Artificial leaf sensor could revolutionize crop management

By precisely detecting moisture ranges, this synthetic leaf sensor may assist improve crop yields whereas decreasing the necessity for pesticides.

In agriculture, extra water provokes plant illness, resulting in decrease crop yield and an estimated world annual lack of a whole lot of billions of {dollars}. This occurs as a result of moist leaves current optimum situations for pathogens. By carefully controlling the time water stays on the leaf floor after rain or irrigation, not solely can crop loss be decreased nevertheless it may additionally assist keep away from pointless pesticide use.

Growers can use industrial leaf wetness sensors to estimate the time leaves stay moist. The sensors encompass an digital circuit that measures electrical impedance modifications brought on by a water movie or drops deposited on the sensor’s floor. Though useful, they’re designed as a blanket sensor for every type of leaves. Nevertheless, completely different crops’ leaves have distinctive morphology and compositions that have an effect on their “wettability”.

Relying on the crop, custom-made sensors may higher measure wetness, say a crew of researchers from the Environmental Research and Electrical and Pc Engineering Departments of the College of California Santa Cruz (UCSC).

In a examine not too long ago revealed in Superior Sensor Analysis, the scientists launched a variety of synthetic leaf sensors that carefully mimic the form and texture of the true leaves higher than commercially out there sensors.

“The sensors encompass two parts: a capacitive sensor that operates equally to commercially out there leaf wetness sensors, and a silicone duplicate of the leaf of curiosity created with tender lithography strategies,” mentioned Marco Rolandi, professor on the UCSC and lead writer of the examine. “The duplicate floor mimics the leaf’s floor form and texture, and the chemistry of the silicone mimics its wetting habits.”

Bricolage silicone leaves

To review the sensor perform, Rolandi and the crew created replicas for 3 completely different leaves from crops usually present in coastal California: California Bay (Umbellularia californica), Western Sycamore (Platanus racemosa), and a horticultural number of escallonia (Escallonia x Iveyi), through which wettability varies from excessive for Sycamore to low for California Bay.

First, they made a damaging mould of every leaf with an answer of a polymer referred to as polydimethylsiloxane, or PDMS for brief, that when cured creates a tender silicone. The duplicate mould was positioned face down over one other layer of uncured PDMS positioned on the digital element of the sensor that measures moisture ranges. When cured, the feel and form of the leaves are imprinted, creating a duplicate in silicone of the unique leaf.

To evaluate how comparable measured wetness was between the leaf sensors and their pure counterparts, the scientists measured the angle fashioned by droplets of water on the leaves’ floor. A much bigger angle signifies the leaf is much less wettable, and a smaller angle signifies the leaf is extra wettable, that means the water takes longer to go away the leaf floor.

Their experiments decided that the wettable properties of the factitious leaves had been much like the pure leaves, whereas a industrial sensor used for comparability confirmed poor outcomes when in comparison with the three examined leaves.

Beneath a microscope, the crew noticed that their silicone leaves contained the identical advanced venation patterns discovered within the unique leaves, which may clarify their superior skill to imitate the water-retaining properties in comparison with the industrial sensor with its generic floor. However even when the form and texture of the leaf could be replicated, chemical composition impacts wettability and wanted to be taken under consideration.

“Within the case of the silicone we used, its composition has hydrophobicity [ability to repel water] much like the floor of the leaves we had been excited about, which allowed us to reduce the necessity for additional therapy,” mentioned Rolandi. “Nevertheless, completely different plant species range so much in how wettable their leaves are; if we had been making an attempt to copy the superhydrophobic properties of a lotus leaf, for instance, we might have wanted to include extra hydrophobic performance.”

When working with hydrophilic or “water-loving” leaves, the authors defined they may add extra hydrophilicity to the leaf replicas by performing a chemical response referred to as oxygen plasma, which provides hydroxyl (-OH) teams to the PDMS floor. These -OH teams chemically work together with water molecules by way of a reversible bond referred to as a hydrogen bond, which permits the water to remain longer on the factitious leaf sensor floor.

Wetness sensors for each crop and each grower

Earlier than these leaf wetness sensors can be utilized in agricultural administration, additional enhancements are wanted. For one, the oxygen plasma therapies final solely a number of hours, which suggests a longer-lasting resolution is required earlier than they can be utilized within the subject. Furthermore, when making an attempt to copy water-repelling leaves, extra modifications should be made to the PDMS floor to make it repel water.

The authors defined the supplies to provide a {custom} sensor value about $5 USD per unit, making it inexpensive for all agricultural producers. “Our objective has at all times been to provide sensors which can be accessible and helpful for small-scale growers in addition to giant industrial enterprises, as a result of monitoring leaf wetness is a important software in illness administration in any respect scales,” mentioned Rolandi.

“This sensor may have purposes in natural agriculture, to help in cultural practices that scale back illness stress, in addition to in typical farming, to help illness forecasting fashions that assist farmers scale back the usage of pesticides. We stay optimistic that our tutorial analysis could ultimately result in the creation of a product that may profit society,” he added.

Reference: Brian H. Nguyen, et. al., A Bio-Mimetic Leaf Wetness Sensor from Duplicate Molding of Leaves, Superior Sensor Analysis (2023). DOI: 10.1002/adsr.202200033

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