Tattoo-like Flexible Ethylene Sensor for Plant Stress Monitoring in Real-time

This paper presents a flexible tattoo sensor for real-time monitoring of gaseous ethylene released from plant leaves. To the best of our knowledge, this is the first reported plant tattoo sensor that can measure and monitor a plant hormone in situ . The tattoo sensor can be easily installed on leaves and removed when required using a stick-and-peel mechanism. Furthermore, temperature and humidity sensors were incorporated to correct the ethylene measurements based on the specific microclimate of the leaf. All sensors were chemiresistive in nature, causing variations in resistance as a result of changes in temperature, humidity, or ethylene. The ethylene sensor demonstrated a sensitivity of 0.6295 kΩ/ppm and a limit of detection of 0.13 ppm. The measurements were processed by an onboard data logger, transmitted wirelessly to the cloud, and accessed on a smartphone. Plants were subjected to multiple stressors, including water, temperature, and dark stressors, and the real-time ethylene measurements were recorded with the tattoo sensor. A statistically significant difference, characterized by p values less than 0.05, was observed between different types of stresses. Roll-to-roll fabrication of these tattoos will enable their large-scale implementation in greenhouses and agricultural fields.