Intermediate wetting state at nano/microstructured surfaces

Nagayama, Gyoko; Zhang, Dejian

doi:10.1039/c9sm02513h

Cited by 67 publications

(56 citation statements)

References 46 publications

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“…This effect could be explained by the increasing level of porous silicon fractalization and the topography, which reduce the contact of the solid surface with the drop of the liquid [31] (Figure 3). Figure 4 illustrates the water contact angles (WCAs) on porous structures as a function of solid fraction (Φ), which was calculated by 1-Apore/A, where Apore is the summation of the pore area in a given area (A) [42]. It was measured several times in order to check the uniformities of the surface.…”

Section: Hydrophobic and Superhydrophobic States On Macropsimentioning

confidence: 99%

“…In the case of flat silicon (Φ = 1), the CA was 69 • . Figure 4 illustrates the water contact angles (WCAs) on porous structures as a function of solid fraction (Φ), which was calculated by 1-Apore/A, where Apore is the summation of the pore area in a given area (A) [42]. It was measured several times in order to check the uniformities of the surface.…”

Section: Hydrophobic and Superhydrophobic States On Macropsimentioning

confidence: 99%

“…However, a perfect state model is infrequent in real experiments. An intermediate state occurs between the Wenzel and Cassie-Baxter states, and several experimental water CAs disagree with these models [42]. [42].…”

Section: Intermediate Wetting State On Macropsi Structuresmentioning

confidence: 99%

“…An intermediate state occurs between the Wenzel and Cassie-Baxter states, and several experimental water CAs disagree with these models [42]. [42]. In this published work, a theoretical partial wetting model is developed in order to explain that in structured surfaces there is a derivation between experimental and theoretical models for hydrophobic substrates.…”

Section: Intermediate Wetting State On Macropsi Structuresmentioning

confidence: 99%

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Hydrophobic/Oleophilic Structures Based on MacroPorous Silicon: Effect of Topography and Fluoroalkyl Silane Functionalization on Wettability

Formentı́n

Marsal

2021

Nanomaterials

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The effect of the morphology and chemical composition of a surface on the wettability of porous silicon structures is analyzed in the present work. Hydrophobic and superhydrophobic macroporous substrates are attractive for different potential applications. Herein, different hydrophobic macroporous silicon structures were fabricated by the chemical etching of p-type silicon wafers in a solution based on hydrofluoric acid and coated with a fluoro silane self-assembled monolayer. The surface morphology of the final substrate was characterized using a scanning electron microscope. The wettability was assessed from contact angle measurements using water and organic solvents that present low surface energy. The experimental data were compared with the classical wetting states theoretical models described in the literature. Perfluoro-silane functionalized macroporous silicon surfaces presented systematically higher contact angles than untreated silicon substrates. The influence of porosity on the surface wettability of macoporous silicon structures has been established. These results suggest that the combination of etching conditions with a surface chemistry modification could lead to hydrophobic/oleophilic or superhydrophobic/oleophobic structures.

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Section: Hydrophobic and Superhydrophobic States On Macropsimentioning

confidence: 99%

Section: Hydrophobic and Superhydrophobic States On Macropsimentioning

confidence: 99%

Section: Intermediate Wetting State On Macropsi Structuresmentioning

confidence: 99%

Section: Intermediate Wetting State On Macropsi Structuresmentioning

confidence: 99%

See 2 more Smart Citations

Hydrophobic/Oleophilic Structures Based on MacroPorous Silicon: Effect of Topography and Fluoroalkyl Silane Functionalization on Wettability

Formentı́n

Marsal

2021

Nanomaterials

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“…RoA increased from an initial 15 • (19 • for dip-coated C) to ≥40 • , after 1000 h of UV or DH exposure, which was above the module tilt angle in many regions. The formation of blisters caused an increase in surface roughness and this effect shifted the coating wetting regime to the combined Cassie-Baxter/Wenzel intermediate state [22,23]. This caused the WCA to decrease only slowly and remain in the hydrophobic range, while the RoA rapidly deteriorated.…”

Section: Degradation Mode: Blister Formationmentioning

confidence: 99%

Degradation of Hydrophobic, Anti-Soiling Coatings for Solar Module Cover Glass

et al. 2020

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Soiling of solar module cover glass is a serious problem for solar asset managers. It causes a reduction in power output due to attenuation of the incident light, and reduces the return on investment. Regular cleaning is required to mitigate the effect but this is a costly procedure. The application of transparent hydrophobic, anti-soiling coatings to the cover glass is a promising solution. These coatings have low surface energy and contaminants do not adhere well. Even if soiling does remain on the coated surface, it is much more easily removed during cleaning. The performance of the coatings is determined using the water contact angle and roll-off angle measurements. However, although hydrophobic coatings hold out great promise, outdoor testing revealed degradation that occurs surprisingly quickly. In this study, we report on results using laboratory-based damp heat and UV exposure environmental tests. We used SEM surface imaging and XPS surface chemical analysis to study the mechanisms that lead to coating degradation. Loss of surface fluorine from the coatings was observed and this appeared to be a major issue. Loss of nanoparticles was also observed. Blistering of surfaces also occurs, leading to loss of coating material. This was probably due to the movement of retained solvents and was caused by insufficient curing. This mechanism is avoidable if care is taken for providing and carrying out carefully specified curing conditions. All these symptoms correlate well with observations taken from parallel outdoor testing. Identification of the mechanisms involved will inform the development of more durable anti-soiling, hydrophobic coatings for solar application.

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Wetting Effect on Patterned Substrates

Wang

Nestler

2023

Advanced Materials

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A droplet deposited on a solid substrate leads to the wetting phenomenon. A natural observation is the lotus effect, known for its superhydrophobicity. This special feature is engendered by the structured microstructure of the lotus leaf, namely, surface heterogeneity, as explained by the quintessential Cassie-Wenzel theory (CWT). In this work, recent designs of functional substrates are overviewed based on the CWT via manipulating the contact area between the liquid and the solid substrate as well as the intrinsic Young's contact angle. Moreover, the limitation of the CWT is discussed. When the droplet size is comparable to the surface heterogeneity, anisotropic wetting morphology often appears, which is beyond the scope of the Cassie-Wenzel work. In this case, several recent studies addressing the anisotropic wetting effect on chemically and mechanically patterned substrates are elucidated. Surface designs for anisotropic wetting morphologies are summarized with respect to the shape and the arrangement of the surface heterogeneity, the droplet volume, the deposition position of the droplet, as well as the mean curvature of the surface heterogeneity. A thermodynamic interpretation for the wetting effect and the corresponding open questions are presented at the end.

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Intermediate wetting state at nano/microstructured surfaces

Abstract: A general partial wetting model to describe an intermediate wetting state is proposed in this study to explain the deviations between the experimental results and classical theoretical wetting models for hydrophobic surfaces.

Cited by 67 publications

References 46 publications

Hydrophobic/Oleophilic Structures Based on MacroPorous Silicon: Effect of Topography and Fluoroalkyl Silane Functionalization on Wettability

Hydrophobic/Oleophilic Structures Based on MacroPorous Silicon: Effect of Topography and Fluoroalkyl Silane Functionalization on Wettability

Degradation of Hydrophobic, Anti-Soiling Coatings for Solar Module Cover Glass

Wetting Effect on Patterned Substrates

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