Swedish tech could help fight counterfeit clothing

A Swedish researcher has developed a way to protect designer clothing from counterfeiting using a novel thread with unique optical properties.

The thread can be used to create invisible patterns in fabrics that are only visible under polarised light, according to Chalmers University of Technology scientist Christian Müller. The partially invisible thread - made of polyethylene and a dye molecule - absorbs visible light and can be weaved into a pattern that is invisible to the naked eye, but which can be seen using a polarisation filter.

"The production process itself uncomplicated," says Müller. "Clothing manufacturers could start using the thread right away to put a signature pattern in their garments," he adds noting that the equipment needed to see the pattern is fairly simple, and is already in place at Swedish Customs.

The invisible thread can be created using several different dye molecules and several different synthetic fibre textiles such as nylon. The dye molecule can also be bonded to natural fibres such as wool and silk. The technology can be used both for clothes and for different types of expensive speciality fabrics such as the textile used in vehicles and caravans.

The idea is for a brand to be associated with its own special combination of textile fibres and dye molecules. The thread is easy and inexpensive for a company to produce.

"It is very difficult for pirate manufacturers to copy the unique combination," says Müller. "They can obtain the equipment needed to read the pattern and ascertain the optical spectrum produced by a specific signature, but they cannot know which combination of components will produce the specific spectrum. And there are loads of different dye molecules available for use."

A similar technology is already used in banknotes - for example in Switzerland - but this is thought to be the first time the approach has been applied to textiles.

Müller's work was published last year in the journal Applied Physics Letters.