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The Synergistic Antibacterial Performance of a Cu/WO3-Added PTFE Particulate Superhydrophobic Composite Material  [PDF]
Kentaro Yamauchi, Tsuyoshi Ochiai, Goro Yamauchi
Journal of Biomaterials and Nanobiotechnology (JBNB) , 2015, DOI: 10.4236/jbnb.2015.61001
Abstract: The synergistic antibacterial performance against Escherichia coli (E. coli), Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA) of a Cu/WO3-added PTFE (polytetrafluoroethylene) particulate composite was reported in the previous paper. The origin of the synergistic antibacterial performance investigated by evaluating the photocatalytic decomposition of the Cu/WO3-added PTFE particulate composite material is reported in the present paper. Addition of Cu/WO3, visible-light-sensitive photocatalyst, to the PTFE particle dispersed superhydrophobic composite does not deteriorate the superhydrophobic property of the composite. Furthermore the existence of the polytetrafluoroethylene (PTFE) particles dispersed in the composite enhances the antibacterial property caused by the Cu/WO3. The authors call this “The synergistic effect”. In this study, a novel synergistic property of the Cu/WO3-added PTFE particulate composite was investigated by evaluating the degradation of gaseous acetaldehyde on the composite surface using visible light (10,000 lx) and UV-A (1 mW·cm-1) illumination. The 12 wt% Cu/WO3-8 wt% binder-80 wt% PTFE composite shows the synergistic visible-light-sensitive photocatalytic property. But 12 wt% Cu/WO3-44 wt% PTFE-44 wt% binder composite no longer shows the synergistic property of visible-light-sensitive photocatalytic property. The synergetic performance of visible-light-sensitive photocatalytic property appears only when PTFE concentration is larger than the critical point over which superhydrophobic property appears in accordance with the particulate composite model derived by the one of the authors. The hydrophobic surface leads to the low surface free energy derived by the revised Fowkes’s theory, which makes it difficult for bacteria to stick to the hydrophobic surface of the composite. Even if bacteria stick to the surface, they are decomposed by the visible-light-sensitive photocatalyst. This is the reason why the synergistic antibacterial performance against bacteria appears.
Synergistic Antibacterial Performance of a Cu/WO3-Added PTFE Particulate Superhydrophobic Composite under Visible-Light Exposure  [PDF]
Yanyan Yao, Kentaro Yamauchi, Goro Yamauchi, Tsuyoshi Ochiai, Taketoshi Murakami, Yoshinobu Kubota
Journal of Biomaterials and Nanobiotechnology (JBNB) , 2012, DOI: 10.4236/jbnb.2012.34042
Abstract: Addition of TiO2 to a polytetrafluoroethylene (PTFE) particle-dispersed composite contributes to the self-cleaning properties of the water-repellent composite. However, its application is limited to outdoor usage or under ultraviolet (UV) irradiation. In this study, a novel visible-light-sensitive photocatalytic and superhydrophobic material was developed by adding Cu/WO3 to a PTFE particulate composite material to overcome this deficit. A remarkable property of this novel composite material is the synergistic antibacterial performance against Escherichia coli (E. coli), Staphylo-coccus aureus, and methicillin-resistant Staphylococcus aureus compared with the addition of Cu/WO3 without PTFE particles material. During 24-h exposure in visible light at 2000 lx, the number of viable cells of the three strains on the surface of the 8wt% Cu/WO3-added PTFE particulate composite decreased from 2 – 4 × 105 colony-formation units (CFUs) to less than 10, the limit of detection. This bactericidal rate is four times higher than that of 8wt% Cu/WO3 without PTFE particles material, which is attributed to the air trapped in the rough surface of the novel material providing additional oxygen to the photocatalytic reaction. Even for exposure to visible light at 100 lx, the decrease in CFUs of E. coli on the 12wt% Cu/WO3-added PTFE particulate composite reached nearly 2.0 logs. The characterization of the Cu/WO3-added PTFE particulate composite indicated that the composite material containing 80wt% PTFE maintained a superhydrophobic or water-repellent property with a water contact angle >150, although the Cu/WO3 in the composite material remained hydrophilic under visible light. The Cu/WO3-added PTFE particulate composite displayed photo-catalytic reactions to decompose oleic acid adsorbed on its surface and gaseous acetaldehyde under UV-A and visible-light illumination. All results demonstrate that the Cu/WO3-added PTFE particulate composite material may be used in sterilization, as a water repellent, for self-cleaning, and in the oxidative decomposition of volatile organic compounds (VOC) both indoors and outdoors.
