Acoustic resonances in microfluidic chips: full-image micro-PIV experiments and numerical simulations

Hagsäter, S. M.; Jensen, Thomas Glasdam; Bruus, Henrik; Kutter, Jörg Peter

doi:10.1039/b704864e

Cited by 138 publications

(128 citation statements)

References 24 publications

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“…We can also neglect the influence from the Stokes drag due to the acoustic streaming. This was demonstrated experimentally by Hags€ ater et al 32 In a direct comparison of the acoustic forces on microbeads in a microfluidic chamber it was shown that the motion of 1 mm beads was governed entirely by Stokes drag from the acoustic streaming, while the motion of the 5 mm beads was dominated by the acoustic radiation force. Moreover, in this work we never observed any traces of acoustic flow rolls.…”

Section: Transverse Particle Pathmentioning

confidence: 79%

Measuring the local pressure amplitude in microchannel acoustophoresis

et al. 2010

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A new method is reported on how to measure the local pressure amplitude and the Q factor of ultrasound resonances in microfluidic chips designed for acoustophoresis of particle suspensions. The method relies on tracking individual polystyrene tracer microbeads in straight water-filled silicon/glass microchannels. The system is actuated by a PZT piezo transducer attached beneath the chip and driven by an applied ac voltage near its eigenfrequency of 2 MHz. For a given frequency a number of particle tracks are recorded by a CCD camera and fitted to a theoretical expression for the acoustophoretic motion of the microbeads. From the curve fits we obtain the acoustic energy density, and hence the pressure amplitude as well as the acoustophoretic force. By plotting the obtained energy densities as a function of applied frequency, we obtain Lorentzian line shapes, from which the resonance frequency and the Q factor for each resonance peak are derived. Typical measurements yield acoustic energy densities of the order of 10 J/m 3 , pressure amplitudes of 0.2 MPa, and Q factors around 500. The observed half wavelength of the transverse acoustic pressure wave is equal within 2% to the measured width w ¼ 377 mm of the channel.

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Section: Transverse Particle Pathmentioning

confidence: 79%

Measuring the local pressure amplitude in microchannel acoustophoresis

et al. 2010

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“…43 This is mainly due (i) to the fact that the acoustic primary radiation force scales with particle's volume, 45 and (ii) to the increased particle susceptibility with respect to hydrodynamic drag forces resulting from acoustic streaming or thermal convection. 52,53 It has been found that at diameters of around 1 μm there is a transition to drag-dominated behaviour for operating frequencies of ~2 MHz. 52,54 For these reasons, few studies have demonstrated acoustofluidic concentration of flowing particles with diameter <2 μm 49,55 (Table I).…”

Section: Introductionmentioning

confidence: 99%

A thin-reflector microfluidic resonator for continuous-flow concentration of microorganisms: a new approach to water quality analysis using acoustofluidics

et al. 2014

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An acoustofluidic device has been developed for concentrating vegetative bacteria in a continuous-flow format. We show that it is possible to overcome the disruptive effects of acoustic streaming which typically dominate for small target particles, and demonstrate flow rates compatible with the testing of drinking water. The device consists of a thin-reflector multi-layered resonator, in which bacteria in suspension are levitated towards a glass surface under the action of acoustic radiation forces. In order to achieve robust device performance over long-term operation, functional tests have been carried out to (i) maintain device integrity over time and stabilise its resonance frequency, (ii) optimise the operational acoustic parameters, and (iii) minimise bacterial adhesion on the inner surfaces. Using the developed device, a significant increase in bacterial concentration has been achieved, up to a maximum of ~60-fold. The concentration performance of thin-reflector resonators was found to be superior to comparable half-wave resonators.

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“…On the one hand, acoustic streaming and acoustophoretic motion of microparticles in acoustofludic devices have been measured using various methods, most notably micro particle image velocimetry (μPIV) and particle tracking velocimetry (PTV). Experimental investigations have shown that μPIV [11][12][13] and PTV 14,15 are powerful tools for analysing 2D microchannel acoustophoresis. Fully 3D particle tracking has been demonstrated using μPIV with depth of correlations 16 and astigmatism particle tracking velocimetry [17][18][19] .…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation of 3D boundary-driven acoustic streaming in microfluidic devices

2014

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This article discusses three-dimensional (3D) boundary-driven streaming in acoustofluidic devices. Firstly, the 3D Rayleigh streaming pattern in a microchannel is simulated and its effect on the movement of microparticles of various sizes is demonstrated. The results obtained from this model show good comparisons with 3D experimental visualisations and demonstrate the fully 3D nature of the acoustic streaming field and the associated acoustophoretic motion of microparticles in acoustofluidic devices. This method is then applied to another acoustofluidic device in order to gain insights into an unusual in-plane streaming pattern. The origin of this streaming has not been fully described and its characteristics cannot be explained from the classical theory of Rayleigh streaming. The simulated in-plane streaming pattern was in good agreement with the experimental visualisation. The mechanism behind it is shown to be related to the active sound intensity field, which supports our previous findings on the mechanism of the in-plane acoustic streaming pattern visualised and modelled in a thin-layered capillary device.

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Acoustic resonances in microfluidic chips: full-image micro-PIV experiments and numerical simulations

Cited by 138 publications

References 24 publications

Measuring the local pressure amplitude in microchannel acoustophoresis

Measuring the local pressure amplitude in microchannel acoustophoresis

A thin-reflector microfluidic resonator for continuous-flow concentration of microorganisms: a new approach to water quality analysis using acoustofluidics

Numerical simulation of 3D boundary-driven acoustic streaming in microfluidic devices

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