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No need for the sniff test with this sensor that detects spoiled food

We’ve all been there: standing in front of the fridge, staring at a Tupperware container, afraid to sniff the contents in case they’ve gone bad. A new technology hopes to make that trepidation a thing of the past.

Chemists at MIT have created cheap sensors that detect gases, from the hazardous to the heinous, including hydrogen peroxide, ammonia, and more. Not only are the sensors affordable, they don’t require a lot of maintenance. “There’s no wiring involved, there’s no power, “ MIT Chemistry Professor Timothy Swager tells MIT News.

That longevity, coupled with the sensors’ ability to communicate with smartphones, means there are lots of possibilities for the sensors. Made from modified near-field communication tags, known as CARDs, they run on the power they draw from devices that read them, including smartphones.

Related: Make your food last longer with an in-home freeze dryer

Researchers cut the electrical circuit in the RFID tags, then re-completed the circuit by drawing a wire with a pencil. Instead of graphite, the pencil is made from a carbon-nanotube-based material programmed to detect a certain chemical. When the chemical is present, it changes the current. A smartphone is then able to read the sensor and determine if the chemical is in the air.

The researchers envision their CARDs will become a part of “smart packaging” to detect food spoilage, monitor gas exposure levels in manufacturing plants, and help doctors diagnose diseases.

A recent winner of the UK James Dyson Award, the Bump Mark, similarly helps detect food spoilage. The food label decays along with the food inside the package, signaling whether its safe to eat. The labels are also still in the prototype phase, but it’s heartening to know there’s a lot of interest in decreasing the amount of food wasted around the world each year. For now, you’ll just have to rely on old-fashioned techniques (is it moldy?) to determine if your leftovers are still safe to eat.