New invisible barcodes based on the unique thermal properties of nanoparticles have been developed to track both solid and liquid objects, a US study reports.
The technique could be used to tag explosives, drugs and ink.
Visible barcodes, currently used to label objects, can be altered, duplicated and counterfeited.
These new covert tags represent a promising alternative, although existing techniques are not suitable for large-scale labelling.
The researchers say nanoparticle barcodes can be added to solid and liquid drugs, where they remain stable and seem to have no appreciable toxic effects.
Ming Su of Worcester Polytechnic Institute in the US and her team demonstrate that this technique could be used forensically to trace the origins of explosives.
They also suggest that adding selected nanoparticles to ink and polymers used in printing could be used for
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