Developments for SAW-based aerosol generation: Miniaturized, cost-efficient, mass-producible, and reproducible systems

Abstract

Surface Acoustic Wave (SAW) aerosol generators, also known as SAW nebulizers or SAW atomizers, are gaining widespread interest in a variety of technical processes due to their ability to produce directed fine mist aerosols with a narrow size distribution and at low shear forces. The interaction of a regulated microscale liquid film with an acoustic wave field on a microfluidic chip surface results in SAW aerosol generation. Future real-world applications require on-chip integrated microfluidic channels for low-cost fabrication of acoustofluidic chips with the required high fluid supply accuracy and reproducibility. In this work, SAW aerosol generation chips employing focused and straight IDTs as well as wafer-scale integrated microfluidic fluid feed channels created by a dry film photoresist multi-stage lamination and lithographic patterning technique were fabricated and validated regarding their performance. The manufactured chips were used with a highly-compact, cost-effective, and easy-to-handle chip holder for experimental studies. Using different SAW chips and liquids, atomization working regimens were determined. The aerosol generator achieved operation at flow rates of 10 μL/min and input power levels of 1 W. The implications of SAW wavelength, IDT type, applied power, liquids, and flow rate on device functionality are explored. Using laser diffraction analysis, it is shown that a simple chip-scale platform is capable of achieving a variable droplet size range. The developed SAW aerosol sources are currently the most advanced demonstrated in the literature and can be used in a variety of technical processes, including mass-spectrometry, olfactory displays, and aerosol-based printing.