Showing papers in "Surface Innovations in 2016"

Superwettability integration: concepts, design and applications

Abstract: Functional surfaces exhibiting superwettability offer great opportunities to develop advanced science and technology. To unite the advantages of different surfaces with special wettability, superwettability integration has been proposed and fabricated, showing a co-operative and complementary effect on material properties. This paper discusses how to combine different wettabilities and what functions can be achieved based on superwettability integration. Superwettability integration is defined as a unified system combining different superwetting materials or assembling superwetting materials with other functional materials. Four types of superwettability integrations are summarized: (a) surfaces with microscopic wettability patterns, (b) surfaces with macroscopic wettability patterns, (c) Janus interface materials with asymmetric wettability and (d) surfaces with specific wettability boundary. The functions and applications of the integrated systems are reviewed, particularly for use in fluid control, vap...

Importance of oxide film in endovascular biodegradable zinc stents

Abstract: A better understanding of the surface oxide film on biodegradable metals could lead to the design of smarter, surface-responsive biodegradable stents with good biocompatibility and controlled degra...

Improvement of lubricant-infused surfaces for anti-icing applications

Abstract: Slippery lubricant-infused porous surfaces (SLIPS) were developed recently where a textured solid is impregnated with an immiscible lubricant with a low surface tension to create a smooth liquid overlayer to minimize ice nucleation and ice adhesion. Later, many similar surfaces were produced for the same objective using various liquids (perfluorinated, silicone oil, hydrocarbon and water), which were sometimes termed as ‘liquid-impregnated surfaces’. The favourable and adverse properties of SLIPS in anti-icing applications are discussed in this review. The importance of the ice-accretion experiments is also highlighted to evaluate the anti-icing performance. The use of SLIPS containing fluorinated or silicone lubricating layers for anti-icing applications has several drawbacks because of the lubricant loss due to drainage, evaporation and cloaking by contacting water droplets. On the other hand, SLIPS containing water and other aqueous lubricating layers on hygroscopic polymer supports seem to be more pro...

Organic–inorganic hybrid sol–gel coatings for corrosion protection of aluminum alloys

Abstract: Chromium-based pretreatments are among the most successful systems for aluminum-based alloys, however, due to environmental and health concerns, chromium-based compounds are a target for replacement. Sol–gel approach has emerged as a versatile method for preparing a host of sol–gel hybrid coatings that are candidates for use in protective coating applications. Organic–inorganic hybrid sol–gel coatings are among the most attractive alternatives to the use of chromium-based coatings because they are highly adherent and chemically inert coatings that are covalently bonded on the metal substrates at low temperature near ambient. In this review, the authors aim to summarize the latest achievements and strategies for the sol–gel process parameters as well as other factors that influence the corrosion properties of the organic–inorganic hybrid sol–gel coatings for the corrosion protection of aluminum-based alloys. The authors also discuss the existing issues and challenges in anticorrosion performance of the org...

Encapsulation of urea and caffeine in Cu3(BTC)2 metal–organic framework

Abstract: The Cu3(BTC)2 metal–organic framework (MOF) (BTC = 1,3,5-benzenetricarboxylate), also known as HKUST-1 (or MOF-199), is one of the most studied MOFs because it has a large surface area, high pore volume, high chemical stability and the ability to bind water, among other molecules, by coordinating to the unsaturated Cu(II) sites. In this study, Cu3(BTC)2 was used for the first time to remove the pharmaceutical products of urea and caffeine. Two strategies for retention of urea and caffeine in Cu3(BTC)2 were studied. The first strategy corresponds to in situ encapsulation, where urea and caffeine were added to Cu3(BTC)2 synthesis precursors and the porous structure was formed around the urea or caffeine molecules resulting in the encapsulation. The second one corresponds to post-synthesis encapsulation. The adsorption of urea or caffeine in MOF structure was realized by adding the as-synthesized dry Cu3(BTC)2 into urea or caffeine aqueous solution. The results show that in situ encapsulation of caffeine and...

