• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.297-300
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• 2006

This article discusses about the droplet movement on the super-hydrophobic surface by the electro-wetting on dielectric and the effect of particles on the contact angle as well as the movement is investigated. The movement of droplet, driven by the principle of electro-wetting on dielectric, and the effect of particles are experimentally verified according to the driving voltage and different particles concentrations (fluorescent, charged particles). To increase the contact angle, the super-hydrophobic surface is fabricated and applied to the dielectric layer for the EWOD device. Then its performance is verified and discussed.

• Applied Microscopy
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• v.46 no.4
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• pp.201-205
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• 2016

Functional surfaces in nature have been continuously observed because of their ability to adapt to the environment. To this end, methods such as scanning electron microscopy (SEM) have been widely used, and their wetting functions have been characterized via environmental SEM. We investigated the superhydrophobic hairy leaves of Pelargonium tomentosum, i.e., peppermint-scented geranium. Their surface features and wettability were studied at multiple-scales, i.e., macro-, micro-, and sub-micro scales. The surfaces of the investigated leaves showed superhydrophobicity at the macro-, and micro-scales. The wetting or condensing behavior was studied for molecule-size water vapors, which easily adhered to the hairy surface owing to their significantly lower size in comparison to that of the surface.

• Korean Journal of Metals and Materials
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• v.50 no.8
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• pp.563-568
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• 2012

The wetting property and reflectivity of Sn-3.5Ag solder which was dip coated on a LED lead frame were investigated. The wettability of molten solder on Cu substrate was evaluated by the wetting balance tester, and surface tension was calculated from maximum withdrawal force and withdrawal time. Temperature of the molten solder in a bath was varied in the range of $250-290^{\circ}C$. With increasing temperature, the surface tension decreased a little. The reflectivity of Sn-3.5Ag coated on a substrate became a little lower than the highest current LED lead frame reflectivity.

• Journal of the Korean Ceramic Society
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• v.19 no.1
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• pp.24-34
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• 1982

The effect of the several variables on wetting of AISIB1113 steel by molten glass was studied by Sessible-drop method. Experimental variables were temperature, firing atmospheres, Fe2O3 addition to the sealing glass and steel surface conditions. The degree of wetting in terms of contact angles between molten glass and metal tested at different test conditions was analyzed by using Young's equation. The results showed that contact angles in H2 atmosphere in the glass metal systems were high but in N2 atmosphere, were small for studied glass metal systems. Especially, when the glass drop was in contact with oxidized steel in N2 atmosphere, The best adherence with contact angle of approximately 9°was obtained. In the case of Fe2O3 addition in glass contact angles subtantially increased due to the increase of surface tension of glass. Wetting phenomena were also discussed under the basis of these experimental results.

• Nano
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• v.13 no.10
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• pp.1850120.1-1850120.9
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• 2018

Two-dimensional poly(dimethylsiloxane) (PDMS) films with wavy patterns were studied in order to investigate reversible and irreversible wetting effects. Pre-strained, surface oxidized layers of PDMS were used to form relieved wavy geometries, on which hydrophobic functionalization was carried out in order to produce irreversible wetting effects. Wavy-patterned PDMS films showed time-dependent reversible wetting effects. The degree of surface wettability could be tuned by the choice of wavy groove geometries. And the groove geometries were controlled via $O_2$ plasma treatment and mechanical pre-straining. The pre-strained, buckled PDMS films were applied to the fabrication of hydrophobic polystyrene nano-patterns using colloidal self-assembly, where the colloids were arrayed in two-dimensional way. The wavy polystyrene films were found to be more hydrophobic relative to flat polystyrene films. The grooving methodology used in this study could be applied to enhancing the hydrophobicity of other types of polymeric thin films, eliminating the need for chemical treatment.

