Stretchable Sensor for Sustainable Precision Agriculture

Abstract

This paper presents the design, fabrication, and characterization of a stretchable strain sensor designed for sustainable precision agriculture, specifically targeting real-time fruit growth monitoring. The sensor is fabricated using eco-flex 00-30, a highly stretchable elastomer as substrate and encapsulation, with liquid metal (Galinstan) serving as the conductive channel, deposited through a liquid metal spray deposition technique. The sensor is formed into a cylindrical shape to ensure optimal contact and conformability with the fruit skin and shape. This allows it to conform seamlessly and accommodate growth variations in the 20-80mm range, which is particularly suitable for deployment in orchard environments where continuous growth tracking is essential. At 0%, i.e., 20mm in diameter, the sensor exhibits a base resistance of 2.40 Ω, and at 300%, which is equal to 80mm in diameter, the sensor shows a response of 20.7 Ω. The sensor was tested using a tensile machine to validate the stretchability and stability of up to 300% strain. Environmental stability was further assessed by evaluating the sensor response for outdoor applications by integrating multiple sensors in climate chambers and in the open environment. The proposed sensor is cost-efficient, reliable, and well-suited for real-time growth monitoring. This work presents a significant advancement in developing an innovative contact-based sensing platform for precision agriculture.