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Superhydrophobic Coatings
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Superhydrophobic Coatings

A special issue of Coatings (ISSN 2079-6412).

Deadline for manuscript submissions: closed (31 October 2022) | Viewed by 101353

Special Issue Editor

Prof. Dr. Ioannis Karapanagiotis

E-Mail Website1 Website2
Guest Editor
Department of Chemistry, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
Interests: coatings; surfaces and interfaces; wetting and dewetting; superhydrophobicity and superomniphobicity; water repellency and self-cleaning; nanostructured materials; biomimetics; nanocomposites; nanoparticles; polymers; archaeological chemistry; textile history; conservation science
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The bioinspired surfaces of special wetting properties, from superhydrophobicity to superhydrophilicity and superoleophobicity to superoleophilicity, have recently attracted considerable attention. Among these special surfaces, supehydrophobic surfaces (which can be either water-repellent or water-adhesive) can have numerous potential applications and therefore deserve, and have attracted, special attention.

Hundreds of different methods have been devised and applied to produce hierarchically structured, superhydrophobic surfaces such as, for instance, sol-gel, controlled nanoparticle embedding into polymer matrices (composites), wet chemical reaction, electrochemical deposition, plasma etching, chemical vapor deposition, lithography, electrospinning, solution immersion, emulsion, and so on.

Coatings produced using the aforementioned methods is a usual strategy to induce superhydrophobicity to various surfaces-substrates.

In particular, the topics of interest include, but are not limited to:

  • Anti-sticking, anti-contamination for any outdoor surface (buildings, automobiles, monuments)
  • Stain resistant clothing
  • Anti-biofouling paints (e.g., for boats)
  • Anti-icing i.e. anti-sticking of snow for aircrafts, wind generators, antennas, windows etc.
  • Self-cleaning windshields for automobiles
  • Microfluidics, i.e., droplet manipulation and controlled transport of small volumes of liquids; single-molecule spectroscopy
  • Metal refining
  • Lab-on-a-chip devices
  • Membranes, e.g., water harvesting, cleaning of water

Prof. Dr. Ioannis Karapanagiotis
Guest Editor

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.


Published Papers (15 papers)