‘Green’ surface treatment for water-repellent cotton fabrics

Abstract: An environment-friendly ‘green’ method to obtain water-repellent (hydrophobic) cotton fabrics has been developed. Aliphatic fatty chains were grafted onto cotton (cellulose) fiber surface to decrease the surface energy and, thus, obtain water repellency. A benign accelerator was used to facilitate the reaction between fatty acids and cellulosic hydroxyl groups. Microwave heating, an energy-efficient method, was used to reach the reaction temperature. Fatty anhydride, considered to have a higher reactivity than fatty acids, was initially prepared. This process was monitored using high-performance liquid chromatography and attenuated total reflectance-Fourier transform infrared (ATR-FTIR) techniques. The effects of fatty acid chain length as well as microwave heating parameters on the hydrophobicity of the cotton fabrics were studied. The resulting hydrophobic cotton fabrics were characterized by water contact angle, laundry durability test, tensile test, and ATR-FTIR spectroscopy. The green method develope...

Biomimetic lipid bilayers on solid surfaces: models for biological interactions

Abstract: Biomimetic lipid bilayer platforms on solid supports, or solid-supported lipid bilayers (SLBs), are important model membrane systems for studying the fundamental properties of biological membranes and their constituent lipid and protein molecules. SLBs with different properties and functionalities can be designed by changing their lipid content (charged, uncharged, saturated, etc.), adding various membrane components (glycolipids, cholesterol, etc.) or incorporating membrane proteins (receptors, ion channels, etc.). They allow the usage of surface-sensitive characterization techniques such as atomic force spectroscopy, surface plasmon resonance (SPR) and the use of acoustic sensors such as quartz crystal microbalance with dissipation monitoring (QCM-D). Both QCM-D and SPR can supply information about binding events on surfaces and the properties of the resulting lipid films in real time by using frequency-dissipation changes and refractive index shift, respectively. In recent years, the potential of SLBs ...

Rapid and scalable lubrication and replenishment of liquid-infused materials

Abstract: Liquid-infused surfaces (LIS) consist of a porous or textured solid matrix infused with a lubricating liquid. The presence of a thin film of the lubricant on the exterior surface facilitates dramatically the shedding of a wide range of liquids and solids, making LIS potential candidates for a variety of applications. However, before LIS can transition into industrial use, durability issues posed by lubricant depletion need to be addressed. In this paper an ‘inside-out-in’ system is introduced for rapid lubrication or relubrication of polymeric LIS. The system consists of an embedded millichannel liquid distribution network connected to the exterior polymer surface using periodically spaced vias and could be used to, for example, lubricate LIS-based personal protective gear. By using periodic contact angle measurements and spray impingement experiments, the authors show that release of a lubricant using this system leads to diminishing contact angle hysteresis of the exterior LIS surface nearly instantaneo...

Biosilver nanoparticle interface offers improved cell viability.

Abstract: Silver nanoparticles (AgNP) are promising candidates for fighting drug-resistant infections because of their intrinsic antimicrobial effect The design of high-yield antimicrobial molecules may inadvertently cause variation in host cells' biological responses While many factors affect AgNPs' efficacy, their surface is exposed to the biological environment and thus plays a critical role in both the preservation of antimicrobial efficacy against pathogens and the modulation of host cells cytotoxicity This work investigated an engineered biomimetic interface approach to controlling AgNP surface properties to provide them a competitive advantage in a biological environment Here, a fusion protein featuring a silver-binding peptide (AgBP) domain was engineered to enable self-assembly and track assembly by a green fluorescent protein (GFP) reporter Following AgNP functionalisation with GFP-AgBP, their antimicrobial and cytotoxic properties were evaluated GFP-AgBP binding affinity to AgNPs was evaluated using localized surface plasmon resonance sensing The GFP-AgBP biomimetic interface on AgNPs' surfaces provided sustained antibacterial efficacy at low concentrations based on bacterial growth inhibition assays Viability and cytotoxicity measurements in fibroblast cells exposed to GFP-AgBP protein-functionalised AgNPs showed significant improvement compared to controls Biointerface engineering offers promise towards tailoring AgNP antimicrobial efficacy while addressing safety concerns to maintain optimum cellular interactions

Tailoring the surface of polymeric nanofibres generated by pressurised gyration

Abstract: Polymeric nanofibres with smooth, rough and porous surfaces were prepared by pressurised gyration, which is a novel method for producing nanofibres, utilising the combination of centrifugal spinning and solution blowing. A series of fibres were prepared by using polyacrylonitrile (Pan), poly(methyl methacrylate) (PMMA) and 50:50 Pan–PMMA polymer solutions without pressure and with 0·2 MPa working pressure. The surface morphology of the nanofibres was analysed by scanning electron microscopy, and their thermal properties were studied by thermogravimetry and hot-stage microscopy. Nanofibres with a smooth surface were generated at 0·2 MPa working pressure, and those with a rough surface were generated without any working pressure. Porous Pan nanofibres were prepared by using PMMA as a sacrificial polymer. The 50:50 Pan–PMMA blend fibres were subjected to heat treatment to obtain porous fibres. The less thermally stable PMMA decomposes when heated, generating pores on the surface of the Pan fibres. The porous...

