Wireless sensor tells your smartphone if your food is going off

The device, created by a team from MIT, is then able to share its data with a smartphone, potentially alerting users to mouldy food. "The beauty of these sensors is that they are really cheap," says Professor Timothy Swager. "You put them up, they sit there, and then you come around and read them. There's no wiring involved. There's no power. You can get quite imaginative as to what you might want to do with a technology like this." Essentially, the sensors are modified Near Field Communication (NFC) tags. The team began by punching a hole in the tag's electronic circuit and before replacing the missing link with carbon nanotubes designed to detect particular gases. The nanotubes were then drawn on using mechanical pencils. The devices are powered by short pulses of magnetic fields emitted by the smartphone used to read them. Normally, these pulses induce an electric current in the tag's circuit that keeps it running. However, in the modified tags, once the carbon nanotubes smell a targeted gas in the air the radio frequencies at which it receives, these pulses are shifted. The sensor will only respond to the reading smartphone if the frequencies are unchanged, therefore indicating whether or not a targeted gas is present. At the moment, each sensor is only able to detect one gas, and the smartphone must be held within 5cm to pick up a reading. However, the researchers are seeking to integrate Bluetooth technology to expand the range. They say the sensors could be used for everything from detecting dangerous gas levels in manufacturing plants to identifying explosives and environmental pollutants.