"Smart" sticker would let shoppers know if food hasn't been kept cold
If you're buying food that should have been kept cold right up until you took it off the shelf, it would certainly be good to know if it had actually reached room temperature at some point. An experimental new sticker could help, as it's designed to tell you if that happened.
Developed by scientists at the Korea Research Institute of Chemical Technology, the disposable device is intended to be adhered to the packaging of temperature-sensitive foods such as meat, fish, fruits and vegetables. It could also be applied to other products that need to be kept frozen or refrigerated, like medications.
The thin, flexible sticker incorporates a surface film made of polymer nanofibers, which neatly intersect one another as long as the ambient temperature is cold. This causes the film to appear opaque, keeping an underlying image on the sticker from being seen.
Should that film reach a temperature of at least 10 ºC (50 ºF) for a given amount of time, though, the fibers "melt" and their structure collapses, causing them to become entangled with one another. As a result, the film turns transparent and the image becomes visible. Even if the sticker is subsequently brought back down to a colder temperature, the film will remain clear.
Because some foods are more temperature-sensitive than others, though, the amount of room-temperature time that it takes for the film to degrade can be tweaked by utilizing nanofibers of specific compositions and thicknesses. This means that at room temperature, the sticker's image may show up in as little as 30 minutes, or not until a maximum of up to 24 hours has elapsed.
The technology is additionally claimed to be inexpensive, with the production cost estimated to be about one cent per sticker.
A paper on the research was recently published in the journal Advanced Materials.