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Research

Jump to: Review

17 pages, 3572 KiB  
Article
Oleo/Hydrophobic Coatings Containing Nano-Particles for the Protection of Stone Materials Having Different Porosity
by Mariateresa Lettieri, Maurizio Masieri, Alessandra Morelli, Mariachiara Pipoli and Mariaenrica Frigione
Coatings 2018, 8(12), 429; https://doi.org/10.3390/coatings8120429 - 27 Nov 2018
Cited by 20 | Viewed by 4287
Abstract
Conservation strategies to limit the degradation of stone materials are being constantly developed. To this aim, new materials are designed to confer hydrophobic properties and anti-graffiti protection to the treated surfaces. Hybrid nanocomposites, based on inorganic nano-particles added to an organic matrix, have [...] Read more.
Conservation strategies to limit the degradation of stone materials are being constantly developed. To this aim, new materials are designed to confer hydrophobic properties and anti-graffiti protection to the treated surfaces. Hybrid nanocomposites, based on inorganic nano-particles added to an organic matrix, have been recently proposed for treatments of stone surfaces, obtaining promising and innovative properties. In the present paper, an experimental product based on fluorine resin containing SiO2 nano-particles, a commercial fluorine-based product and a silicon-based material were applied as protective coatings on two calcareous stones (compact and porous) widely employed in the Mediterranean region. All the studied products are expected to provide both water and anti-graffiti protection to both stones’ surfaces. The rheological characterization of the liquid products, changes in color of the surfaces, and variations in water vapor permeability allowed the compatibility of the protective systems applied to stones to be evaluated. Water–stone contact angle measurements and water absorption by capillarity were used to control the action against water ingress. The oleophobicity was assessed by measuring the oil–stone contact angle. The experimental nano-filled product proved to be a suitable hydrophobic coating for compact and porous stones; furthermore, it provides high oleophobicity to the treated surfaces, as required for anti-graffiti systems. Full article
(This article belongs to the Special Issue Superhydrophobic Coatings)
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11 pages, 3121 KiB  
Article
Toward Superhydrophobic/Superoleophilic Materials for Separation of Oil/Water Mixtures and Water-in-Oil Emulsions Using Phase Inversion Methods
by Chih-Feng Wang, Yi-Jung Tsai, Shiao-Wei Kuo, Kuo-Jung Lee, Chien-Chieh Hu and Juin-Yih Lai
Coatings 2018, 8(11), 396; https://doi.org/10.3390/coatings8110396 - 11 Nov 2018
Cited by 14 | Viewed by 8133
Abstract
In this study, a method that can simultaneously separate oil/water mixtures and water-in-oil emulsions were developed. Various substrates (synthetic polymers and stainless steel meshes) were coated by rough hydrophobic polymer films. The prepared materials possessed superhydrophobicity and superoleophilicity. These superhydrophobic sponges can isolate [...] Read more.
In this study, a method that can simultaneously separate oil/water mixtures and water-in-oil emulsions were developed. Various substrates (synthetic polymers and stainless steel meshes) were coated by rough hydrophobic polymer films. The prepared materials possessed superhydrophobicity and superoleophilicity. These superhydrophobic sponges can isolate extensive amounts of oil from water when connected to a related vacuum framework. Moreover, the superhydrophobic meshes (SHM) can separate both surfactant-free and -stabilized water-in-oil emulsions via gravity with high separation efficiency (oil purity: >99.99%) and flux (up to 4760 L m−2 h−1). The extraordinary performance of our materials and their low-energy, efficient, low-cost preparation propose that they have great potential for real-time applications. Full article
(This article belongs to the Special Issue Superhydrophobic Coatings)
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10 pages, 2456 KiB  
Article
Superhydrophobic Fabrics with Mechanical Durability Prepared by a Two-Step Plasma Processing Method
by Kosmas Ellinas, Angeliki Tserepi and Evangelos Gogolides
Coatings 2018, 8(10), 351; https://doi.org/10.3390/coatings8100351 - 02 Oct 2018
Cited by 16 | Viewed by 4740
Abstract
Most studies on superhydrophobic fabrics focus on their realization using additive manufacturing (bottom-up) techniques. Here we present the direct modification of three different fabrics using a plasma-based method to obtain anti-adhesive and self-cleaning properties. A two-step plasma processing method is used: (a) for [...] Read more.
