Study on the Generation of Surface Acoustic Waves by Using a Ring-Type Piezoelectric Actuator on a Thick Ringdisk

In this paper we report on a new method to generate radial surface acoustic waves (SAW) on a thick ringdisk. We set up a 0.25mm thick ring-type piezoelectric actuator to generate surface acoustic waves on a surface of a 1mm long stainless-steel pipe with a 5.5mm wall thickness. The boundaries are set to be free at all the edges and surfaces. Finite element simulations were employed to identify corresponding resonance modes and driving frequencies. Radial-type Rayleigh waves were selected and used to design interdigital electrodes on the piezoelectric actuator surface. Based on our design, it is found that a radial Rayleigh-wave-type surface acoustic wave will be generated at 7.42MHz with a substantial amplitude enhancement at the inner surface, which converges from the outer ring to the inner ring on the opposite surface of the disk. Applying this radial Rayleigh wave, we demonstrated that this surface acoustic wave can be used to create acoustic streaming in a droplet.