derived from stained glass, which is traditionally made by mixing tiny fragments of metal into the glass. It was found that nanoparticles from these metal fragments scattered light passing through the glass to give stained glass its colors. Using a similar concept with the help of modern nanotechnology tools, the researchers precisely patterned metal nanostructures, and designed the surface to reflect the light to achieve the color images.
“The resolution of printed color images very much depends on the size and spacing between individual ‘nanodots’ of color,” explained Dr Karthik Kumar, one of the key researchers involved. “The closer the dots are together—and because of their small size—the higher the resolution of the image. With the ability to accurately position these extremely small color dots, we were able to demonstrate the highest theoretical print color resolution of 100,000 dpi.”
“Instead of using different dyes for different colors, we encoded color information into the size and position of tiny metal disks,” added Dr Joel Yang, the project leader of the research. “These disks then interact with light through the phenomenon of plasmon resonances. The team built a database of color that corresponded to a specific nanostructure pattern, size and spacing. These nanostructures were then positioned accordingly.
“Similar to a child’s ‘coloring-by-numbers’ image, the sizes and positions of these nanostructures defined the ‘numbers’. But instead of sequentially coloring each area with a different ink, an ultrathin and uniform metal film was deposited across the entire image causing the ‘encoded’ colors to appear all at once, almost like magic!” continued Dr. Yang.
The researchers from IMRE had also collaborated with A*STAR’s Institute of High Performance Computing (IHPC) to design the pattern using computer simulation and modeling. IHPC’s Dr Ravi Hegde said, “The computer simulations were vital in understanding how the structures gave rise to such rich colors. This knowledge is currently being used to predict the behavior of more complicated nanostructure arrays.”