High capacity tagging using nanostructured diffraction barcodes

We describe a new non-contact high capacity optical tagging technique based on the use of nanostructured barcodes. The tags are generated from a number of superimposed diffraction gratings. Capacity for up to 68,000 distinguishable tags has been demonstrated, however current technological capability shall allow encoding of up to 10(9) distinguishable particles, each of which is only 100 microm long.