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This paper shows the feasibility of a High Frequency RFID passive sensor tag equipped with a novel humidity sensor based on a Si substrate, properly functionalized with a solution of nanoparticles of TiO 2 in order to increase its sensitivity. The characterization of the sensor is performed at variable humidity and using a properly designed front-end circuit. The reading circuit employed in the final prototype is tailored on the energy harvesting requirement. The obtained results prove that the solution conceived is satisfactory and that the sensor has good sensing properties in a large humidity range. The proposed system can be applied in the IoT framework in manifold monitoring scenarios, especially in humidity and soil moisture applications.

Metal oxide gas sensors (MOX) are widely used in olfactory systems for their high sensitivity and low-cost. These sensors vary their conductivity in presence of oxidizing and reducing gases and their performance is strictly dependant on the measurement technique adopted. In this paper the authors present results concerning the selectivity enhancement of an electronic nose based on MOX sensors, proposing also a gray-box model to describe the sensor response in presence of oxygen and CO during sensor temperature modulation.