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.