Most studies on superhydrophobic fabrics focus on their realization using additive manufacturing (bottom-up) techniques. Here we present the direct modification of three different fabrics using a plasma-based method to obtain anti-adhesive and self-cleaning properties. A two-step plasma processing method is used: (a) for the creation of micro-nanoscale features on the fabric surface (plasma texturing step) and (b) the minimization of the fabric surface energy (by a short plasma deposition step of a very thin, low surface energy layer). The entire process takes only 14 min and all fabrics after processing exhibit high water static contact angles (WSCA > 150°), low contact angle hysteresis (CAH < 7°) and advantageous mechanical durability against hand-rumpling. The method is simple and generic, and it can be therefore expanded to other polymeric fabrics (i.e., acrylic) in addition to polyester, without any limitation rising from the weaving characteristics of the fabric or the starting nature of the material (i.e., hydrophobic or hydrophilic). Full article
(This article belongs to the Special Issue Superhydrophobic Coatings)
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14 pages, 4204 KiB  
Article
Optimal Patterned Wettability for Microchannel Flow Boiling Using the Lattice Boltzmann Method
by Young Jin Wi, Jong Hyun Kim, Jung Shin Lee and Joon Sang Lee
Coatings 2018, 8(8), 288; https://doi.org/10.3390/coatings8080288 - 17 Aug 2018
Cited by 12 | Viewed by 4959
Abstract
Microchannel flow boiling is a cooling method studied in microscale heat-cooling, which has become an important field of research with the development of high-density integrated circuits. The change in microchannel surface characteristics affects thermal fluid behavior, and existing studies have optimized heat transfer [...] Read more.
Microchannel flow boiling is a cooling method studied in microscale heat-cooling, which has become an important field of research with the development of high-density integrated circuits. The change in microchannel surface characteristics affects thermal fluid behavior, and existing studies have optimized heat transfer by changing surf ace wettability characteristics. However, a surface with heterogeneous wettability also has the potential to improve heat transfer. In this case, heat transfer would be optimized by applying the optimal heterogeneous wettability surface to channel flow boiling. In this study, a change in cooling efficiency was observed, by setting a hydrophobic and hydrophilic wettability pattern on the channel surface under the microchannel flow boiling condition, using a lattice Boltzmann method simulation. In the rectangular microchannel structure, the hydrophobic-hydrophilic patterned wettability was oriented perpendicular to the flow direction. The bubble nucleation and the heat transfer coefficient were observed in each case by varying the length of the pattern and the ratio of the hydrophobic-hydrophilic area. It was found that the minimum pattern length in which individual bubbles can occur, and the wettability pattern in which the bubble nucleation-departure cycle is maintained, are advantageous for increasing the efficiency of heat transfer in channel flow boiling. Full article
(This article belongs to the Special Issue Superhydrophobic Coatings)
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13 pages, 23711 KiB  
Article
Hot Embossing for Whole Teflon Superhydrophobic Surfaces
by Jie Li, Wentao Yu, Deyin Zheng, Xin Zhao, Chang-Hwan Choi and Guangyi Sun
Coatings 2018, 8(7), 227; https://doi.org/10.3390/coatings8070227 - 22 Jun 2018
Cited by 16 | Viewed by 6968
Abstract
In this paper, we report a simple fabrication process of whole Teflon superhydrophobic surfaces, featuring high-aspect-ratio (>20) nanowire structures, using a hot embossing process. An anodic aluminum oxide (AAO) membrane is used as the embossing mold for the fabrication of high-aspect-ratio nanowires directly [...] Read more.
