Cassie–Baxter to Wenzel state wetting transition: a 2D numerical simulation

Lopes, Daisiane M.; Ramos, S.M.M.; Oliveira, Luciana R. de; Mombach, José C. M.

doi:10.1039/c3ra45258a

Cited by 36 publications

(33 citation statements)

References 25 publications

(23 reference statements)

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“…Transition between these two wetting modes has been studied through experiments, analytical models, and simulations . So far investigation of Cassie–Wenzel transition (CW transition) has concentrated on static droplets that undergo transition to Wenzel state by mechanical compression, magnetic force, electrostatic force, evaporation, gravity or by vibration …”

Section: Introductionmentioning

confidence: 99%

Friction and Wetting Transitions of Magnetic Droplets on Micropillared Superhydrophobic Surfaces

Al‐Azawi

Latikka

Jokinen

et al. 2017

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Reliable characterization of wetting properties is essential for the development and optimization of superhydrophobic surfaces. Here, the dynamics of superhydrophobicity is studied including droplet friction and wetting transitions by using droplet oscillations on micropillared surfaces. Analyzing droplet oscillations by high-speed camera makes it possible to obtain energy dissipation parameters such as contact angle hysteresis force and viscous damping coefficients, which indicate pinning and viscous losses, respectively. It is shown that the dissipative forces increase with increasing solid fraction and magnetic force. For 10 µm diameter pillars, the solid fraction range within which droplet oscillations are possible is between 0.97% and 2.18%. Beyond the upper limit, the oscillations become heavily damped due to high friction force. Below the lower limit, the droplet is no longer supported by the pillar tops and undergoes a Cassie-Wenzel transition. This transition is found to occur at lower pressure for a moving droplet than for a static droplet. The findings can help to optimize micropillared surfaces for low-friction droplet transport.

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Section: Introductionmentioning

confidence: 99%

Friction and Wetting Transitions of Magnetic Droplets on Micropillared Superhydrophobic Surfaces

Al‐Azawi

Latikka

Jokinen

et al. 2017

Small

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“…5,33 Less attention has been given to simulations in three dimensions in which lattice Boltzmann 34,35 methods are feasible but molecular dynamics simulations (MD) are costly. Several theoretical and simu-lation approaches use 2D, 28,29,36 or quasi-2D, 27 systems to simplify the calculations or speed up simulations. For some situations, these approaches provide results in good agreement with experimental observations; however, the use of a 2D model of a three dimensional system can mask important aspects of the real system.…”

Section: Introductionmentioning

confidence: 99%

Modeling of Droplet Evaporation on Superhydrophobic Surfaces

2015

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When a drop of water is placed on a rough surface, there are two possible extreme regimes of wetting: the one called Cassie-Baxter (CB) with air pockets trapped underneath the droplet and the one called the Wenzel (W) state characterized by the homogeneous wetting of the surface. A way to investigate the transition between these two states is by means of evaporation experiments, in which the droplet starts in a CB state and, as its volume decreases, penetrates the surface's grooves, reaching a W state. Here we present a theoretical model based on the global interfacial energies for CB and W states that allows us to predict the thermodynamic wetting state of the droplet for a given volume and surface texture. We first analyze the influence of the surface geometric parameters on the droplet's final wetting state with constant volume and show that it depends strongly on the surface texture. We then vary the volume of the droplet, keeping the geometric surface parameters fixed to mimic evaporation and show that the drop experiences a transition from the CB to the W state when its volume reduces, as observed in experiments. To investigate the dependency of the wetting state on the initial state of the droplet, we implement a cellular Potts model in three dimensions. Simulations show very good agreement with theory when the initial state is W, but it disagrees when the droplet is initialized in a CB state, in accordance with previous observations which show that the CB state is metastable in many cases. Both simulations and the theoretical model can be modified to study other types of surfaces.

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“…The conditions required for reversible degradation can be predicted for highly ordered surface structures, as the hydrodynamic factors that dictate air entrapment at a surface are well established [73,74]. Most materials aimed commercialisation are made up of randomised surface features, and provide an array of trapped air environments.…”

Section: Expected Tolerancesmentioning

confidence: 99%

Approaches for Evaluating and Engineering Resilient Superhydrophobic Materials

Crick¹

2020

Superhydrophobic Surfaces - Fabrications to Practical Applications

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Superhydrophobic materials rely upon highly rough surface morphologies in order to maximise water repellency, and requires surface features on the micro/nanoscale. These tremendously small surface structures are inherently physically weak, relative to characteristics of bulk materials. This limits the real-world applicability of many superhydrophobic surfaces, as degradation and loss of superhydrophobicity readily occurs upon exposure to anticipated stimuli. Consequently, there is an absence of long-lasting commercial products, but instead rely upon frequent regeneration. These materials demonstrate a tremendous potential for application in a range of areas, including antifouling, self-cleaning, drag-reduction, anti-icing, etc. To realise application on these fields, superhydrophobic resilience must be maximised. This chapter summarises evaluation methods and engineering procedures in attaining resilience, both are highly important in the development of robust materials.

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Cassie–Baxter to Wenzel state wetting transition: a 2D numerical simulation

Cited by 36 publications

References 25 publications

Friction and Wetting Transitions of Magnetic Droplets on Micropillared Superhydrophobic Surfaces

Friction and Wetting Transitions of Magnetic Droplets on Micropillared Superhydrophobic Surfaces

Modeling of Droplet Evaporation on Superhydrophobic Surfaces

Approaches for Evaluating and Engineering Resilient Superhydrophobic Materials

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