Science.gov

Sample records for advanced surface modification

  1. Recent advances in liposome surface modification for oral drug delivery.

    PubMed

    Nguyen, Thanh Xuan; Huang, Lin; Gauthier, Mario; Yang, Guang; Wang, Qun

    2016-05-01

    Oral delivery via the gastrointestinal (GI) tract is the dominant route for drug administration. Orally delivered liposomal carriers can enhance drug solubility and protect the encapsulated theraputic agents from the extreme conditions found in the GI tract. Liposomes, with their fluid lipid bilayer membrane and their nanoscale size, can significantly improve oral absorption. Unfortunately, the clinical applications of conventional liposomes have been hindered due to their poor stability and availability under the harsh conditions typically presented in the GI tract. To overcome this problem, the surface modification of liposomes has been investigated. Although liposome surface modification has been extensively studied for oral drug delivery, no review exists so far that adequately covers this topic. The purpose of this paper is to summarize and critically analyze emerging trends in liposome surface modification for oral drug delivery. PMID:27074098

  2. Advancing Sustainable Catalysis with Magnetite Surface Modification and Synthetic Applications

    EPA Science Inventory

    This article surveys the recent developments in the synthesis, surface modification, and synthetic applications of magnetitenanoparticles. The emergence of iron(II,III) oxide (triiron tetraoxide or magnetite; Fe3O4, or FeO•Fe2O3) nanoparticles as a sustainable support in het...

  3. Advances in the surface modification techniques of bone-related implants for last 10 years

    PubMed Central

    Qiu, Zhi-Ye; Chen, Cen; Wang, Xiu-Mei; Lee, In-Seop

    2014-01-01

    At the time of implanting bone-related implants into human body, a variety of biological responses to the material surface occur with respect to surface chemistry and physical state. The commonly used biomaterials (e.g. titanium and its alloy, Co–Cr alloy, stainless steel, polyetheretherketone, ultra-high molecular weight polyethylene and various calcium phosphates) have many drawbacks such as lack of biocompatibility and improper mechanical properties. As surface modification is very promising technology to overcome such problems, a variety of surface modification techniques have been being investigated. This review paper covers recent advances in surface modification techniques of bone-related materials including physicochemical coating, radiation grafting, plasma surface engineering, ion beam processing and surface patterning techniques. The contents are organized with different types of techniques to applicable materials, and typical examples are also described. PMID:26816626

  4. New advanced surface modification technique: titanium oxide ceramic surface implants: long-term clinical results

    NASA Astrophysics Data System (ADS)

    Szabo, Gyorgy; Kovacs, Lajos; Barabas, Jozsef; Nemeth, Zsolt; Maironna, Carlo

    2001-11-01

    The purpose of this paper is to discuss the background to advanced surface modification technologies and to present a new technique, involving the formation of a titanium oxide ceramic coating, with relatively long-term results of its clinical utilization. Three general techniques are used to modify surfaces: the addition or removal of material and the change of material already present. Surface properties can also be changed without the addition or removal of material, through the laser or electron beam thermal treatment. The new technique outlined in this paper relates to the production of a corrosion-resistant 2000-2500 A thick, ceramic oxide layer with a coherent crystalline structure on the surface of titanium implants. The layer is grown electrochemically from the bulk of the metal and is modified by heat treatment. Such oxide ceramic-coated implants have a number of advantageous properties relative to implants covered with various other coatings: a higher external hardness, a greater force of adherence between the titanium and the oxide ceramic coating, a virtually perfect insulation between the organism and the metal (no possibility of metal allergy), etc. The coated implants were subjected to various physical, chemical, electronmicroscopic, etc. tests for a qualitative characterization. Finally, these implants (plates, screws for maxillofacial osteosynthesis and dental root implants) were applied in surgical practice for a period of 10 years. Tests and the experience acquired demonstrated the good properties of the titanium oxide ceramic-coated implants.

