Silver nanowire-studded currency would be almost impossible to counterfeit

Silver nanowires. Photo courtesy of Argonne National Laboratory.

South Korean researchers have discovered a way to make items like credit cards and bills nearly impossible to replicate: Attach a small tag sprinkled with carbon nanotubes that acts as a totally unique fingerprint.

“Compared to other anti-counterfeit methods, the fingerprints are cheap and simple to produce, they are extremely difficult to replicate and can be authenticated very straightforwardly,” lead author Hyotcherl Ihee said in a release. His team, which is composed of scientists from the Korea Advanced Institute of Science and Technology and Institute for Basic Science, published their work today in Nanotechnology.

Silver nanowires are microscopic slivers of silver that, on the fingerprints, measured less than half a millimeter across. Their tininess means that they are difficult to manipulate outside of an advanced laboratory. The fingerprints are manufactured by adding 20 to 30 nanotubes to a thin plastic film in a random pattern.

Thin films are coated with silver nanowires dipped in fluorescent dye. Photo courtesy of Nanotechnology.

Thin films are coated with silver nanowires dipped in fluorescent dye. Photo courtesy of Nanotechnology.

While counterfeiters could get their hands on silver nanowires, it’s highly unlikely that they would have the equipment to place the nano-scale structures in the exact same formation. Buying and using the equipment would be more expensive than the good they are trying to counterfeit.

To further complicate the manufacturing process, the researchers dipped the nanowires in fluorescent dye before adding them to the film. And while the silver nanowires would be difficult to see, the pattern created by the dye can be viewed under a microscope to verify if a fingerprint is legitimate. The person checking the item could then compare it against a database to see if it is real.

The team estimates it would cost less than $1 to manufacture each fingerprint, and they could be integrated into bills, credit cards and large goods like statues and paintings.

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