RFID Battles the Elements

Metal can be friend or foe. Water is always troubling. And even glass and plastic can impede success. Making RFID work in a pharmaceutical setting takes materials and packaging expertise, and a little black magic. We survey the experts on what they know, and what they don’t.

By Paul Thomas, Managing Editor

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Radio frequency identification, or RFID, is best known as the technology inside those little boxes on windshields that allow drivers to cruise, unimpeded, through tollway “E-Z Pass” lanes. While RFID has applications across all industries, the place where the action has been lately is the pharmaceutical industry.

RFID’s promise of enabling what some have called “supply chain management on steroids,” and FDA’s backing of the technology as a preventative measure against counterfeiting, have prodded the industry into the RFID era. Manufacturers and their partners are installing RFID equipment at key points along production and packaging lines, at entry and exit doors of warehouses, at dock doors of distribution centers, and even behind pharmacy desks. RFID transmits data about where the product is, who’s handling it, even what temperature it’s at.

Like any new-ish technology, RFID has bugs to be worked out. Most have to do with immature hardware — either the tags (comprised of a microchip, antenna and substrate on which they reside) or readers with which they communicate. “Dead” tags are just one reason RFID communication can break down and frustrate implementations.

But the technology has matured dramatically, aided by standards set by ISO and EPCglobal, and pharmaceutical RFID experts are now turning their attention toward other technical matters. One is how packaging materials impact tag readability. They’re also looking at other factors that can inhibit RFID performance: how the product is packaged, the environment in which it is packaged and shipped, and even the makeup of the product itself.

Growing pains

Purdue Pharma (Stamford, Conn.) began putting RFID tags on individual bottles of Oxycontin two years ago. There were few problems reading those tags along the production line, but when the bottles were loaded into cases of 48 and shipped to warehouses, readers had difficulty picking up their transmissions. Several factors were likely at play, says Harry Ramsey, senior package development engineer. The bottles were packed tightly, and the UHF (ultra high frequency) tags that Purdue used were unable to distinguish one bottle from another. And the aluminum induction seals on the bottles may have confused the RF signals, as metals are prone to do. Even today, “Anything at the case level is really up for grabs,” Ramsey says.

Purdue deserves credit for sharing the lessons it learned with the industry (Pharmaceutical Manufacturing, July/August 2005, p. 36). All major drug manufacturers have RFID pilots going, at the product, case or pallet level — or all three. Some are collaborating with supply chain partners downstream. And some, like Purdue, were prodded by the so-called “Wal-Mart mandate,” but these days it’s more about exploring the potential drug security and supply chain benefits of RFID that has Pfizer (with Viagra), GlaxoSmithKline (with its Trizivir HIV medication) and others devoting precious research dollars and key staff to RFID projects.

Along with the bugs, there have been battles — particularly that waged between camps championing the use of high frequency (or HF, which operates at 13.56 MHz) and UHF (at 915 MHz) technologies and their respective tags and readers. UHF technology, with long read ranges of up to 30 feet or more, works best for case- and pallet-level applications. But at the product- or item-level, HF and UHF camps have battled tooth and nail. Item-level applications will be the biggest slice of the RFID market pie; a lot of money is at stake.

HF appears to be the clear victor, as Pfizer, GSK and others would attest, mainly because it is relatively independent from influence by metals, liquids, glasses, plastics and other elements of the pharmaceutical environment. But even HF can fall victim to RF-hostile materials.

“Nobody is getting near 100% read rates consistently,” says Robb Clarke, assistant professor in the school of packaging at Michigan State University. “We’re working on it. Everyone is.”

It’s all in the physics

Three factors help determine how efficiently RF tags, particularly UHF, respond to reader interrogation, and how materials might affect this communication, says Daniel Deavours, Ph.D., who heads up the RFID Alliance Laboratory at the University of Kansas (Lawrence):

    • The dialectric constant of the material, which influences how fast RF’s electromagnetic signals travel through it. Plastic can slow down the RF by 40%-50%, Deavours says, while glass slows it down even more. Water, with a high dialectric constant, can slow down the RF by a factor of nine. As a result, RF equipment that has been tuned to operate at, say, 915 MHz, will be functioning at lower frequencies — with glass at around 800 MHz, for example, and water as low as 100 MHz.


    • How much the material absorbs electromagnetic energy and reduces the current emanating from the tag, also described as how “lossy” the material is. Water is very lossy, Deavours notes, while most plastics are not.


  • The material’s effect on the power transfer efficiency, as measured by a reflection coefficient, or the voltage standing wave ratio (VSWR) in RFID terminology. Antennas and chips, in particular, exchange energy at a given impedence. Metal greatly affects the impedence of the antenna, fouling communication within the tag. Water impacts impedence somewhat, while plastic not much at all, Deavours notes.

Taking all three factors into consideration, water presents a “triple whammy,” says Deavours. The net result: water and metal are tough, glass can be tricky, plastic isn’t too bad, and paper doesn’t do much at all. That doesn’t mean that RFID won’t work in the vicinity of metals and liquids, Deavours says, only that custom-designed tags will be required.

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