In this paper, we report a simple fabrication process of whole Teflon superhydrophobic surfaces, featuring high-aspect-ratio (>20) nanowire structures, using a hot embossing process. An anodic aluminum oxide (AAO) membrane is used as the embossing mold for the fabrication of high-aspect-ratio nanowires directly on a Teflon substrate. First, high-aspect-ratio nanowire structures of Teflon are formed by pressing a fluorinated ethylene propylene (FEP) sheet onto a heated AAO membrane at 340 °C, which is above the melting point of FEP. Experimental results show that the heating time and aspect ratios of nanopores in the AAO mold are critical to the fidelity of the hot embossed nanowire structures. It has also been found that during the de-molding step, a large adhesive force between the AAO mold and the molded FEP greatly prolongs the length of nanowires. Contact angle measurements indicate that Teflon nanowires make the surface superhydrophobic. The reliability and robustness of superhydrophobicity is verified by a long-term (~6.5 h) underwater turbulent channel flow test. After the first step of hot-embossing the Teflon nanowires, microstructures are further superimposed by repeating the hot embossing process, but this time with microstructured silicon substrates as micromolds and at a temperature lower than the melting temperature of the FEP. The results indicate that the hot embossing process is also an effective way to fabricate hierarchical micro/nanostructures of whole Teflon, which can be useful for applications of Teflon material, such as superhydrophobic surfaces. Full article
(This article belongs to the Special Issue Superhydrophobic Coatings)
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13 pages, 5857 KiB  
Article
Anti- and De-Icing Behaviors of Superhydrophobic Fabrics
by Yuyang Liu, Dong Song and Chang-Hwan Choi
Coatings 2018, 8(6), 198; https://doi.org/10.3390/coatings8060198 - 23 May 2018
Cited by 20 | Viewed by 5563
Abstract
This paper reports the application of superhydrophobic coatings on cotton fabrics and their functionalities for anti- and de-icing efficacy. Superhydrophobic cotton fabrics with different water-repellent properties have been achieved by decorating the surface of pristine cotton fibers with ZnO structures of varying sizes [...] Read more.
This paper reports the application of superhydrophobic coatings on cotton fabrics and their functionalities for anti- and de-icing efficacy. Superhydrophobic cotton fabrics with different water-repellent properties have been achieved by decorating the surface of pristine cotton fibers with ZnO structures of varying sizes and shapes through an in situ solution growth process, followed by the treatment of the surface with low-surface-energy coating such as Teflon. The surface morphology of the treated cotton fabrics was characterized using scanning electron microscopy (SEM). The surface wettability of the treated fabrics was evaluated through the measurement of static contact angle (SCA), contact angle hysteresis (CAH), and sliding angle (SA) of a water droplet. The anti- and de-icing behaviors of the treated fabrics were evaluated through both static (sessile droplet) and dynamic (spraying) tests. The results show that the superhydrophobic fabric with a higher SCA and the lower CAH/SA has superior anti- and de-icing behaviors in both the static and dynamic conditions. Compared to hard substrates, the soft, flexible, and porous (air-permeable) superhydrophobic fabrics can lead to broader applicability of textile-based materials for the design and fabrication of anti- and de-icing materials. Furthermore, the multi-scale surface structures of fabrics (fibers, yarns, and weaving constructions) combining with the hierarchical micro-nanostructures of the ZnO coating provides an ideal platform for anti-icing studies. Full article
(This article belongs to the Special Issue Superhydrophobic Coatings)
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15 pages, 13838 KiB  
Article
Superhydrophobic Bilayer Coating Based on Annealed Electrospun Ultrathin Poly(ε-caprolactone) Fibers and Electrosprayed Nanostructured Silica Microparticles for Easy Emptying Packaging Applications
by Juliana Lasprilla-Botero, Sergio Torres-Giner, Maria Pardo-Figuerez, Mónica Álvarez-Láinez and Jose M. Lagaron
Coatings 2018, 8(5), 173; https://doi.org/10.3390/coatings8050173 - 03 May 2018
Cited by 26 | Viewed by 6685
Abstract
A coating rendering superhydrophobic properties to low-density polyethylene (LDPE) films used in packaging applications was herein generated by means of the electrohydrodynamic processing (EHDP) technique. To this end, electrospun ultrathin poly(ε-caprolactone) (PCL) fibers, followed by electrosprayed nanostructured silica (SiO2) microparticles, were [...] Read more.
