Every day, huge amounts of goods travel around the world—including fragile products that must stay within a safe temperature and humidity range.
Vaccines, certain medicines, and fresh foods can easily spoil if they get too warm or too humid during transport.
But it’s not practical or environmentally friendly to put expensive electronic sensors on every single item shipped.
A team of researchers from Empa, EPFL, and CSEM has spent four years working on a clever solution.
Their project, called Greenspack, has produced a completely biodegradable smart sensor tag that can monitor temperature and humidity in real time.
Even more impressively, the tag can “remember” if a shipment ever got too warm. The results were recently published in Nature Communications.
Unlike traditional electronics, this new sensor contains no silicon, no battery, and no transmitter. Instead, it works a bit like an RFID sticker.
The tag contains printed electrical circuits made from conductive materials.
When a device passes an electromagnetic field over the tag, the circuits produce a resonance signal. This signal changes depending on the surrounding temperature and humidity, allowing a reader to identify the exact conditions the shipment has experienced.
The most innovative part is the tag’s built-in “memory.” If the temperature ever rises above 25°C, a tiny part of the circuit melts and permanently breaks the electrical path.
When the tag is scanned later, it clearly shows that the shipment was exposed to unsafe heat.
For delicate items like vaccines, this simple indicator could prevent unsafe products from ever reaching consumers.
It could also help redirect goods earlier in the supply chain, reducing waste, saving money, and lowering the carbon footprint of global shipping.
The researchers can design the tag to respond to different temperatures, depending on the needs of each product. For example, frozen foods or specialized medicines might require different limits. This flexibility means the technology could be used across many industries.
The sustainability aspect is also central to the project. The tag’s base is made from a biodegradable biopolymer combined with cellulose fibers, developed by Empa scientists. The conductive ink is printed using zinc, a bio-absorbable metal. After the shipment reaches its destination, the tag can be composted or recycled along with cardboard, instead of ending up as electronic waste.
Creating biodegradable electronics is not easy. The materials must stay stable long enough to complete their job, then break down afterward. The sensors must also respond only to the conditions they are designed for.
For example, the temperature sensor should not be triggered by humidity, and the humidity sensor should not react to heat. The research teams worked closely to overcome these challenges through careful material choice and clever circuit design.
The project has already sparked commercial interest. Two researchers from EPFL are launching a start-up called Circelec to bring this technology to the market. Meanwhile, the Empa team plans to explore how similar green electronic labels could be used for agriculture, environmental monitoring, and other sustainability-focused applications.
This new smart tag shows how innovative design can make modern supply chains both safer and more environmentally friendly—one biodegradable sticker at a time.
