Mechanism and stability investigation of a nozzle-free droplet-on-demand acoustic ejector

This paper investigates the mechanism of a new acoustic micro-ejector using a Lamb wave transducer array, which can stably generate picoliter (pL) droplet jetting without nozzles. With eight transducers arranged as an octagon array, droplets are ejected based on the mechanism of combined acoustic pressure waves and acoustic streaming. The acoustic focusing area is designed as a line at the liquid center, which is the key factor for a large working range of liquid height. The experimental results show that the ejector can produce uniform water droplets of 22 mu m diameter (5.6 pL in volume) continuously at a rate of 0.33 kHz with high ejection stability, owing to a large liquid height window and high acoustic wave frequency. By delivering precise similar to pL droplets without clogging issues, the acoustic ejector has great potential for demanding biochemical applications.

Automated summary

This study explores the mechanism of a new acoustic micro-ejector using a Lamb wave transducer array, which can stably generate picoliter droplet jetting through a combination of acoustic pressure waves and acoustic streaming. Experimental results demonstrate that the ejector can continuously produce uniform small water droplets at a high rate, thanks to a large liquid height window and high ejection stability, making it suitable for demanding biochemical applications.