Acoustofluidics 7: The acoustic radiation force on small particles

Bruus, Henrik

doi:10.1039/c2lc21068a

Cited by 799 publications

(645 citation statements)

References 20 publications

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“…The results indicate that the size parameter is not important for acoustic manipulation when the particle size is much smaller than the acoustic wavelength. According to the previous theory,23, 24, 45, 46, 47, 48 the primary acoustic radiation force F on small particles can be calculated as Equation (1)

F_{\max} = \frac{π P^{2} V_{normalP}}{2 λ} \frac{1}{ρ_{normalM} C_{normalM}^{2}} (\frac{5 ρ_{P} - 2 ρ_{M}}{2 ρ_{P} + ρ_{M}} - \frac{ρ_{M} C_{M}^{2}}{ρ_{P} C_{P}^{2}})

where P is acoustic pressure, V P is the volume of metal particle, ρ P and ρ M are the density of metal particle and medium, C P and C M are the speed of sound in particle and medium, respectively. Details are listed in Table S1 (Supporting Information).…”

Section: Discussionmentioning

confidence: 99%

Observation of Metal Nanoparticles for Acoustic Manipulation

et al. 2017

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Use of acoustic trapping for the manipulation of objects is invaluable to many applications from cellular subdivision to biological assays. Despite remarkable progress in a wide size range, the precise acoustic manipulation of 0D nanoparticles where all the structural dimensions are much smaller than the acoustic wavelength is still present challenges. This study reports on the observation of metal nanoparticles with different nanostructures for acoustic manipulation. Results for the first time exhibit that the hollow nanostructures play more important factor than size in the nanoscale acoustic manipulation. The acoustic levitation and swarm aggregations of the metal nanoparticles can be easily realized at low energy and clinically acceptable acoustic frequency by hollowing their nanostructures. In addition, the behaviors of swarm aggregations can be flexibly regulated by the applied voltage and frequency. This study anticipates that the strategy based on the unique properties of the metal hollow nanostructures and the manipulation method will be highly desirable for many applications.

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F_{\max} = \frac{π P^{2} V_{normalP}}{2 λ} \frac{1}{ρ_{normalM} C_{normalM}^{2}} (\frac{5 ρ_{P} - 2 ρ_{M}}{2 ρ_{P} + ρ_{M}} - \frac{ρ_{M} C_{M}^{2}}{ρ_{P} C_{P}^{2}})

Section: Discussionmentioning

confidence: 99%

Observation of Metal Nanoparticles for Acoustic Manipulation

et al. 2017

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“…Indeed, the acoustic radiation force responsible for the acoustophoresis in the channel is proportional to H ch [1], and thus to η. As η approaches unity, the acoustic radiation force in the fluid attains the maximum radiation force achievable for a device, as all of the energy is stored as acoustic energy in the fluid.…”

Section: Definition Of System Indicatorsmentioning

confidence: 99%

“…These devices exploit standing acoustic pressure waves that, through the purely mechanical parameters, such as compressibility, density, and size, induce fluid-and particle-specific forces [1][2][3] leading to acoustophoresis [4]. This phenomenon is the basis of the development of gentle [5,6] and robust methods for concentrating [7], trapping [8], washing [9], aligning [10], and separating cells [11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Performance Study of Acoustophoretic Microfluidic Silicon-Glass Devices by Characterization of Material- and Geometry-Dependent Frequency Spectra

2017

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The mechanical and electrical response of acoustophoretic microfluidic devices attached to an ac-voltage-driven piezoelectric transducer is studied by means of numerical simulations. The governing equations are formulated in a variational framework that, introducing Lagrangian and Hamiltonian densities, is used to derive the weak form for the finite-element discretization of the equations and to characterize the device response in terms of frequency-dependent figures of merit or indicators. The effectiveness of the device in focusing microparticles is quantified by two mechanical indicators: the average direction of the pressure gradient and the amount of acoustic energy localized in the microchannel. Furthermore, we derive the relations between the Lagrangian, the Hamiltonian, and three electrical indicators: the resonance Q value, the impedance, and the electric power. The frequency response of the hard-to-measure mechanical indicators is correlated to that of the easy-to-measure electrical indicators, and, by introducing optimality criteria, it is clarified to which extent the latter suffices to identify optimal driving frequencies as the geometric configuration and the material parameters vary. The latter have been varied by considering both Pyrex and aluminium nitroxide top-lid materials.

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“…Particles generally have positive acoustic contrast factor and therefore, when subjected to an acoustic standing wave, they experience a force that steers them towards the pressure node. 11,15,36 Some materials such as air bubbles and lipid vesicles have density and compressibility values that result in a negative contrast factor, which means that these objects agglomerate at the pressure antinodes. 17 Thus, a separation occurs if particles with acoustic contrast factors of different signs are present.…”

Section: Introductionmentioning

confidence: 99%

“…The incident and scattered acoustic fields result in a second-order time-averaged primary radiation force. [12][13][14][15]36 The analysis of the acoustic radiation force dates to the work of King,12 where the treatment of both standing and traveling acoustic fields was carried out on incompressible spheres, much smaller in size than the wavelength of the field, at the Rayleigh scattering limit. 15 Yosioka and Kawasima 13 extended this discussion by introducing compressibility of the spheres.…”

Section: Introductionmentioning

confidence: 99%

Particle separation by phase modulated surface acoustic waves

et al. 2017

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High efficiency isolation of cells or particles from a heterogeneous mixture is a critical processing step in lab-on-a-chip devices. Acoustic techniques offer contactless and label-free manipulation, preserve viability of biological cells, and provide versatility as the applied electrical signal can be adapted to various scenarios. Conventional acoustic separation methods use time-of-flight and achieve separation up to distances of quarter wavelength with limited separation power due to slow gradients in the force. The method proposed here allows separation by half of the wavelength and can be extended by repeating the modulation pattern and can ensure maximum force acting on the particles. In this work, we propose an optimised phase modulation scheme for particle separation in a surface acoustic wave microfluidic device. An expression for the acoustic radiation force arising from the interaction between acoustic waves in the fluid was derived. We demonstrated, for the first time, that the expression of the acoustic radiation force differs in surface acoustic wave and bulk devices, due to the presence of a geometric scaling factor. Two phase modulation schemes are investigated theoretically and experimentally. Theoretical findings were experimentally validated for different mixtures of polystyrene particles confirming that the method offers high selectivity. A Monte-Carlo simulation enabled us to assess performance in real situations, including the effects of particle size variation and non-uniform acoustic field on sorting efficiency and purity, validating the ability to separate particles with high purity and high resolution.

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Acoustofluidics 7: The acoustic radiation force on small particles

Cited by 799 publications

References 20 publications

Observation of Metal Nanoparticles for Acoustic Manipulation

Observation of Metal Nanoparticles for Acoustic Manipulation

Performance Study of Acoustophoretic Microfluidic Silicon-Glass Devices by Characterization of Material- and Geometry-Dependent Frequency Spectra

Particle separation by phase modulated surface acoustic waves

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