Development of acoustic-wedge-mode humidity sensor using a wedge with hydroscopic film

Anti-symmetric flexural (ASF) modes are anti-symmetric type of guided waves propagating along the tip of wedge-shaped waveguides. While the wedge tips are coated a thin layer of hydroscopic film, the velocity of ASF mode is sensitive the moisture through its contact with the film. This study presents a combined numerical experimental investigation on the effects of moisture for the propagation behaviors of ASF modes. A laser ultrasound technique is applied to measure dispersion spectra of ASF modes propagating along the wedge tips with hydroscopic film under various humidity controlled by a chamber. Finite element simulations are used to simulate the effects of moisture on the dispersion curves of the ASF modes.