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Pennies or Less

Designed to speed up checkout counters and eliminate the drudgery of physical price marking, the bar code has come a long way since 1974-when it was introduced into retail sales on a pack of chewing gum in an Ohio supermarket. Far exceeding initial expectations, five billion codes are scanned every day in 140 countries. But even as retailers tip their hat to the bar code’s success, few deny that a more sophisticated kind of tagging would be a great improvement. Bar codes identify only classes of products, not individual items, whereas a digital numbering scheme built into a tag has the capacity to identify every single manufactured item that is currently made and sold. Bar codes also have to be deliberately scanned at specific orientations; tags need only be within a reader’s range. “Once the infrastructure is in place, managing inventory in warehouses and retail stores could become highly automated,” says Alan Haberman, co-founder and governor-at-large of the Uniform Code Council, the organization that administers the bar code.

While attractive in concept, saturating the global supply chain with radio tags and readers poses huge challenges-chief among them the cost of the tag, typically more than a dollar. That’s fine for a choice Hereford steer but much too expensive for consumer items. The high cost results from the silicon chip and from the antenna, a pricey metal coil that serves two functions. First, it uses a magnetic field emitted by the reader to power the chip. Then, when the chip is powered, the antenna transmits data from the chip back to the reader. Most manufacturers of radio tags, including Texas Instruments and Everett, WA-based Intermec, have developed tags based on this model, which is known as “inductive coupling.”

It is the cost of the inductively coupled tags, hovering around a dollar, that lit a fire under Noel Eberhardt, vice president for advanced technology at Motorola. “The words that burned in my ears were ‘this is interesting technology, but it’s too expensive,’” Eberhardt says. “So I set out to build the lowest-cost silicon chip possible. And my first objective was to get rid of that coil.”

In late 1995, Eberhardt started collaborating with Neil Gershenfeld, director of the MIT Media Lab’s Physics and Media Group, on a cost-effective design. Eberhardt experimented with “capacitive coupling,” an alternative method in which the tag is powered not by magnetic forces but by electrostatic charges emitted by the reader, charges similar to those that cause your clothes to stick together when you pull them out of the dryer. Using this mechanism, he found that coil antennas could be replaced with conductive carbon ink printed on paper which would pick up the electrostatic charges from the reader and create a current across the chip. The silicon chip-itself less than three millimeters square-could be mounted atop a sheet of paper lined with the special ink.

Without the metal coil, the cost of the tag dropped to less than 50 cents. The added flexibility of the paper material also meant Eberhardt’s prototype tag could function when bent, cut or crumpled, as long as a remnant of the carbon ink-based antenna remained connected to the chip. Eberhardt and Gershenfeld announced their innovation in February 1999. Within weeks of the announcement, Motorola released the first and so far the only capacitively coupled tag.

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