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Superhydrophobic Surface

Nastasia Okulova, Peter Johansen, Lars Christensen, Rafael Taboryski
Super-hydrophobic natural surfaces usually have multiple levels of structure hierarchy. Here, we report on the effect of surface structure hierarchy for droplet evaporation. The two-level hierarchical structures studied comprise micro-pillars superimposed with nanograss. The surface design is fully scalable as structures used in this study are replicated in polypropylene by a fast roll-to-roll extrusion coating method, which allows effective thermoforming of the surface structures on flexible substrates. As one of the main results, we show that the hierarchical structures can withstand pinning of sessile droplets and remain super-hydrophobic for a longer time than their non-hierarchical counterparts...
October 13, 2018: Nanomaterials
Michael Z Hu, Chaiwat Engtrakul, Brian L Bischoff, Mi Lu, Mussie Alemseghed
Surface wettability-tailored porous ceramic/metallic membranes (in the tubular and planar disc form) were prepared and studied for both vapor-phase separation and liquid pervaporative separations of water-ethanol mixtures. Superhydrophobic nanoceramic membranes demonstrated more selective permeation of ethanol (relative to water) by cross-flow pervaporation of liquid ethanol⁻water mixture (10 wt % ethanol feed at 80 °C). In addition, both superhydrophilic and superhydrophobic membranes were tested for the vapor-phase separations of water⁻ethanol mixtures...
October 12, 2018: Membranes
Yudong Lu, Changji Wu, Ruiyun You, Yang Wu, Huiying Shen, Lanjin Zhu, Shangyuan Feng
Superhydrophobic silver films were fabricated by silver-mirror reaction and surface functionalization with thiol. The thiol-functionalization significantly improved the hydrophobic property of the Ag films (AFS), and their contact angle values slightly increased with the extension of a thiol alkyl chain, reaching about 160°. The surface-enhanced Raman scattering (SERS) detection capacity of these films were investigated, and AFS-Dodec showed the best substrate for R6G molecule detection with the concentration limit of 10-11 M...
October 1, 2018: Biomedical Optics Express
Qingqing Zhou, Biaobiao Yan, Tieling Xing, Guoqiang Chen
A superhydrophobic caffeic acid/Fe@cotton fabric (CfA/Fe@cotton fabric) was fabricated by a simple, high efficiency and environmentally friendly approach and the polymerization of caffeic acid was catalyzed by laccase. This superhydrophobic cotton fabric and caffeic acid/Fe hybrid particles (CfA/Fe) were characterized by scanning electron microscopy (SEM), atomic force microscope (AFM), X-ray diffraction (XRD) and so on. The results showed that the surface of cotton fiber was coated by CfA/Fe composite deposition film, and the ferrous ions can be reduced to zero valent iron particles with good crystal structure in the aging process of reaction...
January 1, 2019: Carbohydrate Polymers
Xiaoying Qiao, Chunyan Yang, Qian Zhang, Shengke Yang, Yangyang Chen, Dan Zhang, Xiaoyu Yuan, Wenke Wang, Yaqian Zhao
In order to prepare parabolic superhydrophobic materials, copper meshes were used as the substrate and ultrasonic etching and oxidative corrosion were carried out with FeCl₃ solution and H₂O₂ solution, respectively, and then the surface was modified with stearic acid (SA). The topological structure and surface wettability of the prepared mesh were characterized by fluorescence microscope, scanning electron microscopy and contact angle measurement. Finally, the as-prepared copper meshes were applied to oil-water separation...
October 9, 2018: Materials
Gabriela Ramos Chagas, Franck Celestini, Christophe Raufaste, Anne Gaucher, Damien Prim, Sonia Amigoni, Frédéric Guittard, Thierry Darmanin
We study the wetting and the adhesive behaviour of substrates made by electropolymerization of copolymers of pyrene substituted with fluoroalkyl and adamantyl groups. The hydrophobicity and water adhesion properties can be tuned by the molar percentage (mol%) of each pyrene monomer so that the substrate properties can vary from superhydrophobic to parahydrophobic, with respectively low and high water adhesion. The ejection test method (ETM) is proposed as an original tool to discriminate and characterize such substrates...
October 10, 2018: Journal of Physical Chemistry. A
Prashant Agrawal, Kyle J Bachus, Gabrielle Carriere, Phoenix Grouse, Richard D Oleschuk
Magnetic actuation on digital microfluidic (DMF) platforms may provide a low-cost, less cumbersome alternative for droplet manipulation in comparison to other techniques such as electrowetting-on-dielectric. Precise control of droplets in magnetically driven DMF platforms is achieved using a low-friction surface, magnetically susceptible material/droplet(s), and an applied magnetic field. Superhydrophobic (SH) surfaces offer limited friction for aqueous media as defined by their high water contact angles (WCA) (>150°) and low sliding angles (<10°)...
