“RFID is known for communication uses such as identification and tracking but RFID sensor tags present a new paradigm of RFID applications as a sensing technology where RFID microchip is embedded with sensors. The RFID sensor allows you to monitor temperature, pressure, humidity, CO2, battery levels, light intensity etc.”
There are various IoT based devices that can be used for sensing various environmental and indoor parameters such as temperature, humidity, and harmful gases etc. but use of radio frequency technology for sensing application presents a transformative change in this arena.
Most sensors we have seen so far are battery powered which offer obvious advantages in data transmission over long range but battery operated sensors are also complex and require maintenance. It limits its use cases, life cycle and sensing range. Though various small battery form factor such as thin film or micro-battery sensors are available in the market but you’ll need to replace the batteries every few days.
RFID sensor tags on the other hand can be fully passive or even battery powered but unlike others, here you don’t have to change batteries very often as in the case of traditional wireless sensor network (WSN) architecture with large number of tiny sensor nodes.
What are RFID Sensors?
Radio frequency identification is an AIDC technology popular for its wireless automatic identification and data capture functions using radio frequency signals. The technology employs a set of RFID tag, RFID reader, antenna and a computer software system to systematically identify tagged items and record the detail in a computer software database for future uses.
But that is what we know about RFID, RFID tags and readers. RFID sensors are slightly different than RFID tags. First of all RFID sensing applications involve the use of RFID sensor tags for sensing temperature, humidity, moisture content, harmful gases, content of a bin (full or empty) etc. For that RFID sensor tags are used.
RFID sensors are made by embedding the sensor with the microchip (in the case of chipped RFID tags) itself and in the case of chipless RFID, the sensing is performed by using smart materials such as iconic plastic crystals, nanostructured metal oxide, and conductive polymers (PEDOTs), on the surface of the chip instead of embedding the sensor with the silicon chip. These materials are very susceptible to environmental changes such as temperature, pressure, or electric fields. These materials when used on chipless RFID surface allow for new innovative sensing applications.
MIT engineers developed a new RFID sensing method
Recently a new type of RFID sensing method is devised by some scientists at MIT (Massachusetts Institute of Technology) where they used off the shelf integrated microchip that is capable of switching between two modes, one battery assisted passive (BAP) mode and secondly fully passive mode. The fully passive mode of the RFID sensor tag is used when the tag is operating normally for identification and tracking purpose and it switches to battery assisted passive mode when these sensor are detect some stimulus and send some sensing data. These RFID sensor tags when placed in the environment, on waste bins, on pallets, food packages, food containers etc. detect changes in temperature, humidity, gases, full or empty status of bins etc. and send the data to the RFID reader.
RFID Sensors and Sensing Applications
RFID sensor tags are used in various sensing applications in day-to-day operations. Unlike other sensors, RFID sensor tags don’t use wireless sensor network (WSN) where nodes are created. This in turn doesn’t use a lot of power and the battery assisted RFID tags last significantly longer than other battery operated sensors. More importantly, RFID sensors are also cost-effective. These tags cost only few cents and do the sensing job quite effectively.
Let’s see some of the RFID sensing application:
1. RFID sensors are used on waste bins to create smart waste bins. These tags effectively inform you when the waste bin is full and waste needs to be emptied out.
- 2. RFID sensors are also most prominently used in food supply chain where these tags are used on food containers and packages. It detects changing temperature and moisture content of the package and alerts you about food spillage and prevents food wastage and losses.
- 3. In cold stores, RFID sensors allow you to effectively monitor temperature and humidity of the store.
- 4. RFID sensors are also effectively used to detect motion.
- 5. In supply chain and inventory management, RFID sensors are used to detect pallet movement and record the packages coming in and going out of the warehouses.
- 6. In healthcare sector, RFID sensors are used to maintain the temperature of medicines and vaccine vials.
- 7. In retail, RFID sensors are also used to prevent shoplifting and potential losses.
To conclude, RFID sensor tags are primarily used in chipped RFID and chipless RFID configurations. These sensing tags are cost effective for they use either less battery power or no battery at all. When placed in the extreme environmental conditions, RFID sensor tags work effectively and sense the temperature, location, pressure, harmful gases in the environment as well as detect the intensity of light quite effectively. Being cost effective, the tags find far greater applications in low cost RFID application in healthcare, retail and supply chain and logistics.