Sliding Behavior of Water Droplets on Flat Polymer Surface

Yoshida, Naoya; Abe, Yumi; Shigeta, Hiroaki; Nakajima, Akira; Ohsaki, Hisashi; Hashimoto, Kazuhito; Watanabe, Toshiya

doi:10.1021/ja050617m

Cited by 59 publications

(31 citation statements)

References 19 publications

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“…Along with the contact angle, surface roughness and surface chemical composition (molecule length [51]) aff ect the sliding angle and the contact angle hysteresis. For a smooth hydrophobic surface, a surface with low surface energy provides a small sliding angle.…”

Section: Dynamic Hydrophobicitymentioning

confidence: 99%

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Design of hydrophobic surfaces for liquid droplet control

Nakajima

2011

NPG Asia Mater

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141

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During rainfall, small water droplets can be observed to roll off hydrophobic umbrella surfaces at diff erent speeds. A droplet on a round hydrophobic surface does not always slide down on the surface easily at a small tilt angle, but even if it does, large moving acceleration is not always observed. What determines the motion of droplets on solid surfaces?Diff erences in droplet shape on solid surfaces are often explained by variations in wettability. Th e wetting of a solid surface has persisted through the ages as a research subject at the border between physics and chemistry. Wettability control of a solid against a liquid has been widely explored in industry for application in daily life because it can engender various physical and chemical phenomena related to solids and liquids. Wettability is an important property of solid surfaces from both fundamental and practical aspects. Th e degree of adhesion of liquid droplets onto a solid surface is commonly described in terms of the contact angle (θ), which is given by Young's equation aswhere γ sv , γ sl , and γ lv represent the interfacial free energies per unit area of the solid-gas, solid-liquid and liquid-gas interfaces. Although the defi nition and measurement of the contact angle are simple and easy, the nature of wettability is complex because it is related to three phases: solid, liquid and gas. Moreover, various factors aff ect the surface wettability of a solid. When one factor of a solid surface such as roughness is altered, other factors such as the surface topography or its chemical composition often change simultaneously. Th erefore, it is usually diffi cult to discuss the results of surface wettability obtained from experiments while retaining academic rigor. Th e main research interest for industrial materials is the behavior of millimeter-size droplets on a solid surface of more than a few centimeters in area. Th erefore, the discussion of wettability among samples with great diff erences in surface character is sometimes conducted with ignorance of the infl uence of other characteristics.Hydrophobic coatings are extremely important for wettability control. Th e coatings are anticipated for various industrial uses such as anti-wetting, anti-snow (or ice), anti-rust and reduced friction resistance by reducing solid-liquid interaction. Generally, a hydrophobic surface is one on which water forms a round droplet that is easily removed. Recent advances in probe microscopy and surface spectroscopy and the wider availability of such techniques have revealed that macroscopic surface hydrophobicity, especially dynamic hydrophobicity, is aff ected by nanolevel characteristics such as structure, chemical composition and their alignment and homogeneity. Th e expected properties for a hydrophobic surface cannot always be obtained unless precise design and control of the solid surface are applied. Th is report presents the results of recent studies on the design of hydrophobic surfaces for droplet removal or control from the viewpoint of materials science....

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Section: Dynamic Hydrophobicitymentioning

confidence: 99%

“…Yoshida et al [51] prepared various smooth (Ra of ca. 0.3-0.5 nm) fl uoromethacrylate-methylmethacrylate (FMA-MMA) polymer coatings, and investigated the contact angle, sliding angle and sliding acceleration.…”

Section: Dynamic Hydrophobicitymentioning

confidence: 99%

Design of hydrophobic surfaces for liquid droplet control

Nakajima

2011

NPG Asia Mater

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141

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“…0.30.5 nm) fluoromethacrylate (FMA)-methylmethacrylate (MMA) polymer coatings, and investigated the contact angle, sliding angle and sliding acceleration. 23) Both the contact angle and the sliding acceleration on the coatings increased concomitantly with an increased number of fluorocarbons in FMAs like silanes. However, the contact angle hysteresis shows a different trend.…”

Section: Surface Chemical Compositionmentioning

confidence: 98%

Control of static and dynamic hydrophobicity of solid surface and its application

Nakajima

2011

J. Ceram. Soc. Japan

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Technologies of hydrophobic coating on solid surface are important for various industrial items to impart functions such as antibeading, anti-rusting, anti-snow adhesion, self-cleaning, and lubrication. In recent, the demands of these functions are upgrading, and further improvements of performance are necessary. To meet today's requirements, detailed understandings on the relation between solid characteristics (such as structure, chemical composition, and their arrangement) and static/dynamic hydrophobicity is indispensable. So far, the research on this relation has been conducted in the part of fluid mechanics, tribology, and surface chemistry. However, recent researches revealed that static and dynamic liquid droplet behaviors are affected by nano-scale surface characteristics on hydrophobic solids, and the importance of the viewpoint from materials science is gradually increasing in this topic. This paper presents a review of recent studies on the relation between solid characteristics and static/ dynamic hydrophobicity, mainly of the past decade of our group.

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“…The sliding angle a critical angle at which a droplet starts sliding down an inclined surface by gradual tilting , and contact angle hysteresis the difference between the receding and advancing contact angles of a sliding droplet on an inclined surface are often evaluated as criteria for assessing water-shedding properties from a hydrophobic surface [2][3][4][5][6] .…”

mentioning

confidence: 99%

“…However, these values are insufficient to represent watershedding kinetics such as sliding acceleration and the velocity of water droplets 1,6 . For surface materials' design, information related to how fast the droplet can be removed from the surface at a certain tilt angle is becoming more important than information related to the lowest tilt angle at which the droplet slides downward.…”

mentioning

confidence: 99%

Sliding Behavior of Water Droplets on Smooth Hydrophobic Fluoroalkylsilane Coatings with Different Surface Coverage Ratio

Suzuki¹,

Sakai²,

Yoshida³

et al. 2010

Journal of the Japan Society of Colour Material

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Smooth fluoroalkylsilane FAS17 coatings Ra 0.2 nm with different surface coverage ratios were prepared on a Si substrate by changing the deposition time. Then the internal fluidity of water droplets sliding on the coatings was evaluated using particle image velocimetry PIV . The water droplets slid downward with acceleration by a caterpillar-like rotation with slippage on the solid-liquid interface. The sliding acceleration of the advancing contact line decreased concomitantly with the decreasing surface coverage ratio. However, the slipping/rolling ratio to the overall sliding acceleration was almost constant against surface coverage ratio. This result suggests that physical roughness and chemical composition contributed differently to slipping and rolling motions of the droplets.

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Sliding Behavior of Water Droplets on Flat Polymer Surface

Cited by 59 publications

References 19 publications

Design of hydrophobic surfaces for liquid droplet control

Design of hydrophobic surfaces for liquid droplet control

Control of static and dynamic hydrophobicity of solid surface and its application

Sliding Behavior of Water Droplets on Smooth Hydrophobic Fluoroalkylsilane Coatings with Different Surface Coverage Ratio

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