Leakiness of Pinned Neighboring Surface Nanobubbles Induced by Strong Gas–Surface Interaction

Maheshwari, Shantanu; Hoef, Martin van der; Rodriguez, Javier Rodriguez; Lohse, Detlef

doi:10.1021/acsnano.7b08614

Cited by 54 publications

(56 citation statements)

References 33 publications

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“…The LJ potential pair parameters used for the mW and N 2 model simulations are also shown in Table II, using similar values from past surface nanobubble simulations. 33,42,43 Potential parameters between mW molecules and the S o and S i atom types were calibrated in pre-simulations to obtain equilibrium gasside contact angles of 35 • and 99 • , respectively. Potential parameters between the nitrogen molecules and the wall atom types were calibrated to achieve similar density fluctuation Pressure was applied by the piston, with all piston atoms subjected to a mean force F z = −P ∞ A p /N, where A p is the area of the piston in the (x, y) plane, and N is the number of piston wall atoms.…”

Section: Molecular Dynamics Simulation Setupmentioning

confidence: 99%

“…MD is a high-fidelity simulation technique that can model such behavior, for example, the contact line stick/slip dynamics, surface tension effects and diffusive growth, via fundamental Newtonian dynamics and chemical intermolecular potentials. 33,[41][42][43][44] The penalty of MD is its extreme computational cost, which limits the bubble sizes that can be modeled (R ∼ 10 nm) as well as the largest time scales of the dynamics (∼ 10 ns). Other techniques exist for modeling surface nanobubbles, such as lattice density functional theory, 26 and more recently with continuum-based solvers, coupling a finite difference scheme with the immersed boundary method to simulate pinned growth under various saturation conditions for µm sized surface nanobubbles.…”

Section: Introductionmentioning

confidence: 99%

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Forced oscillation dynamics of surface nanobubbles

Dockar

Gibelli

Borg

2020

The Journal of Chemical Physics

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Surface nanobubbles have potential applications in manipulation of nanoscale and biological materials, waste-water treatment and surface cleaning. These spherically capped bubbles of gas can exist in stable diffusive equilibrium on chemically patterned or rough hydrophobic surfaces, under supersaturated conditions. Previous studies have investigated their long-term response to pressure variations, which is governed by the surrounding liquid's local supersaturation, however, not much is known about their short-term response to rapid pressure changes, i.e. their cavitation dynamics. Here, we present Molecular Dynamics simulations of a surface nanobubble subjected to an external oscillating pressure field. The surface nanobubble is found to oscillate with a pinned contact line, while still retaining a mostly spherical cap shape. The amplitude frequency response is typical of an underdamped system, with a peak amplitude near the estimated natural frequency, despite the strong viscous effects at the nanoscale. This peak is enhanced by the surface nanobubble's high internal gas pressure, a result of the Laplace pressure. We find that accurately capturing the gas pressure, bubble volume and pinned growth mode is important for estimating the natural frequency, and we propose a simple model for the surface nanobubble frequency response, with comparisons made to other common models for a spherical bubble, a constant contact angle surface bubble, and a bubble entrapped within a cylindrical micropore. This work reveals the initial stages of growth of cavitation nanobubbles on surfaces, common in heterogeneous nucleation, where classical models based on spherical bubble growth break down.

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Section: Molecular Dynamics Simulation Setupmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Forced oscillation dynamics of surface nanobubbles

Dockar

Gibelli

Borg

2020

The Journal of Chemical Physics

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“…[ 34] have revealed that in certain cases (very strong attraction between the dissolved gas molecules and the surface) surface nanobubbles very close to each other can communicate through a "new channel", namely diffusion of gas from one surface bubble to the other along the surface, and not through the bulk. If this is the case, some sort of ripening process of neighboring surface bubbles may be possible in spite of hydrodynamic stability against Ostwald ripening.…”

Section: Ray Of Bubblesmentioning

confidence: 99%

Diffusive interaction of multiple surface nanobubbles: shrinkage, growth, and coarsening

et al. 2018

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Surface nanobubbles are nanoscopic spherical-cap shaped gaseous domains on immersed substrates which are stable, even for days. After the stability of a single surface nanobubble has been theoretically explained, i.e. contact line pinning and gas oversaturation are required to stabilize it against diffusive dissolution [Lohse and Zhang, Phys. Rev. E, 2015, 91, 031003(R)], here we focus on the collective diffusive interaction of multiple nanobubbles. For that purpose we develop a finite difference scheme for the diffusion equation with the appropriate boundary conditions and with the immersed boundary method used to represent the growing or shrinking bubbles. After validation of the scheme against the exact results of Epstein and Plesset for a bulk bubble [J. Chem. Phys., 1950, 18, 1505] and of Lohse and Zhang for a surface bubble, the framework of these simulations is used to describe the coarsening process of competitively growing nanobubbles. The coarsening process for such diffusively interacting nanobubbles slows down with advancing time and increasing bubble distance. The present results for surface nanobubbles are also applicable for immersed surface nanodroplets, for which better controlled experimental results of the coarsening process exist.

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“…refs. [58,59]. The downsides of MD are that (i) only small nanodroplets (∼50 nm) can be simulated, that (ii) one is restricted to short physical times of at most microseconds, and that (iii) molecular interaction potentials are needed, which are not from first principles.…”

Section: Introductionmentioning

confidence: 99%

Physicochemical hydrodynamics of droplets out of equilibrium

2020

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Droplets abound in nature and technology. In general, they are multicomponent, and, when out of equilibrium, with gradients in concentration, implying flow and mass transport. Moreover, phase transitions can occur, with either evaporation, solidification, dissolution, or nucleation of a new phase. The droplets and their surrounding liquid can be binary, ternary, or contain even more components, and with several even in different phases. In the last two decades the rapid advances in experimental and numerical fluid dynamical techniques has enabled major progress in our understanding of the physicochemical hydrodynamics of such droplets, further narrowing the gap from fluid dynamics to chemical engineering and colloid & interfacial science and arriving at a quantitative understanding of multicomponent and multiphase droplet systems far from equilibrium, and aiming towards a one-to-one comparison between experiments and theory or numerics. This review will discuss various examples of the physicochemical hydrodynamics of droplet systems far from equilibrium and our present understanding of them. These include immiscible droplets in a concentration gradient, coalescence of droplets of different liquids, droplets in concentration gradients emerging from chemical reactions (including droplets as microswimmers) and phase transitions such as evaporation, solidification, dissolution, or nucleation, and droplets in ternary liquids, including solvent exchange, nano-precipitation, and the so-called ouzo effect. We will also discuss the relevance of the physicochemical hydrodynamics of such droplet systems for many important applications, including in chemical analysis and diagnostics, microanalysis, pharmaceutics, synthetic chemistry and biology, chemical and environmental engineering, the oil and remediation industries, inkjet-printing, for micro-and nano-materials, and in nanotechnolgoy.

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Leakiness of Pinned Neighboring Surface Nanobubbles Induced by Strong Gas–Surface Interaction

Cited by 54 publications

References 33 publications

Forced oscillation dynamics of surface nanobubbles

Forced oscillation dynamics of surface nanobubbles

Diffusive interaction of multiple surface nanobubbles: shrinkage, growth, and coarsening

Physicochemical hydrodynamics of droplets out of equilibrium

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