Abstract
This paper reports the numerical and experimental analysis of the acoustic streaming effect in a fluidic domain. The actuation of a piezoelectric transducer generates acoustic waves that propagate to the fluids, generating pressure gradients that induce the flow. The number and positioning of the transducers affect the pressure gradients and, consequently, the resultant flow profile. Two actuation conditions were considered: (1) acoustic streaming generated by a 28 μm thick β-poly(vinylidene fluoride) (β-PVDF) piezoelectric transducer placed asymmetrically relative to the fluidic domain and (2) acoustic streaming generated by two 28 μm thick β-PVDF piezoelectric transducers placed perpendicularly to each other. The transducers were fixed to the lower left corner of a poly(methyl methacrylate) (PMMA)cuvette and were actuated with a 24 Vpp and 34.2 MHz sinusoidal voltage. The results show that the number of transducers and their positioning affects the shape and number of recirculation areas in the acoustic streaming flows. The obtained global flows show great potential for mixing and pumping, being an alternative to the previous geometries studied by the authors, namely, a single transducer placed symmetrically under a fluidic domain.
Highlights
One of the major requirements for a fully-integrated microfluidic device is the ability to automatically mix and control fluids in a reasonable time [1,2]
The results show that the number of transducers and their positioning affects the shape and the number of recirculation areas in the acoustic streaming flows and, affects the mixture
When compared to the authors’ previous works, where a single transducer was placed in the center of a cuvette face, the acoustic actuation lead to the formation of two large symmetric recirculation areas, which does not occur in the present work, showing that the position of the transducer relatively to the fluidic domain has a great impact on the acoustic streaming flow
Summary
One of the major requirements for a fully-integrated microfluidic device is the ability to automatically mix and control fluids in a reasonable time [1,2]. Acoustic streaming has become one of the most effective techniques, with no mechanical parts, for promoting mixing and pumping in fluidic devices [2,3,4,5], since this technique overcomes the limitations of mixing in micro scale systems. Acoustic streaming uses a piezoelectric transducer for generating acoustic waves that are absorbed by the fluids. This mechanism promotes pressure gradients that, when properly induced, generate the fluid flow and mixing [11,12,13]. The harmonic oscillation of the solid boundary near the fluid generates the propagation of the acoustic waves in the fluid as well as a steady mean flow field [12]
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