A polyethylene film under development at Case Western Reserve University changes its fluorescence color from orange to green when ripped. The color change is invisible to the naked eye.
A technology that could, in the near future, be used for covert tamper evidence is in development at Case Western Reserve University (www.case.edu), Cleveland. Researchers are formulating polymers (see photo, right) that incorporate a small amount of fluorescent dye. When the polymers are mechanically stressed by tearing, pin-holing or deformation, the dye dramatically changes color.
The plastic may change from red to green, for example, or from yellow to blue. The color change is not perceptible to the naked eye; an ultraviolet-light instrument is required for detection. The technology could be used to create films, tapes and/or labels that change colors when the package is tampered with.
"We're just a step away from commercialization of this technology in the form of tamper-evident tape and other products," says Christoph Weder, associate professor of macromolecular science and engineering at the Case School of Engineering. Led by Weder, the research team includes graduate engineering students Brent Crenshaw and Jill Kunzelman.
Because the polymers and some of the dyes used in this research are commercially available already, the technology should prove cost-effective when it makes the leap from the lab to commercial applications.
And because the dyes are added at a very low level, the plastic's physical properties remain unchanged. "The dye molecules are added at the level of 0.2 percent. That's similar to the level for polymer additives such as antioxidants and ultraviolet stabilizers. The addition of the dye does not change the polymer's characteristics," Weder says.
Although the compatible dye molecules vary by polymer, the concept is compatible with a range of plastics used for rigid and flexible food packaging. These include polypropylene, polyethylene and polyester.
To be sure, bioterrorists, extortionists and even benign sneak-a-taste consumers are a tricky lot. But they've met their match in the researchers and packaging professionals who continue to develop new tamper-evident technologies and find creative applications for existing ones.
NOTE TO LOGISTICS
Radio frequency identification (RFID), most commonly used today to manage the supply chain, also has the potential to flag tampering. RFID-tagged cases and pallets can be rigorously tracked, and if a tagged object for some reason becomes unreadable, the failure may point to tampering.
"Say the monitoring system is continually probing to hear from 100 tags, and all of a sudden it only hears from 99," says Mike Sheriff, president of AirGate Technologies Inc. (www.airgatetech.com), Allen, Texas. Clearly, "Something happened."
As prices for RFID tags become more affordable, the technology could even be used for tamper evidence at the item level. One scenario would be to mount an RFID tag over the lid of a jar in such a position that unscrewing the lid would break the connection between the tag's chip and its antenna. That connection is essential for proper tag function.
When RFID tags eventually find a place in mass-market, tamper-evident packaging, they likely will be combined with bar codes and other technologies that combat tampering, counterfeiting and theft.
"We expect multiple technologies will be nested together to provide the level of sophisticated detection the food supply chain will expect," says John Thorn, general manager of the RFID Group of Checkpoint Systems Inc. (www.checkpt.com), Thorofare, N.J.