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Polytetrafluoroethylene (PTFE) is a fully fluorinated linear polymer with a (CF2-CF2)n backbone. High molecular weight PTFEs are chemically inert while possessing excellent hydrophobic surface properties attributed to their low surface energy. These characteristics make PTFE an excellent candidate for membrane distillation application among all other hydrophobic polymers. In this review, the electrospinning processes of PTFE fibers are discussed in detail with a focus on various electrospinning effects on the resulting fiber morphologies and structures. Due to the high chemical resistance and low solvent solubility, PTFE is typically electrospin with a polymer carrier, such as polyvinyl alcohol (PVA) and/or polyethylene oxide (PEO), using emulsion electrospinning followed by a sintering process. The amount of PTFE in emulsion, types of polymer carriers, electrospinning parameters, and sintering conditions have interconnected effects on the resulting morphological structures of PFTE fibers (e.g., beading or continuous fibers). In addition, electrospun PTFE fibers are further functionalized using methods of co-electrospinning with other hydrophobic polymers as well as incorporations of metallic (ZnO) and inorganic particles (POSS) to improve their performance in membrane distillation. Water contact angles, permeation fluxes, salt rejection rates, and hours of operations are reported for various functionalized electrospun PTFE fibrous membranes to demonstrate their feasibility in membrane distillation applications. In general, this article provides a scientific understanding of electrospun PTFE fibers and their engineering application in membrane distillation.

Polytetrafluoroethylene (PTFE) is a fully fluorinated linear polymer with a (CF2-CF2)n backbone. High molecular weight PTFEs are chemically inert while possessing excellent hydrophobic surface properties attributed to their low surface energy. These characteristics make PTFE an excellent candidate for membrane distillation application among all other hydrophobic polymers. In this review, the electrospinning processes of PTFE fibers are discussed in detail with a focus on various electrospinning effects on the resulting fiber morphologies and structures. Due to the high chemical resistance and low solvent solubility, PTFE is typically electrospin with a polymer carrier, such as polyvinyl alcohol (PVA) and/or polyethylene oxide (PEO), using emulsion electrospinning followed by a sintering process. The amount of PTFE in emulsion, types of polymer carriers, electrospinning parameters, and sintering conditions have interconnected effects on the resulting morphological structures of PFTE fibers (e.g., beading or continuous fibers). In addition, electrospun PTFE fibers are further functionalized using methods of co-electrospinning with other hydrophobic polymers as well as incorporations of metallic (ZnO) and inorganic particles (POSS) to improve their performance in membrane distillation. Water contact angles, permeation fluxes, salt rejection rates, and hours of operations are reported for various functionalized electrospun PTFE fibrous membranes to demonstrate their feasibility in membrane distillation applications. In general, this article provides a scientific understanding of electrospun PTFE fibers and their engineering application in membrane distillation. [ABSTRACT FROM AUTHOR]

Polyamide/elastane warp-knitted fabrics were separately dyed with gall oak (Quercus infectoria Olivier) and madder (Rubia tinctorum L.). Chromatographic and spectroscopic methods were used to analyze dyed warp-knitted fabrics. A reserved phase high-performance liquid chromatography with the diode-array detection (RP-HPLC-DAD) method was utilized to determine the components of dyes present in the dyed fabrics. Scanning electron microscopy-energy X-ray spectroscopy (SEM-EDX) was utilized for morphological analysis. The undyed and dyed warp-knitted fabrics were characterized by FT-IR. The CIEL*a*b* values of the dyed polyamide-elastane warp-knitted fabrics were measured. Further, in physical testing, the pilling and abrasion resistance of raw and dyed fabrics were examined, and the water contact angle values of all fabrics were measured. Pilling test results were evaluated with a grade of 5 for all fabrics as the best score, and the resistance of fabrics to abrasion was very good. The formation of the fiber-metal-dye complex caused the fabric’s contact angle to drop, giving the fabric a hydrophilic character. The colorfastness characteristics of the dyed fabrics to light, rub, wash, and perspiration have been evaluated. The light fastness scores vary from 3 to 5, and they are satisfactory for using natural dyes to color textiles since they are in the good to moderate range. Overall, the dyed samples displayed a score of 5, which is excellent, on the Gray Scale for washing fastness.

