"He observed a whole range of colors," Yang said. "So we thought, ‘Wow we have colors, why don't we try to make a picture?'" The scientists replicated a well-known picture of a woman's face, called Lena. Originally published in Playboy, Lena has become a traditional test for imaging processing quality.
When they presented their Lena image at a conference, participants asked how small could they make the color pixel elements, and how closely could they put two colors together without it appearing as a single color. "When we thought about this question a little bit more and did some calculations, we found that indeed we were printing at very high resolutions already without realizing it," Yang said.
Other researchers have successfully put different colors extremely close together, Yang said, but those approaches involved dyes and pigments. The processes to place color molecules side-by-side were also tedious. Instead, the scientists in Singapore simply used nanoprinting techniques.
"What we did here was to basically encode color information into nanostructures," Yang said. Then they applied a uniform metal, silver, on top of those structures to produce the colors. An analogy would be filling up glasses with water at different heights to play notes around the rims. When filled correctly, each glass has a true resonance. The scientists arranged a version of glassware that resonates optically, not sonically. As a result, they can tune the colors of light reflected back to the viewer.