Plasmonic devices are made by punching nano-scale holes in thin sheets of metal, imitating the patterns on the wings of the South American Blue Morpho butterfly (right). The technology could soon replace holograms as anti-counterfeit devices on banknotes.
By Tyler Irving
Posted March 2011
Quick — what do a butterfly and a banknote have in common? Maybe not much right now, but thanks to a B.C. researcher and entrepreneur, the same phenomenon that makes a butterfly’s wing a brilliant blue could soon make your $20 bill harder to counterfeit.
Engineer Clint Landrock became interested in plasmonic meta-materials while doing research at Simon Fraser University. These consist of extremely thin (5 to 200 nanometres) metal sheets perforated with holes ranging from 30 to 200 nanometres (nm) in diameter. The holes themselves are spaced 350 to 800 nm apart, corresponding with the wavelengths of visible light. Specific photons can resonate with free electrons on the surface of the metal between the holes, creating what’s called surface plasmonic resonance. The resonating light is eventually transmitted or reflected back out as a beam of one pure colour. The phenomenon is also responsible for the bright blue iridescent wings of the Blue Morpho butterfly of Central America.
Landrock, along with his supervisor Bozena Kaminska, were studying plasmonic materials as possible coatings for solar cells. However, once they realized that the unique light-bending properties could be used to deter counterfeiters, they pioneered a process to mass-produce them. This consisted of using a focused ion beam to create a master die, which is then used to print thousands of tiny plasmonic devices. Because the holes are so tiny, it’s almost impossible to reverse-engineer the devices and make a counterfeit die.
The technology has already given rise to a spin-off company, NanoTech Security Corp., which is negotiating with several world banks and banknote suppliers. “The banks are hungry for new technology, because their main security features are things like holograms, which are already on everything now,” says Landrock. “We were the first ones to actually manufacture these on a large scale.” If all goes well, Landrock says he thinks we might see the devices on banknotes as early as 2012.
Photo Credit: SFU Media relations
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