Abstract
Nozzleless jetting of droplets with different jetting angles is a crucial requirement for 2D and 3D printing/bioprinting applications, and Rayleigh mode surface acoustic waves (SAWs) could be a potential technique for achieving this purpose. Currently, it is critical to vary the jetting angles of liquid droplets induced by SAWs and control the liquid jet directions. Generally, the direction of the liquid jet induced by SAWs generated from a bulk piezoelectric substrate such as LiNbO3 is along the theoretical Rayleigh angle of ∼22°. In this study, we designed and manufactured thin-film SAW devices by depositing ZnO films on different substrates (including silicon and aluminium) to realize a wide range of jetting angles from ∼16° to 55° using propagating waves generated from one interdigital transducer. We then systematically investigated different factors affecting the jetting angles, including liquid properties, applied SAW power and SAW device resonant frequency. Finally, we proposed various methods using thin-film SAW devices together with different transducer designs for realizing a wide range of jetting angles within the 3D domain. A nozzleless jetting method is proposed using thin-film based surface acoustic wave devices to achieve a wide range of jetting angles for droplets.
Highlights
In the past a few decades, acoustofluidics has attracted significant interests in the fields of microfluidics [1], xxxx-xxxx/xx/xxxxxx us ∂vj ∂vi ∂(ρv⃗ + ∇. = −∇p⃗ + ∇. [μ ( + fσ )] + ρg⃗ + ⃗⃗⃗⃗ ∂t ∂xi ∂xj + ⃗⃗⃗⃗⃗⃗⃗ FEx
We revealed that the jetting angle is not necessarily equal to the Rayleigh angle of the SAW device
The present results show that using thin-film SAW devices, a wide range of jetting angles can be readily achieved
Summary
In the past a few decades, acoustofluidics has attracted significant interests in the fields of microfluidics [1], xxxx-xxxx/xx/xxxxxx us. When SAWs reach the droplet located on its path, SAW energy is transferred into the liquid medium along the Rayleigh angle [28]: cri pt enabling droplet-based and microchannel-based microfluidics [6,7] Owing to their simple operations as sessile dropletbased devices, they have been demonstrated for various types of droplet manipulation applications such as mixing/streaming [8,9,10], transportation [11,12,13], jetting [14], nebulization [15], and heating [16]. Ce pte where VL and VS are sound velocities in the liquid medium and on the piezoelectric substrate, respectively This energy is capable of creating a large velocity field, which can deform the droplet, leading to the formation of a jet beam We showed that by applying different IDT patterns and electrode designs, including standing wave based IDTs, jetting angles could be varied in a significant wide range in a 3D space, which is useful for printing and bioprinting applications
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