On the acoustic levitation of droplets

Yarin, Alexander L.; Pfaffenlehner, M.; Tropea, Cameron

doi:10.1017/s0022112097007829

Cited by 179 publications

(117 citation statements)

References 17 publications

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“…Indeed, during the levitation of droplets this represents a typical shape (Yarin et al 1998). As seen in figure 4, the axial force induces a compression of the droplet along its semiminor axis a, while the radial force stretches the droplet along its semimajor axis b.…”

Section: Viscous Medium-cfd Model: Ellipsoidmentioning

confidence: 96%

“…Owing to its material independency, acoustic levitation has found a wide spectrum of applications in contactless processing and analysis of liquid samples (Trinh, Thiessen & Holt 1998;Yarin, Pfaffenlehner & Tropea 1998). The contactless manipulation and transportation of particles and droplets is one of the most interesting challenges in the acoustic levitation field (Koyama & Nakamura 2010;Foresti et al 2011;Foresti, Nabavi & Poulikakos 2012) with applications ranging from the handling of living cells in lab-on-a-chip devices (Bruus et al 2011) to millimetre-size sample manipulations in air (Bjelobrk et al 2010).…”

Section: Introductionmentioning

confidence: 99%

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On the acoustic levitation stability behaviour of spherical and ellipsoidal particles

2012

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We present here an in-depth analysis of particle levitation stability and the role of the radial and axial forces exerted on fixed spherical and ellipsoidal particles levitated in an axisymmetric acoustic levitator, over a wide range of particle sizes and surrounding medium viscosities. We show that the stability behaviour of a levitated particle in an axisymmetric levitator is unequivocally connected to the radial forces: the loss of levitation stability is always due to the change of the radial force sign from positive to negative. It is found that the axial force exerted on a sphere of radius R s increases with increasing viscosity for R s /λ < 0.0125 (λ is the acoustic wavelength), with the viscous contribution of this force scaling with the inverse of the sphere radius. The axial force decreases with increasing viscosity for spheres with R s /λ > 0.0125. The radial force, on the other hand, decreases monotonically with increasing viscosity. The radial and axial forces exerted on an ellipsoidal particle are larger than those exerted on a volume-equivalent sphere, up to the point where the ellipsoid starts to act as an obstacle to the formation of the standing wave in the levitator chamber.

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Section: Viscous Medium-cfd Model: Ellipsoidmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

On the acoustic levitation stability behaviour of spherical and ellipsoidal particles

2012

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“…Even SAW is known to be able to levitate objects, although for applications in motors, as reported by Asai and Kurosawa (2005), the gap that forms between the object and the SAW substrate is seen as a problem. Yarin et al (1998) provided a seminal analysis of the shape of levitated drops. With experimental results at 56 kHz for comparison and verification, they determined both the shape and displacement from the pressure node of 3-5 ' drops of n-hexadecane C 49 H 67 while exposed to ultrasound.…”

Section: Jetting and Levitationmentioning

confidence: 99%

Microscale acoustofluidics: Microfluidics driven via acoustics and ultrasonics

2011

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This article reviews acoustic microfluidics: the use of acoustic fields, principally ultrasonics, for application in microfluidics. Although acoustics is a classical field, its promising, and indeed perplexing, capabilities in powerfully manipulating both fluids and particles within those fluids on the microscale to nanoscale has revived interest in it. The bewildering state of the literature and ample jargon from decades of research is reorganized and presented in the context of models derived from first principles. This hopefully will make the area accessible for researchers with experience in materials science, fluid mechanics, or dynamics. The abundance of interesting phenomena arising from nonlinear interactions in ultrasound that easily appear at these small scales is considered, especially in surface acoustic wave devices that are simple to fabricate with planar lithography techniques common in microfluidics, along with the many applications in microfluidics and nanofluidics that appear through the literature.

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“…Collas [18] showed results on acoustic levitation in ground experiments. Yarin et al [19] calculated acoustic radiation pressure using a boundary element method and predicted shapes of levitated droplets, which showed good agreement with experimental measurements. They showed that displacement of the droplet center relative to the pressure node due to the presence of gravity (or other steady force) was significant and could be computed.…”

Section: Previous Workmentioning

confidence: 78%