• Journal of the Korean Society of Visualization
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• v.16 no.2
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• pp.16-22
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• 2018

This study investigates dynamic wetting behaviors of a water droplet placed on surfaces with different wettability and nano-structures. Hydrophobic and hydrophilic properties on as-received silicon wafers were prepared by fabricating thin films of hydrophobic polymer and hydrophilic nanoparticles via layer-by-layer coating. Dynamic advancing contact angle of droplets on the prepared surfaces was measured at various moving velocities of triple contact line with a high-speed video camera. As advancing velocity of triple contact line increased, dynamic advancing contact angle on the as-received silicon and hydrophobic surfaces sharply increased up to $80^{\circ}$ in the range of order of mm/sec whereas the SiO2 nanoparticle-coated hydrophilic surface maintained low contact angles of about $30^{\circ}$ and then it gradually increased in the velocity range of order of hundred mm/sec. The improved dynamic wetting ability observed on the nanostructured hydrophilic surface can benefit the performance of various phase-change heat transfer phenomena under forced convective flow.

• Applied Chemistry for Engineering
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• v.21 no.3
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• pp.317-322
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• 2010

In this study, poly(methyl methacrylate) (PMMA) was treated with changing mixing ratios of $F_2$ and $O_2$ using oxyfluorination method for hydrophilic modification of PMMA film. For the characterizations of oxyfluorinated PMMA surface, contact angle, surface free energy, X-ray photoelectron spectroscopy (XPS) and optical transmittance (UV-vis) were carried out. After the oxyfluorination, PMMA surface became more hydrophilic showing the decrease of water contact angle from $69^{\circ}$ to $44^{\circ}$. So, surface free energy of oxyfluorinated PMMA film was increased from 46 to $58\;mN\;m^{-1}$. These results are attributed to hydrophilic functional groups such as hydroxyl group formed oxyfluorination method on the PMMA surface. From XPS results, it was confirmed that O/C concentration ratio on the surface of PMMA was increased, the amount of C-OH bonding which shows hydrophilicity was also largely increased from 6.7 to 24.8% with increasing fluorine partial-pressure via the oxyfluorination, The oxyfluorination conditions, room temperature, 1 bar with one mixture ratio of $F_2$ to $O_2$ had little influence on optical transmittance properties of PMMA film but enhanced its surface hydrophilicity. This result suggests that oxyfluorination method could be useful to change hydrophobic PMMA surface to hydrophilic.

• Textile Coloration and Finishing
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• v.23 no.2
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• pp.118-130
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• 2011

In this study, hydrophilic polyurethane (PU) was synthesized by one shot process to get good non-swelling effect and to keep high breathability using reactive silicone oil of mono terminal and bi-terminal types. We also blended non reactive silicone oil with pure hydrophilic PU to compare non-swelling effect and breathability with hydrophilic PU synthesized by the two types of reactive silicone oils. The hydrophilic films were analyzed by nuclear magnetic resonance (NMR) spectroscopy, scanning electron microscope (SEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray photo electron (XPS) spectroscopy, energy dispersive spectrometry (EDS), breathability, waterproofness, tensile strength, contact angle and swelling effect. The results showed that the film made by hydrophilic PU which was synthesized with mono terminal type silicone oil provided good non-swelling effect and acceptable moisture permeability due to the modified surface properties.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.6
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• pp.41-48
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• 2015

Stainless steel mesh has been used as a filter in various fields, including domestic, medical, etc. However, the surface before machining may have an adverse effect the product quality and performance because it is not smooth. Especially, adsorbed impurities in the surface result in difficulty in cleaning. Therefore, in this paper, we propose an improved surface quality through electrochemical polishing (ECP). Two electrodes, composed of STS304 (anode) and copper (cathode) underwent machining with two conditions according to polishing time and current density. As the polishing time and current density increase, the surface of curvature decreases, and roughness and material removal rate (MRR) improves. The machined surface roughness and image were obtained through the atomic force microscope (AFM) and stereoscopic microscope. The study also analyzed hydrophilic effect through contact angles. This obtains corrosion resistance, smoothness, hydrophilic property, etc.

