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Nanofibrous Composite Membranes for Membrane Distillation
Published in Ahmad Fauzi Ismail, Nidal Hilal, Juhana Jaafar, Chris J. Wright, Nanofiber Membranes for Medical, Environmental, and Energy Applications, 2019
To enhance membrane performance in MD processes, one strategy is to conduct post-modification of nanofibers. Most reported works have focused on altering the hydrophobic surfaces of ENMs to be superhydrophobic. The methods used to achieve superhydrophobic surfaces are to create hierarchically structured surfaces on hydrophobic substrates or modify a hierarchical rough surface with a low surface energy chemical (Ma and Hill 2006). As shown in Figure 7.5, chemical modifications have been conducted on a PVDF nanofibrous membrane (Figure 7.5A) to construct a hierarchically rough surface (Figure 7.5B) with both microscale and nanoscale asperities and a nanostructured rough surface(Figure 7.5C) (Liao et al. 2013a). Both hierarchical and nanostructured surfaces provided air pockets between water droplets and the membrane surface, reduced the contact area between the liquid and membrane and consequently enhanced the in-air water contact angles of resultant membranes. Both membranes exhibited water contact angles above 150° and water roll-off angles below 10°. Compared with unmodified membrane, the integral-modified superhydrophobic membrane achieved higher and more stable MD flux.
Superhydrophobic Organic-Inorganic Nanohybrids
Published in Chang-Sik Ha, Saravanan Nagappan, Hydrophobic and Superhydrophobic Organic-Inorganic Nanohybrids, 2018
Chang-Sik Ha, Saravanan Nagappan
Superhydrophobic surfaces are of considerable importance in many applications, such as self-cleaning, anti-icing, antibacterial, antireflective, oil sorption and separation, photocatalysts, and solar cells due to the excellent water-repellent properties [1–7]. Superhydrophobic surfaces have been inspired by many biological systems. Superhydrophobic surfaces can show excellent water-repellent behavior, even under severe environmental conditions. This inspiration can lead to the modification or mimicking of the surface properties of various natural superhydrophobic surfaces for use in many applications. Nagappan and Ha briefly reviewed the fabrication of superhydrophobic and magnetic superhydrophobic surfaces using a variety of methods, aspects of fabrication and methods, and their potential applications [8,9].
Interfacial Control of Multiphase Fluids in Miniaturized Devices
Published in Šeila Selimovic, Nanopatterning and Nanoscale Devices for Biological Applications, 2017
The fascination with superhydrophobic surfaces arises from the fact that such surfaces have very low adhesion, the liquid droplets are very mobile, and the friction of liquids flowing past such surfaces is very low.45 Superhydrophobic surfaces are therefore desirable in a variety of applications including microfluidics (see Section 1.4.2). Despite the research efforts, most superhydrophobic surfaces are mechanically fragile and are easily contaminated. A significant improvement was achieved by locking a lubricating fluid among the surface nano- and microstructure. Various liquids (including complex fluids) show very low adhesion and low contact angle hysteresis, restore after physical damage, resist ice adhesion, and function at up to several hundred atmospheres of pressure.46
Efficient fog collector with superhydrophobic coated surface
Published in The Journal of The Textile Institute, 2023
Musaddaq Azeem, Muhammad Tayyab Noman, Muhammad Zaman Khan, Azam Ali, Jakub Wiener, Michal Petru, Pavel Kejzlar, Ivan Masin
Generally, to achieve superhydrophobicity, surface roughness and surface free energy are two main factors. Surface roughness is an essential aspect to attain superhydrophobicity. The coating of materials with low surface energy is used to form superhydrophobic surface. This surface traps air bubbles when it touches the water droplets because it is not exposed to all surface points homogeneously. The Wenzel and Cassie-Baxter models explain the phenomena of superhydrophobicity that the presence of air and low energy of the surface, restrict water droplets to enter into the valley, therefore friction reduces and droplets slide on the surface as shown in Figure 7. A superhydrophobic surface usually has an even level of trapped air that guides to high contact angle (≃180°) and a small roll-off angle (≃ 0°) (Darband et al., 2020). PE monofilament was not a reliable substrate baseline for WCA measurements due to its cylindrical shape and that fact may deviate from the results.
Durable superhydrophobic coatings based on flower-like zinc oxide via layer by layer spraying
Published in The Journal of Adhesion, 2022
Yan Bao, Pei Tang, Xiujuan Shi, Lu Gao
Nowadays, superhydrophobic coatings have attracted more and more attention due to their special surface wettability, which enables water droplets to bounce or roll away from the surface of the materials before absorbed by the substrate, and take away the dust spread on the surface of the materials. Therefore, superhydrophobic coatings have shown tremendous industrial application value in many fields, such as self-cleaning, [1] anti-icing, [2] anti-corrosion, [3] oil/water separation, [4] anti-bacterial adhesion, and non-wetting.[5,6] For example, superhydrophobic coatings can isolate the corrosion media and achieve remarkable anti-corrosion performance, preventing ship, train, pipe, construction, and so on from corrosion. However, hydrophobicity properties are easy to break and cannot enduringly protect the substrate when subjected to friction or exposed to severe environmental conditions (high- and low-temperature cycling, ultraviolet radiation, alkaline, etc.). Thus, the durability of superhydrophobic coatings is a crucial problem for its further industrial application.
Robust transferrable superhydrophobic surfaces
Published in Surface Engineering, 2020
Jeong-Hyun Kim, Rohit Puranik, Jessica K. Shang, Daniel M. Harris
The static contact angles on the superhydrophobic surfaces were measured with an in-house goniometer to characterize the surface wettability. Both a hydrodynamic water jet and mechanical abrasive test were performed to investigate the robustness of the AlSHS and the adhesive strips. The experimental setup for the durability tests is shown in Figure 2. For each hydrodynamic durability test, the surface was exposed to 11 kPa dynamic pressure of a water jet for 37.5 s. For each cycle of the abrasive test, 400-grit sandpaper beneath a 200 g weight was dragged along the surfaces with a velocity of 0.3 cm s−1. After each durability test, the static advancing and receding contact angles were measured again to probe degradation of the surfaces. The detailed experimental description is provided in the supplementary information.