Technology

Chipless sensors cut electronic waste in temperature monitoring systems

University of Glasgow researchers demonstrate wireless temperature monitoring without semiconductor chips, offering enhanced performance and reduced environmental impact compared to traditional electronic sensors.

Device prototype with thermal cameraResearchers at the University of Glasgow have developed a new type of wireless temperature sensor that could significantly reduce electronic waste from tracking systems. The innovation replaces traditional electronic chips with a smart material that can be more easily recycled.

The new sensor uses a flexible plastic material enhanced with common industrial materials like carbon fibers. This enhanced plastic can detect temperature changes and transmit readings wirelessly, performing the same function as conventional electronic tags but without the hard-to-recycle semiconductor chips found in current systems.

Dr Mahmoud Wagih, lecturer at Glasgow's James Watt School of Engineering, commented:  "By eliminating the need for microchips, these chipless tags could significantly reduce both cost and electronic waste compared to traditional RFID sensors.”

How It Works

The research team created their sensors by mixing a flexible silicone-based plastic (known as PDMS) with small amounts of conductive materials - essentially creating a smart plastic that responds to temperature changes. The best results came from adding carbon fibers, which produced sensors that were 40 times more sensitive than using the plastic alone.

In testing, the sensors proved capable of measuring temperatures from room temperature up to 110°C with particular accuracy in the 20-60°C range - making them ideal for food safety and medical applications.

These new sensors can be read using a portable scanner costing less than £100, compared to the expensive specialised equipment often needed for temperature monitoring. The sensors performed reliably at different distances from the scanner and were largely unaffected by humidity.

Simple Manufacturing

Unlike traditional electronic tags, which require complex manufacturing processes, these new sensors can be made using standard plastic processing equipment. The manufacturing process is straightforward: mixing the plastic base material with carbon fibers or similar conductive materials, removing any air bubbles, and then molding it into the desired shape.

The research team tested different conductive materials, including carbon fibers, graphite (similar to pencil lead), and copper powder. They found that carbon-based materials mixed more evenly through the plastic, making them better suited for mass production than metal powders, which tended to sink to the bottom of the mixture.

Multiple Monitoring Points

In a significant advance for warehouse and logistics applications, the team demonstrated that multiple sensors could work together as a network. They created a test system with six sensors working simultaneously, each monitoring temperature at different locations. This capability could be particularly valuable for tracking temperature-sensitive goods throughout storage and transport.

The system is also scalable - as more monitoring points are needed, additional sensors can be added to the network. Each sensor operates at a different frequency, allowing the scanning system to identify and track them individually.

Waste Reduction Benefits

Currently, the retail and logistics sectors use over 10 billion RFID tags annually. These tags typically contain integrated circuits - tiny electronic chips that are difficult to recycle and often end up as residual waste.

The new sensors are made primarily from polymers (plastics) mixed with simple conductive materials, making them much easier to process at end-of-life compared to conventional electronic devices containing precious metals and rare earth elements.

Dr Benjamin King, co-author of the study from the James Watt School of Engineering, noted: "The new technology we've developed uses materials which are cheap and widely-available, and the tags can be manufactured using a simple, scalable process. Our hope is that those unique characteristics could help the technology become widely-adopted in the years to come, helping to reduce the environmental harms currently being caused by single-use RFID tags."

Future Applications

The research team has already demonstrated how these sensors could be integrated into smart packaging for food safety monitoring. Their tests showed the sensors could detect temperature changes within 14 seconds, making them suitable for real-time monitoring.

The combination of low cost, simple manufacturing, and high performance could make these sensors valuable across multiple sectors, including food safety and cold chain logistics, pharmaceutical storage and transport, industrial process monitoring, medical supply tracking, and consumer goods condition monitoring.

The researchers are now exploring commercial scale-up possibilities and investigating whether similar principles could be applied to create sensors for other environmental conditions, such as humidity and acidity levels.

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