Laser-perforated polymer films for possible use in tissue engineering

Abstract: Ablation experiments were carried out to modify surfaces of poly(3-hydroxybutyrate) (PHB), poly(lactic acid) (PLA), poly(methyl methacrylate) (PMMA), and polyurethane (PU)/poly(dimethylsiloxane) (PDMS) films using a krypton fluoride excimer laser, which was employed to produce cavities and orderly perforated holes on the films for tissue engineering. Surface patterning was assisted by prefabricated stainless steel masks with different mesh sizes. Film surfaces modified in this manner were studied and analyzed for different laser parameters (such as pulse energy and pulse repetition rate), and characterized using optical microscopy and surface profilometry. The present study demonstrated that laser surface modification of PHB, PLA, PMMA, and PU/PDMS films can be achieved with a high degree of success and precision. The effect of the surface changes on the tendency of cells to adhere to the polymers, as well as its effect on cell growth, were subsequently investigated. Cell–polymer film interfacial interact...

Using bulk properties of UV-polymerized thin layers for fiber modification

Abstract: The surface properties of fibers can be regarded as instrumental toward innovative functional textiles as applied in many high-end industries. Accordingly, not only the modification of surface chemistry, but also of the physical and morphological properties is an important objective in modern materials science and technology. Besides other powerful chemical and physical techniques, UV-induced graft copolymerization and photopolymerization are interesting ways to improve or introduce surface functionalities of the fiber. While the majority of reported work focused on the surface of the deposited thin layer itself and its potential effect on – for example, wettability, adhesion, protein adsorption and microbial activity, this paper reviews earlier studies by the authors which were devoted to bulk properties of these thin, less than 500-nm thick layers and the resulting effect on fiber properties. One major factor is the high and controllable cross-linking of polymerized layers, which affects mechanical, the...

Biological path for functional nanostructure fabrication and nanodevices

Abstract: The fabrication of nanostructures by biomolecules is proposed. The process utilises biotemplated biomineralisation of inorganic materials and self-assembly, termed the ‘bio–nano process’ (BNP). Artificial proteins are designed to construct functional nanometric structures in combination with top–down miniaturisation technologies. Genetically modified cage-shaped proteins, ferritin and deoxyribonucleic acid-binding protein from starved cells, are the most studied biotemplates for the BNP. The inner cavity is used as a spatially restricted chamber for the synthesis of homogeneous metal, metal-complex and semiconductor nanoparticles (NPs). Proteins with NP cores are delivered onto specific substrate locations or carbon nanotube surfaces by electrostatic interaction or specific binding peptides. These NPs realise a variety of functions such as charge storage nodes for floating gate memory, catalysts for carbon nanotube growth, quantum wells in heterogeneous junctions and nanoetching masks. Cage-shaped protein...

Assessing graphene oxide/polymer interfacial interactions by way of peeling test

Abstract: The design of graphene/polymer nanocomposites with improved mechanical properties requires characterization of the interfacial interactions between different types of graphene sheets and different polymers. In this study, the interactions in a graphene oxide (GO)/polymer nanocomposite were explored and the effect of thermal reduction of GO on adhesion was tested. A versatile peeling test was demonstrated and applied on a wide range of nanosheet fillers and polymers, which has great potential for expedited development of enhanced nanocomposites. The interactions of GO and reduced graphene oxide (rGO) nanofillers were tested with widely used polymers, including poly(methyl methacrylate), polystyrene, acrylic, polyvinyl alcohol, polyetherimide and polyimide. The results show the effect of thermal reduction of GO on the interactions in polymer nanocomposites and rank the interfacial preferences of GO and rGO for different polymers. In terms of surface energy considerations, some of the results are in agreemen...

Hydrophobicity and tribology of large-area textured copper with nanogrown copper oxide

Abstract: Copper (Cu) is widely used as an engineering material for automotive industries. Herein, a two-step surface innovation process was evolved to enhance the hydrophobicity and wear resistance of the c...

