Invisible inks could help foil counterfeit products

Scientists have invented new inexpensive fluorescent inks that could be used as multicoloured barcodes for consumers to authenticate products that are often counterfeited.
Consumers can snap a photo with their smartphone, and it will tell them if the item is real and worth the money, researchers said.
The new fluorescent inks give manufacturers and consumers an authentication tool that would be very difficult for counterfeiters to mimic.
These inks, which can be printed using an inkjet printer, are invisible under normal light but visible under ultraviolet light.
The inks could be stamped as barcodes or QR codes on anything from banknotes and bottles of whisky to luxury handbags and expensive cosmetics, providing proof of authenticity, researchers said.

A key advantage is the control one has over the colour of the ink; the inks can be made in single colours or as multicolour gradients.

An ink's colour depends on the amounts and interaction of three different "ingredient" molecules, providing a built-in "molecular encryption" tool. Even a tiny tweak to the ink's composition results in a significant colour change.
"We have introduced a level of complexity not seen before in tools to combat counterfeiters," said Sir Fraser Stoddart, from Northwestern University, senior author of the study.
"Our inks are similar to the proprietary formulations of soft drinks. One could approximate their flavor using other ingredients, but it would be impossible to match the flavor exactly without a precise knowledge of the recipe," said Stoddart.

With a manufacturer controlling the ink's "recipe," or chemical composition, counterfeiters would find it virtually impossible to reverse engineer the colour information encoded in the printed barcodes, QR codes or trademarks.
Even the inks' inventors would not be able to reverse engineer the process without a detailed knowledge of the encryption settings.
The fluorescent inks are prepared from simple and inexpensive commodity chemicals.
Stoddart's research team, led by Xisen Hou and Chenfeng Ke, stumbled across the water-based ink composite serendipitously.
A series of rigorous follow-up investigations unravelled the mechanism of the unique behaviour of the inks and led the scientists to propose an encryption theory for security printing.

The research was published in the journal Nature Communications.