Gravimetric response of the rod acoustic wave sensors

Theoretical and experimental investigations of mass sensitivities of thin rod acoustic gravimetric sensors are presented. Effects of the elasticity and the inertia of the mass loading layer are included in the model. Gravimetric sensing experiments are based on a computer monitored electrodeposition process which involves the deposition of loading material on thin metallic fibres. The deposited mass and the phase shift of the acoustic fibre delay line are monitored simultaneously which enables the determination of detailed gravimetric response curves. Both flexural and extensional wave modes have been excited in gold and nickel fibres whose diameters are 25 μm. Copper and polypyrrole have been used as loading materials. Results obtained theoretically and experimentally are consistent. A porous graphite fibre of 12 μm diameter has also been used to detect various concentrations of CO₂ in a controlled gas chamber