• Journal of Korean Ophthalmic Optics Society
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• v.16 no.1
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• pp.31-40
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• 2011

Purpose: This study was performed to investigate the actual state about ultrasonic cleaning of soft contact lenses in local optical shops and evaluate the removal effect of protein deposit on soft contact lenses with different lens containers by ultrasonic cleaner for eyeglasses. Methods: The actual state about ultrasonic cleaning of soft contact lenses was surveyed in total 75 local optical shops in Seoul, Korea. The cleaning efficacy of different lens containers was compared by measuring the protein remained on ocufilcon D contact lenses after washing by an ultrasonic cleaner for eyeglasses. The changes on surfaces and wetting angles of ocufilcon D contact lenses by repeat ultrasonication were further investigated. Results: The main purpose to use ultrasonic cleaners in local optical shops was rapid cleaning. The ultrasonic cleaning efficacy of ocufilcon D contact lenses with glass containers was little higher than it with plastic containers, but was not significantly different. The changes on surfaces and wetting angles of ocufilcon D contact lenses in a plastic lens container by repeat ultrasonication such as 30 and/or 60 times were shown. Conclusions: There was not significant difference in cleaning efficacy between glass and plastic lens containers. However, repeat cleaning with ultrasonic cleaner for eyeglasses would be carefully considered since some significant changes in the parameters of lens surface and wetting angles were detected by repeat ultrasonification even when lens containers were used for ocufilcon D contact lens during ultrasonictions.

• Nuclear Engineering and Technology
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• v.43 no.3
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• pp.205-216
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• 2011

Recently, many research studies have investigated the enormous critical heat flux (CHF) enhancement caused by nanofluids during pool boiling and flow boiling. One of the main reasons for this enhancement is nanoparticle deposition on the heated surface. However, in real applications, nanofluids create many problems when used as working fluids because of sedimentation and aggregation. Therefore, artificial surfaces on silicon and metal have been developed to create an effect similar to that of nanoparticle deposition. These modified surfaces have proved capable of greatly increasing the CHF during pool boiling, and good results have also been observed during flow boiling. In this study, we demonstrate that the wetting ability of a surface, i.e., wettability, and the liquid spreading ability (hydrophilic surface property), are key parameters for increasing the CHF during both pool and flow boiling. We also demonstrate that when the fuel surface in nuclear power plants is modified in a similar manner, it has the same effect, producing a large CHF enhancement.

• Journal of the Korean institute of surface engineering
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• v.31 no.2
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• pp.101-108
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• 1998

The effect of oxidation-reduction heating conditions on coating adherence of hot-dip galvanized steel containing silicon has beeninvestigated. The presence of a stbke sillicon oxide formed on the steel surface has been shown to be very detrimenal to proper wetting by liquid zinc. When the steel has more than the critical sillicon content neeled to from a stable external oxide, the use of oxidation-reduction method has been found successful in obtaining a good quality, coated product with excellence adhreence. This can be explained by the formation of an iron oxide. The iron oxrtion of the scale is reduced, leaving the stable oxides dispersed in a fresh metallic iron surface layer. This reduced iron surface is easily wetted by the liquid zinc and excellent adherence is obtained.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.357.1-357.1
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• 2014

Superhydrophobic WOx nanowire (NW) arrays were fabricated using a thermal evaporation and surface chemistry modification methods by self-assembled monolayer (SAM). As-prepared non-wetting WOx NWs surface shows water contact angle of $163.2^{\circ}$ and has reliable stability in underwater conditions. Hence the superhydrophobic WOx NWs surface exhibits silvery surface by total reflection of water layer and air interlayer. The stability analysus of underwater superhydrophobicity of WOx NWs arrays was conducted by changing hydrostatic pressure and surface energy of WOx NWs arrays. The stability of superhydrophobicity in underwater conditions decreased exponentially as hydrostatic pressure applied to the substrates increased3. In addition, as surface energy decreased, the underwater stability of superhydrophobic surface increased sharply. Specifically, sueprhydrophobic stability increased exponentially as surface energy of WOx NWs arrays was decreased. Based on these results, the models for explaining tendencies of superhydrophobic stability underwater resulting from hydrostatic pressure and surface energy were designed. The combination of fugacity and Laplace pressure explained this exponential decay of stability according to hydrostatic pressure and surface energy. This study on fabrication and modeling of underwater stability of superhydrophobic W18O49 NW arrays will help in designing highly stable superhydrophobic surfaces and broadening fields of superhydrophobic applications even submerged underwater.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.601-601
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• 2013

