Thanks to 3-D printing, you never again have to find out the hard way if your milk is spoiled.
A team of engineers at the University of California, Berkeley, joined forces with colleagues at National Chiao Tung University in Taiwan to create a 3-D printed "smart cap" for milk cartons. Using wireless sensors embedded in the plastic, the cap can detect signs of spoilage.
The corresponding paper was published in the Nature science journal Microsystems & Nanoengineering. In it, the team outlines how the bottle caps are created with regular 3-D printers but use liquid metal paste to produce the electronic components embedded within a simple-looking cap. Combining a capacitor and an inductor printed with the liquid metal, the cap becomes a "resonant circuit," and when milk was caught in the cap during testing, the smart cap could read the milk for signs of growing bacteria.
"This 3-D printing technology could eventually make electronic circuits cheap enough to be added to packaging to provide food safety alerts for consumers," said Liwei Lin, a professor of mechanical engineering and the paper's senior author, in a UC Berkeley press release. "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."
Lin said printing liquid metal circuits like this doesn't so much mean 3-D printed iPhones are in the near future as much as it implies more custom applications like the smart cap. But the frugality of 3-D printed circuits means we could turn mundane objects into smart tools: Think sunscreen bottles that can read the sun's UV rays and tell you if your SPF is enough to prevent skin damage, or sneaker insoles that let you know if you're growing toe cheese.
No, Lin didn't give those specific examples in his paper. But this is 3-D printing. It's never long before someone figures out how to use it to improve our lives. For now, being able to tell if milk has gone bad is proof of concept — and can keep us from a mouth full of sour dairy.