Antibacterial coatings are becoming increasingly attractive for application in the field of biomaterials. In this framework, we developed polymer coating zirconia with antibacterial activity using the "grafting from" methodology. First, 1-(4-vinylbenzyl)-3-butylimidazolium chloride monomer was synthesized. Then, the surface modification of zirconia substrates was performed with this monomer via surface-initiated photo atom transfer radical polymerization for antibacterial activity. X-ray photoelectron spectroscopy, ellipsometry, static contact angle measurements, and an atomic force microscope were used to characterize the films for each step of the surface modification. The results revealed that cationic polymers could be successfully deposited on the zirconia surfaces, and the thickness of the grafted layer steadily increased with polymerization time. Finally, the antibacterial adhesion test was used to evaluate the antibacterial activity of the modified zirconia substrates, and we successfully showed the antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa strains. [ABSTRACT FROM AUTHOR]

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The results of surface modification of solvent casting films made from polyhydroxyalkanoates (PHAs) of various compositions are presented: homopolymer poly-3-hydroxybutyrate P(3HB) and copolymers comprising various combinations of 3-hydroxybutyrate (3HB), 3-hydroxyvalerate (3HV), 4-hydroxybutyrate(4HB), and 3-hydroxyhexanoate (3HHx) monomers treated with a CO2 laser in continuous and quasi-pulsed radiation modes. The effects of PHAs film surface modification, depending on the composition and ratio of monomers according to the results of the study of SEM and AFM, contact angles of wetting with water, adhesion and growth of fibroblasts have been revealed for the laser radiation regime used. Under continuous irradiation with vector lines, melted regions in the form of grooves are formed on the surface of the films, in which most of the samples have increased values of the contact angle and a decrease in roughness. The quasi-pulse mode by the raster method causes the formation of holes without pronounced melted zones, the total area of which is lower by 20% compared to the area of melted grooves. The number of viable fibroblasts NIH 3T3 on the films after the quasi-pulse mode is 1.5–2.0 times higher compared to the continuous mode, and depends to a greater extent on the laser treatment mode than on the PHAs' composition. The use of various modes of laser modification on the surface of PHAs with different compositions makes it possible to influence the morphology and properties of polymer films in a targeted manner. The results that have been obtained contribute to solving the critical issue of functional biodegradable polymeric materials. [ABSTRACT FROM AUTHOR]

The frictional performance between impregnated graphite materials and YG-8 cemented carbide is investigated on a self-developed rotating-type tribometer. The test configuration is a cemented carbide plate rotating against the graphite surface. Three types of concave-type textures, including linear grooves, circular dimples and isosceles triangular dimples, are fabricated by laser process on the graphite surfaces to improve the tribological properties. The test environments include dry condition and water lubrication. The corresponding friction coefficients, surface micrographs of graphite samples and cemented carbide plates are analyzed. To reveal the underlying mechanism of the frictional modification effect under water lubrication, the formation of graphite transfer film on cemented carbide plates, the water contact angles of graphite surface and the hydrodynamic effect are further discussed. It is verified that the introduction of textures on graphite surfaces can significantly improve the tribological performance of water-lubricated graphite materials.

