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Superhydrophobic Surface

Werner Schlemmer, Armin Zankel, Katrin Niegelhell, Mathias Hobisch, Michael Süssenbacher, Krisztina Zajki-Zechmeister, Michael Weissl, David Reishofer, Harald Plank, Stefan Spirk
This study investigates flexible (polyamide 6.6 PA-6.6, polyethylene terephthalate PET, Cu, Al, and Ni foils) and, for comparison, stiff substrates (silicon wafers and glass) differing in, for example, in surface free energy and surface roughness and their ability to host cellulose-based thin films. Trimethylsilyl cellulose (TMSC), a hydrophobic acid-labile cellulose derivative, was deposited on these substrates and subjected to spin coating. For all the synthetic polymer and metal substrates, rather homogenous films were obtained, where the thickness and the roughness of the films correlated with the substrate roughness and its surface free energy...
November 30, 2018: Materials
Jiafu Shi, Yu Tian, Weiran Li, Yang Zhao, Yizhou Wu, Zhongyi Jiang
In our study, plant polyphenol-inspired chemistry is explored to nano-engineer the topological and chemical structures of commercial melamine sponge surface for preparing superhydrophobic sponges. Briefly, tannic acid (TA, a typical plant polyphenol) is applied to induce the co-assembly of silica nanoparticles (SiO2 ) and silver ions (Ag+ ) to form SiO2 @TA@Ag nanostructures on a melamine sponge surface. After further chemical fluorination, the superhydrophobic sponge with a "lotus leaf-mimic" surface is formed...
November 26, 2018: Chemosphere
Jongtaek Lee, Taehee Park, Junyoung Lee, Jonghee Yang, Whikun Yi
Contact angle measurements are investigated on the surface of single-walled carbon nanotube (SWNT) films directly formed on flat and textured Si substrates using a thermal chemical vapor deposition method. The SWNT films on the textured Si consist of a multiscale structure composed of nanoscale SWNTs and a microscale textured Si. They show superhydrophobic properties in which the water contact angle was around 161°. A direct surface treatment to them increase the contact angle to 174°. The reversible wettability of the SWNT films formed on the textured Si substrates is confirmed through the oxidation process using an acid mixture of nitric and sulfuric acids and a successive reduction procedure via heating treatment in an NH₃ environment...
April 1, 2019: Journal of Nanoscience and Nanotechnology
Suset Barroso-Solares, Javier Pinto, Despina Fragouli, Athanassia Athanassiou
Superhydrophobic and oleophilic polyurethane foams were obtained by spray-coating their surfaces with solutions of thermoplastic polyurethane and hydrophobic silicon oxide nanoparticles. The developed functionalized foams were exploited as reusable oil absorbents from stable water-in-oil emulsions. These foams were able to remove oil efficiently from a wide range of emulsions with oil contents from 10 to 80 v.%, stabilized using Span80. The modified foams could reach oil absorption capacities up to 29 g/g, becoming a suitable candidate for water-in-oil stable emulsions separation...
November 27, 2018: Materials
Chang Wan Kang, Jaewon Jin, Yoon-Joo Ko, Sang Moon Lee, Hae Jin Kim, Seung Uk Son
This work shows that the surface properties of polyurethane acrylate (PUA) films can be controlled by the coating of na-noporous organic networks (NONs). By the NON coating, the hydrophilic nature of nanostructured PUA (N-PUA) film was converted to superhydrophobic surface. The NON-coated N-PUA films (N-PUA-NONs) were applied as stationary adsor-bents for the capture of particulate matter (PM) in air. Compared with the original PUA films, the N-PUA-NON films showed much enhanced capture performance toward PM and recyclability through water washing, indicating the potential of out-door application as stationary self-cleaning adsorbents under natural surroundings...
November 27, 2018: ACS Applied Materials & Interfaces
Haryeong Choi, Vinayak G Parale, Kyu-Yeon Lee, Ha-Yoon Nah, Zied Driss, Dorra Driss, Abdallah Bouabidi, Souhir Euchy, Hyung-Ho Park
Silica aerogels possess low thermal conductivity but have a brittle nature, while their polymers tend to exhibit enhanced mechanical properties. In this study, we introduce a new approach to overcoming this brittle property of silica aerogels. Polypropylene/silica aerogel composites were prepared by thermally induced phase separation followed by a supercritical CO₂ drying method. Silica aerogel was formed onto a polypropylene scaffold using a two-step sol-gel process with methyltrimethoxysilane as the silica precursor...
