Acoustically Driven Liquid Atomization on the Bottom Surface of SAW Device with Physical Separating from IDTs

In traditional surface acoustic wave (SAW) atomization, the liquid is directly positioned on the top surface of the device where the interdigital transducers (IDTs) are attached. During atomization, large droplets are continuously generated and tend to settle onto the IDTs, weakening the driving capability of the SAW device and, in severe cases, irreversibly damaging the IDTs and leading to device failure. To address this issue, this study optimizes the h_s/λ parameter (where h_s is the thickness of the piezoelectric substrate and λ is the wavelength) through finite element simulation, concentrating energy in the central region of the IDTs projection on the bottom surface. Droplet translation experiments confirm that the droplets positioned at various locations on the bottom surface of the SAW device always move toward the center area under coupling SAW excitation. When the input power reaches a threshold, the liquid located behind the IDTs is first stretched into a thin film on both sides, which then fragments into micrometer-scale aerosols under the action of surface capillary waves. This design achieves physical separation between the liquid supply and the atomization zone, as well as the IDT electrodes. By enabling atomization on the bottom surface, it facilitates rapid heat dissipation from the top electrode area, significantly extending the operational lifespan of SAW devices while avoiding electrode damage caused by droplet settling.