Effect of contact diameter of the sessile droplet on saw attenuation for potential microfluidic applications

This paper reports the effect of contact diameter of the sessile droplet on surface acoustic wave (SAW) attenuation for potential microfluidic applications. An aluminum nitride (AlN) based SAW device, operating at 120.44 MHz, was fabricated for liquid sensing. It has been firstly demonstrated that when the droplet contact diameter is larger than the SAW attenuation length (L
Saw
∼ 420 μm), the SAW attenuation mostly depends on the contact diameter of the droplet more than the contact angle. Whereas, for multiple droplets on the propagation surface, the SAW attenuation is determined by the contact width of the droplet rather than the contact area.