Screen-printed, biodegradable soil sensors that can be composted at their end of their lifecycle could enable farmers to improve crop yields while reducing electronic waste, researchers say.

The sensors, developed by engineers from the University of Glasgow, UK, in collaboration with colleagues from the Łukasiewicz Institute of Microelectronics and Photonic (IMiF), Poland, are made from electronic materials which degrade into plant nutrients, acting as fertilizer to help crops grow.

The research is a key development in a wider international project called TESLA, which stands for Transient Electronics for Sustainable ICT in DigitaL Agriculture. The £1.8m project is funded by UK Research and Innovation and CHIST-ERA, a consortium of research funding organisations in Europe and beyond.

The project aims to develop a complete system where the biodegradable sensors are powered by solar cells and supercapacitors also made from sustainable materials, enabling a fully environmentally friendly solution for precision agriculture monitoring.

The biodegradable front-end sensors are paired with conventional electronics to monitor crop health. The research team say their modular approach enhances the reusability of the overall existing electronic systems and significantly reduces electronic waste, resulting in a much lower overall environmental impact. Detailed environmental impact assessments conducted by the researchers shows that operating the electronics in this way improves sustainability.

In a paper published in the journal ACS Applied Electronic Materials, the team describe how they made a digital agriculture sensor from sustainable materials, combining a biodegradable patch with a matchbook-sized reusable electronic module. The sensor patches are manufactured using a screen printing process, similar to that used in t-shirt printing. In this work, conductive tracks are printed onto a biodegradable polymer substrate using graphene-carbon ink. Then, a sensing layer made from molybdenum disulfide is printed on top – so all materials used naturally break down into plant nutrients.

Data from the sensors, which are sensitive to the changes in pH and temperature which can be caused by infections in crops, are collected by the electronic module. The data can be sent wirelessly to computers, which could in the future help farmers build up a detailed picture of the health of their crops.

Lab tests showed the sensors can reliably monitor soil pH levels, with consistent performance demonstrated in solutions ranging from pH 3 to pH 8 over the course of two weeks. The team also demonstrated that that the sensors can detect traces of ethephon, a widely used plant growth regulator that can be toxic to humans and wildlife if it contaminates groundwater. At the end of their useful lifecycle, the sensors degrade into key primary and secondary nutrients to support future plant growth.

The James Watt School of Engineering’s Professor Jeff Kettle led the research. He said: “We’re keen to continue expanding our biodegradable sensor’s ability to detect other key indicators of plant growth and soil health. That could include adding sensitivity to ‘forever chemicals’ like PFAs, which have significant environmental impact.”

The international project TESLA is led by the University of Glasgow and brings together partners from McGill University in Canada, Tampere University and VTT Technical Research Centre of Finland Ltd in Finland, Łukasiewicz Research Network – Institute of Microelectronics and Photonics in Poland, and the CSEM Centre Suisse d’Electronique et de Microtechnique SA in Switzerland. Researchers from the Łukasiewicz Research Network – Institute of Microelectronics and Photonics and Central South University of Forestry and Technology co-authored the paper.

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