Generation of droplets for lab-on-a-piezoelectric-substrate utilizing surface acoustic wave

The generation of droplet is indispensable for micro-fluidic device. A new method for generation of droplet was proposed. An interdigital transducer and reflector were fabricated on a 128°yx-LiNbO₃ substrate. A PDMS micro-channel with back taper shape was used to connect a syringe and a needle with sub-micron inside diameter, which was supported by arc PDMS. The tip of the needle was above the piezoelectric substrate with small distance. Fluid was aggregated at the tip of the needle due to the syringe pump. As soon as the fluid was large enough and contacted to the piezoelectric substrate, the fluid was driven by surface acoustic wave and finished the generation of one droplet. Red dye solution was used to generation experiment of droplet. Results show that the volume of generated droplet is decided on the needle radius, the gap between the needle and the piezoelectric substrate and RF signal power. The method of droplet generation is useful for lab-on-a-piezoelectric-substrate for biochemical analysis.