Preparation and Characterization of Superhydrophobic PTFE-PPS Composite Coating

WANG Hao,WANG Chang-song,CHEN Ying,FENG Xin,LU Xiao-hua,

过程工程学报 , 2007,
Abstract: 通过喷涂工艺在铝基片表面制备出聚四氟乙烯(PTFE)-聚苯硫醚(PPS)复合超疏水涂层,该复合涂层具有与荷叶表面类似的二次结构,与水的静态接触角为155°,滚动角为7°.与纯PTFE超疏水涂层相比,PTFE涂层中引入PPS后,涂层的粘附力从5级提高到1级,铅笔硬度从4B提高到4H,柔韧性从(10±0.1)mm提高到(1±0.1)mm,可以更好地满足工业应用要求.
Nanoarchitectonics of a Au nanoprism array on WO3 film for synergistic optoelectronic response  [cached]
Xiaoqing Chen, Peng Li, Hua Tong, Tetsuya Kako and Jinhua Ye
Science and Technology of Advanced Materials , 2011,
Abstract: A layered photoelectrode consisting of a conductive indium tin oxide substrate, a WO3 nanocrystalline film and an array of Au nanoprisms was fabricated via a multistep process. Scanning electron microscopy and atomic force microscopy showed that the Au nanoprisms had a uniform size and shape and formed periodic hexagonal patterns on the WO3 film. The optical absorption of the photoelectrode combined the intrinsic absorption of WO3 and plasmonic absorption of Au. Using this photoelectrode, we investigated the effect of the Au nanoprism array on the optoelectronic conversion performance of the WO3 film. Photoelectrochemical measurement indicated that the array substantially enhanced the photocurrent in the WO3 film. Electrochemical impedance measurements revealed that the Schottky junctions formed between Au and WO3 can facilitate the separation of photogenerated carriers as well as the interfacial carrier transfer. In this study, we demonstrate that covering a semiconductor with plasmonic noble metal nanoparticles can improve its optoelectronic conversion efficiency.
Improving the Hydrophobicity of ZnO by PTFE Incorporation  [PDF]
Meenu Srivastava,Bharathi Bai J. Basu,K. S. Rajam
Journal of Nanotechnology , 2011, DOI: 10.1155/2011/392754
Abstract: The objective of the present study is to obtain a zinc oxide- (ZnO-) based superhydrophobic surface in a simple and cost-effective manner. Chemical immersion deposition being simple and economical has been adopted to develop modified ZnO coating on glass substrate. Several modifications of ZnO like treatment with alkanoic acid (stearic acid) and fluoroalkylsilane to tune the surface wettability (hydrophobicity) were attempted. The effect of thermal treatment on the hydrophobic performance was also studied. It was observed that thermal treatment at 70°C for 16?hrs followed by immersion in stearic acid resulted in high water contact angle (WCA), that is, a superhydrophobic surface. Thus, a modified ZnO superhydrophobic surface involves the consumption of large amount of electrical energy and time. Hence, the alternate involved the incorporation of low surface energy fluoropolymer polytetrafluoroethylene (PTFE) in the ZnO coating. The immersion deposited ZnO-PTFE composite coating on modification with either stearic acid or fluoroalkylsilane resulted in a better superhydrophobic surface. The coatings were characterized using Scanning Electron Microscope (SEM) for the surface morphology. It was found that microstructure of the coating was influenced by the additives employed. A flower-like morphology comprising of needle-like structure arranged in a radial manner was exhibited by the superhydrophobic coating. 1. Introduction Superhydrophobic surfaces (water contact angle >150°) are gaining importance in industrial applications and academia due to their unique properties like self-cleaning, deicing, antisticking, and anticontamination. Some of the applications include self-cleaning paints, transparent antireflective coatings, self-cleaning glass, and wiperless windshields. In recent times, their usage in aerospace sector is also being explored, particularly in the tail and wings of the aircraft to reduce drag and thereby improve the efficiency of the engine. Superhydrophobicity can be achieved by obtaining a surface of micro- to nanoscale architecture [1]. Empirical models have been proposed on the basis of experimental data to explain the surface wetting properties and to understand the phenomenon of superhydrophobicity. Interest in this phenomenon increased in 1997 when the origin and the universal principle of “Lotus Effect” in nature were explained by Zhang et al. [1]. Since then, research has been focused on mimicking nature and trying to fabricate such surfaces artificially. Various methods have been recommended for the fabrication of such a surface.
Thermocapillary Flow on Superhydrophobic Surfaces  [PDF]
Tobias Baier,Clarissa Steffes,Steffen Hardt
Physics , 2010, DOI: 10.1103/PhysRevE.82.037301
Abstract: A liquid in Cassie-Baxter state above a structured superhydrophobic surface is ideally suited for surface driven transport due to its large free surface fraction in close contact to a solid. We investigate thermal Marangoni flow over a superhydrophobic array of fins oriented parallel or perpendicular to an applied temperature gradient. In the Stokes limit we derive an analytical expression for the bulk flow velocity above the surface and compare it with numerical solutions of the Navier-Stokes equation. Even for moderate temperature gradients comparatively large flow velocities are induced, suggesting to utilize this principle for microfluidic pumping.