A coating rendering superhydrophobic properties to low-density polyethylene (LDPE) films used in packaging applications was herein generated by means of the electrohydrodynamic processing (EHDP) technique. To this end, electrospun ultrathin poly(ε-caprolactone) (PCL) fibers, followed by electrosprayed nanostructured silica (SiO2) microparticles, were deposited on top of the LDPE film. Various electrospinning and electrospraying times were tested and optimized followed by a thermal post-treatment to provide physical adhesion between the bilayer coating and the LDPE substrate. The morphology, hydrophobicity, permeance to limonene, and thermal stability of the resultant nanostructured coatings were characterized. It was observed that by controlling both the deposition time of the electrospun ultrathin PCL fibers and the electrosprayed SiO2 microparticles, as well as the conditions of the thermal post-treatment, effective superhydrophobic coatings were developed onto the LDPE films. The resultant multilayer presented a hierarchical micro/nanostructured surface with an apparent contact angle of 157° and a sliding angle of 8°. The addition of silica reduced, to some extent, the limonene (aroma) barrier, likely due to the increased surface-to-volume ratio, which allowed permeant sorption to occur but improved the thermal stability of the LDPE/PCL film. As a result, the developed multilayer system of LDPE/PCL/SiO2 has significant potential for use in easy-to-empty packaging applications of high water activity products. Full article
(This article belongs to the Special Issue Superhydrophobic Coatings)
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12 pages, 3766 KiB  
Article
Anti-Icing Performance of Hydrophobic Silicone–Acrylate Resin Coatings on Wind Blades
by Ke Xu, Jianlin Hu, Xingliang Jiang, Wei Meng, Binhuan Lan and Lichun Shu
Coatings 2018, 8(4), 151; https://doi.org/10.3390/coatings8040151 - 23 Apr 2018
Cited by 16 | Viewed by 5512
Abstract
The icing of wind blades poses a serious threat to the operation of wind turbines. The application of superhydrophobic coatings on wind blades can serve as a potential anti-icing method. This study presents the findings of simulations of the icing environment of wind [...] Read more.
The icing of wind blades poses a serious threat to the operation of wind turbines. The application of superhydrophobic coatings on wind blades can serve as a potential anti-icing method. This study presents the findings of simulations of the icing environment of wind blades coated with hydrophobic silicone–acrylate resin in an artificial climate chamber. Artificial icing tests were performed on NACA7715 wind blades with four different silicone–acrylate resin coatings and on uncoated wind blades, with test performed at five different wind speeds and three different angles of attack. Results show that wind blade surfaces with higher hydrophobicity yield better anti-icing performance, and that the ice mass of the wind blades decreases with increasing wind speeds and angles of attack. In addition, variations in ice mass, shape, and distribution on different wind blades indicate that increased hydrophobicity can help limit the areas that are subject to freezing. Hydrophobicity can affect the air cavities of the ice deposited on the wind blades, and surfaces with increased hydrophobicity can lead to lower ice mass and less ice adhesion. In brief, surfaces with higher hydrophobicity demonstrate better anti-icing performance and benefit from active de-icing. Full article
(This article belongs to the Special Issue Superhydrophobic Coatings)
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14 pages, 6755 KiB  
Article
Fabrication of Self-healing Superhydrophobic Surfaces from Water-Soluble Polymer Suspensions Free of Inorganic Particles through Polymer Thermal Reconstruction
by Yalun Shen, Yitian Wu, Zhehong Shen and Hao Chen
Coatings 2018, 8(4), 144; https://doi.org/10.3390/coatings8040144 - 16 Apr 2018
Cited by 16 | Viewed by 6027
Abstract
Self-healing superhydrophobic surfaces have been fabricated by casting and drying water-soluble amphiphilic polymer suspensions at room temperature through thermal reconstruction. When compared with previous methods, this approach exploits modified natural hierarchical microstructures from wood instead of artificially constructing them for superhydrophobic morphology, which [...] Read more.
Self-healing superhydrophobic surfaces have been fabricated by casting and drying water-soluble amphiphilic polymer suspensions at room temperature through thermal reconstruction. When compared with previous methods, this approach exploits modified natural hierarchical microstructures from wood instead of artificially constructing them for superhydrophobic morphology, which involves neither organic solvent nor inorganic particles nor complex procedures. The obtained superhydrophobic surface has acceptable resistance to abrasion. The surface can recover superhydrophobicity spontaneously at room temperature upon damage, which can be accelerated at a higher temperature. After depleting healing agents, the polymer suspension can be sprayed or cast onto wood surfaces to replenish healing agents and to restore self-healing ability. The superhydrophobic surface greatly increases the mold inhibition and water resistance of wood, which would prolong the service life of wood based materials. Full article
