"Honey, is this milk stale?"
"I don't know, scan it with your phone."
Tufts University scientists have developed silk stickers that determine the freshness of perishable food.
Spoiling food goes through chemical changes that alter its dielectric properties. These intrinsic properties control the way electromagnetic energy interacts with the food.
The silk stickers hold tiny gold antennae, as fine as dessert-grade gold leaf, which pick up on changes in the food's dielectric properties.
The antennae can then send an electromagnetic signal to a reader device, possibly within a cell phone, that the food has spoiled.