Wettability Switching Techniques on Superhydrophobic Surfaces  [cached]
Verplanck Nicolas,Coffinier Yannick,Thomy Vincent,Boukherroub Rabah
Nanoscale Research Letters , 2007,
Abstract: The wetting properties of superhydrophobic surfaces have generated worldwide research interest. A water drop on these surfaces forms a nearly perfect spherical pearl. Superhydrophobic materials hold considerable promise for potential applications ranging from self cleaning surfaces, completely water impermeable textiles to low cost energy displacement of liquids in lab-on-chip devices. However, the dynamic modification of the liquid droplets behavior and in particular of their wetting properties on these surfaces is still a challenging issue. In this review, after a brief overview on superhydrophobic states definition, the techniques leading to the modification of wettability behavior on superhydrophobic surfaces under specific conditions: optical, magnetic, mechanical, chemical, thermal are discussed. Finally, a focus on electrowetting is made from historical phenomenon pointed out some decades ago on classical planar hydrophobic surfaces to recent breakthrough obtained on superhydrophobic surfaces.
Large-area fabrication of superhydrophobic surfaces for practical applications: an overview  [cached]
Chao-Hua Xue, Shun-Tian Jia, Jing Zhang and Jian-Zhong Ma
Science and Technology of Advanced Materials , 2010,
Abstract: This review summarizes the key topics in the field of large-area fabrication of superhydrophobic surfaces, concentrating on substrates that have been used in commercial applications. Practical approaches to superhydrophobic surface construction and hydrophobization are discussed. Applications of superhydrophobic surfaces are described and future trends in superhydrophobic surfaces are predicted.
Permeability of Electrospun Superhydrophobic Nanofiber Mats  [PDF]
Sarfaraz U. Patel,Gabriel M. Manzo,Shagufta U. Patel,Prashant S. Kulkarni,George G. Chase
Journal of Nanotechnology , 2012, DOI: 10.1155/2012/483976
Abstract: This paper discusses the fabrication and characterization of electrospun nanofiber mats made up of poly(4-methyl-1-pentene) polymer. The polymer was electrospun in different weight concentrations. The mats were characterized by their basis weight, fiber diameter distribution, contact angles, contact angle hysteresis, and air permeability. All of the electrospun nonwoven fiber mats had water contact angles greater than 150 degrees making them superhydrophobic. The permeabilities of the mats were empirically fitted to the mat basis weight by a linear relation. The experimentally measured air permeabilities were significantly larger than the permeabilities predicted by the Kuwabara model for fibrous media. 1. Introduction Superhydrophobic properties of electrospun nanofiber mats are of interest for a number of applications. In fabrics and filters, the air permeability, in addition to their hydrophobicity, is important. Few publications report on the permeability of such mats. In this paper, we report on the measured air permeability and compare it with the permeability predicted using a common correlation for fibrous media. Superhydrophobic surfaces are indiscriminately defined as surfaces with water contact angles (WCAs) greater than 150 degrees. Many examples of superhydrophobic surfaces are observed in nature. A well-known example of superhydrophobic surface is lotus leaf. Barthlott and Neinhuis [1] studied the lotus leaf and found that the rough-surface microstructures on the lotus leaf help the leaf to repel water off the surface, keeping it clean. In another example, Gao and Jiang [2] showed that a pond skater is able to walk on the water because of the surface structure of the legs. The legs have microhairs and nanoscaled grooves on the leg hairs, making the leg surfaces superhydrophobic. Conventionally, superhydrophobic surfaces are fabricated by creating a nanoscaled roughness on the surface and by making the surface out of low surface energy materials. Plasma etching [3], mechanical stretching [4], and electrospinning are some of the methods employed to create rough surfaces. Low surface energy compounds, typically fluorinated [5] or silicone compounds [6], have been used to create superhydrophobic surfaces. Superhydrophobic surfaces are characterized by WCA but in some applications contact angle hysteresis and critical tilt angle between the substrate and the horizontal, below which the water droplet begins to move upon elevating one end of the substrate, are also necessary [7]. It is desired to have a large contact angle and small tilt angle
Drop dynamics on hydrophobic and superhydrophobic surfaces  [PDF]
B. M. Mognetti,H. Kusumaatmaja,J. M. Yeomans
Physics , 2010,
Abstract: We investigate the dynamics of micron-scale drops pushed across a hydrophobic or superhydrophobic surface. The velocity profile across the drop varies from quadratic to linear with increasing height, indicating a crossover from a sliding to a rolling motion. We identify a mesoscopic slip capillary number which depends only on the motion of the contact line and the shape of the drop, and show that the angular velocity of the rolling increases with increasing viscosity. For drops on superhydrophobic surfaces we argue that a tank treading advance from post to post replaces the diffusive relaxation that allows the contact line to move on smooth surfaces. Hence drops move on superhydrophobic surfaces more quickly than on smooth geometries.
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