Transistor-based plant sensors for agriculture 4.0 measurements

Sensing technologies are the basic perception layer of the so called "Agriculture 4.0", a novel and fast-growing agricultural revolution playing a promising role in enhancing sustainable farming. Among the different types of sensing locations for "Agriculture 4.0", sensors positioned on the surface of plants or inserted directly in the plants are very important as they enable an early detection of both biotic and abiotic stresses, allowing an early-stage intervention and thereby leading to a possible yield increase. This is why efficient real-time plant sensing technologies enabling continuous measurements of plant health are extremely needed. Common plant measurement approaches are based on non-electrical methods, such as imaging and spectroscopy. Nevertheless, these methods present several drawbacks, e.g., weak specificity, expensive equipment or non-continuous monitoring, which do not make them the ideal choice for this application. In this context, electrical-based approaches and especially field-effect transistor (FET)-based sensors are particularly promising, thanks to their ability to monitor plants continuously with enhanced selectivity and at the same time possibility to use bio-compatible materials. This paper summarizes state-of-the-art literature of FET-based sensors used to monitor plants for agriculture 4.0 applications.