The role of gas in ultrasonically driven vapor bubble growth

Shpak, Oleksandr; Stricker, Laura; Versluis, Michel; Lohse, Detlef

doi:10.1088/0031-9155/58/8/2523

Cited by 76 publications

(64 citation statements)

References 29 publications

(35 reference statements)

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“…5 The proposed mechanism contradicted results suggesting that onset of ADV originates within the droplet and is cavitation independent. 2,16,17 More recently, Shpak et al observed the nucleation process in single and double emulsion PFC droplets where in the latter case consistent localization of vaporization was observed, originating at 0.4 R away from the center of the droplet along the axis of the ultrasound, where R is the droplet radius. 18,19 The goal for this study is to directly visualize the nucleation site formation in liquid PFC microdroplets due to the ADV process and propose a potential mechanism initiating vaporization.…”

mentioning

confidence: 82%

Initial nucleation site formation due to acoustic droplet vaporization

Kripfgans

Fabiilli

et al. 2014

Applied Physics Letters

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Acoustic droplet vaporization (ADV) is the selective vaporization of liquid microdroplets using ultrasound, resulting in gas bubbles. The ADV process has been proposed as a tool in biomedical applications such as gas embolotherapy, drug delivery, and phase-change contrast agents. Using a 7.5 MHz focused transducer, the initial gas nucleus formed in perfluorocarbon microdroplets was directly visualized using ultra-high speed imaging. The experimental results of initial nucleation site location were compared to a 2D axisymmetric linear acoustic model investigating the focal spot of the acoustic wave within the microdroplets. Results suggest a wavelength to droplet diameter dependence on nucleation site formation. V C 2014 AIP Publishing LLC.

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mentioning

confidence: 82%

Initial nucleation site formation due to acoustic droplet vaporization

Kripfgans

Fabiilli

et al. 2014

Applied Physics Letters

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“…The acoustic driving pulse was delivered from an arbitrary waveform generator (Tabor 8026; Tabor Electronics) amplified by an rf amplifier (ENI 350L; Electronic Navigation Industries, Inc.). Droplet samples were vaporized with a single ultrasound pulse, consisting of a burst between 6 and 10 cycles and a driving pressure with a peak negative pressure P − inc = − 4:5 MPa at 45°angle to the horizontal OptiCell plane (22,24). The pressure value was calibrated in the same setup at the position of the droplets using a 0.2-mm PVDF probe hydrophone (DC27/000658; Precision Acoustics Ltd.).…”

Section: Methodsmentioning

confidence: 99%

“…The acoustic pressure amplitudes required to nucleate the droplet have been observed to be very high. In a typical ADV experiment, before impinging on the droplet the ultrasound wave from a focused transducer travels a distance on the order of a few centimeters (7,(17)(18)(19)(22)(23)(24). Under these conditions the wave that arrives at the focus of the transducer can be highly distorted owing to nonlinear propagation (25,26).…”

Section: Significancementioning

confidence: 99%

Acoustic droplet vaporization is initiated by superharmonic focusing

Shpak

Verweij

Vos

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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169

148

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Acoustically sensitive emulsion droplets composed of a liquid perfluorocarbon have the potential to be a highly efficient system for local drug delivery, embolotherapy, or for tumor imaging. The physical mechanisms underlying the acoustic activation of these phase-change emulsions into a bubbly dispersion, termed acoustic droplet vaporization, have not been well understood. The droplets have a very high activation threshold; its frequency dependence does not comply with homogeneous nucleation theory and localized nucleation spots have been observed. Here we show that acoustic droplet vaporization is initiated by a combination of two phenomena: highly nonlinear distortion of the acoustic wave before it hits the droplet and focusing of the distorted wave by the droplet itself. At high excitation pressures, nonlinear distortion causes significant superharmonics with wavelengths of the order of the droplet size. These superharmonics strongly contribute to the focusing effect; therefore, the proposed mechanism also explains the observed pressure thresholding effect. Our interpretation is validated with experimental data captured with an ultrahigh-speed camera on the positions of the nucleation spots, where we find excellent agreement with the theoretical prediction. Moreover, the presented mechanism explains the hitherto counterintuitive dependence of the nucleation threshold on the ultrasound frequency. The physical insight allows for the optimization of acoustic droplet vaporization for therapeutic applications, in particular with respect to the acoustic pressures required for activation, thereby minimizing the negative bioeffects associated with the use of high-intensity ultrasound.

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“…But the noncondensable gas does not contract as a result leaving an extremely small gas bubble that will contribute to form a larger bubble on the next acoustic cycle. This process has been observed [56] and helps to manifest that the size of gas bubbles after cessation of ultrasound irradiation is much bigger than the size expected in the initial PFC droplets [57,58].…”

Section: Bubble Growthmentioning

confidence: 53%

Phase-transition Perfluorocarbon Nanoparticles for Ultrasound Molecular Imaging and Therapy

Xu¹,

Cao²,

Xu³

et al. 2015

Nano BioMed ENG

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Recently, the advances in perfluorocarbon nanoparticles have been introduced to expand the diagnostic and therapeutic capability of ultrasound molecular imaging, a non-invasive diagnostic imaging, which passed from robust anatomical presentation to detection of physiological processes and recognition of specific tissue epitopes at the cellular level. The good properties of perfluorocarbon nanoparticles, such as nontoxicity, small size, phase-shift capability, etc., have been resulted in tremendous potential prospects in clinical application. Herein, this review focuses on the mechanisms of perfluorocarbon nanoparticles in terms of phase transition and ultrasonic theranostic. And the potential applications of perfluorocarbon nanoparticles in ultrasound medicine are also discussed.

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The role of gas in ultrasonically driven vapor bubble growth

Cited by 76 publications

References 29 publications

Initial nucleation site formation due to acoustic droplet vaporization

Initial nucleation site formation due to acoustic droplet vaporization

Acoustic droplet vaporization is initiated by superharmonic focusing

Phase-transition Perfluorocarbon Nanoparticles for Ultrasound Molecular Imaging and Therapy

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