Smart eco-label to revolutionize supply chains
Researchers from Empa, EPFL and CSEM have developed a battery-free, fully biodegradable sensor label that monitors temperature and humidity and documents whether cold chains have been violated - for example in the case of vaccines or food.
A new type of smart label measures temperature and relative humidity in real time and recognizes when a defined temperature threshold has been exceeded. This closes a key gap in global supply chains, in which sensitive goods such as medicines or perishable foods have so far only been checked selectively. The «Greenspack» project has been developed over the past four years by Empa, EPFL and CSEM and was funded by the SNSF and Innosuisse as part of the BRIDGE Discovery Program.
Technically, the sticker is similar to an RFID system: conductive tracks are printed on a special biopolymer cellulose substrate, which combine resistive and capacitive elements to form resonant circuits. If the label is read without contact, resonance frequencies change depending on the ambient temperature and humidity, so that measured values can be obtained without the need for a separate energy source. If the temperature exceeds 25 degrees, a tiny element in the conductor melts and the circuit breaks irreversibly - a clear signal that the shipment was once too warm.
The researchers see this as a lever for significantly reducing waste and the carbon footprint in logistics. Potentially damaged goods can be detected at an early stage, stopped or redirected to nearby locations if only the shelf life has been shortened. Depending on the material used, the temperature threshold can also be adjusted for frozen products or other sensitive applications.
The team placed particular emphasis on the ecological balance: the substrate and conductor tracks are designed in such a way that the eco-label can be composted after use or recycled with cardboard. To this end, the researchers developed a new carrier material made of biopolymer and cellulose fibers as well as a printing ink with the biodegradable metal zinc. While CSEM worked on the structure and the selection technology, two EPFL researchers are driving commercialization forward in the start-up «Circelec». In the future, the smart labels will also be used as sensors in agriculture and environmental monitoring.
Source: Empa
