Inter-digital transducers activated acoustic streaming in viscous liquid

Acoustic streaming induced by surface acoustic waves (SAWs) has been widely utilized in various medical and biology applications. For most of the applications, the microfluidic channel is attached to a piezoelectric substrate where the inter-digital transducers (IDTs) are fabricated on it to activate acoustic waves. The acoustic waves would propagate along the substrate surface and generate the “leaky wave” in the channel which causes the acoustic streaming. However, few studies are conducted to analyze the vibration mode of the substrate in the IDTs area and the following phenomenon (e.g., acoustic streaming generated by substrate vibration). In this study, we demonstrate a novel method which includes both simulation and experiment results to identify the substrate vibration and corresponding streaming while the liquid is loading upon the IDTs directly. With this method, we show that the acoustic streaming on top of the IDTs area has a “stagnation point” with a velocity potential to trap and manipulate the objects floating on the surface of the liquid, which is promising in many contactless biomedical applications.