Irène Esteban

Mass sensitivity of SH-APM sensors: potentialities for organophosphorous vapors detection

Abstract Using the mathematical software MapleV, a model was previously developed to determine the mass sensitivity of Shear Horizontal Acoustic Plate Mode (SH-APM) sensors. The theoretical approach and results obtained are briefly recalled in this paper. They led to the realization of test devices. To validate the model in the case of a mass loading effect, SH-APM devices were tested in gas medium and allowed the detection of organophosphorous vapors.

Using a formal mathematics software for SH-APM sensor modelling

Abstract Shear horizontal acoustic plate mode (SH-APM) sensors have been receiving a great deal of attention in biochemical applications for a few years [1–3]. They consist of a quartz plate with two interdigital transducers (IDTs) deposited on one surface, and a sensitive and selective coating layered on the opposite surface along which the wave interferes. The sensor sensitivity to mass loading, the acousto-electric effects, and the influence of viscosity, conductivity and temperature depend strongly on the considered mode and on the geometrical parameters of the delay line. Moreover, the nature and the crystallographic cut of the substrate, the ratio between the plate thickness and the wavelength, and the operating temperature are also important parameters. Systematic experimental studies are all the more difficult to achieve since there are many propagation modes and various detection mechanisms. As a consequence, our research on SH-APM sensors involves modelling devices. The modelling based on a ‘matrix approach’ was carried out with the help of the formal mathematics software MapleV. In this paper are reported the analytical and numerical results obtained with the software, as well as the calculation of the SH-APM phase velocity that can propagate in thin quartz plates of particular crystallographic cuts. These theoretical results are compared with experimental responses.

Temperature-compensated SH-APM sensors: new theoretical and experimental results

Our aim is to study acoustic wave devices for sensing applications in gas or liquid media. Compared to surface acoustic wave (SAW) devices, shear horizontal acoustic plate mode (SH-APM) devices are based on thin piezoelectric plates, so that a great number of stationary waves, or plate modes, can propagate. SH-APM devices present two main advantages. Firstly, they are able to work in a liquid medium without excessive acoustic loss. Secondly, they can work in an aggressive medium, by using the unmetallized quartz surface for detection. As temperature variation is a critical parameter, it is important to know the device behaviour with temperature. This was already achieved for SAW devices, and it has been done partially for SH-APM devices. In this paper, we propose to recall main theoretical results, and to use the model approach to study particular SH-APM devices, from a theoretical and an experimental point of view.