Concentrated vertical jetting mechanism for isotropically focused Zno/Si surface acoustic waves

Abstract

This paper investigates vertical droplet jetting using circular surface acoustic wave (CSAW) devices with annular interdigitated transducers (AIDTs) fabricated on ZnO film coated silicon substrate. The surface vibration on the CSAW devices was simulated using finite element analysis and characterised using laser vibrometry. Results showed that focused wave patterns and compact nodal distributions of vibration were formed at the centre of ZnO/Si CSAW device, which is contrast to an anisotropic wave distribution patterns generated by the same pattern of AIDTs fabricated on 128 o Y-cut LiNbO3. Simulation of liquid jetting induced by the isotropically focused 2 CSAW was performed using coupled Volume of Fluid and Level-Set method. Results showed that a sharp and cylindrical liquid column was generated from the ZnO/Si CSAW device induced by acoustic energy coming from all directions within the plane due to the in-plane isotropic nature of the ZnO thin films. The simulation enabled us to capture the different streaming/jetting processes induced by the anisotropic distributions of acoustic pressure generated by the AIDTs on the 128 o Y-cut LiNbO3 CSAW device. The concentrated vertical droplet jetting behaviour from the ZnO/Si CSAW devices was investigated experimentally and supported the simulated results.

Acoustic Waves for Active Reduction of Contact Time in Droplet Impact

“…An interface capturing method based on the coupled level-set volume of fluid (CLSVOF) method was developed in OpenFOAM 4.x. Opensource toolbox, and used to capture a sharp and smooth liquid/gas interface and conserve the mass during the calculation [52,53]. A series of validation simulations were performed to reproduce the experimental results and test the capability of the developed numerical method.…”

“…Ca 0.54 (8) Here the capillary number ( a = μU CL γ LV ⁄ ) is defined based on the three-phase contact line velocity, U CL and K was set to 9.63 in all the simulations. More details regarding the CLSVOF method used in simulations are presented in our previous works [52,53].…”

Computational and experimental analysis of droplet transportation/jetting behaviours driven by thin film surface acoustic waves

“…Droplet jetting can happen when the acoustic energy transferred from solid surface to the liquid phase is large enough to overcome the surface tension and gravitational force, and the droplet interface deforms until the droplet is separated from the surface along the Rayleigh angle [45]. To show that the newly developed code is capable of simulating droplet jetting, we reproduce the jetting phenomena for a droplet of 5 µl on a SAW device with the resonant frequency of 271.32 MHz.…”

Numerical and experimental investigations of interdigital transducer configurations for efficient droplet streaming and jetting induced by surface acoustic waves

“…Interfacial phenomena between the solid-liquid-gas interfaces for the liquid actuated by SAWs can be categorized into three main issues for investigation: (1) the liquid-gas interface deformation and two-phase flow problems; (2) TPCL dynamics; (3) the solidliquid interactions. Simulation of the two-phase flow of droplet deformation within the gas (normally atmospheric air) medium has been performed using interface tracking methods (Jangi et al, 2019) and mesoscopic models such as Lattice Boltzmann (LBM) (Sheikholeslam Noori et al, 2020). The dynamics of the TPCL and the interaction between solid-liquid phases have been extensively studied for the droplet motion/impact on the solid surface (Ahmed et al, 2014;Ashish Saha and Mitra, 2009;Griebel and Klitz, 2014;Li et al, 2016;Šikalo et al, 2005).…”