March 1, 2019: Journal of Nanoscience and Nanotechnology
Hannu Teisala, Hans-Jürgen Butt
Many surfaces possessing robust super liquid repellency, are hierarchically structured on the nano- and micrometer scale. Several examples are found in nature such as the self-cleaning leaves of lotus plants and anisotropic, water guiding rice leaves. Each surface design has unique properties optimized for specific wetting conditions. In this article, we review both natural and artificial hierarchical surface structures and their function in repelling liquids. We discuss different types of structures needed in various wetting situations and draw some general conclusions as a guideline for designing robust superhydrophobic and superoleophobic surfaces...
November 22, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Gustav Graeber, Oskar B Martin Kieliger, Thomas M Schutzius, Dimos Poulikakos
Macro-textured superhydrophobic surfaces can reduce droplet-substrate contact times of impacting water droplets; however, surface designs with similar performance for significantly more viscous liquids are missing, despite their importance in nature and technology such as for chemical shielding, food staining repellency, and supercooled (viscous) water droplet removal in anti-icing applications. Here, we introduce a deterministic, controllable and up-scalable method to fabricate superhydrophobic surfaces with a 3D-printed architecture, combining arrays of alternating surface protrusions and indentations...
November 19, 2018: ACS Applied Materials & Interfaces
Miaomiao Zhu, Ranhua Xiong, Chaobo Huang
Air pollution is becoming more and more severe especially in developing countries. It is urgent to seek an effective protection for the unacceptable levels of the air pollution. Up to date, the air filtration is a widely used method to protect us from the air pollution. However, most of the air filtration membranes in fabrication process is required to use harmful organic solvents. Here, we report a human friendly, multifunctional and bio-based chitosan/poly (vinyl alcohol) air filtration membrane via green electrospinning and UV-cured...
February 1, 2019: Carbohydrate Polymers
Muhammad Imran Jamil, Abid Ali, Fazal Haq, Qinghua Zhang, Xiaoli Zhan, Fengqiu Chen
Ice formation and accretion on surfaces is a serious economic issue in energy supply and transports. Recent strategies for developing icephobic surfaces are intimately associated with superwettability. Commonly, the superwettability of icephobic materials depends on their surface roughness and chemical composition. This review critically categorizes the possible strategies to mitigate the icing problems from daily life. The wettability and classical nucleation theories are used to characterize the icephobic surfaces...
November 16, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Cornelia Rosu, Yeongseon Jang, Lu Jiang, Julie Champion
We demonstrate that the molecular structure of a synthetic homopolypeptide that resembles the leg architecture of water strider insects is effective to impart flexible polymeric surfaces with superhydrophobic behavior. Filter paper (FP) and polyester (PET) were modified with a coating consisting of low-molecular weight α-helical poly(γ-stearyl-α,l-glutamate) (PSLG, Mw = 4500 Da) homopolypeptide. PSLG-coated substrates displayed near to and superhydrophobic behavior (≥150°) as reflected by the contact angle values...
November 16, 2018: Biomacromolecules
Jihoon Chung, Deokjae Heo, Banseok Kim, Sangmin Lee
Energy harvesting is a method of converting energy from ambient environment into useful electrical energy. Due to the increasing number of sensors and personal electronics, energy harvesting technologies from various sources are gaining attention. Among energy-harvesting technologies, triboelectric nanogenerator (TENG) was introduced as a device that can effectively generate electricity from mechanical motions by contact-electrification. Particularly, liquid-solid contact TENGs, which use the liquid itself as a triboelectric material, can overcome the inevitable friction wear between two solid materials...
November 13, 2018: Micromachines
Alexey Zhizhchenko, Aleksandr Kuchmizhak, Oleg Vitrik, Yuri Kulchin, Saulius Juodkazis
Controllable targeted deposition of an analyte dissolved in a liquid drop evaporating on a superhydrophobic surface has recently emerged as a promising concentrator approach with various applications ranging from ultrasensitive bioidentification to DNA molecule sorting. Here, we demonstrate that surface textures with non-uniform wettability fabricated using direct easy-to-implement femtosecond-pulse filament-assisted ablation of polytetrafluoroethylene substrates can be used to concentrate and deposit an analyte at a designated location out of a water droplet...
December 7, 2018: Nanoscale
Yutaku Kita, Coinneach Mackenzie Dover, Alexandros Askounis, Yasuyuki Takata, Khellil Sefiane
Manipulation of drop motion has attracted considerable attention recently as it is pertinent to industrial/biological applications such as microfluidics. Wettability gradients/contrasts applied to microtextured, superhydrophobic surfaces are probable candidates for engineering drop motion by virtue of their wettability controllability and low contact angle hysteresis. In the present work, we present a systematic study of drop mobility induced via wettability contrasts. A millimetre-sized water drop, placed on the boundary between two surfaces with distinct, uniform arrays of pillars, immediately moved toward the surface more densely populated with asperities, which was relatively more hydrophilic...