  5. Surface Modification of Intraocular Lenses

    PubMed Central

    Huang, Qi; Cheng, George Pak-Man; Chiu, Kin; Wang, Gui-Qin

    2016-01-01

    Objective: This paper aimed to review the current literature on the surface modification of intraocular lenses (IOLs). Data Sources: All articles about surface modification of IOLs published up to 2015 were identified through a literature search on both PubMed and ScienceDirect. Study Selection: The articles on the surface modification of IOLs were included, but those on design modification and surface coating were excluded. Results: Technology of surface modification included plasma, ion beam, layer-by-layer self-assembly, ultraviolet radiation, and ozone. The main molecules introduced into IOLs surface were poly (ethylene glycol), polyhedral oligomeric silsesquioxane, 2-methacryloyloxyethyl phosphorylcholine, TiO2, heparin, F-heparin, titanium, titanium nitride, vinyl pyrrolidone, and inhibitors of cytokines. The surface modification either resulted in a more hydrophobic lens, a more hydrophilic lens, or a lens with a hydrophilic anterior and hydrophobic posterior surface. Advances in research regarding surface modification of IOLs had led to a better biocompatibility in both in vitro and animal experiments. Conclusion: The surface modification is an efficient, convenient, economic and promising method to improve the biocompatibility of IOLs. PMID:26830993

  6. Advanced Natural Gas Reciprocating Engine: Parasitic Loss Control through Surface Modification

    SciTech Connect

    Farshid Sadeghi; Chin-Pei Wang

    2008-12-31

    This report presents results of our investigation on parasitic loss control through surface modification in reciprocating engine. In order to achieve the objectives several experimental and corresponding analytical models were designed and developed to corroborate our results. Four different test rigs were designed and developed to simulate the contact between the piston ring and cylinder liner (PRCL) contact. The Reciprocating Piston Test Rig (RPTR) is a novel suspended liner test apparatus which can be used to accurately measure the friction force and side load at the piston-cylinder interface. A mixed lubrication model for the complete ring-pack and piston skirt was developed to correlate with the experimental measurements. Comparisons between the experimental and analytical results showed good agreement. The results revealed that in the reciprocating engines higher friction occur near TDC and BDC of the stroke due to the extremely low piston speed resulting in boundary lubrication. A Small Engine Dynamometer Test Rig was also designed and developed to enable testing of cylinder liner under motored and fired conditions. Results of this study provide a baseline from which to measure the effect of surface modifications. The Pin on Disk Test Rig (POD) was used in a flat-on-flat configuration to study the friction effect of CNC machining circular pockets and laser micro-dimples. The results show that large and shallow circular pockets resulted in significant friction reduction. Deep circular pockets did not provide much load support. The Reciprocating Liner Test Rig (RLTR) was designed to simplifying the contact at the PRCL interface. Accurate measurement of friction was obtained using 3-axis piezoelectric force transducer. Two fiber optic sensors were used to measure the film thickness precisely. The results show that the friction force is reduced through the use of modified surfaces. The Shear Driven Test Rig (SDTR) was designed to simulate the mechanism of the

  7. Nanoscale surface modification of plastic substrates for advanced tissue engineering applications

    NASA Astrophysics Data System (ADS)

    Donkov, N.; Safonov, V.; Zykova, A.; Smolik, J.; Rogovska, R.; Goltsev, A.; Dubrava, T.; Rossokha, I.; Georgieva, V.

    2012-12-01

    Modified surface properties such as composition, nano roughness, wettability have effect on the most important processes at biomaterial interface. The research of stem cells (MSCs) adhesive potential, morphology, phenotypical characteristics on oxide coated and plastic substrate with different surface parameters was made. The oxide coatings deposition on plastic substrates shifts the surface properties at the more hydrophilic region and results in next positive cell/ biomaterial response in vitro tests. The MSCs marker number increases on the oxide nano structural surface of plastic substrates.

  8. Inorganic Surface Modification of Nonwoven Polymeric Substrates

    NASA Astrophysics Data System (ADS)

    Halbur, Jonathan Chandler

    In this study, atomic layer deposition (ALD), a vapor phase inorganic thin film deposition technique, is used to modify the surface of a range of industrially relevant polymers to enhance surface properties or impart additional functionalities. Several unique demonstrations of polymer surface modification are presented including uniform nanomaterial photodeposition to the surface of nonowoven fabrics and the first application of photocatalytic thin film coated nonwovens for advanced filtration of heavy metals from solution. Recent advances in polymer synthesis and processing technologies have resulted in the production of novel polymer systems with unique chemistries and sub-micron scale dimensions. As a result, advanced fiber systems have received much attention for potential use in a wide range of industrially and medically important applications such as advanced and selective filtration, catalysis, flexible electronics, and tissue engineering. However, tailoring the surface properties of the polymer is still needed in order to realize the full range of advanced applications, which can be difficult given the high complexity and non-uniformity of nonwoven polymeric structures. Uniform and controllable inorganic surface modification of nonwovens allows the introduction or modification of many crucial polymer properties with a wide range of application methods.