(This article belongs to the Special Issue Superhydrophobic Coatings)
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13 pages, 2133 KiB  
Article
Superhydrophobic, Superoleophobic and Antimicrobial Coatings for the Protection of Silk Textiles
by Dimitra Aslanidou and Ioannis Karapanagiotis
Coatings 2018, 8(3), 101; https://doi.org/10.3390/coatings8030101 - 09 Mar 2018
Cited by 47 | Viewed by 7408
Abstract
A method to produce multifunctional coatings for the protection of silk is developed. Aqueous dispersion, free of any organic solvent, containing alkoxy silanes, organic fluoropolymer, silane quaternary ammonium salt, and silica nanoparticles (7 nm in mean diameter) is sprayed onto silk which obtains [...] Read more.
A method to produce multifunctional coatings for the protection of silk is developed. Aqueous dispersion, free of any organic solvent, containing alkoxy silanes, organic fluoropolymer, silane quaternary ammonium salt, and silica nanoparticles (7 nm in mean diameter) is sprayed onto silk which obtains (i) superhydrophobic and superoleophobic properties, as evidenced by the high contact angles (>150°) of water and oil drops and (ii) antimicrobial properties. Potato dextrose agar is used as culture medium for the growth of microorganisms. The protective coating hinders the microbial growth on coated silk which remains almost free of contamination after extensive exposure to the microorganisms. Furthermore, the multifunctional coating induces a moderate reduction in vapor permeability of the treated silk, it shows very good durability against abrasion and has a minor visual effect on the aesthetic appearance of silk. The distinctive roles of the silica nanoparticles and the antimicrobial agent on the aforementioned properties of the coating are investigated. Silica nanoparticles induce surface structures at the micro/nano-meter scale and are therefore responsible for the achieved extreme wetting properties that promote the antimicrobial activity. The latter is further enhanced by adding the silane quaternary ammonium salt in the composition of the protective coating. Full article
(This article belongs to the Special Issue Superhydrophobic Coatings)
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10 pages, 3944 KiB  
Article
Corrosion Resistance and Durability of Superhydrophobic Copper Surface in Corrosive NaCl Aqueous Solution
by Chun-Wei Yao, Divine Sebastian, Ian Lian, Özge Günaydın-Şen, Robbie Clarke, Kirby Clayton, Chiou-Yun Chen, Krishna Kharel, Yanyu Chen and Qibo Li
Coatings 2018, 8(2), 70; https://doi.org/10.3390/coatings8020070 - 11 Feb 2018
Cited by 43 | Viewed by 7475
Abstract
Artificial superhydrophobic copper surfaces play an important role in modern applications such as self-cleaning and dropwise condensation; however, corrosion resistance and durability often present as major concerns in such applications. In this study, the anti-corrosion properties and mechanical durability of superhydrophobic copper surface [...] Read more.
Artificial superhydrophobic copper surfaces play an important role in modern applications such as self-cleaning and dropwise condensation; however, corrosion resistance and durability often present as major concerns in such applications. In this study, the anti-corrosion properties and mechanical durability of superhydrophobic copper surface have been investigated. The superhydrophobic copper surfaces were achieved with wet chemical etching and an immersion method to reduce the complexity of the fabrication process. The surface structures and materials were characterized using scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), and Fourier transform infrared spectrometer (FTIR). The corrosion resistance and mechanical properties of the superhydrophobic copper surface were characterized after immersing surfaces in a 3.5 wt % NaCl solution. The chemical stability of the superhydrophobic copper surface in the NaCl solution for a short period of time was also evaluated. An abrasion test and an ultrasound oscillation were conducted to confirm that the copper surface contained durable superhydrophobic properties. In addition, an atomic force microscope was employed to study the surface mechanical property in the corrosion conditions. The present study shows that the resulting superhydrophobic copper surface exhibit enhanced corrosion resistance and durability. Full article