November 28, 2018: Soft Matter
Ke Du, Youhua Jiang, Yuyang Liu, Ishan Wathuthanthri, Chang-Hwan Choi
The manipulation of droplet mobility on a nanotextured surface by oxygen plasma is demonstrated by modulating the modes of hydrophobic coatings and controlling the hierarchy of nanostructures. The spin-coating of polytetrafluoroethylene (PTFE) allows for heterogeneous hydrophobization of the high-aspect-ratio nanostructures and provides the nanostructured surface with "sticky hydrophobicity", whereas the self-assembled monolayer coating of perfluorodecyltrichlorosilane (FDTS) results in homogeneous hydrophobization and "slippery superhydrophobicity"...
June 18, 2018: Micromachines
Peter Gregorčič, Marjetka Conradi, Luka Hribar, Matej Hočevar
Controlling the surface wettability represents an important challenge in the field of surface functionalization. Here, the wettability of a stainless-steel surface is modified by 30-ns pulses of a Nd:YAG marking laser (λ = 1064 nm) with peak fluences within the range 3.3⁻25.1 J cm-2 . The short- (40 days), intermediate- (100 days) and long-term (1 year) superhydrophilic-to-(super)hydrophobic transition of the laser-textured surfaces exposed to the atmospheric air is examined by evaluating its wettability in the context of the following parameters: (i) pulse fluence; (ii) scan line separation; (iii) focal position and (iv) wetting period due to contact angle measurements...
November 11, 2018: Materials
Minglei Wang, Maojiang Zhang, Lijuan Pang, Chenguang Yang, Yumei Zhang, Jiangtao Hu, Guozhong Wu
Developing a universal strategy to improve the properties of polyethylene terephthalate (PET) fibers, such as UV resistance, hydrophobicity, and thermal resistance, is highly desirable in expanding the application of PET fibers. Herein, a highly durable and robust ZnO layer was deposited onto PET fabric via radiation-induced graft polymerization (RIGP) of γ-methacryloxypropyl trimethoxysilane (MAPS) and the subsequent sol-gel in situ mineralization with zinc acetate to produce wurtzite nanocrystalline ZnO...
November 2, 2018: Journal of Colloid and Interface Science
Pinar Beyazkilic, Abtin Saateh, Mehmet Bayindir, Caglar Elbuken
We introduce a droplet-based biomolecular detection platform using robust, versatile, and low-cost superhydrophilic patterned superhydrophobic surfaces. Benefitting from confinement and evaporation-induced shrinkage of droplets on wetted patterns, we show enrichment-based biomolecular detection using very low sample volumes. First, we developed a glucose assay using fluorescent polydopamine (PDA) based on enhancement of PDA emission by hydrogen peroxide (H2 O2 ) produced in enzyme-mediated glucose oxidation reaction...
October 31, 2018: ACS Omega
Zhiru Yang, Chongchong Zhu, Nan Zheng, Dezheng Le, Jianzhong Zhou
Microstructures are applied to various hydrophobic/hydrophilic surfaces due to the role of adjusting the surface wettability. In this paper, a 1064 nm pulsed picosecond laser was applied to prepare a micro/nano hierarchical structure on the surface of the titanium alloy (Ti-6Al-4V). The microstructures consist of dimple arrays with various diameters, depths, and areal densities. They are obtained by controlling the pulse energy and the number of pulses. The nanostructures are periodic ripples, which are defined as laser-induced periodic surface structure (LIPSS), and the dimensional parameter of LIPSS can be adjusted by changing the laser energy density and scanning speed...
November 7, 2018: Materials
Jing Zhang, Chenxi Zhu, Jian Lv, Weicheng Zhang, Jie Feng
In recent years, polymer films containing deep color and near-infrared (NIR)-reflective pigments have received much attention for their potential applications in energy-saving fields. However, in practical environments, dust present in the air is easily adsorbed and adheres to the surface of these films, thus gradually reducing their NIR reflectance. In this work, black or deep-red infrared-reflective pigments were firstly mixed with melted low-density polyethylene (LDPE) and then the resulting composite was thermally pressed on to a metal template possessing micro- and nanostructure surface roughness...
November 21, 2018: ACS Applied Materials & Interfaces
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