Chip-free wireless sensors could reduce the environmental impact of electronic tags

Researchers say a more sustainable new electronic tag could help decrease the vast environmental impact caused by single-use RFID technologies.

Engineers from the University of Glasgow have developed a new wireless tag system that can identify objects and measure temperature without using microchips.

Instead, the tags use inexpensive coils and a sensing material made from a form of silicon rubber called PDMS and carbon fibres. The coils, smaller than those in credit cards, absorb electromagnetic signals from a hand-held reader using electromagnetic waves.

The researchers say their new, less wasteful tags could help lower the retail sector's reliance on RFID chips, which use more than 10 billion tags annually. Most tags are used just once, and end up in a landfill without appropriate recycling of the electronics.

The team's new tags can carry identifying information and take real-time temperature measurements. The tags can be read by wireless hand-held devices costing less than £100.

The tags could help create future generations of 'smart packaging', which could also measure pH or humidity, warning retailers when food is at risk of spoiling or carrying harmful bacteria.

The flexible and lightweight tags could also be used in healthcare and smart clothing, which could unobtrusively monitor wearers' vital signs.

In a paper published in the journal Advanced Science, the researchers discuss how they developed the technology and tested it in lab conditions. They show how the sensors can detect variations in temperature between 20C and 110C. This could help make future wireless sensors cheaper and more sustainable, as fewer devices will now be required to cover the same temperature sensing range.

The tags performed particularly well between 20C and 60C, the range most relevant for food safety and medical applications. They can react quickly to temperature changes, taking just seconds to register significant changes.

They also demonstrate how multiple tags can be read at once, showing three sensors providing information to the reader device simultaneously and can function equally well at different distances from the reader.

Dr Mahmoud Wagih, lecturer at the University of Glasgow's James Watt School of Engineering, is the study's corresponding author. He said: "Developing wireless sensing tags is crucial for monitoring temperature across supply chains, particularly in food safety and medical applications. By eliminating the need for microchips, these chipless tags could significantly reduce both cost and electronic waste compared to traditional RFID sensors.

"While there have been various efforts in recent years to develop chipless smart devices, many require expensive specialised equipment for readout, limiting their potential in commercial applications.

"Our paper shows how multiple temperature sensors can be read simultaneously using an inexpensive portable device, which could make it an attractive prospect for adoption by a wide range of industries."

The James Watt School of Engineering's Dr Benjamin King is a co-author of the paper. He said: "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."

The team's paper, 'Large-Area Conductor-Loaded PDMS Flexible Composites for Wireless and Chipless Electromagnetic Multiplexed Temperature Sensors', was published in Advanced Science.

The UK Engineering and Physical Sciences Research Council (EPSRC) and the Royal Society supported the research.