Focusing of sub-micrometer particles and bacteria enabled by two-dimensional acoustophoresis

Antfolk, Maria; Müller, Peter; Augustsson, Per; Bruus, Henrik; Laurell, Thomas

doi:10.1039/c4lc00202d

Cited by 135 publications

(127 citation statements)

References 43 publications

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“…Antfolk et al recently demonstrated focusing of bacteria using a combination of streaming and a two-dimensional resonance; their paper is not included in Table I, as comparable concentration data was not included; however, impressive performance with polystyrene beads as small as 0.5 µm was shown. 56 Hammarström et al…”

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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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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“…1. This system even has the added benefit of having been studied extensively and characterized well both theoretically and experimentally in the steady oscillatory state [2,3,10,11,19,21], thus providing a strong benchmark for the present analysis in the transient regime.…”

Section: Numerical Modelmentioning

confidence: 99%

“…We only consider acoustic perturbation in fluids, and treat the surrounding solid material as ideal rigid walls, a good approximation for water channels in glass-silicon systems. Moreover, extensive theoretical and experimental work [2,3,10,11,19,21] has shown that the adiabatic model describes the observed phenomena qualitatively correctly, while thermoviscous effects may lead to relative quantitative changes up to 30%. Thus by employing an adiabatic model, we can provide an analysis of experimental relevance while at the same time restricting the complexity and vast parameter space of the full problem.…”

Section: Basic Adiabatic Acoustic Theorymentioning

confidence: 99%

“…However, an experimental study by Hoyos and Castro [18] indicates that a pulsed actuation, instead of steady, can reduce the drag force from the streaming flow relative to the radiation force and thus allow the latter also to dominate manipulation of submicrometer particles. This might provide an alternative method to the one proposed by Antfolk et al [19], which used an almost square channel with overlapping resonances to create a streaming flow that did not counteract the focusing of submicrometer particles.…”

Section: Introductionmentioning

confidence: 99%

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Theoretical study of time-dependent, ultrasound-induced acoustic streaming in microchannels

Müller

Bruus

2015

Phys. Rev. E

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Based on first-and second-order perturbation theory, we present a numerical study of the temporal buildup and decay of unsteady acoustic fields and acoustic streaming flows actuated by vibrating walls in the transverse cross-sectional plane of a long straight microchannel under adiabatic conditions and assuming temperatureindependent material parameters. The unsteady streaming flow is obtained by averaging the time-dependent velocity field over one oscillation period, and as time increases, it is shown to converge towards the well-known steady time-averaged solution calculated in the frequency domain. Scaling analysis reveals that the acoustic resonance builds up much faster than the acoustic streaming, implying that the radiation force may dominate over the drag force from streaming even for small particles. However, our numerical time-dependent analysis indicates that pulsed actuation does not reduce streaming significantly due to its slow decay. Our analysis also shows that for an acoustic resonance with a quality factor Q, the amplitude of the oscillating second-order velocity component is Q times larger than the usual second-order steady time-averaged velocity component. Consequently, the well-known criterion v 1 c s for the validity of the perturbation expansion is replaced by the more restrictive criterion v 1 c s /Q. Our numerical model is available as supplemental material in the form of COMSOL model files and MATLAB scripts.

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“…These are generally considered to be a disturbance as they place a practical lower limit on the particle size that can be manipulated by the primary acoustic radiation force. 1,2 However, acoustic streaming can also play an active role in the functioning of such systems, such as particle trapping, 3-7 two-dimensional particle focusing, 8 and particle separation. 9 Most acoustofluidic particle manipulation devices utilise standing wave fields, and the acoustic streaming field is generally dominated by boundary-driven streaming which arises from the acoustic attenuation within the acoustic boundary layer due to the non-slip condition on the walls of the fluid channel.…”

Section: Introductionmentioning

confidence: 99%

Modal Rayleigh-like streaming in layered acoustofluidic devices

2016

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Classical Rayleigh streaming is well known and can be modelled using Nyborg’s limiting velocity method as driven by fluid velocities adjacent to the walls parallel to the axis of the main acoustic resonance. We have demonstrated previously the existence and the mechanism of four-quadrant transducer plane streaming patterns in thin-layered acoustofluidic devices which are driven by the limiting velocities on the walls perpendicular to the axis of the main acoustic propagation. We have recently found experimentally that there is a third case which resembles Rayleigh streaming but is a more complex pattern related to three-dimensional cavity modes of an enclosure. This streaming has vortex sizes related to the effective wavelength in each cavity axis of the modes which can be much larger than those found in the one-dimensional case with Rayleigh streaming. We will call this here modal Rayleigh-like streaming and show that it can be important in layered acoustofluidic manipulation devices. This paper seeks to establish the conditions under which each of these is dominant and shows how the limiting velocity field for each relates to different parts of the complex acoustic intensity patterns at the driving boundaries.

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Focusing of sub-micrometer particles and bacteria enabled by two-dimensional acoustophoresis

Abstract: Handling of sub-micrometer bioparticles e.g. bacteria is becoming increasingly important in the biomedical field and in environmental and food analysis.

Cited by 135 publications

References 43 publications

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

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

Theoretical study of time-dependent, ultrasound-induced acoustic streaming in microchannels

Modal Rayleigh-like streaming in layered acoustofluidic devices

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