Surface modification of PEN treated with ozone and UV photooxidation

Abstract: Poly(ethylene 2,6-naphthalate) (PEN) was treated with ozone in the absence of radiation and the results were compared with ultraviolet (UV) photooxidation using 253·7 and 184·9 nm radiations. The surface modification of the top 2–5 nm was analyzed by X-ray photoelectron spectroscopy (XPS) for chemical changes. Higher saturation levels of oxidation were achieved using UV photooxidation than ozonation. Both treatment methods increased the amounts of C–O–C, C=O and O–C=O bondings while UV photooxidation also increased the concentration of the anhydride/carbonate moieties on the surface. Atomic force microscopy detected smoother surfaces with increasing treatment time for both the treatments. The changes in functional groups and surface roughness with both treatments contributed to an increase in hydrophilicity as determined by advancing water contact angle measurements. A greater increase in hydrophilicity was observed for the UV photooxidized PEN samples. Initial results showed a slight increase in hydrophi...

Prevention of biofilm attachment by plasma treatment of polyethylene

Abstract: In this work, ultrahigh molecular weight polyethylene (UHMWPE) was treated with low-pressure nitrogen plasma for improved biofouling resistance. The plasma-treated surface showed a decrease in water contact angle from 85° for the untreated surface to 40° for the nitrogen (N2) plasma-treated surface. Optical emission spectroscopy analysis reveals the presence of excited species of carbon and hydrogen (unstable ionised forms) associated with bond breaking, hydrogen abstraction and chain scission processes. The average roughness for the untreated UHMWPE surface was 1·0 μm, which increased to 2·2 μm due to etching with plasma treatment. The nanomechanical properties of the samples such as hardness and modulus were assessed by nanoindentation tests. These tests showed that plasma affects only a few nanometres of the polymer. The polymers were studied for Escherichia coli biofilm formation, and they were imaged using an optical microscope and atomic force microscope. It was observed that plasma treatment signif...

Deposition of zeolite nanoparticles onto porous silica monolith

Abstract: A facile and effective method of deposition of ZSM-5 (MFI framework topology) zeolite nanoparticles (nanocrystals) onto macro-/mesoporous silica monolith is demonstrated in this paper. The electrostatic interaction between zeolite and silica monolith was controlled by cationic polyelectrolytes, which were adsorbed onto either silica monolith or zeolite nanocrystals. The effects of time, concentration of zeolite nanocrystals, type of polyelectrolyte and ultrasound treatment were examined. It was found that deposition of nanocrystals on silica monolith modified with polyelectrolyte resulted in a monolayer coverage. Adsorption of nanocrystals modified with polyelectrolyte resulted in a multilayer coverage on the silica monolith due to the agglomeration of particles. On the other hand, the use of excess amounts of polyelectrolyte in the modification of nanoparticles leads to a low coverage of silica monolith by zeolite nanoparticles and is the result of the competition between polyelectrolyte and modified nan...

Evaluation of organic coatings condition with AFM-based method

Abstract: The paper presents an atomic force microscopy (AFM)-based approach to evaluation of local protective properties of organic coatings. Apart from topography, it provides local AC and DC characteristics of examined coating. The method consists in application of AC voltage perturbation signal between conductive AFM tip and coated metal substrate. The resulting current is used to determine local impedance characteristics. Both impedance imaging and impedance spectroscopy modes are available. The measurements are performed in contact AFM regime either for continuous scanning of the tip over the surface or for stationary positioning of the tip over the area of interest. Application of DC bias voltage between the AFM tip and the coated metal substrate makes it possible to verify coating continuity and to identify the potential sites with through-the-coating defects, which penetrate the coating down to the metal substrate. Description of the fundamentals of the technique is supported with selected examples of rese...

Evaluation of adhesion of asphalt binders using wicking experiments

Abstract: The objective of this study was to develop a methodology to evaluate the adhesion of liquids to porous by solids using wetting/wicking experiments. The surface area of porous materials significantly increases compared with that of their solid analogs. Hence, pores play an important role in the adhesion of resins and binders to solids. The authors developed an experimental protocol allowing one to evaluate the work of adhesion, a characteristic thermodynamic parameter of the liquid/porous solid pair. It is shown that for the determination of the work of adhesion, one needs to know the pore size distribution, the wicking constant of the wetting liquid and the surface tension of the liquid. Asphalt binders and different rocks were studied to illustrate the methodology.