Metamorphic barcodes based on lithographically defined microdots incorporating nanoparticles of phase change materials

Printed barcode lacks distributability as each barcode associated with sample cannot be divided when multiple copies of the same barcode are needed for forensic analysis. This article reports a metamorphic barcode with desired distributability to label objects (liquids or solids) in a covert and high-fidelity manner using polymer microdots containing a panel of phase change nanoparticles (low melting point metal or alloy). The microdots can be made with photolithography at large quantity or serial laser fabrication and have unique serialization numbers based on the melting characteristics of nanoparticles. The microdots can be distributed evenly in liquid or attached on various location of an object and decoded with differential scanning calorimeter. Incorporation of magnetic nanoparticles allows facile collection of polymer microdots with a magnet. The microdots are non-toxic and stable over one year without losing coding information and have higher large labeling capacity than other covert barcode systems.