The anti-friction function of superwetting surfaces with superhydrophobicity has been demonstrated. However, the influence regularity of wettability to tribological performance, and the underlying mechanism are still unclear. Here, two kinds of microstructured surfaces with different wettability are fabricated on the substrate of steel by controlling surface chemical compositions. The water contact angles on these surfaces range from 0° to 151°. The ball-plate tribological tests are performed under water lubrication. The results show that the tribological performance is closely related to surface wettability. The friction coefficient increases with the increase of contact angles when the surfaces are hydrophilic rather than superhydrophilic. In contrast, the friction coefficient on the hydrophobic surfaces decreases with the increase of contact angles. Furthermore, the best anti-friction capability is obtained on the superhydrophobic surfaces, and the anti-friction mechanism is elucidated. The lowest friction coefficient was 0.12 under the load of 10 N. This work provides strong evidence of an association between tribological property and wettability, which may inspire the fabrication and application of special wetting surfaces in friction control.

Maintaining stable surface properties, such as wetting, remains a challenge for many applications of functional coatings. Here, this paper reports a study on the stability of the surface properties of polydivinylbenzene (PDVB). The PDVB thin films are synthesized via initiated chemical vapor deposition (iCVD). The decrease of receding water contact angles and increase of contact angle hysteresis of iCVD PDVB over time are found to be related with surface oxidation during air exposure. Fourier transform infrared and X-ray photoelectron spectroscopy reveal the generation carbonyl and epoxy groups and the consumption of pendant vinyl groups in the oxidation process. A modified first-order kinetic model describes the dynamic process, and the apparent reaction rate constant for the oxidation of iCVD PDVB is 0.0238-0.0294 h−1. In order to inhibit the oxidation and stabilize the wettability of iCVD PDVB, an in situ thermal annealing process is developed. This thermal treatment is effective in improving the cross-linking degree of iCVD PDVB, slowing down the rate of oxidation, and therefore significantly enhancing the long-term wettability. The advancing and receding contact angles of annealed iCVD PDVB are stable even after exposure to air for two months. The reported thermal annealing approach also improves the mechanical properties of iCVD PDVB. [ABSTRACT FROM AUTHOR]

The marine hydrocarbonoclastic bacterium Alcanivorax borkumensis is well known for its ability to successfully degrade various mixtures of n-alkanes occurring in marine oil spills. For effective growth on these compounds, the bacteria possess the unique capability not only to incorporate but also to modify fatty intermediates derived from the alkane degradation pathway. High efficiency of both these processes provides better competitiveness for a single bacteria species among hydrocarbon degraders. To examine the efficiency of A. borkumensis to cope with different sources of fatty acid intermediates, we studied the growth rates and membrane fatty acid patterns of this bacterium cultivated on diesel, biodiesel and rapeseed oil as carbon and energy source. Obtained results revealed significant differences in both parameters depending on growth substrate. Highest growth rates were observed with biodiesel, while growth rates on rapeseed oil and diesel were lower than on the standard reference compound (hexadecane). The most remarkable observation is that cells grown on rapeseed oil, biodiesel, and diesel showed significant amounts of the two polyunsaturated fatty acids linoleic acid and linolenic acid in their membrane. By direct incorporation of these external fatty acids, the bacteria save energy allowing them to degrade those pollutants in a more efficient way. Such fast adaptation may increase resilience of A. borkumensis and allow them to strive and maintain populations in more complex hydrocarbon degrading microbial communities.

Layer by Layer (LbL) deposition is a simple and inexpensive method of multilayer self-assembly, that relies on the electrostatic interactions of oppositely charged polyelectrolytes. Functional biopolymers used to build such nanostructured multilayers can keep serving their inherent functions in food systems. A good example is chitosan, a positively charged biopolymer which has antimicrobial properties and forms stable complexes with negatively charged polymers. This study investigates the potential of commercially available food grade biopolymers to substitute synthetic polyelectrolytes when building nanostructured multilayers. Chitosan molecular weight, carrageenan charge density and pectin degree of esterification and amidation was varied to investigate their respective effects on the nanoscale morphology and wettability of these surfaces. Extracellular Ice Nucleators (ECINs), functional lipoglycoproteins of negative charge known to increase ice nucleation temperatures in food systems, were used to confirm the suitability of biopolymer multilayers for fabricating functional food grade nano-thin films. High molecular weight chitosan and iota-carrageenan created the most appropriate biopolymer pair to serve this purpose, as demonstrated by the nanoscale evaluation of these ultra-thin layers. ECINs successfully adsorbed onto the multilayer system, and ice nucleation activity of the nano-thin film was confirmed via the cooling bath experiments. [ABSTRACT FROM AUTHOR]

