RFID Battles the Elements

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.

Understanding how the elements might impact RF signals takes a bit of “black magic,” since little hard data exists, notes Bert Moore of IDAT Consulting (Atlanta). Often, the product is the problem. Geritol, he says, is not RF-friendly because of its high iron content. Products that contain electrolytes can be also be hostile. Viscosity and pH can factor in as well.

As far as packaging is concerned, “Anything with metal is a killer,” Clarke says. Radio signals, like light, don’t travel through metal. “It doesn’t matter whether it’s a micron or a foot thick,” he says. Aluminum or other foils or metal packaging equipment can reflect RF signals unpredictably, compromising readability. But metal can be friend as well as foe — and some tag technologies are using backplanes to reflect more signal toward an interrogation device. The backplane must be separated from the tag by a substrate that’s at least a few millimeters thick.

Glass and plastic packaging can also pose RFID challenges, Clarke notes. He and colleagues conducted tests in which they read UHF tags that were placed first outside, and then inside, standard glass bottles. Reading distances for the inside tags were half of those for the tags placed outside the bottles. Chemical additives within glasses and plastics can have unpredictable effects on RF transmissions as well. No public studies have been done, says Clarke.

These materials generally affect UHF antennas, and have much less of an impact on HF antennas. A typical UHF wavelength is about a foot long, while HF is roughly 1/70th of that, says Patrick Sweeney II, president and CEO of RFID solutions provider ODIN Technologies (Dulles, Va.) and author of “RFID for Dummies.” UHF travels farther, he notes, but for obvious reasons has problems in small spaces.

“The best value for the pharmaceutical industry is high frequency,” says Sweeney. ODIN and partner Unisys (Blue Bell, Pa.) recently conducted studies comparing how efficiently HF and UHF “backscatter” data to interrogators in the presence of different material types (to see relevant tables, click here). A large amount of backscatter is good, but UHF tags showed no backscatter at all near water or blister pack foils. Sweeney also notes that HF tag quality tends to be much better, and the tolerances are also better, resulting in less performance variability.

The item level

UHF has other issues as well. For one, it operates at near-microwave frequencies, and manufacturers of biologics and other liquid products question whether, and to what degree, these signals may have thermal or non-thermal impact upon liquid drug products. FDA is looking into the matter and is expected to weigh in later this year (see WILL RFID COOK MY PRODUCT?, below).

It was an easy decision for Pfizer to go with HF for its Viagra pilot, notes Tim Marsh, technology manager for global package technology (Peapack, N.J.). UHF’s immaturity and lack of performance meant that “we would have had to pay a much higher price to achieve the same results,” he says. There have been few difficulties achieving high read rates at the item level, he notes. Viagra is a solid tablet in plastic bottles with flat sides — so labels embedded with the RFID tags can be placed flush on the outside. (Curved containers are harder to work with: RF antennas may be damaged or influenced as they are wrapped around a bottle or vial, and the labels may rotate as they travel along conveyors, making them harder to read consistently.)

To date, Pfizer’s only real RFID headaches have been downstream, Marsh says, involving dead UHF tags in the field, at the case or pallet level. The tags may have been damaged during shipping, Marsh says, though the exact cause is unknown. While the tablets do not have an impact within individual bottles, collectively, within cases, they may. Internal studies comparing cases of empty bottles against those filled with Viagra show lower RFID signal strength. The tablets may have a cumulative effect of absorbing RF, Marsh says.

On the whole, oral-dose pills and the plastic bottles they come in are very RF-friendly, says Paul Chang, associate partner with IBM Business Consulting Services. IBM has coached GlaxoSmithKline and other manufacturers and distributors on pilot projects implementing HF tags at the item level. In these situations, manufacturers can install RFID equipment and implement programs without having to modify existing filling or packaging equipment, he says.

Many of the drugs targeted most by counterfeiters and diverters, however, come in blister packs, which present their own issues, says Chang. Blisters have no label to house an RFID tag, and will likely require an additional process step to attach the tag to the inside of a paperboard backing, where it can spaced appropriately from the foil. Still, manufacturers must deal with the issue of the blister foil detuning the RF antenna and inhibiting performance. “They may have to play around with the packaging,” Chang says. This might mean reconfiguring the blister, thickening the paperboard, or enlarging the carton containing the packs.

Foil tends to be even more RF-hostile when it’s curved or wrinkled, notes Bert Moore. Manufacturers are finding success orienting the tags “edge on” to the blister packs. In a box of blisters, the tag would be placed on the small side. This concept also applies to positioning tags on cases of product, he says.

