A biodegradable magnetic field sensor printed on a tomato – an example of sustainable bioelectronics. © Lin Guo
The small magnetic field sensor that was printed on the tomato is tiny and hard to see. While such sensors are often made of environmentally harmful materials, this sustainable alternative is biodegradable and resource-saving.
The new product was developed by an international team led by scientists from the Helmholtz Center Dresden-Rosendorf (HZDR). The sensor is made of iron and iron oxide embedded in a layer of cellulose, beeswax and starch. The cover made of natural materials serves as protection against moisture. If this dissolves, only oxidized iron, i.e. rust, remains.
Magnetic field sensors are used in numerous products and can perform various tasks. They measure movements, positions or distances and are installed in packaging or cell phones, among other things. Magnetic field sensors can also be used in smart agriculture, for example to monitor harvest conditions. The organic coating of the sensors plays a special role here, as it can rot without polluting the environment.
In contrast to conventional magnetic field sensors, the sustainable alternative does not contain materials such as nickel or cobalt, which are harmful to the environment or can endanger human health. In addition, the new sensors save resources and energy in production. However, producing highly sensitive sensors from degradable materials also represents a technical challenge. That is why the scientists have developed core-shell particles in which an iron core is surrounded by a thin layer of oxide in order to achieve high sensitivity.
The sensors are manufactured using a screen printing process. Instead of laboriously removing material, as is common in other areas of application, the sensor layer is applied here in a targeted manner. “We only print sensors where we need them,” explains Marakov, head of the Intelligent Materials department at HZDR. This saves energy and materials.
The printed sensor technology has already been licensed. The team is now working on specific applications. The sensors are intended to be used primarily in disposable medical products or sensor systems for agriculture, where the electronic components are only needed for a limited period of time. By encapsulating the printed sensors, the service life can be individually tailored to different applications. In this way, the sensors can help produce electronics more sustainably in the future.