Mass sensitivity of thin rod acoustic wave sensors

Theoretical and experimental investigations of mass sensitivities of thin rod acoustic wave sensor are presented. From the low-frequency approximation of the dispersion equations, explicit forms of the relation describing the mass sensitivity are derived with the consideration of the effects due to elasticity and inertia of the loading layer. The three lowest thin rod acoustic modes are presented. Mass sensing experiments are based on the electrodeposition of loading material on a thin metallic fiber (the thin rod). Copper has been used to load the propagation of acoustic waves in gold fibers. The mass of copper deposited and the phase shift of the acoustical thin rod delay line were monitored simultaneously by a computer. Mass response curves showing the variation in phase due to the mass deposited per unit surface area were then obtained in order to determine the mass sensitivity. Both flexural and extensional wave modes have been excited. Theoretical and experimental results were found to be consistent in both sign and magnitude.