In present study, a novel and facile strategy of electrophoretic deposition (EPD) with following perfluorodecyltriethoxysilane (FAS-17) modification is successfully introduced to fabricate superhydrophobic ternary composites-Al x Ni y (Bi 2 O 3 ) z with excellent superhydrophobic and thermal stability property. The chemical composition, morphology and heat-release performance of the products were analyzed by XRD, FESEM, FT-IR, EDX, DSC and a high-speed camera, respectively. The stable suspension consisted of isopropyl alcohol and additive-polyethyleneimine. The deposition mechanism of ternary composite coating was firstly given, and EPD kinetics were investigated in detail. Moreover, the water contact angle and roll-off angle of superhydrophobic Al x Ni y (Bi 2 O 3 ) z with as well as significant water bouncing properties can reach to 169 ± 2° and ca. 1°, respectively. In addition, superhydrophobicity and internal chemical energy (ca. 2 MJ kg −1 ) of products all keep almost stable after 300 days, exhibiting a high value of practical application. Thus, this study provides a promising and low cost method for the synthesis of various superhydrophobic composites with long-term storage stability in different humidity environments and zones, even underwater. [ABSTRACT FROM AUTHOR]

Biomaterial‐associated-infection causes failure of biomaterial implants. Many new biomaterials have been evaluated for their ability to inhibit bacterial colonization and stimulate tissue-cell-integration, but neglect the role of immune cells. This paper compares macrophage phagocytosis of adhering Staphylococcus aureus on cationic-coatings and patterned poly(ethylene)glycol-hydrogels versus common biomaterials and stainless steel in order to identify surface conditions that promote clearance of adhering bacteria. Staphylococci were allowed to adhere and grow on the materials in a parallel-plate-flow-chamber, after which murine macrophages were introduced. From the decrease in the number of adhering staphylococci, phagocytosis-rates were calculated, and total macrophage displacements during an experiment determined. Hydrophilic surfaces had the lowest phagocytosis-rates, while common biomaterials had intermediate phagocytosis-rates. Patterning of poly(ethylene)glycol-hydrogel coatings increased phagocytosis-rates to the level of common biomaterials, while on cationic-coatings phagocytosis-rates remained relatively low. Likely, phagocytosis-rates on cationic coatings are hampered relative to common biomaterials through strong electrostatic binding of negatively-charged macrophages and staphylococci. On polymeric biomaterials and glass, phagocytosis-rates increased with macrophage displacement, while both parameters increased with biomaterial surface hydrophobicity. Thus hydrophobicity is a necessary surface condition for effective phagocytosis. Concluding, next-generation biomaterials should account for surface effects on phagocytosis in order to enhance the ability of these materials to resist biomaterial-associated-infection. [ABSTRACT FROM AUTHOR]

Titanium (IV) isopropoxide (TTIP) in methanol, ethanol, hexane, dichloromethane, and isopropanol solvents is used to deposit titanium dioxide thin films on glass and steel substrates at 550 °C using aerosol-assisted (AA)CVD. X-ray diffraction (XRD), and Raman spectra of the as-deposited films show that using methanol as the carrier solvent produces exclusively rutile films on steel, and predominantly rutile on glass substrates, while the use of the other solvents produces exclusively anatase phase on the steel under the same conditions. TiO2 is also deposited by AACVD from a mixture of ethanol and methanol solvents. As little as 15% of methanol in ethanol produces rutile as the predominant phase. Using a dye-ink test, the titanium dioxide thin films produced with ethanol are shown to be more active photocatalysts than films produced with methanol. All the films show photo-induced superhydrophilicity but, surprisingly, films stored in the dark have a water contact angle above 100°. [ABSTRACT FROM AUTHOR]

