These RFID Tags Can Act as Low-Cost Environmental Sensors

RFID (radio-frequency identification) chips are extremely common these days. You’re probably most aware of them when you use an RFID card to unlock your office door, or when you send NFC payments from your smartphone. But, they’re also used in the background in ways that you don’t even notice, such as in casino chips and packaging at retail stores. That’s practical because they’re extremely inexpensive — just a few cents for basic tags — and, researchers at MIT’s Auto-ID Lab are now harnessing that to create low-cost sensors.

A normal passive RFID tag has an antenna and a very low-power IC chip. When a reader is nearby, the RF waves themselves induce a current in the antenna that powers the circuit. The chip then modifies the RF signal, which is returned to the reader with a unique identifier. Active RFID tags work in a similar way, but with a small battery that is recharged by RF waves (or that simply has a limited lifespan). The MIT researchers are taking advantage of the technology to create affordable environmental sensors that return data in addition to the unique identifier.

With passive tags, that works by using the environmental conditions — like moisture — to modify the circuit itself to provide data. Active tags can have more complex sensors that are capable of gathering more granular data. Both designs can be used to gather environmental data like carbon monoxide and glucose levels. The RFID sensors could potentially be used for inexpensive carbon monoxide detection throughout a building, or for monitoring glucose in a diabetes sufferer.