Silver nanowire "fingerprints" may be used to fight counterfeiting

One of KAIST's silver nanowire fingerprints

The counterfeiting of high-end products is a growing problem, and has led to the development of countermeasures such as invisible woven patterns, butterfly wing-inspired printing techniques, and even synthetic DNA. One of the drawbacks of some of these approaches, however, is the fact that implementing them can be quite a complex process. Now, a team from the Korea Advanced Institute of Science and Technology (KAIST) has come up with something simpler – tiny jumbles of nanowires that form item-specific "fingerprints."

To make the prints, the KAIST scientists start by creating a solution that contains silver nanowires, each one measuring about 10 to 50 micrometers in length. The wires are then coated with silica, and doped with fluorescent dyes. Drops of the solution are subsequently deposited onto a thin flexible sheet of polyethylene terephthalate (PET), the 20 to 30 nanowires within them ending up in a random arrangement.

When the dried drops are examined using a fluorescence microscope, the dyes allow the wires to be seen and imaged. From there, an algorithm notes the positions and colors of the wires, and compares that unique signature to one that was obtained when the fingerprint was created, and which has been stored in a database. If the two match, then the product is the real deal.

To help locate the reference print data within an online database, the fingerprint on the product could be combined with its own barcode. While that barcode could conceivably be reproduced by counterfeiters, there would be no point in doing so, if the reference print that it led users to didn't match up.

"It is nearly impossible to replicate the fingerprints due to the difficulty in trying to manipulate the tiny nanowires into a desired pattern" said lead scientist Prof. Hyotcherl Ihee. "The cost of generating such an identical counterfeit pattern would generally be much higher than the value of the typical product being protected."

It is estimated that each print would cost less than one US dollar to produce. While that may not sound like much, it could add up if, for instance, every single iPhone created were to receive its own custom fingerprint. For that reason, Ihee sees the technology being used more on fairly exclusive items, that are made in limited numbers.

Given that such items are often made by small manufacturers, the simplicity and low cost of the system could really be a factor. "The point is that it is so easy to make a pattern," Ihee told us. "Just drop a nanowire solution. Even a normal customer or seller can make their own."

A paper on his research was recently published in the journal Nanotechnology.

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