Last year’s listeriosis outbreak killed almost two dozen people and raised difficult questions about Canada’s food safety system. The incident, and others like it, has led U of T researchers to pose an intriguing scientific query: Can such disasters be averted with “smart” packaging that warns consumers when a food product has gone bad?
This is exactly what Ramin Farnood, a chemical engineering professor, and PhD student Peter Angelo are investigating in a project backed by Canada’s Sentinel Bioactive Paper Network and the University of Toronto’s Pulp and Paper Centre.
The core of Angelo and Farnood’s invention is a specially coated paper that glows when an electrical charge is applied to it. In their U of T lab, they layer special inks, conductive polymer film and electro-luminescent coatings on to conventional paper. These coatings essentially transform a non-conductive surface – in this case, paper – into a luminescent display.
Engineers have used similar technology to create conductive plastic films that provide the back lighting in cellphone displays and digital watches. The trick with paper is that you need to alter the surface structure of the paper and formulate special inks in order to create a functioning device. Farnood and Angelo apply these inks using a conventional electronic printer to make letters and shapes that glow when a charge is supplied, either by “plugging in” the paper or attaching it to a battery. Eventually, they hope to incorporate an ultra-thin battery right into the paper.
According to Farnood, such paper could also be coated with substances that react when exposed to certain pathogens or chemicals. The reaction would act as a switch to turn on the luminescent message printed on the paper’s surface. The message might warn consumers that the food is contaminated.
Farnood also envisions putting a paper-based biosensor in safety or construction masks. The masks will then be able to warn the wearer if he or she is being exposed to a harmful substance.
Because this technology is paper-based, it’s renewable, biodegradable and sufficiently flexible to use in the myriad forms of packaging found in a supermarket. If Farnood and Angelo are able to refine their invention, that familiar “Best Before” stamp may soon be past its expiry date.
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