Pfizer has done exploratory testing with HF tags on blister packs, as well as on packs of Rolaids tablets, which are wrapped in a foil liner, says Marsh. The company has not had complete success yet. The challenge is finding a tag location on the package to manage the effects of the metal, he says, rather than making any expensive changes to the packaging itself.

Vials present unique challenges, because tags on vials can be detuned if wrapped or bent. When vials rotate on conveyors, labels can be oriented away from an RFID interrogator, making them harder to read.

Tag-maker Tagsys (Cambridge, Mass.) and West Pharmaceutical Services (Lyonville, Pa.) have skirted this issue by placing small (8.9 mm in diameter) HF tags within plastic vial caps. The RF readers can then be positioned atop the conveyor. In tests, the West Spectra caps have achieved Six Sigma-level read rates, claims Ken Reich, marketing director for Tagsys.

The other issue with vials, of course, is that the product inside is most often a liquid, which renders UHF unusable at the item level, and can even impede HF success. More studies need to be done, says Clarke of Michigan State. Manufacturers will need to undergo significant trial and error before succeeding with RFID for liquid products.

UHF fights back

Larry Blue, vice president and general manager of Symbol Technologies, made a strong argument in favor of UHF at this year’s Interphex. Data show that UHF would become viable for drugs at the item level, he said. Give it time, Blue argued. UHF is immature and will soon rival HF.

Symbol and others are trying to make that a reality. RFID hardware supplier Impinj (Seattle) has made the most noise with its development of “near-field” UHF technology. Unlike far-field communication, near-field applications transfer energy through “inductive coupling.” The near field also changes the properties of the communication mechanisms, says Kansas’ Deavours, eliminating many issues with water and metals that far-field UHF encounters.

Near field could just reignite the HF vs. UHF item-level debate. “It has given a much-needed shot in the arm to UHF at the item level,” says Ramsey at Purdue Pharma. “It’s definitely something we’re interested in.”

Deavours and colleagues at Kansas have developed the UHF Adamas tag that, he claims, handles metals and liquids quite well. The trick with metal, he says, is understanding its impact on the RF signal, and then designing the antenna. The Adamas tag includes a metallic backplane that predictably reflects the RF signal. The first Adamas tags are too large and expensive for item-level use, and are better suited for warehouse applications, says Deavours.

Perhaps the debate should not be one of HF vs. UHF, Deavours argues, but of the near field vs. the far field, since near-field HF and UHF are, in the grand scheme of things, not really all that different. “Impinj has muddled up the debate,” he says, and that’s a good thing — a healthy and exciting development for the RFID world.

Deavours isn’t sold on near-field just yet. In a pharmaceutical environment, he notes, UHF will probably never be able to read individually tagged bottles deep within a case of product, for example, which may limit its potential for projects incorporating item-level tagging. But improved UHF technology offers the promise, for some manufacturers, of a unified RFID environment from item to case to pallet.

Processing, packaging and shipping equipment and other factors from the external environment are also issues that RF specialists must deal with. Motors, alarms, lights and other equipment can create unwanted “noise.” “The first step of RFID physics is to look at the macro environment, then more specifically at the micro environment where each reader will be installed,” says Sweeney of ODIN technologies. This includes a detailed analysis called a Full Faraday Cycle Analysis and “RF path loss contour mapping,” to determine potential sources of interference within RF interrogation zones and how to address them.

In one of its trials, Pfizer found that UHF hardware was affecting the read reliability of HF hardware nearby. The solution was to reconfigure the orientation of the reader antennas, and to add a logic into the process to alternate when each reader would operate, says Marsh. 

Purdue has had several “bizarre little issues,” says Ramsey. In one instance, a steel rail being used to guide bottles into an RF-reading portal was either carrying the signal extra distance, or reflecting it back. Purdue solved the problem by putting a break in the rail connection. In another instance, nearby wires would pick up RF signal and “leak” it beyond its usual range.

Clearly, with RFID, manufacturers must learn by doing. Getting packaging people involved in implemenations early will help. “The most successful large-scale RFID deployments so far have been those that have worked with all stakeholders, especially with packaging groups,” says Sweeney.

Pfizer enlisted the support of outside RF consultants and packaging experts. “Theory is fine for pristine applications,” Marsh says, “but it can fall short in providing knowledge to make appropriate business decisions.” He believes that it will take years before Pfizer has the in-house RFID expertise that it desires.

Industry has its work cut out for it as well. “We need alignment. We need adoption,” Marsh says. Lab testing RFID is important, he says, “but it’s how well it works in practice that will shape future direction.”