The effects of nanoscale nuclei on cavitation

Gao, Zhan; Wu, Wangxia; Wang, Bing

doi:10.1017/jfm.2020.1049

Cited by 15 publications

(9 citation statements)

References 47 publications

(110 reference statements)

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“…Bulk nanobubbles (NBs) generally refer to suspended bubbles with a diameter of less than 1 μm, which have excellent prospects for applications in many fields, such as water management, nanoscale surface cleaning, ultrasound imaging, drug delivery, and acceleration of the growth of living organisms . NBs can also act as cavitation nuclei, whereby the discrepancy between experiment and theory for the tensile strength of water can be explained. , Unlike surface NBs adhering to solid substrates, bulk NBs proceed with Brownian motion, leading to difficulty in direct observation. Surface NBs can be directly observed with atom force microscopy and attribute their stabilization to the contact line pinning effect, which compels surface NBs to evolve with a constant footprint radius.…”

Section: Introductionmentioning

confidence: 99%

“…6 NBs can also act as cavitation nuclei, whereby the discrepancy between experiment and theory for the tensile strength of water can be explained. 7,8 Unlike surface NBs adhering to solid substrates, bulk NBs proceed with Brownian motion, 9 leading to difficulty in direct observation. Surface NBs can be directly observed with atom force microscopy 10 and attribute their stabilization to the contact line pinning effect, 11 which compels surface NBs to evolve with a constant footprint radius.…”

Section: ■ Introductionmentioning

confidence: 99%

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Understanding the Stabilization of a Bulk Nanobubble: A Molecular Dynamics Analysis

Gao

Sun

et al. 2021

Langmuir

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Bulk nanobubbles (NBs) have received considerable attention because of their extensive potential applications, such as in ultrasound imaging and water management. Although multiple types of experimental evidence have supported the existence and stabilization of bulk NBs, the underlying mechanism remains unclear. This study numerically investigates the bulk NB stabilization with molecular dynamics (MD) methods: the all-atom (AA) MD simulation is used for NBs of several nanometers diameter; the coarse-grained (CG) MD simulation is for the NBs of about 100 nm. The NB properties are statistically obtained and analyzed, including the inner density, inner pressure, surface charge, interfacial hydrogen bond (HB), and gaseous diffusion. The results show that the gas inside an NB has ultrahigh density (tens of kilograms per cubic meter). A double-layer surface charge exists on the NB. The inner/outer layer is positively/negatively charged, and the electrostatic stress can counteract part of the surface tension. In addition, the interfacial HB is weakened by the interaction between gas and water molecules, causing less surface tension. The above features are beneficial to NB stabilization. The NB equilibrium radii solved by the interfacial mechanical equilibrium equation agree with the MD results, indicating that this equation can describe the force balance of an NB as small as several nanometers. Besides, supersaturation appears to be necessary for the NB thermodynamic equilibrium. Based on Henry’s law and the ideal gas law, the theoretical analysis suggests that the stability of the NB thermodynamic equilibrium is conditional: the number of gas molecules in NBs should be more than half that dissolved in liquid. This study unravels a stabilized bulk NB’s properties and discusses the NB equilibrium and stabilization mechanism, which will advance the understanding and application of bulk NBs.

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Section: Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Understanding the Stabilization of a Bulk Nanobubble: A Molecular Dynamics Analysis

Gao

Sun

et al. 2021

Langmuir

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“…Recently, molecular dynamics simulations were performed to study the stability and kinetics of tension-induced cavities. − Theoretical considerations and simulations showed that, for a finite-sized sample, two parameters, stretching factor and the initial unstretched volume of the sample, play a crucial role. It is especially important to understand how large the stretching factor should be, since it is directly connected to the amount of tension.…”

Section: Introductionmentioning

confidence: 99%

Stretch-Induced Cavitation: How Critical Cavity Radius and Barrier Energy, Radius, and Energy of a Stable Cavity Depend on the Stretching Factor

Berkowitz

2021

J. Phys. Chem. B

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Characteristics of tension-induced cavitation, such as free energy at the barrier for cavitation, the size of the critical (barrier) cavity, the stable cavity size, and the free energy of the stable cavity, depend on the amount of tension (stretch) and the initial size of the sample. In this work, we study how the characteristics of the cavitation mentioned above scale with the amount of applied tension. We consider two models characterizing the properties of cavitating liquid: (a) a simple model with a linear tension−strain relation and neglect of curvature dependence of cavity surface tension and (b) a more realistic model with a nonlinear tension−strain relation and curvature-dependent surface tension. For both models, we find the relevant scaling relations when we stretch the initial volume of the liquid sample in the interval between 1% and 20% of the initial volume. Specific numerical tests are performed for the case of liquid water when the initial volume of the sample is a sphere with a radius of 100 nm.

