Milk carton ‘smart caps’ detect signs of spoilage

Engineers at the University of California, Berkeley have created a 3-D printed “smart cap” for milk cartons that detects signs of spoilage.

As detailed in the study 3-D printed Microelectronics for Integrated Circuitry and Passive Wireless Sensors, UC Berkeley engineers working in collaboration with colleagues from Taiwan’s National Chiao Tung University printed a variety of electronic components, including inductors and capacitors, using a mix of polymers and wax.

The wax was removed, and silver was injected into the hollow spaces to create circuits. A wirelessly readable 3-D printed inductor-capacitor tank was then embedded in the milk carton cap. With a flip of the carton, a small amount of milk becomes trapped in the capacitor gap, and any change in the electrical signals that accompany an increase in bacteria levels can then be measured with a reader.

“Many consumers throw away milk too soon—or not soon enough—so having technology that can indicate when milk has spoiled could have a monetary and health savings,” said Tony Banks, a commodity marketing specialist for Virginia Farm Bureau Federation. “The ‘smart cap’ is one example of how technology will help consumers and the food distribution network monitor for freshness, quality and safety.”

According to Liwei Lin, a professor of mechanical engineering at the Berkeley Sensor and Actuator Center, future development of 3-D printed food safety technology is realistic.
“This 3-D printing technology could eventually make electronic circuits cheap enough to be added to packaging to provide food safety alerts for consumers,” he said. “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.”