Preliminary results of the feasibility of hydrogen detection by the use of uncoated silicon microcantilever-based sensors

Abstract

International audienceHydrogen is a key parameter to monitor radioactive disposal facility such as the envisioned French geological repository for nuclear wastes. The use of microcantilevers as chemical sensors usually involves a sensitive layer whose purpose is to selectively sorb the analyte of interest. The sorbed substance can then be detected by monitoring either the resonant frequency shift (dynamic mode) or the quasi-static deflection (static mode). The objective of this paper is to demonstrate the feasibility of eliminating the need for the sensitive layer in the dynamic mode, thereby increasing the long-term reliability. The microcantilever resonant frequency allows probing the mechanical properties (mass density and viscosity) of the surrounding fluid and, thus, to determine the concentration of a species in a binary gaseous. Promising preliminary work has allowed detecting concentration of 200ppm of hydrogen in air with non-optimized geometry of silicon microcantilever with integrated actuation and read-out

Geometry optimization of uncoated silicon microcantilever-based gas density sensors

“…The Euler-Bernoulli equation taking into account the hydrodynamic force acting on the uncoated microcantilever is commonly used to model the behavior of resonating microcantilevers in fluid media when the influence of the beam's shearing deformation and rotational inertia can be neglected [8] and [12]. Fig.…”

“…With a view towards chemical detection in gas media, the variation of the gas density can reflect the variation of a chemical species concentration in a gas mixture [8,[12][13][14]. The operating principle of an uncoated silicon microcantilever (USMC) used as a density or chemical sensor is based on the influence of the mass of the fluid moved by the vibrating cantilever on the resonant frequency.…”

“…The operating principle of an uncoated silicon microcantilever (USMC) used as a density or chemical sensor is based on the influence of the mass of the fluid moved by the vibrating cantilever on the resonant frequency. In fact, when the surrounding fluid mass density increases (decreases), the equivalent effective mass of the cantilever increases (decreases), thereby causing the resonant frequency to decrease (increase) [12].…”

Proof of Concept and Preliminary Results of Gas Detection by Measuring the Admittance at the Resonance and Anti-resonance of an Uncoated CMUT

“…However, it has been shown that using a sensitive coating compromises the long term stability of the sensor (Korotcenkov and Cho, 2011) mostly due to aging of such film (Sharma et al, 2001;Romain and Nicolas, 2010). For this reason, there is an increasing interest toward uncoated sensors, which rely on the change of the physical properties of their surrounding gas such as thermal conductivity (Daynes, 1933;Hale et al, 1992;Simon and Arndt, 2002), or mass density (Tétin et al, 2010;Boudjiet et al, 2014;Rosario and Mutharasan, 2014). Despite the lack of selectivity of uncoated sensors, it is still possible to discriminate from different gases by measuring multiple parameters at once (Iglesias et al, 2019).…”

“…This has been used previously for characterizing liquids (Heinisch et al, 2015) and even gases, despite the fact that their mass density and viscosity are much smaller. Gas detection such as hydrogen, carbon dioxide, argon, helium and methane detection have already been demonstrated using uncoated resonant sensors (Tétin et al, 2010;Boudjiet et al, 2014;Rosario and Mutharasan, 2014;Iglesias et al, 2019). These measurements have been performed either using silicon or piezoelectric cantilevers at frequencies below 200 kHz.…”