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Researchers in South Korea have devised a nano barcode so small they say it could significantly reduce the number of counterfeit goods being traded.
The team from the Korea Advanced Institute of Science and Technology (KAIST) created unique patterns by randomly scattering 20 to 30 silver nanowires, each with an average length of 10 to 50 µm, onto a thin plastic film.
The researchers said the technique could be used to tag a variety of goods from electronics and drugs to credit cards and bank notes.
Lead researcher Professor Hyotcherl Ihee, from KAIST, said: "It is nearly impossible to replicate the fingerprints due to the difficulty in trying to manipulate the tiny nanowires into a desired pattern. The cost of generating such an identical counterfeit pattern would generally be much higher than the value of the typical product being protected."
The nano barcodes could be produced at a cost of less than $1 per single pattern. In their study they synthesised a solution containing individual silver nanowires, coated the nanowires with silica, doped them with specific fluorescent dyes and then randomly dropped them onto a transferable film made from flexible polyethylene terephthalate.
The fluorescent dyes allowed the patterns, which are invisible to the naked eye, to be visually identified and authenticated under an optical microscope. Another layer of complexity could be added if a number of different coloured dyes are used.
The wire patterns could then be tagged with a unique ID to facilitate a quick search in a database and ease the process of authentication or counterfeit identification.
"Once a pattern is tagged and stored on a database using a unique ID, a certain substrate, whether this is a bank note or a credit card, could be authenticated almost immediately by observing the fluorescence images and comparing it with stored images," continued Professor Ihee.
According to the World Customs Organisation, around 6% of global traded goods are counterfeit, which the researchers believe could be reduced by using their technique to authenticate goods.
"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," concluded Professor Ihee.