Scientists from the North Carolina State University have developed a wearable with a difference: It's designed for plants, to attach to their leaves in order to monitor disease and other stressors.
"We've created a wearable sensor that monitors plant stress and disease in a non-invasive way," Qinshang Wei, assistant professor of chemical and biomolecular engineering and co-corresponding author of the paper detailing the work, "by measuring the volatile organic compounds (VOCs) emitted by plants."
"Our technology monitors VOC emissions from the plant continuously, without harming the plant. The prototype we've demonstrated stores this monitoring data, but future versions will transmit the data wirelessly. What we've developed allows growers to identify problems in the field — they wouldn't have to wait to receive test results from a lab."
Typically, plant stress and disease monitoring is a very laborious affair: Samples are taken, sent away to a lab, analysed, and the results sent back. There's a lag, then, between the sample being taken and the results being received - and the results represent only one moment in time.
The 30mm patches, built from a combination of graphene-based sensors and flexible silver nanowires, are coated with chemical ligands that respond to the presence of specific VOCs — detecting the presence and volume of each.
The team's prototype was attached to tomato plants and used to monitor stress caused by physical damage and by infection by the pathogen responsible for blight disease. In the case of physical damage, the stress was detected within one to three hours; for the blight disease, it took longer at three or four days.
"This is not markedly faster than the appearance of visual symptoms of late blight disease," Wei admits. "However, the monitoring system means growers don't have to rely on detecting minute visual symptoms. Continuous monitoring would allow growers to identify plant diseases as quickly as possible, helping them limit the spread of the disease."
"Our prototypes can already detect 13 different plant VOCs with high accuracy, allowing users to develop a customized sensor array that focuses on the stresses and diseases that a grower thinks are most relevant," adds Yong Zhu, co-corresponding author of the paper and Andrew A. Adams Distinguished Professor of Mechanical and Aerospace Engineering at NC State.
"It's also important to note that the materials are fairly low cost. If the manufacturing was scaled up, we think this technology would be affordable. We're trying to develop a practical solution to a real-world problem, and we know cost is an important consideration."
The team's work, which will now shift to adding wireless data gathering and the ability to sense environmental conditions as well as plant VOCs, has been published under closed-access terms in the journal Matter.