Terahertz tagging

22 October 2004

UK researchers have developed an anti-counterfeiting security tag that uses a terahertz scanner to unlock hidden information.

A layer of tamper-proof opaque plastic covers a hologram or image, which can only be viewed using terahertz radiation. The tag will protect high-value goods such as perfume or scotch against counterfeiting, and could also secure printed labels or documents, said the team.

There is already a move in tagging technology towards RFID chips, but these are expensive to manufacture, according to Professor David Cumming of the microsystem technology group at the University of Glasgow.

'Our method is chipless and the information is encoded in a different way; it could be plain text or holographic data,' he said. 'As our tags don't require an embedded chip they could be run off in a conventional print shop. They're unbelievably cheap and easy to make, but very difficult to read.'

According to Cumming, other applications include airline baggage handling. 'You could have labels that could only be read by baggage processing systems. That way you could be sure that bags couldn't be swapped,' he said. 'It's very advantageous in the current climate, and they could be printed on an inkjet printer next to an airport checkout desk.'

But terahertz readers are too expensive for widespread use today. 'That's the big stumbling block,' said Cumming. 'Our technology very much depends on the rate of progress of reader technology, but that is likely to develop in the next five years.'

The method involves stamping a pattern on to a substrate, then coating it in metal, creating a hologram. A protective layer of plastic, opaque to visible light, is then laid over to hide the information. Plastics are transparent to terahertz radiation, but metals act as reflectors.

The terahertz frequency would ideally be around 500GHz. The researchers declined to reveal the materials used, but claimed they are negotiating with electronics firms to develop the technology.