Wetting state on hydrophilic and hydrophobic micro-textured surfaces: Thermodynamic analysis and X-ray visualization

Yu, Dong; Doh, Seung Woo; Kwak, Hee Jin; Kang, Hyungu; Ahn, Ho Seon; Park, Hyun Sun; Moriyama, Kiyofumi; Kim, Moo Hwan

doi:10.1063/1.4919136

Cited by 32 publications

(27 citation statements)

References 38 publications

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“…As a consequence, microscopic contact angle is inadequate to characterize the physics of wetting in a universal way. To date, several attempts have been made to address this problem, primarily relying on the machinery of nonextensive thermodynamics (Blunt et al, 2019;Lazzari & Brito, 2019;Yu et al, 2015). However, a local equilibrium state is often assumed and the energy dissipation in the system during dynamic fluid displacement events is ignored (Berg et al, 2013;Blunt et al, 2019).…”

Section: 1029/2019gl086151mentioning

confidence: 99%

Probing Effective Wetting in Subsurface Systems

Sun

McClure

Mostaghimi

et al. 2020

Geophysical Research Letters

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Wetting phenomena are of central importance for many natural and technological processes in subsurface geosciences. Surface roughness, chemical heterogeneity, and dynamic effects cause the microscopic contact angle to vary widely in subsurface multiphase systems. These effects must be characterized in a fundamental and transparent way to determine the overall state of wetting. Here, we apply the Gauss‐Bonnet theorem to establish a direct link between the contact angle and bulk fluid topology based on a newly defined term, deficit curvature. The resulting macroscopic measure is able to capture the average effects of complex microscopic variations in contact angle based on intrinsic geometric constraints that are imposed on the curvature of the contact line as a consequence of fluid topology. We show that deficit curvature is able to capture the effects of contact angle hysteresis and describe wetting in multiphase systems where geometrically complex contact lines are present along with surface heterogeneity.

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Section: 1029/2019gl086151mentioning

confidence: 99%

Probing Effective Wetting in Subsurface Systems

Sun

McClure

Mostaghimi

et al. 2020

Geophysical Research Letters

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“…Figure 2 shows the parameters of the pattern on the substrates: the radius of a nanopillar R , the distance between each two nanopillars S , the height of a nanopillar a , the length side of rough substrate L , and the number of nanopillars patterned on the same basal area of the substrate n . The roughness ratio of substrate r and area fraction f c was calculated using the following formulas [ 26 ] (the values adopted in our calculation is as shown in Table 1 ):

…”

Section: Methods and Modelsmentioning

confidence: 99%

“…In consideration of such limitations, how to control the wetting transitions of liquid metals on a substrate remains a significant challenge. At present, wetting transitions of liquid droplets on the substrate have gained notable achievements, and two parameters are mainly referred: the surface energy of the materials and the surface roughness [ 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ].…”

Section: Introductionmentioning

confidence: 99%

Wetting Transitions of Liquid Gallium Film on Nanopillar-Decorated Graphene Surfaces

Wang

Tao

et al. 2018

Molecules

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Molecular dynamics (MD) simulation has been employed to study the wetting transitions of liquid gallium droplet on the graphene surfaces, which are decorated with three types of carbon nanopillars, and to explore the effect of the surface roughness and morphology on the wettability of liquid Ga. The simulation results showed that, at the beginning, the Ga film looks like an upside-down dish on the rough surface, different from that on the smooth graphene surface, and its size is crucial to the final state of liquid. Ga droplets exhibit a Cassie–Baxter (CB) state, a Wenzel state, a Mixed Wetting state, and a dewetting state on the patterned surfaces by changing distribution and the morphology of nanopillars. Top morphology of nanopillars has a direct impact on the wetting transition of liquid Ga. There are three transition states for the two types of carbon nanotube (CNT) substrates and two for the carbon nanocone (CNC) one. Furthermore, we have found that the substrates show high or low adhesion to the Ga droplet with the variation of their roughness and top morphology. With the roughness decreasing, the adhesion energy of the substrate decreases. With the same roughness, the CNC/graphene surface has the lowest adhesion energy, followed by CNT/graphene and capped CNT/graphene surfaces. Our findings provide not only valid support to previous works but also reveal new theories on the wetting model of the metal droplet on the rough substrates.

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“…One of the most fascinating wetting behaviour on nanorough substrates is the deviation from the predicted wetting diagram, such as the adoption of a Cassie‐like wetting state despite an unfavorable energy balance. Metastable Cassie state have intrigued researchers over the years and several approaches have been brought forwards to explain their occurrence first on micro and now on nano textured surfaces . These metastable states arise from the presence of high free energy barrier between local and absolute energy minima .…”

Section: The Difference Of Nanomentioning

confidence: 99%

Questions and Answers on the Wettability of Nano‐Engineered Surfaces

MacGregor

Vasilev

2017

Adv Materials Inter

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Surface roughening has long been used to confer materials remarkable wetting properties, such as super hydrophobicity. When roughness belongs to the microscale, existing models can, to some extent, explain and predict real‐world wetting states. With the advent of nanotechnology, however, a multitude of nano‐engineered materials are being developed and unexpected wetting behaviors have been observed which cannot be described by conventional theories. While it is clear that advanced nanotextured materials are essential to a vast range of ground breaking technologies, the intricate mechanisms governing the wetting of such surfaces—at the limit of validity of continuum theories—also need to be clarified. This review aims at presenting what is known and what remains to be discovered about the wettability of nanoengineered materials. The advantages and uniqueness of nanostructured substrates is highlighted first, with a focus on practical applications benefitting from the distinctive wetting properties of nanorough substrates. Classic wetting theories and their limitations are briefly discussed, before describing with a top down vision, why the wetting of nanostructured substrates differ from that of microtextured surfaces. Recent experimental and theoretical studies which contributed to the progress in this field are considered, before outlining potential future areas of research.

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Wetting state on hydrophilic and hydrophobic micro-textured surfaces: Thermodynamic analysis and X-ray visualization

Cited by 32 publications

References 38 publications

Probing Effective Wetting in Subsurface Systems

Probing Effective Wetting in Subsurface Systems

Wetting Transitions of Liquid Gallium Film on Nanopillar-Decorated Graphene Surfaces

Questions and Answers on the Wettability of Nano‐Engineered Surfaces

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