Acoustofluidic Behaviors of Zno/Al Plate/Sheet Acoustic Wave Devices Using Hybrid Modes

In this paper, we report acoustofluidic behaviors of zinc oxide (ZnO) thin film surface acoustic wave (SAW) devices fabricated on aluminum (Al) plate/sheet (600µm/200µm) substrates using hybrid modes. Finite element analysis (FEA) simulation and experimental results indicate that the wave vibration modes are changed from Rayleigh mode to hybrid modes and subsequently to Lamb wave modes with the increased device's wavelength or decreased substrate thickness. For the Rayleigh, hybrid and zero-order Lamb wave modes, the droplet movement is a combination of rolling and sliding, whereas for Sezawa mode and one-order Lamb wave modes, the droplet movement is a combination of jumping and sliding. Moreover, for Lamb wave modes, the asymmetrical modes present a better pumping performance than those of symmetrical modes.