  9. Plasma surface modification of polymers

    NASA Technical Reports Server (NTRS)

    Hirotsu, T.

    1980-01-01

    Thin plasma polymerization films are discussed from the viewpoint of simplicity in production stages. The application of selective, absorbent films and films used in selective permeability was tested. The types of surface modification of polymers discussed are: (1) plasma etching, (2) surface coating by plasma polymerized thin films, and (3) plasma activation surface graft polymerization.

  10. Surface modification to waveguides

    DOEpatents

    Timberlake, John R.; Ruzic, David N.; Moore, Richard L.; Cohen, Samuel A.; Manos, Dennis M.

    1983-01-01

    A method of treating the interior surfaces of a waveguide to improve power transmission comprising the steps of mechanically polishing to remove surface protrusions; electropolishing to remove embedded particles; ultrasonically cleaning to remove any residue; coating the interior waveguide surfaces with an alkyd resin solution or electrophoretically depositing carbon lamp black suspended in an alkyd resin solution to form a 1.mu. to 5.mu. thick film; vacuum pyrolyzing the film to form a uniform adherent carbon coating.

  11. Surface modification to waveguides

    DOEpatents

    Timberlake, J.R.; Ruzic, D.N.; Moore, R.L.; Cohen, S.A.; Manos, D.M.

    1982-06-16

    A method is described for treating the interior surfaces of a waveguide to improve power transmission comprising the steps of mechanically polishing to remove surface protrusions; electropolishing to remove embedded particles; ultrasonically cleaning to remove any residue; coating the interior waveguide surfaces with an alkyd resin solution or electrophoretically depositing carbon lamp black suspended in an alkyd resin solution to form a 1..mu.. to 5..mu.. thick film; vacuum pyrolyzing the film to form a uniform adherent carbon coating.

  12. Ion beam surface modification

    NASA Technical Reports Server (NTRS)

    Dwight, D. W.

    1982-01-01

    The essential details of a study on the practical applications and mechanisms of polymer sputtering via Argon ion impact are summarized. The potential to modify the properties of polymer surfaces to improve their adherence, durability, biocompatibility, or other desirable properties by ion beam sputtering was emphasized. Ion beam milling can be of benefit as an analytical tool to obtain composition versus depth information. Ion impact from a directed ion gun source specifically etches polymer structures according to their morphologies, therefore this technique may be useful to study unknown or new morphological features. Factors addressed were related to: (1) the texture that arises on a polymer target after ion impact; (2) the chemistry of the top surface after ion impact; (3) the chemistry of sputtered films of polymeric material deposited on substrates placed adjacent to targets during ion impact; and (4) practical properties of textured polymer targets, specifically the wettability and adhesive bonding properties.

  13. Surface modification of nano-silica on the ligament advanced reinforcement system for accelerated bone formation: primary human osteoblasts testing in vitro and animal testing in vivo

    NASA Astrophysics Data System (ADS)

    Li, Mengmeng; Wang, Shiwen; Jiang, Jia; Sun, Jiashu; Li, Yuzhuo; Huang, Deyong; Long, Yun-Ze; Zheng, Wenfu; Chen, Shiyi; Jiang, Xingyu