(This article belongs to the Special Issue Superhydrophobic Coatings)
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16 pages, 9940 KiB  
Article
New Electrospun Polystyrene/Al2O3 Nanocomposite Superhydrophobic Coatings; Synthesis, Characterization, and Application
by Ahmed Bahgat Radwan, Aboubakr M. Abdullah, Adel M. A. Mohamed and Mariam A. Al-Maadeed
Coatings 2018, 8(2), 65; https://doi.org/10.3390/coatings8020065 - 08 Feb 2018
Cited by 33 | Viewed by 6109
Abstract
The effect of electrospinning operational parameters on the morphology, surface roughness, and wettability of different compositions of electrospun polystyrene (PS)–aluminum oxide (Al2O3) nanocomposite coatings was investigated using different techniques. For example, a scanning electron microscope (SEM) coupled with an [...] Read more.
The effect of electrospinning operational parameters on the morphology, surface roughness, and wettability of different compositions of electrospun polystyrene (PS)–aluminum oxide (Al2O3) nanocomposite coatings was investigated using different techniques. For example, a scanning electron microscope (SEM) coupled with an energy dispersive X-ray (EDX) unit, a Fourier transform infrared (FTIR) spectrometer, an atomic force microscope (AFM), and water contact angle (WCA), and contact angle hysteresis (CAH) measurements using the sessile droplet method, were used. The latter used 4 µL of distilled water at room temperature. PS/Al2O3 nanocomposite coatings exhibited different morphologies, such as beaded fibers and microfibers, depending on the concentration ratio between the PS and Al2O3 nanoparticles and the operational parameters of the electrospinning process. The optimum conditions to produce a nanocomposite coating with the highest roughness and superhydrophobic properties (155° ± 1.9° for WCA and 3° ± 4.2° for CAH) are 2.5 and 0.25 wt % of PS and Al2O3, respectively, 25 kV for the applied potential and 1.5 mL·h−1 for the solution flow rate at 35 °C. The corrosion resistance of the as-prepared coatings was investigated using the electrochemical impedance spectroscopy (EIS) technique. The results have revealed that the highly porous superhydrophobic nanocomposite coatings (SHCs) possess a superior corrosion resistance that is higher than the uncoated Al alloy by three orders of magnitude. Full article
(This article belongs to the Special Issue Superhydrophobic Coatings)
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7451 KiB  
Article
Fabrication of an Anisotropic Superhydrophobic Polymer Surface Using Compression Molding and Dip Coating
by Kyong-Min Lee, Chi-Vinh Ngo, Ji-Young Jeong, Eun-chae Jeon, Tae-Jin Je and Doo-Man Chun
Coatings 2017, 7(11), 194; https://doi.org/10.3390/coatings7110194 - 10 Nov 2017
Cited by 18 | Viewed by 5793
Abstract
Many studies of anisotropic wetting surfaces with directional structures inspired from rice leaves, bamboo leaves, and butterfly wings have been carried out because of their unique liquid shape control and transportation. In this study, a precision mechanical cutting process, ultra-precision machining using a [...] Read more.
Many studies of anisotropic wetting surfaces with directional structures inspired from rice leaves, bamboo leaves, and butterfly wings have been carried out because of their unique liquid shape control and transportation. In this study, a precision mechanical cutting process, ultra-precision machining using a single crystal diamond tool, was used to fabricate a mold with microscale directional patterns of triangular cross-sectional shape for good moldability, and the patterns were duplicated on a flat thermoplastic polymer plate by compression molding for the mass production of an anisotropic wetting polymer surface. Anisotropic wetting was observed only with microscale patterns, but the sliding of water could not be achieved because of the pinning effect of the micro-structure. Therefore, an additional dip coating process with 1H, 1H, 2H, 2H-perfluorodecythricholosilanes, and TiO2 nanoparticles was applied for a small sliding angle with nanoscale patterns and a low surface energy. The anisotropic superhydrophobic surface was fabricated and the surface morphology and anisotropic wetting behaviors were investigated. The suggested fabrication method can be used to mass produce an anisotropic superhydrophobic polymer surface, demonstrating the feasibility of liquid shape control and transportation. Full article
(This article belongs to the Special Issue Superhydrophobic Coatings)
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Review