The amine fluoride (AmF) N′-octadecyltrimethylendiamine-N,N,N′-tris(2-ethanol)-dihydrofluoride is a cationic antimicrobial which can have beneficial effects on plaque formation. Here, we determine changes in pellicle and bacterial cell surface properties of the strains Actinomyces naeslundii HM1, Streptococcus mutans NS, S.mutans ATCC 700610, S. sobrinus HG1025 and S. oralis HM1 upon adsorption of this AmF and accompanying effects on bacterial adhesion and biofilm growth. In vitro pellicles had a zeta potential of –12 mV that became less negative upon adsorption of AmF. The chemical functionalities in which carbon and oxygen were involved changed after AmF adsorption and AmF-treated pellicles had a greater surface roughness than untreated pellicles. Water contact angles in vitro decreased from 56 to 45° upon AmF treatment, which corresponded with water contact angles (44°) measured intraorally on the front incisors of volunteers immediately after using an AmF-containing toothpaste. All bacterial strains were negatively charged and their isoelectric points (IEP) increased upon AmF adsorption. Minimal inhibitory concentrations were smallest for strains exhibiting the largest increase in IEP. Adhesion to salivary pellicles and biofilm growth of the mutans streptococcal strains were significantly reduced after AmF treatment, but not of A. naeslundii or S. oralis. However, regardless of the strain involved, biofilm viability decreased significantly after AmF treatment. The electrostatic interaction between cationic AmF and negatively charged bacterial cell surfaces is pivotal in establishing reduced biofilm formation by AmF through a combination of effects on initial adhesion and killing. The major effect of AmF treatment, however, was a reduction brought about in biofilm viability. Copyright © 2007 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Abstract: A low-density polyethylene (LDPE) surface with a sharp wettability gradient and high hysteresis was prepared, on which a unique behavior of water drops was found. The water contact angle of one water drop on the less hydrophobic region was larger than that on the more hydrophobic end, which was much different from the general phenomenon. The unique behavior is believed to be induced by the high hysteresis of the LDPE surface and the sharp change in wettability. The driving and hysteresis forces acting on the water drops were calculated and analyzed in detail. The reasons resulting to such a unique phenomenon were further explained. [Copyright &y& Elsevier]

The study reports results of using a CO2-laser in continuous wave (3 W; 2 m/s) and quasi-pulsed (13.5 W; 1 m/s) modes to treat films prepared by solvent casting technique from four types of polyhydroxyalkanoates (PHAs), namely poly-3-hydroxybutyrate and three copolymers of 3-hydroxybutyrate: with 4-hydroxybutyrate, 3-hydroxyvalerate, and 3-hydroxyhexanoate (each second monomer constituting about 30 mol.%). The PHAs differed in their thermal and molecular weight properties and degree of crystallinity. Pristine films differed in porosity, hydrophilicity, and roughness parameters. The two modes of laser treatment altered these parameters and biocompatibility in diverse ways. Films of P(3HB) had water contact angle and surface energy of 92° and 30.8 mN/m, respectively, and average roughness of 144 nm. The water contact angle of copolymer films decreased to 80–56° and surface energy and roughness increased to 41–57 mN/m and 172–290 nm, respectively. Treatment in either mode resulted in different modifications of the films, depending on their composition and irradiation mode. Laser-treated P(3HB) films exhibited a decrease in water contact angle, which was more considerable after the treatment in the quasi-pulsed mode. Roughness parameters were changed by the treatment in both modes. Continuous wave line-by-line irradiation caused formation of sintered grooves on the film surface, which exhibited some change in water contact angle (76–80°) and reduced roughness parameters (to 40–45 mN/m) for most films. Treatment in the quasi-pulsed raster mode resulted in the formation of pits with no pronounced sintered regions on the film surface, a more considerably decreased water contact angle (to 67–76°), and increased roughness of most specimens. Colorimetric assay for assessing cell metabolic activity (MTT) in NIH 3T3 mouse fibroblast culture showed that the number of fibroblasts on the films treated in the continuous wave mode was somewhat lower; treatment in quasi-pulsed radiation mode caused an increase in the number of viable cells by a factor of 1.26 to 1.76, depending on PHA composition. This is an important result, offering an opportunity of targeted surface modification of PHA products aimed at preventing or facilitating cell attachment. [ABSTRACT FROM AUTHOR]