Superhydrophobic W18O49 nanowire (NW) arrays were synthesizedusing a thermal evaporation and surface chemistry modification methods by self-assembled monolayer (SAM). As-prepared non-wetting W18O49 NWs surface shows water contact angle of $163.2^{\circ}$ and has reliable stability in underwater conditions. Hence the superhydrophobic W18O49 NWs surface exhibits silvery surface by total reflection of water layer and air interlayer. The stability analysus of underwater superhydrophobicity of W18O49 NWs arrays was conducted by changing hydrostatic pressure and surface energy of W18O49 NWs arrays. The stability of superhydrophobicity in underwater conditions decreased exponentially as hydrostatic pressure applied to the substrates increased3. In addition, as surface energy decreased, the underwater stability of superhydrophobic surface increased sharply. Specifically, sueprhydrophobic stability increased exponentially as surface energy of W18O49 NWs arrays was decreased. Based on these results, the models for explaining tendencies of superhydrophobic stability underwater resulting from hydrostatic pressure and surface energy were designed. The combination of fugacity and Laplace pressure explained this exponential decay of stability according to hydrostatic pressure and surface energy. This study on fabrication and modeling of underwater stability of superhydrophobic W18O49 NW arrays will help in designing highly stable superhydrophobic surfaces and broadening fields of superhydrophobic applications even submerged underwater.

• Journal of the Korean Applied Science and Technology
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• v.33 no.3
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• pp.449-458
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• 2016

Detergency and surface active properties of mixed anionic surfactants with amphoteric and nonionic were investigated. Sodium dodecyl sulfate (SDS) and ammonium dodecyl sulfate (ADS) as anionic surfactants and cocamidopropyl betaine (CAPB) as an amphoteric surfactant were used. Nonionic surfactants, which are butyl glucoside (BG), octyl glucoside (OG), decyl glucoside (DG), lauryl dimethylamine oxide (AO) and saponin were also used. To study the synergy effects of mixed SDS/ADS anionic surfactant systems, amphoteric and nonionic surfactants were added into the mixed anionic surfactants. Investigated properties of surfactant mixtures were critical micelle concentration (CMC), surface tension (${\gamma}$), wettability. In addition, based on these properties, detergency of each sample was examined. Surfactant mixtures are anionics (SDS/ADS), anionic/amphoteric/nonionic (SDS/ADS/CAPB/saponin), and anionic/nonionic (SDS/ADS/BG/saponin, SDS/ADS/OG/saponin, SDS/ADS/DG/saponin, and SDS/ADS/AO/saponin). With the addition of amphoteric and nonionic to mixed anionic surfactants, CMC and ${\gamma}$ were decreased. Addition of CAPB, which is amphoteric, showed the best property at CMC and ${\gamma}$. Furthermore, as the chain length of hydrocarbon in alkyl glucosides was increased, the CMC and ${\gamma}$ were enhanced. However, the wettability did not exactly match up with CMC and ${\gamma}$. The surfactant mixture, which contained DG, showed the best performance at wetting time. Detergency was measured at various temperatures ($15^{\circ}C$, $30^{\circ}C$, $50^{\circ}C$). The cleaning performance was enhanced by increasing washing temperature. Moreover, detergency was influenced by not only CMC and ${\gamma}$ but also wettability. Although CMC and ${\gamma}$ were not minimum at surfactant mixture that included DG, the best cleaning performance showed in that sample.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.3
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• pp.247-255
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• 2004