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33 pages, 9416 KiB  
Review
Recent Progress in Preparation and Anti-Icing Applications of Superhydrophobic Coatings
by Yuebin Lin, Haifeng Chen, Guanyu Wang and Aihui Liu
Coatings 2018, 8(6), 208; https://doi.org/10.3390/coatings8060208 - 31 May 2018
Cited by 128 | Viewed by 11452
Abstract
Aircraft icing refers to ice formation and accumulation on the windward surface of aircrafts. It is mainly caused by the striking of unstable supercooled water droplets suspended in clouds onto a solid surface. Aircraft icing poses an increasing threat to the safety of [...] Read more.
Aircraft icing refers to ice formation and accumulation on the windward surface of aircrafts. It is mainly caused by the striking of unstable supercooled water droplets suspended in clouds onto a solid surface. Aircraft icing poses an increasing threat to the safety of flight due to the damage of aerodynamic shape. This review article provides a comprehensive understanding of the preparation and anti-icing applications of the superhydrophobic coatings applied on the surface of aircrafts. The first section introduces the hazards of aircraft icing and the underlying formation mechanisms of ice on the surface of aircrafts. Although some current anti-icing and de-icing strategies have been confirmed to be effective, they consume higher energy and lead to some fatigue damages to the substrate materials. Considering the icing process, the functional coatings similar to lotus leaf with extreme water repellency and unusual self-cleaning properties have been proposed and are expected to reduce the relied degree on traditional de-icing approaches and even to replace them in near future. The following sections mainly discuss the current research progress on the wetting theories of superhydrophobicity and main methods to prepare superhydrophobic coatings. Furthermore, based on the bouncing capacity of impact droplets, the dynamic water repellency of superhydrophobic coatings is discussed as the third evaluated parameter. It is crucial to anti-icing applications because it describes the ability of droplets to rapidly bounce off before freezing. Subsequently, current studies on the application of anti-icing superhydrophobic coatings including the anti-icing mechanisms and application status are introduced in detail. Finally, some limitations and issues related to the anti-icing applications are proposed to provide a future outlook on investigations of the superhydrophobic anti-icing coatings. Full article
(This article belongs to the Special Issue Superhydrophobic Coatings)
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32 pages, 9888 KiB  
Review
Chemical and Physical Pathways for Fabricating Flexible Superamphiphobic Surfaces with High Transparency
by Bichitra Sahoo, Kukro Yoon, Jungmok Seo and Taeyoon Lee
Coatings 2018, 8(2), 47; https://doi.org/10.3390/coatings8020047 - 25 Jan 2018
Cited by 23 | Viewed by 8882
Abstract
Since the discovery of the self-cleaning properties of the lotus effect, the wetting of surfaces were intensively investigated due to their potential application in many industrial sectors. The transparency of flexible liquid repellent coatings are a major industrial problem and their economic consequences [...] Read more.
Since the discovery of the self-cleaning properties of the lotus effect, the wetting of surfaces were intensively investigated due to their potential application in many industrial sectors. The transparency of flexible liquid repellent coatings are a major industrial problem and their economic consequences are widely known. Hence, a comprehensive understanding of the developments of flexible and transparent superamphiphobic surfaces is required in a number of technological and industrial situations. In this review, we aim to discuss the progress in the design, synthesis, fabrication techniques, and applications of flexible and transparent superamphiphobic surfaces. We start with an introduction, exploring the contact angles and wetting states for superhydrophilic, superhydrophobic, and superoleophobic surfaces, and continue with a review of the wetting transition of such surfaces. Then, we highlight the fabrication techniques involved for the preparation of flexible and transparent superamphiphobic surfaces. This review also discusses the key issues in the fabrication process and surfaces, and their features in improving durability characteristics and self-repellent performance. Then we suggest various recommendations for the improvement of mechanical durability along with potential future directions towards more systematic methods that will also be acceptable for industry. Finally, we conclude with some challenges and potential applications. Full article
(This article belongs to the Special Issue Superhydrophobic Coatings)
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