    2015-04-01

    The Ligament Advanced Reinforcement System (LARS) has been considered as a promising graft for ligament reconstruction. To improve its biocompatibility and effectiveness on new bone formation, we modified the surface of a polyethylene terephthalate (PET) ligament with nanoscale silica using atom transfer radical polymerization (ATRP) and silica polymerization. The modified ligament is tested by both in vitro and in vivo experiments. Human osteoblast testing in vitro exhibits an ~21% higher value in cell viability for silica-modified grafts compared with original grafts. Animal testing in vivo shows that there is new formed bone in the case of a nanoscale silica-coated ligament. These results demonstrate that our approach for nanoscale silica surface modification on LARS could be potentially applied for ligament reconstruction.The Ligament Advanced Reinforcement System (LARS) has been considered as a promising graft for ligament reconstruction. To improve its biocompatibility and effectiveness on new bone formation, we modified the surface of a polyethylene terephthalate (PET) ligament with nanoscale silica using atom transfer radical polymerization (ATRP) and silica polymerization. The modified ligament is tested by both in vitro and in vivo experiments. Human osteoblast testing in vitro exhibits an ~21% higher value in cell viability for silica-modified grafts compared with original grafts. Animal testing in vivo shows that there is new formed bone in the case of a nanoscale silica-coated ligament. These results demonstrate that our approach for nanoscale silica surface modification on LARS could be potentially applied for ligament reconstruction. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr01439e

  14. [Advances in genetic modification technologies].

    PubMed

    Zhang, Baixue; Sun, Qixin; Li, Haifeng

    2015-08-01

    Genetic modification technology is a new molecular tool for targeted genome modification. It includes zinc finger nucleases (ZFN) technology, transcription activator-like effector nucleases (TALEN) technology and clustered regularly interspaced short palindromic repeat (CRISPR)-associated (Cas) (CRISPR-Cas) nucleases technology. All of these nucleases create DNA double-strand breaks (DSB) at chromosomal targeted sites and induce cell endogenous mechanisms that are primarily repaired by the non-homologous end joining (NHEJ) or homologous recombination (HR) pathway, resulting in targeted endogenous gene knock-out or exogenous gene insertion. In recent years, genetic modification technologies have been successfully applied to bacteria, yeast, human cells, fruit fly, zebra fish, mouse, rat, livestock, cynomolgus monkey, Arabidopsis, rice, tobacco, maize, sorghum, wheat, barley and other organisms, showing its enormous advantage in gene editing field. Especially, the newly developed CRISPR-Cas9 system arose more attention because of its low cost, high effectiveness, simplicity and easiness. We reviewed the principles and the latest research progress of these three technologies, as well as prospect of future research and applications. PMID:26762038

  15. Energy conservation potential of surface modification technologies

    SciTech Connect

    Le, H.K.; Horne, D.M.; Silberglitt, R.S.

    1985-09-01

    This report assesses the energy conservation impact of surface modification technologies on the metalworking industries. The energy conservation impact of surface modification technologies on the metalworking industries is assessed by estimating their friction and wear tribological sinks and the subsequent reduction in these sinks when surface modified tools are used. Ion implantation, coatings, and laser and electron beam surface modifications are considered.

  16. Surface modification of silica nanoparticles

    NASA Astrophysics Data System (ADS)

    Ranjan, Rajesh

    Surface modification of nanosized silica particles by polymer grafting is gaining attention. This can be attributed to the fact that it provides a unique opportunity to engineer the interfacial properties of these modified particles; at the same time the mechanical and thermal properties of the polymers can be improved. Controlled free radical polymerization is a versatile technique which affords control over molecular weight, molecular weight distribution, architecture and functionalities of the resulting polymer. Three commonly used controlled free radical polymerizations include nitroxide-mediated polymerization (NMP), atom transfer radical polymerization (ATRP) and reversible addition fragmentation transfer (RAFT) polymerization. ATRP and RAFT polymerization were explored in order to modify the silica surface with well-defined polymer brushes. A novel click-functionalized RAFT chain transfer agent (RAFT CTA) was synthesized which opened up the possibility of using RAFT polymerization and click chemistry together in surface modification. Using this RAFT CTA, the surface of silica nanoparticles was modified with polystyrene and polyacrylamide brushes via the "grafting to" approach. Both tethered polystyrene and polyacrylamide chains were found in the brush regime. The combination of ATRP and click chemistry was also explored for surface modification. A combination of RAFT polymerization and click chemistry was also studied to modify the surface via the "grafting from" approach. Our strategy included the (1) "grafting from" approach for brush formation (2) facile click reaction to immobilize the RAFT agent (3) synthesis of R-supported chain transfer agent and (4) use of the more active trithiocarbonate RAFT agent. Grafting density obtained by this method was significantly higher than reported values in the literature. Polystyrene (PS) grafted silica nanoparticles were also prepared by a tandem process that simultaneously employs reversible addition fragmentation

