Acoustofluidics Along Inclined Surfaces Based on AlN/Si Surface Acoustic Wave Devices

In this paper, we report acoustofluidic behaviors (including pumping and jetting) along inclined surfaces using aluminum nitride (AlN)/Si Rayleigh surface acoustic waves (SAWs). It has been demonstrated that when the droplet has a small volume (e.g. below 3 μL), they can be efficiently transported on arbitrary inclined surfaces. The gravity effect plays an important role in uphill climbing of the droplet with the increased inclination angle. At 90° inclination angle, a higher threshold power is needed to pump up the droplet and the pumping velocity also reaches its minimum value. Besides, for smaller size droplet, effects of surface inclination angle on the droplet jetting angles are negligible.