Researchers from Duke University have found a way to effectively print images with colors that could extend to infrared without the need for expensive and bulky machines. Most infrared imaging technologies require much assembly and numerous filters. Duke engineers have developed a manufacturing technique that would revolutionize multispectral printing.
"It's challenging to create sensors that can detect both the visible spectrum and the infrared," said Maiken Mikkelsen, a Nortel Networks Assistant Professor of Electrical and Computer Engineering and Physics at Duke. "Traditionally you need different materials that absorb different wavelengths, and that gets very expensive. But with our technology, the detectors' responses are based on structural properties that we design rather than a material's natural properties. What's really exciting is that we can pair this with a photodetector scheme to combine imaging in both the visible spectrum and the infrared on a single chip."
The new technology was published in the journal Advanced Materials makes use of plasmonics, otherwise known as the use of nanoscale physical phenomena to trap certain frequencies of light. Silver cubes 100 nanometers in size were placed a few nanometers above a thin gold foil. At a certain frequency, the silver electrons of the nanocube can trap the light's energy. By controlling the spacing between the nanoparticles, the researchers could make the system respond to a wide range of colors extending into infrared.
"Similar types of materials have been demonstrated before, but they've all used expensive techniques that have kept the technology from transitioning to the market," said graduate student Jon Stewart, one of the members of Mikkelsen's team. "We've come up with a fabrication scheme that is scalable, doesn't need a clean room and avoids using million-dollar machines, all while achieving higher frequency sensitivities. It has allowed us to do things in the field that haven't been done before."
One major adbantage of the plasmonic color scheme is that it would not fade over time and can be reliably reproduced accurately each time, allowing it to print infrared color schemes.
"Again, the exciting part is being able to print in both visible and infrared on the same substrate," said Mikkelsen. "You could imagine printing an image with a hidden portion in the infrared, or even covering an entire object to tailor its spectral response."
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