• Membrane Journal
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• v.33 no.1
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• pp.1-12
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• 2023

In this review, surface modification methods of hydrophobic poly(tetrafluoroethylene) (PTFE) membrane are introduced and their improved hydrophilicity results are discussed. Fluoropolymer based membranes, represented by PTFE membranes have been used in various membrane separation processes, including membrane distillation, oil separation and gas separation. However, despite excellent physical properties such as chemical resistance, heat resistance and high mechanical strength, the strong hydrophobicity of PTFE membrane surface has become a challenging factor in expanding its membrane separation application. To improve the separation performance of PTFE membranes, wet chemical, hydrophilic coating, plasma, irradiation and atomic layer deposition are applied, modifying the surface property of PTFE membranes while maintaining their inherent properties.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.6
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• pp.288-292
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• 2009

Hydrophobic/hydrophilic patterned substrates were fabricated on a glass substrate by a liquid phase deposition (LPD) method. Hydrophobic surface was obtained by modifying ZnO thin films with a rough surface using a fluoroalkyltrimethoxysilane (FAS) and hydrophilic surface was prepared by decomposing FAS on an exposed to UV light. The hexagonal ZnO rods were perpendicularly grown by LPD method on glass substrates with a ZnO seed layer. The diameter and thickness of hexagonal ZnO rods were increased as a function of increases of immersion time. The surface morphology, thickness, crystal structure, transmittance and contact angle of prepared ZnO thin films were measured by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), UV-visible spectrophotometer (UV-vis) and contact angle measurement. Hydrophilic ZnO thin films with a contact angle of $20^{\circ}{\sim}30^{\circ}$ were changed to a hydrophobic surface with a contact angle of $145^{\circ}{\sim}161^{\circ}$ by a FAS surface treatment. Prepared hydrophobic surface was pattered by an irradiation of UV light using shadow mask with $300\;{\mu}m$ or 3 mm dot size. Finally, the hydrophobic surface exposed to UV light was changed to a hydrophilic surface.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.645-648
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• 2006

Normally, deterioration in the concrete structure is due to carbonation and chloride ion attack. Therefore, concrete structure is needed to surface protection for increase durability using impregnant. Impregnant classify into two large groups in polymeric and silicate materials. Silicate impregnant is included silicate and alkali silicate(sodium and lithium silicate). Thus, this study is concerned with self cleaning hydrophilic property of concrete structure using silicate impregnant. From the experimental test result, TEOS and lithium silicate make good use of hydrophilic impregnant.

• Journal of Biosystems Engineering
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• v.35 no.4
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• pp.257-261
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• 2010

Surface energy is the principal factor of anti-condensation. High surface energy appears hydrophilic itself and low surface energy represents hydrophobic itself. The contact angle is widely being used for measurement of surface energy of materials, evaluation of coating performances, measurement of wettability, and so on. However, the existing contact angle measuring system is so expensive for purchasing and complicated, so it takes a lot of time and money to use. This study was conducted to develop the algorithm for evaluating hydrophilic performance through measuring the contact angle of water droplet automatically, and fabricate relatively simple measuring system using a low-cost monochrome camera and image processing. A constant amount of water was firstly allocated on a slide by a micropipette, and then the image of water droplet was captured by monochrome digital camera and sent to a computer. The image was binarized and then reduced noises by labeling. Finally, the contact angle of water droplet was computed by using three points (left, right, and top coordinates), simple linear mathematics, and trigonometric function. The experimental results demonstrated the accuracy and reproducibility of the developed system showing less deviations and deviation ratio.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.262-262
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• 2010

We introduce a novel and efficient strategy for producing free-standing functional films via photo-crosslinking and electrostatic layer-by-layer (LbL) assembly, which can allow the buildup of hydrophilic multilayers onto hydrophobic surfaces. Hydrophobic multilayers were deposited on ionic substrates by a photo-crosslinking LbL process using photo-crosslinkable polymers. The photo-crosslinked surface was converted to an anionic surface by excess UV light irradiation. This treatment allowed also the stable adhesion between metal electrode or cationic polyelectrolyte and hydrophobic multilayers. After dissolving the ionic substrates in water, the formed free-standing films exhibited unique functionalities of inserted components within hydrophobic and/or hydrophilic multilayers.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.5
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• pp.300-305
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• 2015

$WO_3$, $SiO_2$, and $TiO_2$ films with hydrophilic property are deposited by rf-magnetron sputtering. Their wettability is strongly depends on the presence or absence of the oxygen plasma etching on the glass substrates. The $TiO_2$ film of 50 nm-thick on the plasma etched glass shows a water contact angle (WCA) below $5^{\circ}$ which means a super-hydrophilic surface. However, WCA values are gradually degraded when the films are exposed under atmosphere, especially $WO_3$. In order to improve hydrophilic property, the degraded films can be again recovered by UV illumination for 10 sec using UV-light and the $TiO_2$ film shows a super-hydrophilic surface about $3^{\circ}$.