Flow characteristics in microfluidic devices is turally lamir due to the small channel dimensions. Mixing based on molecular diffusion is generally poor. In this article, we report the fabrication and characterization of active surface-acousticwave-driven micromixers which exploit the acoustic streaming effect to significantly improve the mixing efficiency. A side-by-side flow of water and fluorescent dye solution was driven by a syringe pump. Surface wave with a frequency of 13 MHz was launched perpendicular to the flow. The wave was generated by two designs of interdigitated electrodes on LiNbO3 substrate: parallel electrodes and focusing electrodes. The mixing efficiency was observed to be proportiol to the square of the applied voltage. Under the same applied voltage, the focusing type offers a better mixing efficiency. The fabrication of the micromixer is compatible to current technology such as soft lithography and deep reactive ion etching. Despite the high throughput and fast mixing time, the mixer design is simple and could be integrated into any microfluidic platform.
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