Oki Electric has developed non-powered RFID tags which can be embedded with multiple sensors to measure anything from temperature and humidity to pressure and light.
Unlike conventional active RFID sensors which require batteries, these passive sensors are powered by the RFID reader.
When RFID tag reader writer is placed over the sensor, the reader transmits a signal which generates electricity to be stored in a capacitor. The electricity is used to transmit the information from the sensor to the reader. The electricity is also used to light up the LED lamp to show that the sensor is active.
The smallest RFID sensor comes with a diameter of 8mm and small antennae of 10cm.
These RFID tags are embedded inside construction buildings and bridges to measure earthquake resistance or used to monitor the condition of perishable goods during transportation.