Continuous cell washing and mixing driven by an ultrasound standing wave within a microfluidic channel

Hawkes, Jeremy J.; Barber, Robert W.; Emerson, David R.; Coakley, W. Terence

doi:10.1039/b408045a

Cited by 152 publications

(131 citation statements)

References 18 publications

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“…While there are various resonant acoustofluidic systems, we investigated here the half-wave resonance in the z-direction, which is a widely used system for particle and cell manipulation. [38][39][40][41][42][43][44][45][46][47] The origin of the coordinates in these models was set at the centre of the fluid channels such that the fluid channels are located within coordinates:…”

Section: Modellingmentioning

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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Section: Modellingmentioning

confidence: 99%

Modal Rayleigh-like streaming in layered acoustofluidic devices

2016

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“…[11][12][13][14][15][16] Likewise, the development of continuous-flow-based separation and manipulation of particles and cells has progressed rapidly with the advent of precision microfabricated flow-through resonators operating in the laminar flow regime. [17][18][19][20][21][22][23][24][25][26] Both the area of acoustic trapping and continuous separation/manipulation show great promise for applications within flow cytometry, and much of the current technological development targets cell biology.…”

Section: Introductionmentioning

confidence: 99%

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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“…Generating half wavelength modes at high ultrasonic frequencies, implies sub millimetre chamber depths and such chambers were 20 investigated by Hawkes et al 35 for particle filtration 16 and cell washing 36 .…”

Section: Half Wave Devicesmentioning

confidence: 99%

Acoustofluidics 9: Modelling and applications of planar resonant devices for acoustic particle manipulation

2012

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5This article introduces the design, construction and applications of planar resonant devices for particle and cell manipulation. These systems rely on the pistonic action of a piezoelectric layer to generate a one dimensional axial variation in acoustic pressure through a system of acoustically tuned layers. The resulting acoustic standing wave is dominated by planar variations in pressure causing particles to migrate to planar pressure nodes (or antinodes depending on particle and fluid properties). The consequences of 10 lateral variations in the fields are discussed, and rules for designing resonators with high energy density within the appropriate layer for a given drive voltage presented.  IntroductionThere is a need to manipulate micron-scale particles and cells in many areas of physics, analytical chemistry and the biosciences. Techniques such as filtration, centrifugation and sedimentation are well-established in macro-scale applications, but in microfluidic 15 systems the use of other approaches including optical, magnetic, dielectrophoretic and acoustic forces are of interest. Acoustic radiation forces, typically at ultrasonic frequencies in the hundreds of kHz to tens of MHz region, have wavelengths that are well matched to microfluidic channel scales, yet are capable of generating potential wells with significantly larger length scales. The technology is also relatively straightforward to integrate within microfluidic systems. Acoustic radiation forces 20Acoustic radiation forces can be generated on particles by both travelling and standing acoustic fields. Those in standing wave fields (of primary interest in the applications considered here) are generated by the nonlinear interaction between the acoustic field scattered by the particle and the standing wave field itself. The time averaged radiation force () F r on a small (in comparison with a wavelength) spherical particle of volume V located at r within a stationary acoustic field was shown by Gor'kov 1 to relate to the gradients of the time averaged kinetic and potential energy densities ( kin E and pot E respectively) within the field:The kinetic energy density gradient (a function of the acoustic velocity field within the standing wave) is weighted by a function of the densities ( on them that tends to move them to the acoustic pressure node, and the acoustic velocity antinode. In a planar resonator these are colocated. Generating the required acoustic fieldMany approaches to generating the required acoustic wave field have been reported in the literature. These include the use of near-field effects 2 or focussed ultrasound 3, 4 to trap particles and cells, the excitation of lateral standing waves in which the predominant energy 35 gradients run parallel to the face of the excitation transducer 5,6 , and the generation of cylindrical resonances to focus 7 or arrange

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Continuous cell washing and mixing driven by an ultrasound standing wave within a microfluidic channel

Cited by 152 publications

References 18 publications

Modal Rayleigh-like streaming in layered acoustofluidic devices

Modal Rayleigh-like streaming in layered acoustofluidic devices

Measuring the local pressure amplitude in microchannel acoustophoresis

Acoustofluidics 9: Modelling and applications of planar resonant devices for acoustic particle manipulation

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