The Final Frontier of High Resolution Printing
When it comes to printing, what does the term "high resolution" mean to you? Is it 300 dots per inch? 600? 2400? How about 100,000 dots per inch? Now that's high res, by any standard. It's ten times higer than the highest resolution inkjets and laser printers are capable of. And in fact, it turns out to be the ultimate standard. It is the highest resolution possible by the known laws of physics, and it has been achieved (in full color) by researchers at the Agency for Science, Technology and Research (A*STAR) in Singapore.
The method the A*STAR researchers came up with does not use ink or dye. Instead, they developed a new technique they dubbed "structural color" which creates in tiny metal pillars capped with silver and gold, only a few nanometers tall. A nanometer is one billionth of a meter tall, if you're scoring at home. By varying diameters of the pillars and the gaps between them the researchers were able to make them resonate with a particular wavelength of light, and thus choose which colors they reflected. The technical (totally sci-fi) term for this phenomenon is "plasmon resonance."
As a proof of concept, the researchers printed a copy of the "Lena" test image, well known to printers, at just 50 x 50 micrometers in size.
The reason that 100,000 ppi is the highest possible resolution is that if the objects that create the image were any closer together, light waves reflecting off them would diffract and the objects would blur together, even if you were looking at them through a microscope. So this really is the final limit of printing resolution.
The applications of structural color may include creating nanowatermarks or other security messages, and as a new method of storing data.