Ultrathin sensors could aid precision farming

A new method for making ultrathin sensors, developed by researchers at KAUST, could hold promise for precision farming through real-time crop health monitoring.

Image by Pete Linforth from Pixabay

The team at KAUST (King Abdullah University of Science and Technology), Saudi Arabia, believes that the technique could help farmers to grow more food without putting extra demands on the land. 

Increasing agricultural output in response to growing populations without clearing more land or applying excessive fertilisers is a challenge faced by farmers. 

Precision farming, which involves real-time monitoring of plant needs and responding to them with the necessary amount of water, light or nutrients could provide a solution but comes with challenges, explained KAUST PhD student Abdullah Bukhamsin.

“Precision farming typically relies on soil-based sensors or drones fitted with special cameras,” said Bukhamsin. “But they cannot capture changes in the plant early enough to enable intervention.”

Previous research has shown that measuring bioimpedence — how easily an electrical current passes through organic tissues — can reveal a plant’s physiological information such as its nitrogen and water content, presence of fungal infections or metal contaminants.

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Bioimpedance sensors must pierce a plant’s thick outer layer, which blocks electrical signals, without affecting the properties they wish to measure. Manufacturing instruments small and thin enough to do this is challenging.

Bukhamsin and a research team led by Khaled Salama are now said to have developed an efficient method for making silicone moulds that can be used to manufacture such ultrathin microneedles, which can be released intact by submerging the mould in trichloromethane.

The swelling causes the mould to slightly expand, Bukhamsin said, gently pushing the trapped structure out. According to researchers, the reusable moulds could enable cost-effective mass production of microneedles in various plant-friendly polymers.

When the team tested its microneedle on an Arabidopsis thaliana leaf, the puncture hole reportedly sealed within four days and the plant was unharmed. 

“In our tests, the impedance measurements were closely related to how much light a plant has been exposed to and how dehydrated it is,” Bukhamsin said. “This bioimpedance data could be used alongside shading technologies and an irrigation system that responds to the actual needs of crops, thereby avoiding overwatering.”

The team reported an almost identical relationship in other crops including date palm and barley, highlighting the versatility of the approach. The study is published in Advanced Science.

Next steps, Salama said, will include exploring other environmental factors that affect the impedance of plants and how electrochemical measurements could be used to quantify hormone levels in different plant species, fine tuning the approach for precision farming.