Tiny RFID Makes Even Worse Abuses Possible

For years, radio-frequency identification, or RFID, tags have been used to track everything from highway tolls to pets, but only Hitachi’s newest tag is skinny enough to fit inside a dollar bill. Just 0.15 millimeter square and 7.5 microns thick, it’s a mere 1/15 the size of the next smallest RFID chip. And it can do everything its predecessors can. Hitachi’s tags store up to 128 bits of data—including prices, serial numbers and places of origin—that radio scanners can read from more than 10 feet away.

RFID chips typically use thick metal guard rings to insulate their circuitry. The insulation limits electrical interference but makes the tags too bulky for thin products such as paper. Hitachi’s weight-loss solution is to remove the rings and separate the circuits into individual wells coated with a thin insulating layer of silicon dioxide.

So far, the new insulation trick has worked perfectly. An earlier version of the chip successfully debuted in tickets for the 2005 World Exposition in Aichi, Japan, as a way to stop counterfeiters, and a new, even slimmer version could appear in European and Japanese currency within the next few years. When that happens, banks and businesses can simply scan the tagged bills to confirm their authenticity or trace their origins.—Elizabeth Svoboda