Printed RFID sensing system: The cost-effective way to IoT smart agriculture

The increase in global population, climate change and the scarcity of resources are some of the reasons why the improvement of the agricultural sector has become a crucial issue for the future of our society. Recently, the growth of Internet of Things (IoT) has meant a revolution in many industries, including the agricultural sector, where the employment of this technology is considered the ideal formula to boost crop efficiency. In this work we present a complete high performance IoT solution, consisting of an innovative printed smart radio frequency identification (RFID) tag and an autonomous measuring system based on a robotic platform, designed for soil monitoring purposes. The smart RFID tags are employed to obtain soil parameters, crucial for the correct development of the crops: humidity, oxygen concentration and temperature. The tag is novelly developed on a humidity dependent and flexible transparent foil substrate. The former feature enables the direct measurement of relative humidity (RH) by a capacitive structure defined on the substrate while the latter characteristic allows the sensing of oxygen content via a membrane whose luminescence intensity changes with the influence of this parameter. Effects on the antenna response are measured when the tag is placed in soil environment at root depth to validate the excellent sensing behavior of the tag. Finally, to advance the scope of this work and to show the promising performance of the tags as part of a monitoring system in the field of smart agriculture, a robot equipped with an UHF reader and IoT features, capable of automating the finding and reading of the designed RFID tags, is designed. This robot sends the information via internet for its further processing, thus constituting a low-cost, large-scale and environmentally friendly solution, ideal for enhancing crops performance. • A flexible, customizable RFID tag for complete soil monitoring is proposed. • A cellulose-based transparent substrate integrates the printed antenna and sensors. • A numeric method compensates for the thermal drift of the printed sensors. • The tag can be read even when buried and watered at root depth. • An IoT-enabled robot-based system is designed for tag reading.