The cooling characteristic of water-air mixed spray for high water mass flux is not well defined, compared to that of highly pressurized spray. A series of research program was planned to develop the boiling correlation for whole temperature range in case of water-air mixed spray with high water mass flux. The cooling experiments of hot steel surface with initial temperature of 820$^{\circ}C$ were conducted in unsteady state with relatively high water mass flux. A computer program was developed to calculate the heat flux inversely from measured data by three inserted thermocouples. Finally the effects of water and air mass flux on the averaged film boiling heat flux and wetting temperature were studied. In this 1st report, it is found that the boiling curve was similar to that of highly pressurized spray and the decreased slope of heat flux in film boiling region with respect to surface temperature became steep by increasing air mass flux. Also it is shown that, by increasing air mass flux, the averaged heat flux in film boiling region was increased, and then saturated and the wetting temperature was increased, and then decreased. Finally when the heat flux in film boiling region is compared with that of highly pressurized spray, it is known that the cooling is improved by introducing air up to 60%.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.10
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• pp.659-666
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• 2016

A numerical study, using the molecular dynamics simulation method, was carried out to investigate the wetting characteristics of water droplets on a solid square pillar surface with variable periodic edge length patterns at the nanoscale. In this study, the pillar plane was supposed to be rectangular or square shaped. In addition, the surface area was increased while the shape of the pillar plane was kept fixed. In the case of the square pillar, the edge length increased from $4.24{\AA}$ to $12.72{\AA}$. Also, the rectangular pillar had two types of length edges. In this case, one edge length was fixed at $8.48{\AA}$ and the other edge length was increased from $4.24{\AA}$ to $12.72{\AA}$. Through these length changes, the hydrophobicity and hydrophilicity of a water droplet on the variable pillar surfaces were analyzed.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.320-320
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• 2011

We describe fabrication of superhydrophobic surface on non-woven fabric (NWF) having nano-hairy structures and a hydrophobic surface coating. Oxygen plasma was irradiated on NWF for nano-texuring and a precursor of HMDSO (Hexamethydisiloxane) was introduced as a surface chemical modification for obtaining superhydrophobicity using 13.56 MHz radio frequency-Plasma Enhanced Chemical Vapor Deposition (rf-PECVD). O2 plasma treatment time was varied from 1 min to 60 min at a bias voltage of 400V, which fabricated pillar-like structures with diameter of 30 nm and height of 150 nm on NWF. Subsequently, hydrophobic coating using hexamethyldisiloxane vapor was deposited with 10 nm thickness on NWF substrate at a bias voltage of 400 V. We evaluate superhydrophobicity of the modified NWF with sessile drop using goniometer and high speed camera, in which aspect ratio of nanohairy structures, contact angle and contact angle hysteresis of the surfaces were measured. With the increase of aspect ratio, the wetting angle increased from $103^{\circ}$ to $163^{\circ}$, and the contact angle hysteresis decreased dramatically below $5^{\circ}$. In addition, we had conducted experiment for nucleation and condensation of water via E-SEM. During increasing vapor pressure inside E-SEM from 3.7 Torr to over 6 Torr which is beyond saturation point at $2^{\circ}C$, we observed condensation of water droplet on the superhydropobic NWF. While the condensation of water on oxygen plasma treated NWF (superhydrophilic) occurred easily and rapidly, superhydrophobic NWF which was fabricated by oxygen and HMDSO was hardly wet even under supersaturation condition. From the result of wetting experiment and water condensation via E-SEM, it is confirmed that superhydrophobic NWF shows the grate water repellent abilities.

• Textile Coloration and Finishing
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• v.25 no.1
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• pp.30-36
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• 2013

Swelling and subsequent deformation of membranes by water wetting are regarded as a prime drawback of hydrophilic polyurethane breathable film. Fluoroalkylated surface was prepared by reacting the film with hexamethylene diisocyanate(HDI) and 2-perfluorohexyl ethanol. IR spectra and XPS results showed that the fluoroalkyl group was successfully introduced to the film surface with hexamethylene linkage. Water contact angle was increased from $68.7^{\circ}$ up to $144.2^{\circ}$ with the degree of fluoroalkylation. Decrease in water-vapor permeability was minimized even for the film of highest fluoroalkylation.