• Journal of the Korean institute of surface engineering
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• v.35 no.2
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• pp.129-137
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• 2002

The purpose of solderability assessment is to predict the effectiveness of soldering process. It is important for companies pursuing zero defects manufacturing because poor solderability is the major cause of two third of soldering failures. The most versatile solderability method is wetting balance method. However, there exist so many indices for wettability in the wetting balance test e.g. time to reach 2/3 values of maximum wetting force, tine to reach zero wetting force, maximum withdrawal force. In this study, three solderability assessment methods, which were the maximum withdrawal force, the wetting balance and the dynamic contact angle (DCA), were evaluated by comparing each other. The wetting balance technique measures the solderability by recording the forces exerted from the specimen after being dipped into the molten solder. Then the force at equilibrium state can be used to calculate a contact angle, which is known as static contact angles. The DCA measures contact angles occurred during advancing and withdrawing of the specimen and the contact angles are known as dynamic contact angles. The maximum withdrawal force uses the maximum force during withdrawal movement and then a contact angle can be calculated. In this study, the maximum withdrawal force method was found to be an objective index for measuring the solderability and the experiment results indicated good agreement between the maximum withdrawal force and the wetting balance method.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.328-328
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• 2011

Wetting phenomena have been heavily studied for industrial and academic researches especially tuning the wettability between hydrophilicity and hydrophobicity. Wicking through the surface texture is shown on superhydrophilic surface while rolling (or dewetting) on the patterns of superhydrophobic surface. These wetting phenomena are known to be affected by surface wettability determined with physical surface patterns as well as chemical composition of surface layer. In this research, we introduce a method to control the wettability of a thin C-SiOx film from hydrophobic to hydrophilic using a mixture gas of HMDSO/$O_2$ by plasma polymerization with rf-CVD (radio frequency-Chemical Vapor Deposition). Wettability was finely controlled by changing the ratio of HMDSO/$O_2$. Hydrophilicity increased as the ratio decreased, while hydrophobicity was enhanced by the ratio. Moreover, fine control from superhydrophilicity to superhydrophobicity was achieved by C-SiOx coating on the Si wafer with prepatterns of submicron-sized pillar array formed by $CF_4$ plasma etching.

• Korean Journal of Materials Research
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• v.19 no.2
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• pp.115-118
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• 2009

The use of dolomite refractories has increased during the past several years in the manufacturing of clean steel during the stainless steelmaking process. However, at the same time, the use of dolomite refractories has led to what is known as the skull formation. In the present work, to understand the skull formation, the wetting characteristics of dolomite substrates by liquid Fe-19wt%Cr-10wt%Ni alloys in various oxygen partial pressures were initially investigated at 1753K using the sessile drop technique. For comparison, the wetting characteristics of alumina substrates were investigated with the same technique. It was found that the wetting index, (1+$cos{\theta}$), of dolomite is approximately 40% higher compared to those of alumina. In addition, the oxygen partial pressure to generate the surface oxide, which may capture the liquid metal on the refractory surface, for dolomite is much lower than that for alumina. From this study, it was concluded that the use of dolomite is much more closely associated with the skull formation compared to the use of alumina due to the stronger wettability and the surface oxide formation at a lower oxygen partial pressure of dolomite.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.11a
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• pp.25.1-25.1
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• 2009

The effects of surface energyon the wetting transition for impinging water droplets were experimentally investigated on the chemically modified WOx nanowire surfaces. We could modify the surface energy of the nanostructures through chemisorption of alkyltrichlorosilanes with various carbon chain lengths and by the UV-enhanced decomposition of self assembled monolayer (SAM) molecules chemically adsorbedon the array. Three surface wetting states could be identified through the balance between antiwetting and wetting pressures. This approach establishes simple strategy for the design criteria for water-repellent surface to impinging droplets.

• Textile Coloration and Finishing
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• v.13 no.1
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• pp.18-22
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• 2001

Effects of cationic surfactants old the wetting behavior of the DMDHEU treated cotton fibers were investigated using a technique based on the Wilhelmy principle. The results indicated that Interactions between the fiber and water ill the interface make contributions to wettability of the cotton fiber surface because of reorientation of polar groups at the interface. The effects of types and concentration of cationic surfactant on the wettability of both control and durable press(DP) finished cotton fiber are discussed. Below and near the critical micelle concentration(cmc), the adsorption of hexadecyltrimethylammoniumbromide(HTAB) on the control fiber makes the fiber surface more hydrophobic. Near and above the cmc of octadecyltrimethylammouniumbromide(OTAB) , the decrease in advancing contact angles indicates that the control cotton surface became hydrophilic. By the adsorption of both HTAB and OTAB onto the fiber surface, the hydrophobicity of the DP finished fiber surface became mere hydrophilic.