A modified Cassie–Baxter relationship to explain contact angle hysteresis and anisotropy on non-wetting textured surfaces

Choi, Wonjae; Tuteja, Anish; Mabry, Joseph M.; Cohen, Robert E.; McKinley, Gareth H.

doi:10.1016/j.jcis.2009.07.027

Cited by 512 publications

(469 citation statements)

References 48 publications

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“…We recall that observations of an isotropic receding angle for a drop on striped surfaces have been reported before. 31,36 Note however that the transverse angle shows irregular oscillations of a period w + d, more pronounced for textures with larger w.…”

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confidence: 99%

Regimes of wetting transitions on superhydrophobic textures conditioned by energy of receding contact lines

Dubov

Mourran

Möller

et al. 2015

Applied Physics Letters

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We discuss an evaporation-induced wetting transition on superhydrophobic stripes, and show that depending on the elastic energy of the deformed contact line, which determines the value of an instantaneous apparent contact angle, two different scenarios occur. For relatively dilute stripes the receding angle is above 90 • , and the sudden impalement transition happens due to an increase of a curvature of an evaporating drop. For dense stripes the slow impregnation transition commences when the apparent angle reaches 90 • and represents the impregnation of the grooves from the triple contact line towards the drop center.

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mentioning

confidence: 99%

Regimes of wetting transitions on superhydrophobic textures conditioned by energy of receding contact lines

Dubov

Mourran

Möller

et al. 2015

Applied Physics Letters

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“…We did not measure any dynamic contact angles for the surface structures with a diameter of 11 µm since the drops were stuck even at 90° tilt for these structures. The contact angle hysteresis should in theory scale with the contact area between solid and liquid [12] but due to the random multi-height structures this value is difficult to determine. Instead, we plot the hysteresis as a function of the surface coverage on the mask used to produce the surface.…”

Section: Resultsmentioning

confidence: 99%

Multi-height structures in injection molded polymer

Andersen

Taboryski

2015

Microelectronic Engineering

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We present the fabrication process for injection molded multi-height surface structures for studies of wetting behavior. We adapt the design of super hydrophobic structures to the fabrication constrictions imposed by industrial injection molding. This is important since many super hydrophobic surfaces are challenging to realize by injection molding due to overhanging structures and very high aspect ratios. In the fabrication process, we introduce several unconventional steps for producing the desired shapes, using a completely random mask pattern, exploiting the diffusion limited growth rates of different geometries, and electroforming a nickel mold from a polymer foil. The injection-molded samples are characterized by contact angle hysteresis obtained by the tilting method. We find that the receding contact angle depends on the surface coverage of the random surface structure, while the advancing contact angle is practically independent of the structure. Moreover, we argue that the increase in contact angle hysteresis correlates with the concentration of pinning sites among the random surface structures.

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“…The new model's crucial contribution is the introduction of a parameter that captures the variability of pore geometry. It thus goes beyond the derivations [36][37][38][39] and modifications [40,41] that have previously been used to specialize the Cassie-Baxter model for particular regular geometries such as woven meshes. All of these previously proposed models are entirely deterministic and regard a surface as being capable of being defined by a small set of fixed dimensional parameters.…”

Section: Introductionmentioning

confidence: 99%

A statistical model for the wettability of surfaces with heterogeneous pore geometries

Brockway

Taylor

2016

Mater. Res. Express

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We describe a new approach to modeling the wetting behavior of micro-and nano-textured surfaces with varying degrees of geometrical heterogeneity. Surfaces are modeled as pore arrays with a Gaussian distribution of sidewall reentrant angles and a characteristic wall roughness. Unlike conventional wettability models, our model considers the fraction of a surface's pores that are filled at any time, allowing us to capture more subtle dependences of a liquid's apparent contact angle on its surface tension. The model has four fitting parameters and is calibrated for a particular surface by measuring the apparent contact angles between the surface and at least four probe liquids. We have calibrated the model for three heterogeneous nanoporous surfaces that we have fabricated: a hydrothermally grown zinc oxide, a film of polyvinylidene fluoride (PVDF) microspheres formed by spinodal decomposition, and a polytetrafluoroethylene (PTFE) film with pores defined by sacrificial polystyrene microspheres. These three surfaces show markedly different dependences of a liquid's apparent contact angle on the liquid's surface tension, and the results can be explained by considering geometric variability. The highly variable PTFE pores yield the most gradual variation of apparent contact angle with probe liquid surface tension. The PVDF microspheres are more regular in diameter and, although connected in an irregular manner, result in a much sharper transition from non-wetting to wetting behavior as surface tension reduces. We also demonstrate, by terminating porous zinc oxide with three alternative hydrophobic molecules, that a single geometrical model can capture a structure's wetting behavior for multiple surface chemistries and liquids. Finally, we contrast our results with those from a highly regular, lithographically-produced structure which shows an extremely sharp dependence of wettability on surface tension. This new model could be valuable in designing and evaluating processes for manufacturing liquid-repellent surfaces on an industrial scale.

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A modified Cassie–Baxter relationship to explain contact angle hysteresis and anisotropy on non-wetting textured surfaces

Cited by 512 publications

References 48 publications

Regimes of wetting transitions on superhydrophobic textures conditioned by energy of receding contact lines

Regimes of wetting transitions on superhydrophobic textures conditioned by energy of receding contact lines

Multi-height structures in injection molded polymer

A statistical model for the wettability of surfaces with heterogeneous pore geometries

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