RFID-enabled sensors can be deployed to effectively track ambient parameters, as required by the cold chain, says Soma Sekhar Vedantam.

Well-implemented supply-chain applications provide significant benefits to all organisations involved with increased visibility, tracking and traceability. In the case of cold-chain applications, the ambient parameters are also to be monitored and are important. The emphasis on this issue stems from the social, economic and environmental impact it can have.

RFID technology provides the capability to automate the supply chain. RFID-enabled sensors can track the ambient parameters, as well, as required by the cold chain. RFID-enabled sensors, working with wireless communications infrastructure and providing location and ambience information in real-time, provide the ability to act on adverse conditions and negative events, and prevent products from going bad.

As companies assess their cold-chain practices, RFID-based temperature-monitoring systems offer inherent advantages when compared to standard data loggers/monitors. RFID-enabled data loggers have yet to be widely deployed, yet the need to protect high-value, temperature-sensitive drugs/perishables will focus increasing attention on RFID cold-chain solutions.

Choices of RFID technologies

An RFID system for cold-chain purposes generally encompasses a sensor, a tag and a reader that communicate with one another by means of radio transmission. RFID tags can store an EPC for logistics-management purposes, and if equipped with the appropriate sensor and battery power, a limited number of temperature readings.

RFID tags can be separated into the following categories:

a. Passive RFID tags. These tags rely on the power supplied by the reader. When radio waves from the reader are encountered by a passive RFID tag, the coiled antenna within the tag forms a magnetic field. The tag draws power from it, energising the circuits in the tag. The tag, then, sends the information encoded in the tag’s memory. The lack of an integrated power supply means that passive tags can be very small. Therefore, passive tags can be embedded in stickers and other similarly flat presentations.

b. Active RFID systems (battery-powered). The reliability of active tags is typically higher than that of passive tags due to the ability of active tags to conduct a “session” with a reader. Active tags also transmit at higher power levels than passive tags, allowing them to be more effective in environments commonly found during food distribution. Examples of these situations could be the transmission of information in crowded enclosures (examples: humans and cattle); data transmission from tags attached to boxes, which may be placed in the middle of a tightly packed container of fruit, meat or other products with high moisture content; transmission through metallic walls (examples: shipping containers and trucks) or transmission from long distances (example: containers in transit).

c. Semi-passive tags. These systems are also battery-powered. However, they use the passive RFID interface, thus allowing wireless access to the device without using the internal power source. The battery size is, therefore, smaller than in the active tags.

The preferred RFID embodiments for environmental monitoring of food supply chains are semi-passive or active tags, coupled with sensors. Tags can collect a wide range of information, such as temperature, humidity, shock/vibration, light, radiation and concentration of gases (example: ethylene). The information collected by the tags is “harvested” by a gateway or hub, which then transmits the data to a server, through the use of digital mobile telephony (GSM) or local area networks, which can be wireless (WLAN) or with wired Ethernet connection (LAN). Data collected in the server can, then, be stored and analysed, allowing the automatic generation of notifications and events. A Web portal may display historic temperature data and frequency data and may trigger alerts for the users, transmitted through SMS messages or e-mails. Given that the information is in real-time, or near real-time, sudden situations that endanger the integrity of the goods can be addressed promptly, as opposed to traditional monitoring techniques that only allow analysis of past temperatures and events.

The need for technology for monitoring ambient parameters in real time is not disputed by any party involved. That said, the following limitations and challenges need to be understood:

• Uniformity of global standards across technologies for cold-chain applications
• Cost of technology
• Difficulty of establishing ROI
• Accuracy (sensor accuracy of ±0.5°C and calibrating multiple tags, to be consistent in measurements)
• RFID sensors positioning and representation of spatial variation of entire cargo load temperatures
• Supply chain silos (growers/suppliers/manufacturers, logistics providers, retailers operate without collaboration)

Ongoing research

A heartening feature is that substantial research is taking place in the area of RFID to enhance its usefulness. The areas of study involve:

(a) The combination of RFID technology and time-temperature indicators (TTI). This opens up the possibility of tracking the shelf life of chilled and frozen products remotely.

(b) Wireless technologies that allow gathering of data and exchange of real-time information with supply chain partners.

(c) Multi-sensing RFID nanosensors. The sensor will incorporate ultra-low-power gas sensors along with a thin film battery, allowing data acquisition and storage when no reader is present.

Conclusion

RFID is a promising technology that can provide numerous benefits in temperature monitoring and performance of perishable and pharmaceutical supply chains. The main limitations are a relatively high cost; difficulties in calculating the ROI; accuracy/calibration, which should be further improved.

The writer is Director, TrackIT Solutions, Dubai. He may be contacted at soma@trackitme.com