Mass Sensitivity of the Thin-Rod Acoustic Wave Sensor Operated in Flexural and Extensional Modes

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Abstract
The mass sensitivities of the thin-rod acoustic wave sensor in both flexural and extensional acoustic modes are presented. These are based on experiments involving the electrodeposition of a test loading material onto a thin metal fiber (the thin rod) in a delay line configuration. Only small changes in acoustic loss occur when the device is immersed in an electrolyte, particularly in the flexural mode. Copper and lead have been used as test materials to confirm that the effects of elasticity can give rise to positive and negative mass sensitivities, respectively. The experimental and theoretical values all agree in sign and are of the same order of magnitude. This result confirms a refined theoretical model that includes incorporation of the effects of elasticity and inertia. An increase in experimental mass sensitivity with decrease in fiber radius is one of the advantages for the construction of a sensitive chemical sensor based on the thin-rod device. The sensor can be operated with facility in both gas and liquid phases and offers a new technique for the study of interfacial electrochemistry on metal surfaces. The phenomenon of mechanical resonance was observed during a number of experiments.