  17. Surface Modifications in Adhesion and Wetting

    NASA Astrophysics Data System (ADS)

    Longley, Jonathan

    Advances in surface modification are changing the world. Changing surface properties of bulk materials with nanometer scale coatings enables inventions ranging from the familiar non-stick frying pan to advanced composite aircraft. Nanometer or monolayer coatings used to modify a surface affect the macro-scale properties of a system; for example, composite adhesive joints between the fuselage and internal frame of Boeing's 787 Dreamliner play a vital role in the structural stability of the aircraft. This dissertation focuses on a collection of surface modification techniques that are used in the areas of adhesion and wetting. Adhesive joints are rapidly replacing the familiar bolt and rivet assemblies used by the aerospace and automotive industries. This transition is fueled by the incorporation of composite materials into aircraft and high performance road vehicles. Adhesive joints have several advantages over the traditional rivet, including, significant weight reduction and efficient stress transfer between bonded materials. As fuel costs continue to rise, the weight reduction is accelerating this transition. Traditional surface pretreatments designed to improve the adhesion of polymeric materials to metallic surfaces are extremely toxic. Replacement adhesive technologies must be compatible with the environment without sacrificing adhesive performance. Silane-coupling agents have emerged as ideal surface modifications for improving composite joint strength. As these coatings are generally applied as very thin layers (<50 nm), it is challenging to characterize their material properties for correlation to adhesive performance. We circumvent this problem by estimating the elastic modulus of the silane-based coatings using the buckling instability formed between two materials of a large elastic mismatch. The elastic modulus is found to effectively predict the joint strength of an epoxy/aluminum joint that has been reinforced with silane coupling agents. This buckling

  18. Bioactive Surface Modification of Hydroxyapatite

    PubMed Central

    Okazaki, Yohei; Hiasa, Kyou; Yasuda, Keisuke; Nogami, Keisuke; Mizumachi, Wataru; Hirata, Isao

    2013-01-01

    The purpose of this study was to establish an acid-etching procedure for altering the Ca/P ratio of the nanostructured surface of hydroxyapatite (HAP) by using surface chemical and morphological analyses (XPS, XRD, SEM, surface roughness, and wettability) and to evaluate the in vitro response of osteoblast-like cells (MC3T3-E1 cells) to the modified surfaces. This study utilized HAP and HAP treated with 10%, 20%, 30%, 40%, 50%, or 60% phosphoric acid solution for 10 minutes at 25°C, followed by rinsing 3 times with ultrapure water. The 30% phosphoric acid etching process that provided a Ca/P ratio of 1.50, without destruction of the grain boundary of HAP, was selected as a surface-modification procedure. Additionally, HAP treated by the 30% phosphoric acid etching process was stored under dry conditions at 25°C for 12 hours, and the Ca/P ratio approximated to 1.00 accidentally. The initial adhesion, proliferation, and differentiation (alkaline phosphatase (ALP) activity and relative mRNA level for ALP) of MC3T3-E1 cells on the modified surfaces were significantly promoted (P < 0.05 and 0.01). These findings show that the 30% phosphoric acid etching process for the nanostructured HAP surface can alter the Ca/P ratio effectively and may accelerate the initial adhesion, proliferation, and differentiation of MC3T3-E1 cells. PMID:23862150

  19. Characterization of Surface Modification of Polyethersulfone Membrane

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Surface modification of polyethersulfone (PES) membrane surface using UV/ozone-treated grafting and interfacial polymerization on membrane surface was investigated in order to improve the resistance of membrane surface to protein adsorption. These methods of surface modification were compared in te...

  20. Polymer surface modification by plasmas and photons

    NASA Astrophysics Data System (ADS)

    Chan, C.-M.; Ko, T.-M.; Hiraoka, H.

