Femtosecond Laser Micromachining of the Mask for Acoustofluidic Device Preparation

Surface acoustic wave (SAW)-based acoustofluidic devices have shown broad applications in microfluidic actuation and particle/cell manipulation. Conventional SAW acoustofluidic device fabrication generally includes photolithography and lift-off processes and thus requires accessing cleanroom facilities and expensive lithography equipment. In this paper, we report a femtosecond laser direct writing mask method for acoustofluidic device preparation. By micromachining of steel foil to form the mask and direct evaporation of metal on the piezoelectric substrate using the mask, the interdigital transducer (IDT) electrodes of the SAW device are generated. The minimum spatial periodicity of the IDT finger is about 200 mu m, and the preparation for LiNbO3 and ZnO thin films and flexible PVDF SAW devices is verified. Meanwhile, we have demonstrated various microfluidic functions, including streaming, concentration, pumping, jumping, jetting, nebulization, and particle alignment using the fabricated acoustofluidic (ZnO/Al plate, LiNbO3) devices. Compared to the traditional manufacturing process, the proposed method omits spin coating, drying, lithography, developing, and lift-off processes and thus has advantages of simple, convenient, low cost, and environment friendliness.