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Tiny Tags

Radio frequency identification tags are popping up in everything from windshield toll-paying units to inventory-tracking aids on warehouse pallets. A 250-micrometer-wide tag developed at Sarnoff in Princeton, NJ, is the smallest ever (photo). Its antenna is etched in silicon alongside photocells, logic and 50 bits of memory-enough to code billions of different ID numbers. Costing just pennies each, these microtags broadcast their IDs after receiving a burst of laser energy. Princeton-based PharmaSeq, which hired Sarnoff to develop the device, will initially use it for medical diagnostics. PharmaSeq coats the microtags with DNA sequences from known diseases, then mixes the tags with blood samples labeled with fluorescent dyes. Tags are routed through an optical reader; the ID numbers of any glowing tags provide a diagnosis. Sarnoff’s Jonathan Schepps sees the tags being used to track small, valuable items, like money or gems-or to “covertly label things.”

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