Fabrication of a superhydrophobic surface with fungus-cleaning properties on brazed aluminum for industrial application in heat exchangers

Lee, Jeong-Won,Hwang, Woonbong Elsevier BV * North-Holland 2018 Applied Surface Science Vol.442 No.-

<P><B>Abstract</B></P> <P>Extensive research has been carried out concerning the application of superhydrophobic coating in heat exchangers, but little is known about the application of this technique to brazed aluminum heat exchangers (BAHEs). In this work, we describe a new superhydrophobic coating method, which is suitable for BAHE use on an industrial scale. We first render the BAHE superhydrophobic by fabricating micro/nanostructures using solution dipping followed by fluorination. After the complete removal of the silicon residue, we verify using surface analysis that the BAHE surface is perfectly superhydrophobic. We also studied the fungus-cleaning properties of the superhydrophobic surface by growing fungus for 4 weeks in a moist environment on BAHE fins with and without superhydrophobic coating. We observed that, whereas the fungus grown on the untreated fins is extremely difficult to remove, the fungus on the fins with the superhydrophobic coating can be removed easily with only a modest amount of water. We also found that the coated BAHE fins exhibit excellent resistance to moisture. The superhydrophobic coating method that we propose is therefore expected to have a major impact in the heating, ventilating and air conditioning industry market.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We describe a procedure for creating superhydrophobic surfaces on brazed aluminum. </LI> <LI> We demonstrate the applicability of this method to brazed aluminum heat exchangers. </LI> <LI> We show that our superhydrophobic surfaces have excellent self-cleaning properties. </LI> <LI> Our coating procedure is suitable for industrial applications. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Laser-induced superhydrophobic grid patterns on PDMS for droplet arrays formation

Farshchian, Bahador,Gatabi, Javad R.,Bernick, Steven M.,Park, Sooyeon,Lee, Gwan-Hyoung,Droopad, Ravindranath,Kim, Namwon Elsevier 2017 APPLIED SURFACE SCIENCE - Vol.396 No.-

<P><B>Abstract</B></P> <P>We demonstrate a facile single step laser treatment process to render a polydimethylsiloxane (PDMS) surface superhydrophobic. By synchronizing a pulsed nanosecond laser source with a motorized stage, superhydrophobic grid patterns were written on the surface of PDMS. Hierarchical micro and nanostructures were formed in the irradiated areas while non-irradiated areas were covered by nanostructures due to deposition of ablated particles. Arrays of droplets form spontaneously on the laser-patterned PDMS with superhydrophobic grid pattern when the PDMS sample is simply immersed in and withdrawn from water due to different wetting properties of the irradiated and non-irradiated areas. The effects of withdrawal speed and pitch size of superhydrophobic grid on the size of formed droplets were investigated experimentally. The droplet size increases initially with increasing the withdrawal speed and then does not change significantly beyond certain points. Moreover, larger droplets are formed by increasing the pitch size of the superhydrophobic grid. The droplet arrays formed on the laser-patterned PDMS with wettability contrast can be used potentially for patterning of particles, chemicals, and bio-molecules and also for cell screening applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Superhydrophobic grid patterns were processed on the surface of PDMS using a pulsed nanosecond laser. </LI> <LI> Droplet arrays form instantly on the laser-patterned PDMS with the superhydrophobic grid pattern when the PDMS sample is simply immersed in and withdrawn from water. </LI> <LI> Droplet size can be controlled by controlling the pitch size of superhydrophobic grid and the withdrawal speed. </LI> </UL> </P>

Control of laser-ablated aluminum surface wettability to superhydrophobic or superhydrophilic through simple heat treatment or water boiling post-processing

Ngo, Chi-Vinh,Chun, Doo-Man Elsevier BV * North-Holland 2018 Applied Surface Science Vol.435 No.-

<P><B>Abstract</B></P> <P>Recently, controlling the wettability of a metallic surface so that it is either superhydrophobic or superhydrophilic has become important for many applications. However, conventional techniques require long fabrication times or involve toxic chemicals. Herein, through a combination of pulse laser ablation and simple post-processing, the surface of aluminum was controlled to either superhydrophobic or superhydrophilic in a short time of only a few hours. In this study, grid patterns were first fabricated on aluminum using a nanosecond pulsed laser, and then additional post-processing without any chemicals was used. Under heat treatment, the surface became superhydrophobic with a contact angle (CA) greater than 150° and a sliding angle (SA) lower than 10°. Conversely, when immersed in boiling water, the surface became superhydrophilic with a low contact angle. The mechanism for wettability change was also explained. The surfaces, obtained in a short time with environmentally friendly fabrication and without the use of toxic chemicals, could potentially be applied in various industry and manufacturing applications such as self-cleaning, anti-icing, and biomedical devices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Superhydrophilic/superhydrophobic Al surfaces were made by laser ablation and simple post process. </LI> <LI> Laser-ablated Al surface became superhydrophobic using heat treatment. </LI> <LI> Laser-ablated Al surface became superhydrophilic using boiling water treatment. </LI> <LI> Mechanism of wettability change to superhydrophobic/superhydrophilic was explained. </LI> <LI> The performances of superhydrophobic and superhydrophilic Al were demonstrated. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Guided Transport of WaterDroplets on Superhydrophobic–Hydrophilic Patterned Si Nanowires

