Crackling sound generation during the formation of liquid bridges: A lattice gas model

Almeida, Alexandre B.; Buldyrev, Sergey V.; Alencar, Adriano M.

doi:10.1016/j.physa.2013.03.038

Cited by 11 publications

(6 citation statements)

References 31 publications

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“…For example, capillary forces exerted by liquid bridges provide a major contribution to the tensile strength of soils , and represent the primary source of cohesive forces in granular materials and nanoparticles. , WCBs can form naturally between the tip of an atomic force microscope and the substrate under study depending on the relative humidity of the environment. , In these cases, capillary forces can affect the AFM measurements. , Capillary bridges are important in surface science in general, e.g., WCBs can induce adhesion and/or friction , between the interacting surfaces. Interestingly, capillary bridges are relevant for the physiology of the lung. , …”

Section: Introductionmentioning

confidence: 99%

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How Small Is Too Small for the Capillarity Theory?

et al. 2021

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We perform molecular dynamics (MD) simulations of nanoscale water capillary bridges (WCBs) expanding between two parallel walls and determine the smallest separation between the walls above which the capillarity theory (CT) remains valid. We consider silica-based walls with tuned surface partial charges that expand from hydrophobic to hydrophilic. We find that the CT is valid (i.e., it predicts successfully the WCB geometry and forces induced on the walls) for, approximately, wall separations h ≥ h 0 = 3.0 nm for all surfaces considered. At these separations, the CT holds without including any line tension and the results are robust relative to the method employed to obtain the WCB profile from MD simulations. At approximately 2.0 nm ≤ h < h 0 , the contact angle of water θ varies with h, suggesting that at such wall separations the CT requires the inclusion of a line tension τ. However, we find that the specific behavior of θ(h) and the associated value of τ are inherently dependent on the method employed to calculate the WCB profile from MD simulations. Interestingly, the forces induced by the WCBs on the walls obey the prediction of the CT without the need to include a line tension for approximately h ≥ 2.5 nm for all surfaces considered. Our results are interpreted in terms of the rearrangement of water molecules within the WCBs and show that the CT breaks down at h < h 0 because its assumptions, that the WCB is a bulklike water volume confined by solid−liquid and liquid−vapor interfaces, do not hold.

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Section: Introductionmentioning

confidence: 99%

“…Interestingly, capillary bridges are relevant for the physiology of the lung. 28,29 This paper is organized as follows. In Section II, we describe the computational details.…”

Section: Introductionmentioning

confidence: 99%

How Small Is Too Small for the Capillarity Theory?

et al. 2021

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“…5 CT has been used to explain the origin of lung pressure−volume instabilities 6−8 and crackling sound generation, 6,9 a sound associated with several lung abnormalities, during inhale 10 and exhale. 11 Examples of capillarity phenomena at the nanoscale 12 include capillary filling 13 and imbibition 14 of liquids in nanochannels, and ink-transfer processes via capillary bridges in dip-pen nanolithography. 15 In atomic force microscopy (AFM) experiments, water capillary bridges may be formed between the AFM tip and the substrate depending on the humidity conditions, affecting the measurements.…”

Section: Introductionmentioning

confidence: 99%

“…For example, capillarity affects the rearrangement of particles in liquid phase sintering, and alter the transport of immiscible fluids in porous media . CT has been used to explain the origin of lung pressure–volume instabilities − and crackling sound generation, , a sound associated with several lung abnormalities, during inhale and exhale . Examples of capillarity phenomena at the nanoscale include capillary filling and imbibition of liquids in nanochannels, and ink-transfer processes via capillary bridges in dip-pen nanolithography .…”

