Performance Analysis of a Humidity Sensor Based on a Microresonator Functionalized with TiO2Nanoparticles

This article proposes a novel humidity sensor based on a low-frequency micromachined electromechanical resonator functionalized with nanoparticles of TiO2 deposited on a preparation layer of Al2O3 nanoparticles. Using a low-frequency resonator allows for obtaining a better immunity to the nonidealities of the conditioning electronics components and minimizes the degradation of the resonator quality due to the deposition of the sensing material. In this article, a relationship is derived between the sensor construction parameters, the obtainable sensor resolution, and the requirements in terms of resolution and accuracy of the measurement system, showing the applicability of such sensors in the context of low-cost, low-power distributed sensing systems. An ad hoc characterization system allowed for characterizing the proposed sensor, proving that this solution is viable and requires a simple preparation route and that the sensor has satisfactory performance in a large humidity range. It was shown that the sensitivity can be increased simply by repeating the TiO2 nanoparticle deposition obtaining at least an increase of the relative sensitivity of 5 ppm/1% RH at each deposition step.