Direct Observation of Internal Fluidity in a Water Droplet during Sliding on Hydrophobic Surfaces

Sakai, Munetoshi; Song, Jeong Hwan; Yoshida, Naoya; Suzuki, Shunsuke; Kameshima, Yoshikazu; Nakajima, Akira

doi:10.1021/la060323u

Cited by 109 publications

(65 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Th is result implies that the sliding acceleration depends on the sliding mode and that identifi cation of the contribution of these two sliding modes to overall sliding acceleration or velocity is necessary for comparison of the water-shedding performance of hydrophobic solid surfaces. An eff ective approach for the direct observation of the internal fl uidity of moving droplets is particle image velocimetry [63,64]. Using this technique, internal fl uidity and velocity distribution during sliding are directly obtainable because of the use of tracking particles or their concentration dispersed in water ( Figure 6).…”

Section: Dynamic Hydrophobicitymentioning

confidence: 99%

Design of hydrophobic surfaces for liquid droplet control

Nakajima

2011

NPG Asia Mater

Self Cite

141

View full text Add to dashboard Cite

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....

show abstract

Section: Dynamic Hydrophobicitymentioning

confidence: 99%

Design of hydrophobic surfaces for liquid droplet control

Nakajima

2011

NPG Asia Mater

Self Cite

141

View full text Add to dashboard Cite

show abstract

“…This indicator is a criterion for a classification of the protective coating to the category of hydrophobic (α > 90°) or hydrophilic (α < 90°) one [16]. In turn, the technique of dynamic research was to study the formation and spontaneous movement of the liquid mini-flow in the chute due to its appropriate slope and volume of the liquid critical mass.…”

Section: Figmentioning

confidence: 99%

Hydraulic characteristics of internal protective coatings used for rehabilitation of pipelines of water supply and sanitation systems

Orlov

2018

MATEC Web Conf.

View full text Add to dashboard Cite

“…For many years, the following issues are studied: drops slip from surfaces with different roughness [10], hydrodynamic interaction of flows with superhydrophobic surfaces [11], liquid contact angle measurement with the surface under flow conditions [12], laser research of the superhydrophobic surfaces structure [13], nature of the change in the contact angle during the drop movement on different surfaces [14,15] measurement of viscous droplets speed moving down on inclined surface [16], use of atomic force microscopy to measure the boundary sliding on hydrophilic, hydrophobic and superhydrophobic surfaces [17] spreading and slipping of liquid droplets on solid surfaces [18] and others. For example, in the article [19] in the observation period of water droplets during its movement the contact angles to the hydrophobic surface normal depending on the magnitude of velocity were investigated. With rapid sliding down the superhydrophobic surface the contact angle was 150°, whereas at the slower sliding and rolling the contact angle to the surface normal ranged from 100 to 79.5°.…”

Section: Introductionmentioning

confidence: 99%

Pipeline walls hydrophobic properties study and their protective coatings used in trenchless technologies

Orlov

2016

MATEC Web Conf.

View full text Add to dashboard Cite

Abstract.The results of field and theoretical studies to determine the degree of hydrophobicity of the inner pipe walls in static and dynamic conditions are reported. The water drops spreading nature in contact with the horizontal and concave surface of different materials with the definition of contact angles is determined. The flow pattern formed when the critical mass of liquid miniflow is reached on an inclined surface in the form of an open trough was studied. The geometric parameters of the frontal and coaxial miniflow projections were determined, its dimensions and hydraulic characteristics were studied. The trial stand design for the protective coatings hydrophobic properties study was presented and described and method of evaluation of the pipeline work surfaces hydrophobic properties by applying the relative hydrophobicity ratio. Calculation formulas of the relative hydrophobicity ratio for work surfaces were presented. The relationships of hydrophobicity of various coatings used in the trenchless technologies to relative roughness coefficients were established.

show abstract

Direct Observation of Internal Fluidity in a Water Droplet during Sliding on Hydrophobic Surfaces

Cited by 109 publications

References 14 publications

Design of hydrophobic surfaces for liquid droplet control

Design of hydrophobic surfaces for liquid droplet control

Hydraulic characteristics of internal protective coatings used for rehabilitation of pipelines of water supply and sanitation systems

Pipeline walls hydrophobic properties study and their protective coatings used in trenchless technologies

Contact Info

Product

Resources

About