NFC tags check food freshness
In their implementation, the carbon nanotubes were chemically modified so that their ability to carry an electric current changed in the presence of a particular gas. This chemiresistive property was then integrated into the powering circuit of commercial near-field communication (NFC) tags.
The team first disrupted the electronic circuit by punching a hole in it before reconnecting the circuit with a linker made of the modified carbon nanotubes. Hence, the modified NFC tags can only remain operational and can only be read if the chemiresistors conduct normally, that is without the target chemical in sight.
Now, the researchers have modified the carbon nanotubes with metal-containing compounds called metalloporphyrins, known to be very good at binding to nitrogen-containing compounds such as amines. Of particular interest to the researchers were the so-called biogenic amines, such as putrescine and cadaverine, which are produced by decaying meat.
When the cobalt-containing porphyrin binds to any of these amines, it increases the electrical resistance of the carbon nanotube, which can be easily measured. The researchers tested the sensor on four types of meat: pork, chicken, cod, and salmon. They found that when refrigerated, all four types stayed fresh over four days. Left unrefrigerated, the samples all decayed, but at varying rates.
Designed within NFC-readable RFID labels, the sensors could allow consumers to determine whether the meat in their grocery store or refrigerator is safe to eat. Such sensors could be designed in “smart packaging” that would offer much more accurate safety information than the expiration date on the package, according to Timothy Swager, the John D. MacArthur Professor of Chemistry at MIT who had already proven similar sensors to detect ethylene, a gas that signals ripeness in fruit.
“People are constantly throwing things out that probably aren’t bad,” says Swager, who is the senior author of a paper describing the new sensor this week in the journal Angewandte Chemie.
“There are several potential advantages in having an inexpensive sensor for measuring, in real time, the freshness of meat and fish products, including preventing foodborne illness, increasing overall customer satisfaction, and reducing food waste at grocery stores and in consumers’ homes,” says Roberto Forloni, a senior science fellow at Sealed Air, a major supplier of food packaging, who was not part of the research team.
The researchers have filed for a patent on the technology and hope to license it for commercial development. The research was funded by the National Science Foundation and the Army Research Office through MIT’s Institute for Soldier Nanotechnologies.
Visit MIT at www.mit.edu