Sour milk? The “smart cap”, as pictured above from, could one day be used to detect food spoilage.

Gone may be the days of sniffing the milk carton to see if your milk has spoiled, thanks to a collaboration between engineers at UC Berkeley and Taiwan’s National Chiao Tung University.

This 3D-printed smart cap that the group has developed is meant to find a better way to detect whether a liquid has gone sour, thanks to the wireless electrical sensors that are attached to the milk carton’s smart cap.

Polymers combined with wax were used to create the cap. When the wax was removed, it left behind a hollow tube that allowed for the group to inject silver.

From there, the engineers added electronics, which included a capacitor and inductor to create a circuit that would monitor if and when the milk would spoil.

The group flipped over a milk carton so that milk could be captured in the capacitor. From there, they left the carton unopened for 36 hours in a room that was set at around 72 degrees Fahrenheit.

To determine whether or not the milk was spoiled, the engineers tracked the changes in the electrical signals that were associated with the increase of bacteria in the milk.

They continued to monitor the changes wirelessly by way of a radio-frequency probe.

Through their discovery, the group of engineers clearly demonstrated how 3D printing can work for basic electrical components.

Furthermore, this experiment and the invention of the smart cap intimates that 3D-printed smart caps could one day be used for food packaging purposes.

In fact, the group of engineers are currently working on inventing an implantable device with embedded transducers that can monitor blood pressure, muscle strain and drug concentrations through the smart cap technology.

For now, however, this news might only be a whiff of the smart cap’s innovation. We guess only time will smell, oops, we mean tell!

Copyright Inventionland, 2015