Wearable sensor for plant leaves warns of heat stress in crops

Researchers reporting in ACS Applied Materials & Interfaces, part of the American Chemical Society, have created a wearable sensor for plant leaves to detect water loss earlier.

Remotely monitor plants’ health

Plant-wearable devices could help farmers remotely monitor their plants’ health, including leaf water content. Previously, researchers had developed metal electrodes for this purpose, but the electrodes had problems staying attached, which reduced the accuracy of the data. So, researcher Renato Lima and colleagues wanted to identify an electrode design that was reliable for long-term monitoring of plants’ water stress, while also staying put.

Two types of electrodes

The researchers created two types of electrodes: one made of nickel deposited in a narrow, squiggly pattern, and the other cut from partially burnt paper that was coated with a waxy film. When the team affixed both electrodes to detached soybean leaves with clear adhesive tape, the nickel-based electrodes performed better, producing larger signals as the leaves dried out. The metal ones also adhered more strongly in the wind, which was likely because the thin squiggly design of the metallic film allowed more of the tape to connect with the leaf surface.

Next, the researchers created a plant-wearable device with the metal electrodes and attached it to a living plant in a greenhouse. The device wirelessly shared data to a smartphone app and website, and a simple, fast machine learning technique successfully converted these data to the percent of water content lost.

Exposure to pests and toxic agents

The researchers say that monitoring water content on leaves can indirectly provide information on exposure to pests and toxic agents. Because the plant-wearable device provides reliable data indoors, they now plan to test the devices in outdoor gardens and crops to determine when plants need to be watered, potentially saving resources and increasing yields.

The authors acknowledge support from the São Paulo Research Foundation and the Brazilian Synchrotron Light Laboratory. Two of the study’s authors are listed on a patent filing application for the technology.