RFID: Printed Electronics - Sooner or Later?
Wednesday, November 04, 2009 - RFID Connections
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Editor
The March 2009 Viewpoint talked about advances in organic (also called "plastic") printed RFID and its potential to provide "smart packaging" and make tagging everyday objects more feasible. Recent announcements about inorganic (metallic) inks may bring low cost printed RFID tags even closer and may even bring about printed UHF tags by overcoming one of the key limitations (to date) of organic inks.
By way of background, RFID tags (or any type of electronic logic circuitry) are built up of several alternating layers of conductive, semi-conductive and insulating materials in specific order. The passage of current between (among) these layers at specific points, voltages, and manners is what makes the circuitry work.
Building these layers out of silicon requires a super-clean environment and extremely sophisticated production methods and equipment.
The obvious appeal of being able to literally print each of these layers using specialized ink is obvious in terms of environment and equipment (although equipment may not be inexpensive -- but more on that later).
To date, the front-runner for printed electronics have been organic materials. Tremendous advances have been made with organic inks in the past few years, enabling the production of limited capacity but fully functional 13.56 MHz tags -- a feat some critics had claimed could never be accomplished. However, organic inks have one significant limitation compared to metallic inks. They are less conductive.
This means that organic inks cannot, at present, carry sufficient current to produce reliable UHF or higher tags.
Cold metallic inks, primarily copper or silver, have traditionally been limited by relatively large particle size (in ink jet printers) as well as by corrosion. During the drying process, fine lines of metallic inks have tarnished or corroded, forming a type of insulating layer on the surface of the particles and significantly reducing their ability to transfer electrical charges between them.
Hot stamping of antennas and similar features with metallic inks has been done for years but the temperatures required have prevented their use on many different types of substrates.
In October, Xerox announced that it had perfected a method for printing a silver metallic ink, at essentially room temperatures, using a desktop printer. The method, they claim, can produce fine lines suitable for electronic circuits.
The Xerox process prints three layers: a semiconductive layer, a conductive layer and a dielectric. While the initial samples were produced using a desktop printer, Xerox envisions the technology to be eventually used in continuous roll applications.
The most significant aspect of this new technology is that it has major application in a wide range of consumer products such as games, e-readers, signage, even flexible keyboards and computers. The applicability of the technology to consumer products provides a real incentive to companies to further develop the technology -- with RFID being almost a secondary beneficiary.
Bar code scanners, for example, benefitted from the commercialization of infrared and visible red laser diodes used in CD players. Bar code imagers similarly benefitted from the development of consumer-oriented megapixel cameras, first for conventional digital photography and later for use in mobile phones.
If -- when -- HF and UHF tags are printed with inorganic inks, they will likely have limited capabilities. Capabilities will grow over time as the technology is tried and tested.
Certainly one of the first areas to explore the use of printed RFID tags will be packaging manufacturers. If only three layers of ink are actually required, these same presses could easily turn out RFID tags in huge volumes. Current high quality multi-color presses can have eight or more "stations" (units that print a specific ink color) so even if a few more layers are required, they could be accommodated with existing equipment. Obviously, registration (the exact alignment of the substrate as it moves from one station to the next) would be critical. However, this is routinely achieved in high quality process color work. What might be slightly more problematic would be ensuring that the printed RFID tag on what would become the inside of the packaging is positioned properly for subsequent printing, cutting and folding of the finished package and, ultimately, be positioned to be read.
The most likely scenario for smart packaging would be to leverage the recent merger of electronic article surveillance (EAS) and RFID. The exact placement of the tag would have to be worked out before wide deployment to avoid difficulties with reading tags either for inventory or point-of-sale (POS) applications.
There is, of course, a downside to this. Current RFID chip manufacturers have a significant investment in silicon-based tags. While printed tags will in many cases represent new applications, there is also the likelihood that they will begin to encroach on applications that currently employ silicon-based chips. Companies that produce these chips will eventually have to adapt to compete or shift their focus towards producing more chips with far greater capabilities than can be produced with printed ink. At the same time, the availability of more capable tags wouldn't really be a "downside" for end users. However, it is rumored that some chip manufacturers are already producing more capable chips rather than different ranges of chips. For their lower cost line of products, this would mean simply limiting the available capabilities. This would certainly be more cost-effective than developing multiple lines of chips.
Another consideration is that multi-station high speed presses are not inexpensive (although they are certainly less expensive than silicon chip production equipment). Printing companies would have to dedicate one or more of these presses to producing RFID tags -- either by purchasing additional presses or changing production scheduling to accommodate tag printing. Finding the space for a new multi-station press might also be an issue.
While there may be specialty houses that only print RFID tags, it is equally likely that major printing houses would have their own presses for this. In the near term, the investment required to add one of these presses to each printing facility would somewhat offset the cost savings of producing the tags.
Another potential downside is that printed tags will be easier to counterfeit since they will not need to be produced in an advanced chip foundry.
This brings up the issues of privacy and security.
If printed RFID tags do initially have fewer capabilities or smaller memories than their silicon-based counterparts, they should be used for only the most basic applications -- such as rudimentary item identification -- unless true security and authentication can be built in.
And, if printed RFID tags make tagging of more everyday consumer items feasible, there will need to be a way to cost-effectively deactivate them -- particularly if they are also EAS-capable. In some applications, which are not EAS-capable, frangible (breakable) tags could be an answer -- in other words, where opening the item would break the circuitry and deactivate the tag (but leave it functional prior to use for returns processing). However, privacy concerns may require that all tags that do not offer post-purchase value to the consumer be deactivated at POS.
The need to deactivate tags at POS applications might actually be a greater impediment to the development of smart packaging than the development of the technology itself. It is certain that this issue will ultimately be addressed either from a technology or data content perspective, consumer acceptance, or some combination of all three. But the answer isn't obvious yet.
So, although ink technology may promise that printed RFID may come sooner than expected, the necessity of resolving the knotty problems of privacy and security may suggest it will come later.
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Comments on this column? E-mail me: Bert Moore, Editor
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