October 5, 2018: Analytical and Bioanalytical Chemistry
Poonam Chauhan, Aditya Kumar, Bharat Bhushan
In this paper, superhydrophobicity of cotton fabric was produced by simple immersion method in non-fluorinated hexadecyltrimethoxysilane solution. Modified cotton fabric showed repellency to water and liquids with surface tension of more than 47 mN/m, with a static contact angle of more than 150° and tilt angle of less than 10°. The mechanical, chemical, thermal, and UV stability of superhydrophobic cotton fabric was evaluated. Modified cotton fabric exhibited the self-cleaning and stain-resistant properties...
September 26, 2018: Journal of Colloid and Interface Science
Jing Sun, Chuanzhen Chen, Jinlong Song, Junkai Liu, Xiaolong Yang, Jiyu Liu, Xin Liu, Yao Lu
Extreme wettability surfaces have attracted more and more attention due to their practical applications, however, few reports have shown a universal method to create surface patterns with extreme wettability on a variety of metals. In this paper, a mask-assisted dual-chemical-processing approach without special modification is used to prepare the extreme wettability patterns on various metal substrates. Fabrication of superhydrophilic-superhydrophobic patterns on five kinds of metal substrates of Al, Ti, steel, Zn and Mg alloy proved the versatility of this method...
September 24, 2018: Journal of Colloid and Interface Science
Weidi Hua, Piyush Kar, Partha Roy, Lintong Bu, Lian C T Shoute, Pawan Kumar, Karthik Shankar
The availability of robust superhydrophobic materials with the ability to withstand harsh environments are in high demand for many applications. In this study, we have presented a simple method to fabricate superhydrophobic materials from TiO₂ nanotube arrays (TNTAs) and investigated the resilience of the materials when they are subjected to harsh conditions such as intense cavitation upon ultrasonication, corrosion in saline water, water-jet impact, and abrasion. The TNTAs were prepared by anodization of Ti foil in buffered aqueous electrolyte containing fluoride ions...
October 2, 2018: Nanomaterials
Debasis Nanda, Abanti Sahoo, Aditya Kumar, Bharat Bhushan
Oil spills on the surfaces of bodies of water are now a great concern as they affect marine creatures and the ecosystem. Therefore, a facile technique for removal of oil from water is of much interest. In this study, superhydrophobic and superoleophilic coating is synthesized on stainless steel mesh via chemical etching using a mixture of FeCl3 and HCl followed by treatment with hexadecyltrimethoxysilane. Surface morphology analysis shows the presence of flower like microstructures on the surface after treatment...
September 26, 2018: Journal of Colloid and Interface Science
Rishav Roy, Justin A Weibel, Suresh V Garimella
Electrowetting-based droplet actuation has applications in digital microfluidics. Mobility of droplets on surfaces can be enhanced using structured superhydrophobic surfaces that offer inherently low adhesion to droplets in the Cassie state. However, these surfaces must be designed to prevent transition to the Wenzel state (in which droplets are immobile) at high electrowetting actuation voltages. The electrowetting behavior of cylindrical microposts and mushroom-shaped reentrant microstructures, both of which afford excellent superhydrophobicity, is investigated and compared...
October 2, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Guo Jiang, Liang Chen, Shuidong Zhang, Han-Xiong Huang
For faster and greener anti-icing/deicing, new generation anti-icing materials are expected to possess both passive anti-icing properties and active de-icing properties. The photothermal effect of CNTs is used in the field of photothermal cancer therapy, while the application in anti-icing/deicing is seldom investigated. Superhydrophobic SiC/CNTs coatings with photothermal deicing and passive anti-icing properties were first prepared by a simple spray-coating method. The results of 3D profile and microstructure observed via scanning electron microscopy demonstrates that the micro-nanostructure combined with peak-like SiC microstructure and villiform CNTs nanostructure makes the coatings surface superhydrophobic, exhibiting a water contact angle of up to 161° and a roll angle as low as 2°...