Section: Introductionmentioning

confidence: 99%

Validation of Capillarity Theory at the Nanometer Scale. II: Stability and Rupture of Water Capillary Bridges in Contact with Hydrophobic and Hydrophilic Surfaces

et al. 2018

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We perform molecular dynamics (MD) simulations of water capillary bridges formed between parallel walls. The underlying structure of the walls corresponds to hydroxilated (crystalline) β-cristobalite, modified to cover a wide range of hydrophobicity/hydrophilicity. The capillary bridges are stretched during the MD simulations, from wall–wall separation h = 5 nm up to h ≈ 7.5 nm, until they become unstable and break. During the stretching process, we calculate the profiles of capillary bridges as well as the force and pressure induced on the walls, among other properties. We find that, for all walls separations and surface hydrophobicity/hydrophilicity considered, the results from MD simulations are in excellent agreement with the predictions from capillarity theory (CT). In addition, we find that CT is able to predict very closely the limit of stability of the capillary bridges, i.e., the value of h at which the bridges break. We also confirm that CT predicts correctly the relationship between the surface hydrophobicity/hydrophilicity and the resulting droplets of the capillary bridge rupture. Depending on the contact angle of water with the corresponding surface, the rupture of the capillary bridges results in (i) a single droplet attached to one of the walls, (ii) two identical, or (iii) two different droplets, one attached to each wall. This work expands upon a previous study of nanoscale droplets and (stable) capillary bridges where CT was validated at the nanoscale using MD simulations. The validation of CT at such small scales is remarkable, since CT is a macroscopic theory that is expected to fail at <10 nm scales, where molecular details may become relevant. In particular, we find that CT works for capillary bridges that are ≈2-nm thick, comparable to the thickness of the water–vapor interface.

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“…Formation of liquid bridges during expiration and rapture of the bridges during inspiration [12,13] with subsequent stress relaxation in pulmonary parenchyma [14] are the main mechanisms of crackles. Distraction of liquid bridges and removal of sputum from airways is one of the purposes of physical therapy (see further).…”

Section: Spontaneous Vibrationsmentioning

confidence: 99%

Biophysics of Chest Vibrations

Dyachenko¹

2017

J Apl Theol

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The purpose of this mini-review is to outline diversity of chest wall vibrations, specify biomechanical peculiarities and point out a few problems crucial for development of diagnostic and therapeutic applications of chest wall vibrations. The review considers two types of chest wall vibrations: spontaneous, induced by breathing, and forced (or artificial), induced by external vibration forces. Spontaneous vibrations emerge in airways and lung tissues due to vortexes, flatter and stress relaxation in pulmonary parenchyma. The vibrations propagate in lung to the chest wall and could be registered by a stethoscope at the chest wall surface as respiratory sounds. Another type of vibrations emerges due to heart contraction and become apparent at the chest wall surface as heart sounds. Respiratory and heart sounds are used for diagnostics of respiratory and heart diseases. Computerized respiratory sounds analysis (CRSA) is a new technique emerged last years and based on respiratory acoustics and biomedical engineering. Forced vibrations are the lung and chest wall vibrations induced by external vibrations effecting airways orifice and/or chest wall. Diagnostic and therapeutic forced vibrations differ in both frequency and amplitude. Diagnostic vibrations imposed at the airway orifice include forced oscillatory technique, estimation of airway cross-section by analysis of acoustic pulse response measurements. Stress and deformation oscillations used for diagnostic techniques usually are small to avoid any mechanical nonlinearity. Diagnostic vibrations imposed at the chest surface include a special kind of forced oscillatory technique with pressure oscillation around the entire chest and a technique of percussions imposed locally to the areas of interest on the chest wall. Elastic waves propagate in airways, pulmonary parenchyma and chest wall during vibrations. Peculiarities of elastic waves propagation in these structures are discussed. A high sound or low ultrasound window presents new emerging perspective area for biomedical engineering aimed to develop a technique for lung sound/ultrasound imaging. There are a few kinds of therapeutic forced vibrations aimed to enhance airway sputum removal if the production of sputum is too large due to decease.

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Crackling sound generation during the formation of liquid bridges: A lattice gas model

Cited by 11 publications

References 31 publications

How Small Is Too Small for the Capillarity Theory?

How Small Is Too Small for the Capillarity Theory?

Validation of Capillarity Theory at the Nanometer Scale. II: Stability and Rupture of Water Capillary Bridges in Contact with Hydrophobic and Hydrophilic Surfaces

Biophysics of Chest Vibrations

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