Anti-counterfeit patterns made from nanowires are ‘nearly impossible’ to replicate

March 24, 2014
nanoscale fingerprint

Could you convincingly reproduce this pattern created with colored silver nanowires? (Credit: Nanotechnology/IOP Publishing)

Nanoscale unique patterns* made from tiny, randomly scattered silver nanowires  could authenticate goods, dealing with the growing problem of counterfeiting, say South Korea researchers.

The patterns are made by randomly dumping 20 to 30 individual nanowires, each with a diameter of about 70 nanometers and an average length of 10 to 50 microns, onto a thin plastic film, and could be used to tag a variety of goods from electronics and drugs to credit cards and bank notes.

The research was presented in a paper published March 21 in IOP Publishing’s journal Nanotechnology.

“It is nearly impossible to replicate the [patterns] due to the difficulty in trying to manipulate the tiny nanowires into a desired pattern,” said lead author of the research, Professor Hyotcherl Ihee, from the Korea Advanced Institute of Science and Technology (KAIST) and Institute for Basic Science (IBS). The cost of generating such an identical counterfeit pattern would generally be much higher than the value of the typical product being protected.

The researchers estimate that the patterns could be produced at a cost of less than $1 per single pattern.

How to create a nanoscale pattern

(1) Silver nanowire prepared by self-seeding (2) Coating an amorphous silica shell on the surface of the nanowire. (3) Preparation of fluorescent-dye-coated nanowire, using Fluorescein isothiocyanate (FITC) or rhodamine B-isothiocyanate (RITC). (Credit: Jangbae Kim et al./Nanotechnology/IOP Publishing)

The fluorescent dyes allowed the patterns, which are invisible to the naked eye, to be visually identified and authenticated under an optical microscope. Using different colored dyes could add another layer of complexity to the pattern.

The researchers say the nanoscale patterns could also be tagged with a unique ID, or barcode, which could facilitate a quick search in a database and simplify authentication or counterfeit identification. According to the World Customs Organization, about six per cent of global traded goods are counterfeit.

“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,” said Ihee.

“These authentication processes can be automated by employing an algorithm that recognizes the positions and colors of the silver nanowires and digitizes that information in a database. Such digitized information could significantly reduce the size of the stored data and reduce the time required for the authentication process.”

* In their paper and other materials, the researchers (misleadingly) refer to the patterns as “fingerprints.”

Abstract of Nanotechnology paper

Counterfeiting is conducted in almost every industry, and the losses caused by it are growing as today’s world trade continues to increase. In an attempt to provide an efficient method to fight such counterfeiting, we herein demonstrate anti-counterfeit nanoscale fingerprints generated by randomly distributed nanowires. Specifically, we prepare silver nanowires coated with fluorescent dyes and cast them onto the surface of transparent PET film. The resulting non-repeatable patterns characterized by the random location of the nanowires and their fluorescent colors provide unique barcodes suitable for anti-counterfeit purposes. Counterfeiting such a fingerprint pattern is impractical and expensive; the cost of replicating it would be higher than the value of the typical target item being protected. Fingerprint patterns can be visually authenticated in a simple and straightforward manner by using an optical microscope. The concept of generating unique patterns by randomness is not limited to the materials shown in this paper and should be readily applicable to other types of materials.