Seo, Jungmok,Lee, Soonil,Lee, Jaehong,Lee, Taeyoon AmericanChemical Society 2011 ACS APPLIED MATERIALS & INTERFACES Vol.3 No.12

<P>We present a facile method to fabricate hydrophilic patterns in superhydrophobic Si nanowire (NW) arrays for guiding water droplets. The superhydrophobic Si NW arrays were obtained by simple dip-coating of dodecyltrichlorosilane (DTS). The water contact angles (CAs) of DTS-coated Si NW arrays drastically increased and saturated at the superhydrophobic regime (water CA >= 150 degrees) as the lengths of NW's increased. The demonstrated superhydrophobic surfaces show an extreme water repellent property and small CA hysteresis of less than 7 degrees, which enable the water droplets to easily roll off. The wettability of the DTS-coated Si NW arrays can be converted from superhydrophobic to hydrophilic via UV-enhanced photodecomposition of the DTS, and such wettability conversion was reproducible on the same surfaces by repeating the DTS coating and photodecomposition processes. The resulting water guiding tracks were successfully demonstrated via selective patterning of the hydrophilic region on superhydrophobic Si NW arrays, which could enable water droplets to move along defined trajectories.</P>

Transparent and superhydrophobic surface using dual scale nanostructure

이유진,하영근 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.0

In this study, we demonstrate a simple spin-coating method for the preparation of transparent superhydrophobic surface using dual scale nanostructure.. Various ratios of different size aluminum NPs were chosen to fabricate dual scale nanostructure and to study the effect of the surface roughness, affecting superhydrophobicity and optical transparency. The dual scale nanostructure films were then modified to have the hydrophobicity by dipping in octadecylphosphonic acid (ODPA). The resulting coated surface displayed a static water contact angle of 158° showing excellent superhydrophobicity. Moreover, the spin-coated superhydrophobic films were also highly transparent with greater than 90% transmittance in the visible region.

Facile Fabrication of Non-fluorinated Durable Superhydrophobic Cotton Fabric

Guolin Zheng,Yuhe Wu,Dan Zhang,Shuai Liu,Zhu Long,Rong Li 한국섬유공학회 2020 Fibers and polymers Vol.21 No.11

The superhydrophobic surface is easy to lose the superhydrophobicity in the practical applications, due to the factthat the micro- and nanoscale rough structure is easily damaged. Therefore, it is one of the challenges to endow solid surfacewith durable superhydrophobic property. In this work, the environment-friendly superhydrophobic cotton fabric was preparedby dip-coating methodology. Meanwhile, the cotton fabric was endowed with durable superhydrophobicity. Herein, theoctadecylamine was utilized to reduce the surface free energy of cotton fabric. However, octadecylamine was only adsorbedon the fabric surface. Therefore, the hydrophobic resin was employed to supply enough adhesion force. As a result, thelimitation that traditional methods frequently utilize additional nanoparticles to construct hierarchical rough surfaces wasbroken. The water contact angles of the coated cotton fabric at room temperature and 70 oC reached 154.4±0.6 o and120±1.1 o, respectively. Moreover, the coated cotton fabric still reserved superhydrophobic property after 30th cycle’sabrasion and exhibited excellent hydrophobicity after 500th cycle’s abrasion. In addition, the surface free energy of originalcotton fabric reduced by 54.7 % so that the coated cotton fabric had outstanding repellency to hydrochloric acid, sodiumhydroxide solution, coffee and sodium chloride solution, respectively.

Robust and Chemically Stable Superhydrophobic Aluminum-Alloy Surface with Enhanced Corrosion-Resistance Properties

Sumit Barthwal,임시형 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.7 No.2

We report a simple method for fabricating micro-nanoscale structures consisting of irregular microscale plateaus with a self-assembled network of zinc oxide nanopetals on an aluminum alloy substrate. The method involves a combination of chemical etching with a hydrothermal process, followed by Polydimethylsiloxane coating via a simple vapor deposition method. Following the coating, surface displays superhydrophobicity with water contact angle of 161° and a sliding angle of 4°. The effect of morphological changes on wettability is examined by varying the hydrothermal processing time. The chemical stability of the superhydrophobic surfaces is examined in a wide range of corrosive media. After being immersed in a 3.5 wt% NaCl solution for 1 month, the surface retained its superhydrophobicity. The potentiodynamic polarization test results reveal that the superhydrophobic surface highly improves the corrosion resistance performance of the bare aluminum surface by three orders of magnitude. In addition, surface exhibited good mechanical durability against sandpaper abrasion, and long-term stability in the ambient environment. The proposed fabrication technique operating at relatively low temperature is simple and provides a new approach for production of large-scale three-dimensional superhydrophobic surfaces for various applications.

