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Journal ArticleDOI

Superhydrophobic nanocoatings: from materials to fabrications and to applications

Yifan Si, +2 more
- 26 Mar 2015 - 
- Vol. 7, Iss: 14, pp 5922-5946
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TLDR
This paper reviews the contributions to superhydrophobic nanocoatings reported in recent literature, mainly including materials, fabrication and applications, and introduces application examples, and briefly discusses the principle behind the phenomenon.
Abstract
Superhydrophobic nanocoatings, a combination of nanotechnology and superhydrophobic surfaces, have received extraordinary attention recently, focusing both on novel preparation strategies and on investigations of their unique properties. In the past few decades, inspired by the lotus leaf, the discovery of nano- and micro-hierarchical structures has brought about great change in the superhydrophobic nanocoatings field. In this paper we review the contributions to this field reported in recent literature, mainly including materials, fabrication and applications. In order to facilitate comparison, materials are divided into 3 categories as follows: inorganic materials, organic materials, and inorganic-organic materials. Each kind of materials has itself merits and demerits, as well as fabrication techniques. The process of each technique is illustrated simply through a few classical examples. There is, to some extent, an association between various fabrication techniques, but many are different. So, it is important to choose appropriate preparation strategies, according to conditions and purposes. The peculiar properties of superhydrophobic nanocoatings, such as self-cleaning, anti-bacteria, anti-icing, corrosion resistance and so on, are the most dramatic. Not only do we introduce application examples, but also try to briefly discuss the principle behind the phenomenon. Finally, some challenges and potential promising breakthroughs in this field are also succinctly highlighted.

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Journal ArticleDOI

Design of anti-icing surfaces: smooth, textured or slippery?

TL;DR: Different strategies to achieve ice repellency on various hydrophilic and hydrophobic surfaces are reviewed with a focus on the recent development of superhydrophobic and lubricant-infused surfaces.

The dry-style antifogging properties of mosquito compound eyes and artificial analogues prepared by soft lithography: a superhydrophobic state with high adhesive force

Abstract: Fogging occurs when moisture condensation takes the form of accumulated droplets with diameters larger than 190 nm or half of the shortest wavelength (380 nm) of visible light. This problem may be effectively addressed by changing the affinity of a material’s surface for water, which can be accomplished via two approaches: i) the superhydrophilic approach, with a water contact angle (CA) less than 5°, and ii) the superhydrophobic approach, with a water CA greater than 150°, and extremely low CA hysteresis. To date, all techniques reported belong to the former category, as they are intended for applications in optical transparent coatings. A well-known example is the use of photocatalytic TiO2 nanoparticle coatings that become superhydrophilic under UV irradiation. Very recently, a capillary effect was skillfully adopted to achieve superhydrophilic properties by constructing 3D nanoporous structures from layer-by-layer assembled nanoparticles. The key to these two “wet”-style antifogging strategies is for micrometer-sized fog drops to rapidly spread into a uniform thin film, which can prevent light scattering and reflection from nucleated droplets. Optical transparency is not an intrinsic property of antifogging coatings even though recently developed antifogging coatings are almost transparent, and the transparency could be achieved by further tuning the nanoparticle size and film thickness. To our knowledge, the antifogging coatings may also be applied to many fields that do not require optical transparency, including, for example, paints for inhibiting swelling and peeling issues and metal surfaces for preventing corrosion. These types of issues, which are caused by adsorption of moisture, are hard to solve by the superhydrophilic approach because of its inherently “wet” nature. Thus, a “dry”-style antifogging strategy, which consists of a novel superhydrophobic technique that can prevent moisture or microscale fog drops from nucleating on a surface, is desired. Recent bionic researches have revealed that the self-cleaning ability of lotus leaves and the striking ability of a water-strider’s legs to walk on water can be attributed to the ideal superhydrophobicity of their surfaces, induced by special microand nanostructures. To date, the biomimetic fabrication of superhydrophobic microand/or nanostructures has attracted considerable interest, and these types of materials can be used for such applications as self-cleaning coatings and stain-resistant textiles. Although a superhydrophobic technique inspired by lotus leaves is expected to be able to solve such fogging problems because the water droplets can not remain on the surface, there are no reports of such antifogging coatings. Very recently, researchers from General Motors have reported that the surfaces of lotus leaves become wet with moisture because the size of the fog drops are at the microscale—so small that they can be easily trapped in the interspaces among micropapillae. Thus, lotuslike surface microstructures are unsuitable for superhydrophobic antifogging coatings, and a new inspiration from nature is desired for solving this problem. In this communication, we report a novel, biological, superhydrophobic antifogging strategy. It was found that the compound eyes of the mosquito C. pipiens possess ideal superhydrophobic properties that provide an effective protective mechanism for maintaining clear vision in a humid habitat. Our research indicates that this unique property is attributed to the smart design of elaborate microand nanostructures: hexagonally non-close-packed (ncp) nipples at the nanoscale prevent microscale fog drops from condensing on the ommatidia surface, and hexagonally close-packed (hcp) ommatidia at the microscale could efficiently prevent fog drops from being trapped in the voids between the ommatidia. We also fabricated artificial compound eyes by using soft lithography and investigated the effects of microand nanostructures on the surface hydrophobicity. These findings could be used to develop novel superhydrophobic antifogging coatings in the near future. It is known that mosquitoes possess excellent vision, which they exploit to locate various resources such as mates, hosts, and resting sites in a watery and dim habitat. To better understand such remarkable abilities, we first investigated the interaction between moisture and the eye surface. An ultrasonic humidifier was used to regulate the relative humidity of the atmosphere and mimic a mist composed of numerous tiny water droplets with diameters less than 10 lm. As the fog was C O M M U N IC A IO N
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References
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Journal ArticleDOI

Purity of the sacred lotus, or escape from contamination in biological surfaces

TL;DR: It is shown here for the first time that the interdependence between surface roughness, reduced particle adhesion and water repellency is the keystone in the self-cleaning mechanism of many biological surfaces.
Journal ArticleDOI

Intrinsic peroxidase-like activity of ferromagnetic nanoparticles

TL;DR: It is reported that magnetite nanoparticles in fact possess an intrinsic enzyme mimetic activity similar to that found in natural peroxidases, which are widely used to oxidize organic substrates in the treatment of wastewater or as detection tools.
Journal ArticleDOI

Super-hydrophobic surfaces: From natural to artificial

TL;DR: In this article, a super-hydrophobic surface with both a large contact angle (CA) and a small sliding angle (α) has been constructed from carbon nanotubes.
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