October 1, 2018: ACS Applied Materials & Interfaces
Bahador Farshchian, Jacoby Pierce, Mohammad S Beheshti, Sunggook Park, Namwon Kim
Heterogeneous substrates with moderate and extreme wettability contrasts were fabricated by comprising of superhydrophobic/hydrophilic and superhydrophobic/extremely hydrophilic surfaces, respectively. The interactions of water droplets impinging on the surfaces with sharp wettability contrasts were investigated experimentally. The impinging droplets that slightly touch the hydrophilic or extremely hydrophilic areas on each substrate exhibit a directional rebounding towards the more wetting surfaces, i.e., hydrophilic or extremely hydrophilic surface...
August 5, 2018: Microelectronic Engineering
Koya Prabhakara Rao, Masakazu Higuchi, Suryachandram Jettiboina, Susumu Kitagawa
We demonstrate a new de novo synthetic methodology to achieve high temperature stable compelled composite superhydrophobic porous coordination polymers (PCPs). These new PCPs achieved based on coordination capabilities of 1st-row transition metal ions like Co2+, Ni2+, and Zn2+. The obtained composite PCPs containing, [Zn2M2O]6+ (M = Co or Ni) bimetallic cluster core with open metal sites (OMSs), exhibited distinct iso-steric heats of adsorption and surface areas due to the difference in their open metal Lewis acidic sites of solvent-free state...
September 29, 2018: Journal of the American Chemical Society
The-Hung Dinh, Chi-Vinh Ngo, Doo-Man Chun
In this study, the effects of nanosecond-pulsed laser and pattern design were researched on the wettability of titanium material. Nanosecond-pulsed laser and heat treatment are used to fabricate superhydrophobic titanium surfaces. The effects of laser power (1⁻3 W) and step size (50⁻300 µm) on a microscale patterned titanium surface (line pattern and grid pattern) were investigated to explain the relation between microstructure and superhydrophobicity. The surface morphologies and wettability of the surfaces were analyzed by three-dimensional confocal microscopy and a contact angle meter...
September 27, 2018: Nanomaterials
Sang-Hyeon Lee, Minho Seong, Moon Kyu Kwak, Hyunwook Ko, Minsu Kang, Hyung Wook Park, Seong Min Kang, Hoon Eui Jeong
Anti-icing materials that can efficiently limit ice formation have a strong potential to replace existing anti-icing techniques, such as Joule heating, chemical release, or mechanical removal, which are usually inefficient, expensive, and environmentally harmful. In this study, an anti-icing material based on a magnetically responsive hierarchical hair array that can actively modulate drop bouncing dynamics is presented. The magnetically responsive hair array exhibits an immediate and reversible structural bending motion in response to an external magnetic field...
September 28, 2018: ACS Nano
Peiliu Li, Bo Zhang, Hongbin Zhao, Lunjia Zhang, Zhe Wang, Xiangyu Xu, Tingting Fu, Xiaonan Wang, Yongping Hou, Yuzun Fan, Lei Wang
Water droplet unidirectional transport on the asymmetric superhydrophobic surface has attracted much interest in theory analysis and applications, such as self-cleaning, antifogging, anti-icing, heat transfer, and so on. Different from the symmetrical performance on the uniform topographies, the droplets acting on the asymmetric surface exhibit an anisotropic state and easily roll off the surface along the special direction. This phenomenon is indicated by natural butterfly wings. The flexible asymmetrically arranged microstep induces the droplet to release along the outside radial (RO) direction and to pin against the RO direction...
October 2, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Olga Guselnikova, Roman Elashnikov, Pavel S Postnikov, Vaclav Svorcik, Oleksiy Lyutakov
Design of the smart surfaces with externally triggerable water/oil wettability and adhesion represents one of the most up-to-date challenges in the field of material science. In this work, the intelligent surface with electrically triggerable wettability and water/oil adhesion is presented. As a basic material background exhibiting electric field (EF) sensitivity, the piezo-responsive polymethylmethacrylate/polyvinylidenefluoride polymers fibers were used. To expand the available range of water/oil contact angles (CA) and adhesion, the fibers were grafted with hydrophilic or hydrophobic functional groups using diazonium chemistry...
September 18, 2018: ACS Applied Materials & Interfaces
R Di Mundo, F Bottiglione, G Pascazio, G Carbone
Hydrophobic and superhydrophobic solid Teflon spheres have been observed while settling in water under the action of gravity, starting from different initial conditions, and have been followed until the steady-state is reached. The superhydrophobic sphere features a nano/microtextured surface and advancing and receding water contact angles equal to, respectively, [Formula: see text] and [Formula: see text]. When impacting water from air, both spheres can entrap a conspicuous amount of air deriving from the sealing of a macro-sized air cavity formed upon impact (air cavity trapping) and standing at the rear part of the settling sphere...
November 7, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
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