Investigation of SAW atomization

Surface acoustic wave atomization is promising in various kinds of industrial and pharmaceutical processes. In order to properly apply this technology for a wide range of applications, controlling the aerosol size distribution is crucial. It is widely believed that the aerosol size can be controlled by the driving frequency, our experimental results, show a rather weak frequency dependence, especially when the driving frequency is above 10 MHz. Fundamental studies were therefore carried out to determine the underlying mechanism associated with the destabilization of the liquid interface leading towards atomization with the objective of elucidating this apparent contradiction. Our investigation supports the notion that the droplet sizes appear to be governed by the capillary vibration frequency given by a balance between the capillary stress and viscous forcing, not the driving frequency as previously claimed. Furthermore, the aerosol size can be altered by controlling the surface tension and viscosity. For this case, we employ the laser diffraction to obtain the size distributions of octanol aerosol and water aerosol generated by SAW atomization. The experimental results matches our theocratical prediction that water, with higher surface tension and lower viscosity, generates relatively larger aerosols than octanol.