Facile and cost-effective fabrication of patternable superhydrophobic surfaces via salt dissolution assisted etching

Choi, D.,Yoo, J.,Park, S.M.,Kim, D.S. New York] ; North-Holland 2017 APPLIED SURFACE SCIENCE - Vol.393 No.-

Superhydrophobic surfaces with extremely low wettability have attracted attention globally along with their remarkable characteristics such as anti-icing, anti-sticking, and self-cleaning. In this study, a facile and cost-effective approach of fabricating patternable superhydrophobic surfaces, which can be applied on various substrates (including large area and 3D curvilinear substrates), is proposed with a salt-dissolution-assisted etching process. This novel proposal is environmentally benign (entirely water-based and fluorine-free process). The only required ingredients to realize superhydrophobic surfaces are commercially available salt particles, polydimethylsiloxane (PDMS), and water. No expensive equipment or complex process control is needed. The fabricated superhydrophobic surface shows high static contact angle (~151<SUP>o</SUP>) and a low sliding angle (~6<SUP>o</SUP>), which correspond to the standards of superhydrophobicity. This surface also shows corrosive liquids (acid/alkali)-resistant characteristics. Moreover, the self-cleaning ability of the fabricated surfaces is explored. As a proof-of-concept application of the present approach, the spatially controllable superhydrophobic patterns on flat/curvilinear substrates are directly drawn with a minimum feature size of 500μm without the use of expensive tooling, dies, or lithographic masks.

레이저 가공과 열처리로 제작된 초소수성 알루미늄 합금 표면의 부식 저항 연구

김지훈,천두만 대한기계학회 2020 大韓機械學會論文集A Vol.44 No.3

Fabrication of superhydrophobic metal surfaces by laser texturing and heat treatment has been developed. Subsequent to laser texturing, the metal samples generally require chemical coating or aging in an ambient atmosphere for relatively long periods to achieve superhydrophobicity. Simple heat treatment could promote the transition in wettability from hydrophilic to superhydrophobic without using additional chemical treatment in a relatively shorter timeframe. In this study, a grid pattern was fabricated on an aluminum alloy by a UV (ultraviolet) nanosecond pulsed laser, after which an additional step of heat treatment at 200℃ for 6 hours was carried out. The fabricated aluminum samples showed superhydrophobicity with contact angles greater than 150° and slip angles less than 10°. Corrosion tests were performed using superhydrophobic samples. In some cases, corrosion resistance was improved compared to that of an untreated aluminum alloy surface. 본 연구에서는 레이저 가공과 열처리에 의해 초소수성 금속 표면을 제작하고 평가하였다. 일반적으로 레이저 가공 후, 금속 표면을 초소수성으로 만들기 위해서는 화학물로 코팅하거나 오랜 시간 대기 중에서의 자연 시효가 필요하였지만, 본 연구는 화학 처리 없이 단순한 열처리만으로 친수성의 표면을 초소수성으로 젖음성을 개선하였다. 구체적으로는 자외선 나노초 펄스 레이저를 통해 격자 구조로 알루미늄 합금을 가공하였고, 200℃ 온도에서 6시간 동안 열처리를 진행하였다. 가공한 표면은 접촉각이 150° 이상, 미끄럼각이 10° 이하로 초소수성 특성을 잘 보였다. 이후 제작한 초소수성 표면을 이용하여 내부식성 실험을 하였다. 그 결과 레이저 가공과 열처리를 통해 만들어진 초소수성 표면을 이용하면 부식 성능을 개선할 수 있다는 결과를 도출하였다.

Fast wettability transition from hydrophilic to superhydrophobic laser-textured stainless steel surfaces under low-temperature annealing

Ngo, Chi-Vinh,Chun, Doo-Man Elsevier BV * North-Holland 2017 Applied Surface Science Vol.409 No.-

<P><B>Abstract</B></P> <P>Recently, the fabrication of superhydrophobic metallic surfaces by means of pulsed laser texturing has been developed. After laser texturing, samples are typically chemically coated or aged in ambient air for a relatively long time of several weeks to achieve superhydrophobicity. To accelerate the wettability transition from hydrophilicity to superhydrophobicity without the use of additional chemical treatment, a simple annealing post process has been developed. In the present work, grid patterns were first fabricated on stainless steel by a nanosecond pulsed laser, then an additional low-temperature annealing post process at 100°C was applied. The effect of 100–500μm step size of the textured grid upon the wettability transition time was also investigated. The proposed post process reduced the transition time from a couple of months to within several hours. All samples showed superhydrophobicity with contact angles greater than 160° and sliding angles smaller than 10° except samples with 500μm step size, and could be applied in several potential applications such as self-cleaning and control of water adhesion.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Superhydrophobic surface on SUS304 was fabricated by laser texturing and annealing. </LI> <LI> Wettability transition was done within 4h only with low temperature annealing. </LI> <LI> The effect of grid pattern size upon the wettability change was studied. </LI> <LI> The effect of water droplet contact during wettability change was investigated. </LI> <LI> The mechanism and applications of superhydrophobic surface were proposed. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>