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A possible explanation [13] might be nanoscale solid or 52 gaseous nuclei [14] that reduce the threshold of an oth-53 erwise pure liquid.

54Here, we report on a potentially novel source for cav-55 itation: droplets of a highly non-polar liquid, which is 56 hydrophobic and lipophobic, namely perfluorocarbons 57 (PFC). The atomically smooth surface does not offer 58 hydrophobic cracks for stabilization of pre-existing gas 59 pockets.

…”

mentioning

confidence: 96%

“…A possible explanation [13] might be nanoscale solid or 52 gaseous nuclei [14] that reduce the threshold of an oth-53 erwise pure liquid.…”

mentioning

confidence: 99%

Heterogeneous cavitation from atomically smooth liquid–liquid interfaces

et al. 2022

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A possible explanation [13] might be nanoscale solid or 52 gaseous nuclei [14] that reduce the threshold of an oth-53 erwise pure liquid. 54Here, we report on a potentially novel source for cav-55 itation: droplets of a highly non-polar liquid, which is 56 hydrophobic and lipophobic, namely perfluorocarbons 57 (PFC). The atomically smooth surface does not offer 58 hydrophobic cracks for stabilization of pre-existing gas 59 pockets. Liquid PFCs are very stable, chemically inert, 60 feature high gas solubility, and used for in vivo oxygen 61 delivery and further biomedical applications [15-17]. Its 62 unique properties are an effect of low self cohesion, polar-63 ity, and polarizability [17]. The PFC used in the experi-64 ments, i. e., 1-Bromoheptadecafluorooctane (PFOB), has 65 a high solubility of gases with low cohesivity, such as O 2 , 66 CO 2 , N 2 , NO, etc. [15]. In fact, pure PFOB theoretically 67 dissolves 360 fold more oxygen than water in terms of mo-68 lar fraction and 25 times more in terms of volume frac-69 tion at ambient conditions [15-18]. This novel cavitation 70 nucleus might be of interest for some medical applica-71 tions, such as high intensity focused ultrasound ablation, 72 localized drug delivery, and radiotherapy; or engineer-73 ing technologies that could reduce cavitation in hydraulic 74 machinery as pumps or injectors. Here, we demonstrate 75 cavitation nucleation from liquid-liquid interfaces. The 76 liquids are constrained by two glass plates to form a few 77 micrometer thick liquid gap. Cavitation inception is in-78 duced with strong tensile stresses that are propagated 79 through a Lamb wave travelling within the thin liquid 80 gap. The cavitation nucleating wave is launched by a 81 laser induced plasma; further details are provided in the 82 "Methods" Section and in Ref. [19]. 83 Atomistic simulations are performed on a water/PFC 84 93 to them as secondary cavitation that are formed once the 94 cavitation threshold is locally met. 95 In Fig. 1(c-d) selected PFC droplets are marked with 96 a cyan circle (t = 0). When the Lamb wave passes, on 97 most of these droplets a bubble emerges (t = 0.2−0.4 µs), 98 which will collapse after a short time and no visible bub-99 bles remain. The PFC droplets are still intact and visible. 100 The expansion of the primary cavitation drives a radial 101 flow that transports the droplets from their original posi-102 tion to a slightly shifted one. During this transport some 103 droplets may deform and eventually split up into several 104 droplets. 105 Interestingly, a droplet may nucleate multiple times. 106 Initially, some droplets nucleate a bubble upon tension. 107 A later tension wave, which might be a result of reflec-108 tions of waves within the glass, is able to nucleate bubbles 109 at some of the PFC droplets previously acting as cavita-110 tion nuclei (Supplementary Fig. S1). This demonstrates 111 that the droplets are not used up by one cavitation event 112 but can serve multiple times as a cavitation nucleus (see 113 Suppl. Information). T...

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The effects of nanoscale nuclei on cavitation

Abstract: Abstract

Cited by 15 publications

References 47 publications

Understanding the Stabilization of a Bulk Nanobubble: A Molecular Dynamics Analysis

Understanding the Stabilization of a Bulk Nanobubble: A Molecular Dynamics Analysis

Stretch-Induced Cavitation: How Critical Cavity Radius and Barrier Energy, Radius, and Energy of a Stable Cavity Depend on the Stretching Factor

Heterogeneous cavitation from atomically smooth liquid–liquid interfaces

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