We attempt to predict the water contact angle (WCA) of self-assembled monolayers (SAMs) and protein adsorption on the SAMs from the chemical structures of molecules constituting the SAMs using machine learning with an artificial neural network (ANN) model. After training the ANN with data of 145 SAMs, the ANN became capable of predicting the WCA and protein adsorption accurately. The analysis of the trained ANN quantitatively revealed the importance of each structural parameter for the WCA and protein adsorption, providing essential and quantitative information for material design. We found that the degree of importance agrees well with our general perception on the physicochemical properties of SAMs. We also present the prediction of the WCA and protein adsorption of hypothetical SAMs and discuss the possibility of our approach for the material screening and design of SAMs with desired functions. On the basis of these results, we also discuss the limitation of this approach and prospects.

Remarkable interfacial behaviors are observed in nature. Our efforts, directed toward replicating the structures, chemistries, and therefore functional properties of natural nonwetting surfaces, are competing with the result of billions of years of natural selection. The application of man-made surfaces is challenged by their poor longevity in aggressive environmental or applied service conditions. This study reports on a new approach for the creation of multiscale hierarchical surface patterns in metals, which exploits thermodynamic phenomena in advanced manufacturing processes. While hydrophobic coatings can be produced with relative ease by electrodeposition, these fractal-type structures tend to have poor structural integrity and hence are not durable. In this method, "seed surfaces" are directly written onto substrates by selective electrodeposition, after which they are irradiated by a large-area, pulsed electron beam to invoke a beading phenomenon, which is studied here. The length scale of these beads is shown to depend upon the melt time of the liquid metal. The created surfaces are shown to yield high water contact angles (145°) without subsequent chemical modification, and high adhesion properties reminiscent of the "rose petal" hydrophobic effect. The size and morphology and hence the hydrophobic effect of the surface beads generated are correlated with the thickness of the electrodeposited coating and hence the melt lifetime upon electron irradiation. This new rapid approach for tunable hydrophobic surface creation has applications for developing precision hydrophobic patterns and is insensitive to surface complexity.

Surface wettability gradients were used to elongate and align double stranded λ-DNA. Gradients were prepared by vapor phase deposition of octyltrichlorosilane (C8-silane) and fluorinated octyltrichlorosilane (F-silane) precursors. Gradient formation was confirmed by water contact angle and ellipsometric film thickness measurements. Placement of a droplet of aqueous DNA solution on the hydrophobic end of each gradient led to spontaneous motion of the droplet toward the hydrophilic end and deposition of the DNA. Fluorescence imaging of surface-adsorbed YOYO-1 labeled DNA molecules revealed that they are elongated and aligned perpendicular to the droplet-surface contact line at all positions along the gradient, consistent with a dominant role played by surface tension forces in elongating the DNA. The density of adsorbed DNA was found to be greatest on the C8-silane gradient at its hydrophobic end. DNA density decreased toward the hydrophilic end, while the length of the elongated DNA was less dependent on position. The elongation of DNA molecules by spontaneous droplet motion on chemical gradient surfaces has possible applications in DNA barcoding and studies of DNA-protein interactions.