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

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Abstract

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 μm 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 ∼pL droplets without clogging issues, the acoustic ejector has great potential for demanding biochemical applications.

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... Gentle acoustic fields with the ability to maintain cells in their native state in their original culture without harm shows the potential to generate and print the droplet containing single cells [45,46,[100][101][102][103][104][105]. In 2007, Demirci et al. applied a gentle acoustic field to generate picolitre droplets containing cells from a microfluidic chip and increased the reliability of cell encapsulation efficiency by as high as 98.4% (Figure 2a) [45]. ...
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