Diamond microparticles used to make security labels

Researchers in China have used artificial diamonds to create security labels that they claim are impossible to replicate.

The team led by Dr Zhiqin Chu of the University of Hong Kong (HKU), assisted by Prof Lei Shao of Sun Yat-sen University and Prof Qi Wang from Peking University, have used the diamonds to create physically unclonable functions (PUFs), a term used to describe a physical structure that is easy to evaluate but hard to predict or replicate.

The team made optical PUF-based security labels by planting diamond microparticles of random and different shapes and sizes on a silicon plate using a method called chemical vapour deposition (CVD). The resulting pattern scatters light in a unique way, forming a unique 'fingerprint' that can be scanned using a phone.

A second element of the technology is that the diamond microparticles have defects known as silicon-vacancy (SiV) centres that emit near-infrared photoluminescence when a green light is shone on them.

These unique optic signatures can then be combined and digitised into codes of very high sophistication and security that can be read by a simple smartphone scanner as well as a confocal fluorescence microscope, according to the scientists, who have published their work in the journal Nature Communications.

The diamond-based labels are highly suitable for use in commercial products as they are extremely tough – in trials they withstood heat, the action of chemicals and physical damage – according to the researchers.

Moreover, they are cheap – it costs just one US dollar to make 10,000 labels of 200 µm × 200 µm dimensions - and are ready to be used commercially, according to Dr Chu, who said that that the team’s next step is to focus on "practical applications" of the technology.

"Diamond anti-counterfeiting will be favoured in various high-end products such as jewellery, luxury goods, electronic products, and automobiles," he said.