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Jun 1, 2007 12:00 AM
The hype of printed electronics, especially RFID, is out of sync with reality — at least as far as the printing industry is concerned. There is no doubt that the future will see a wide variety of products printed with tags that broadcast their identity, use and authenticity. The application of printed electronics gives rise to appellations such as “smart labels,” “smart cards” and “smart packaging.” This was all apparent at the RFID Smart Labels USA 2007 conference and exhibition, Feb. 21-22 in Boston.
Radio frequency identification was born during WW II as aircraft were fitted with unique signals to identify friends from foes. In its most basic configuration, RFID is an antenna with a semiconductor chip that responds to specific electromagnetic radiation — this is called passive RFID, and it is a successor to bar codes. The chip is powered by the reader. Sometimes, a battery is needed because reading will be at longer distances or because of certain applications that record data on the chip — this is called active RFID.
Passive tags are in the KiloHertz and MegaHertz low to high frequency range; active tags are in the MegaHertz to GigaHertz UHF range. At the low end of the electromagnetic spectrum, signals can go through most objects and around corners at a range of a few feet to 30 ft. As you approach the high end, the distance increases and, if you add a battery, you get the longest distance.
Today, antennas are either printed or etched. Although printing is less expensive, 90 percent of all antennas are etched. This is because traditional manufacturers come from the semiconductor industry. Flat and rotary screen, gravure and flexography are the most common reproduction techniques for printing, and some form of plastic substrate is more common than paper — 70 percent are printed on polyester. Almost all antennas are printed roll-to-roll and then run through a machine that glues the chip to the antenna. The finished rolls are then combined with traditional printed rolls to form tags, labels, cards or passports. Forms printers have been the group doing the last-stage converting. Specialty companies would print the antenna and attach the chip and/or battery. Right now, offset lithography does not seem to have a role in this new world. What is interesting is that in the world of RFID, there is no such thing as “good enough.”
The silicon chip is about the size of a printed shadow dot. Theoretically, chips could be inserted in paper. Depending on the specialized equipment that glues the chip to the antenna, the chip could be glued directly or first attached to a small strap for more efficient handling. The tag is sized by the antenna and the antenna is sized by the chip.
The largest market for RFID not combined with printing involves inserting a small antenna and chip under the skin of a pet or other animal, like livestock. The biggest market that combines RFID with printing is for tags that are affixed to shipping pallets, and financial/identification cards and systems. China is issuing an RFID-based national identification card for its 970 million residents, and this action alone will make smart cards the largest RFID application through 2010.
The Holy Grail of RFID is printing right on the product. But the cost would have to come down from 10 cents or more per tag to less than five cents, and close to one cent. The chip alone ranges from a nano cent to about eight cents. This means the circuitry of the chip also would have to be printed, and this technology is years away. But so-called chipless technology is progressing, and every day there are announcements about transistors, capacitors and other electronic components being printed, in many cases using inkjet. Printed batteries are just about ready for prime time.
To print the antenna, special conductive inks that contain aluminum, copper or silver are used. In most cases, the ink must be heated after printing. One company, Parelec, showed printing of the antenna directly on corrugated. But the chip still had to be glued to the antenna.
Wal-Mart garnered a lot of attention when it mandated pallet tags. Now, almost all large retailers are using pallet tags to track and move goods through warehouses and into stores. I met a commercial printer who attended the event to see what was going on, and he said he bought a pair of jeans that sets the alarm off as he enters many stores. Branded apparel makers are integrating the tags into their labels to enable the recognition of counterfeit articles.
The market is such right now that one gravure press running 24/7 could satisfy the worldwide demand for UHF tags. Nonetheless, this market is moving aggressively; we will see the confluence of printing as we know it and RFID, as well as other electronics, by 2015 or perhaps earlier.
Frank J. Romano is professor emeritus at RIT. Contact him at firstname.lastname@example.org.