A new 3D printed cap can sense when milk is spoiled.

Engineers at UC Berkeley worked with Taiwan’s National Chiao Tung University to develop a high tech cap for milk jugs using polymers and a wax “spacer” which was then replaced with silver.

Then they added a capacitor and an inductor to sense when the milk spoiled.

To tell if the milk had gone bad, they tracked changes in electrical impulses associated with bacteria in the milk.

The results, according to the team,  though, are about more than whether or not you can tell milk is spoiled. The technique they used resulted in a way to 3D print basic electrical components that one day could make them so cheap that it will be possible to place them in packaging.

“Our paper describes the first demonstration of 3D printing for working basic electrical components, as well as a working wireless sensor,” Senior author Liwei Lin explained.

“One day, people may simply download 3D printing files from the internet with customized shapes and colors and print out useful devices at home.”

He added, this could eventually make electronics more affordable.

“This 3D printing technology could eventually make electronic circuits cheap enough to be added to packaging to provide food safety alerts for consumers. You could imagine a scenario where you can use your cellphone to check the freshness of food while it’s still on the store shelves.”