Effect of fiber orientation on shape and stability of air–water interface on submerged superhydrophobic electrospun thin coatings

Emami, Babak; Tafreshi, H. Vahedi; Gad‐el‐Hak, Mohamed; Tepper, Gary

doi:10.1063/1.3697895

Cited by 47 publications

(29 citation statements)

References 37 publications

(45 reference statements)

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“…However, more integrated numerical methods are needed to characterize the pore structures and quantify the capillary and gravity forces generated by arbitrary cylinder geometries. This is because both the orientations and the cross-sectional shapes of the cylinders/fibres affect the capillary force [32,33]. Therefore, our theory can be a practical guide for designing micro-cylinder rafts with high load-carrying capacity.…”

Section: Discussionmentioning

confidence: 95%

Enhanced load-carrying capacity of hairy surfaces floating on water

Xue

Yuan

et al. 2014

Proc. R. Soc. A.

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Water repellency of hairy surfaces depends on the geometric arrangement of these hairs and enables different applications in both nature and engineering. We investigate the mechanism and optimization of a hairy surface floating on water to obtain its maximum load-carrying capacity by the free energy and force analyses. It is demonstrated that there is an optimum cylinder spacing, as a result of the compromise between the vertical capillary force and the gravity, so that the hairy surface has both high load-carrying capacity and mechanical stability. Our analysis makes it clear that the setae on water striders' legs or some insects' wings are in such an optimized geometry. Moreover, it is shown that surface hydrophobicity can further increase the capacity of a hairy surface with thick cylinders, while the influence is negligible when the cylinders are thin.

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Section: Discussionmentioning

confidence: 95%

Enhanced load-carrying capacity of hairy surfaces floating on water

Xue

Yuan

et al. 2014

Proc. R. Soc. A.

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“…This work is more applicable for electrolyte fuel cells. Other studies were performed to determine the meniscus shape of different surfaces' morphologies at different pressures [99,100]. Meanwhile, Extrand [101] developed a mathematical model to determine the critical pressure of a superhydrophobic surface comprised of microstructure roughness, which is superimposed with a nanostructure one.…”

Section: Air-water Meniscus Stability Under Hydrostatic Pressurementioning

confidence: 99%

Polymeric Slippery Coatings: Nature and Applications

Samaha

Gad‐el‐Hak

2014

Polymers

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Abstract:We review recent developments in nature-inspired superhydrophobic and omniphobic surfaces. Water droplets beading on a surface at significantly high static contact angles and low contact-angle hystereses characterize superhydrophobicity. Microscopically, rough hydrophobic surfaces could entrap air in their pores resulting in a portion of a submerged surface with air-water interface, which is responsible for the slip effect. Suberhydrophobicity enhances the mobility of droplets on lotus leaves for self-cleaning purposes, so-called lotus effect. Amongst other applications, superhydrophobicity could be used to design slippery surfaces with minimal skin-friction drag for energy conservation. Another kind of slippery coatings is the recently invented slippery liquid-infused porous surfaces (SLIPS), which are one type of omniphobic surfaces. Certain plants such as the carnivorous Nepenthes pitcher inspired SLIPS. Their interior surfaces have microstructural roughness, which can lock in place an infused lubricating liquid. The lubricant is then utilized as a repellent surface for other liquids such as water, blood, crude oil, and alcohol. In this review, we discuss the concepts of both lotus effect and Nepenthes slippery mechanism. We then present a review of recent advances in manufacturing polymeric and non-polymeric slippery surfaces with ordered and disordered micro/nanostructures. Furthermore, we discuss the performance and longevity of such surfaces. Techniques used to characterize the surfaces are also detailed. We conclude the article with an overview of the latest advances in characterizing and using slippery surfaces for different applications.

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“…The only exception to this is the case of thin coatings with the air under the AWI completely trapped, like when a coating is fully submerged (in this case the entrapped air significantly contributes to the coating's resistance against the hydrostatic pressure [38,39]). For thick coatings (i.e., coatings for which the volume of the air displaced by a penetrating AWI is negligible compared to the volume of the air in the coating), even when submerged, the capillary pressure is the dominant force balancing the hydrostatic pressure exerted on the coating [40].…”

Section: Coatings Comprised Of Highly Oriented Fibersmentioning

confidence: 94%

“…[40], the closest attempt in predicting the critical pressure of a fibrous SHP coating with random fiber orientations is the work of ref. [39] in which a 2-D projection of the 3-D geometry of a thin fibrous coating was considered as the solution domain for solving an integropartial differential equation (IPDE) to estimate the coating's critical pressure. Obviously, using the projected image of a 3-D structure is only accurate if the coating is very thin.…”

Section: Coatings Comprised Of Orthogonal Fibersmentioning

confidence: 99%

Wetting resistance of heterogeneous superhydrophobic coatings with orthogonally layered fibers

Bucher

Amrei

Tafreshi

2015

Surface and Coatings Technology

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a b s t r a c tSuperhydrophobic coatings comprised of electrospun nanofibers are a low-cost alternative to micro-fabricated surfaces, and can be applied to substrates of any arbitrary geometry. Such coatings with orthogonally oriented layers have properties that allow their wetting resistance to be predictable for a range of solid volume fractions, fiber diameters, and contact angles. In this paper, we have presented a modeling strategy that solves for the airwater interface shape over several layers of such coatings to predict the resistance of superhydrophobic fiber coatings to hydrostatic pressures and to quantify the relationship between microstructure, meniscus penetration depth, and wetted surface area of the fibers. Slip length predictions are also provided to shed some light on the performance of such coatings in drag reduction applications. It was found that while failure pressure for a coating rises with reducing fiber spacing, there is a tradeoff with wetted fiber surface area relative to a bare substrate. This tradeoff can be offset, however, by using smaller fibers for an intended coating. This results in a higher failure pressure for the same wetted area fraction. The results generated in this work are discussed in relation to those reported in the literature whenever possible.

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Effect of fiber orientation on shape and stability of air–water interface on submerged superhydrophobic electrospun thin coatings

Cited by 47 publications

References 37 publications

Enhanced load-carrying capacity of hairy surfaces floating on water

Enhanced load-carrying capacity of hairy surfaces floating on water

Polymeric Slippery Coatings: Nature and Applications

Wetting resistance of heterogeneous superhydrophobic coatings with orthogonally layered fibers

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