    1996-05-01

    Polymers have been applied successfully in fields such as adhesion, biomaterials, protective coatings, friction and wear, composites, microelectronic devices, and thin-film technology. In general, special surface properties with regard to chemical composition, hydrophilicity, roughness, crystallinity, conductivity, lubricity, and cross-linking density are required for the success of these applications. Polymers very often do not possess the surface properties needed for these applications. However, they have excellent bulk physical and chemical properties, are inexpensive, and are easy to process. For these reasons, surface modification techniques which can transform these inexpensive materials into highly valuable finished products have become an important part of the plastics and many other industries. In recent years, many advances have been made in developing surface treatments to alter the chemical and physical properties of polymer surfaces without affecting bulk properties. Common surface modification techniques include treatments by flame, corona, plasmas, photons, electron beams, ion beams, X-rays, and γ-rays. Plasma treatment is probably the most versatile surface treatment technique. Different types of gases such as argon, oxygen, nitrogen, fluorine, carbon dioxide, and water can produce the unique surface properties required by various applications. For example, oxygen-plasma treatment can increase the surface energy of polymers, whereas fluorine-plasma treatment can decrease the surface energy and improve the chemical inertness. Cross-linking at a polymer surface can be introduced by an inert-gas plasma. Modification by plasma treatment is usually confined to the top several hundred ångströms and does not affect the bulk properties. The main disadvantage of this technique is that it requires a vacuum system, which increases the cost of operation. Thin polymer films with unique chemical and physical properties are produced by plasma polymerization

  1. Sustainable environmental nanotechnology using nanoparticle surface modification.

    EPA Science Inventory

    Reactive nanomaterials used for environmental remediation require surface modification to make them mobile in the subsurface. Nanomaterials released into the environment inadvertently without an engineered surface coating will acquire one (e.g. adsorption of natural organic matt...

  2. Surface modification to prevent oxide scale spallation

    DOEpatents

    Stephens, Elizabeth V; Sun, Xin; Liu, Wenning; Stevenson, Jeffry W; Surdoval, Wayne; Khaleel, Mohammad A

    2013-07-16

    A surface modification to prevent oxide scale spallation is disclosed. The surface modification includes a ferritic stainless steel substrate having a modified surface. A cross-section of the modified surface exhibits a periodic morphology. The periodic morphology does not exceed a critical buckling length, which is equivalent to the length of a wave attribute observed in the cross section periodic morphology. The modified surface can be created using at least one of the following processes: shot peening, surface blasting and surface grinding. A coating can be applied to the modified surface.

  3. Chemical modification of surface properties

    SciTech Connect

    Koel, B.E.; Windham, R.G.

    1987-01-01

    Chemically tailoring materials to have new and unique surface properties has enormous potential in a wide variety of applications for interfacial phenomena in materials science and catalysis. Recent work from our laboratory on model systems designed to explain how changes in geometric and electronic structure of metal surfaces affect surface chemistry are discussed. Specifically, the influence of potassium and bismuth coadsorption with small molecules on a Pt(111) single crystal surface will be described. We will also discuss the chemical reactivity of palladium metal monolayers and thin films which have been recently reported to have dramatically altered geometric and electronic structure. 31 refs., 3 figs.

  4. Microscale surface modifications for heat transfer enhancement.

    PubMed

    Bostanci, Huseyin; Singh, Virendra; Kizito, John P; Rini, Daniel P; Seal, Sudipta; Chow, Louis C

    2013-10-01

    In this experimental study, two surface modification techniques were investigated for their effect on heat transfer enhancement. One of the methods employed the particle (grit) blasting to create microscale indentations, while the other used plasma spray coating to create microscale protrusions on Al 6061 (aluminum alloy 6061) samples. The test surfaces were characterized using scanning electron microscopy (SEM) and confocal scanning laser microscopy. Because of the surface modifications, the actual surface area was increased up to 2.8× compared to the projected base area, and the arithmetic mean roughness value (Ra) was determined to vary from 0.3 μm for the reference smooth surface to 19.5 μm for the modified surfaces. Selected samples with modified surfaces along with the reference smooth surface were then evaluated for their heat transfer performance in spray cooling tests. The cooling system had vapor-atomizing nozzles and used anhydrous ammonia as the coolant in order to achieve heat fluxes up to 500 W/cm(2) representing a thermal management setting for high power systems. Experimental results showed that the microscale surface modifications enhanced heat transfer coefficients up to 76% at 500 W/cm(2) compared to the smooth surface and demonstrated the benefits of these practical surface modification techniques to enhance two-phase heat transfer process. PMID:24003985

  5. Surface Modification of Zein Films

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A novel method to derivatize the surface of zein is devised that can modify the water absorption and surface wetting behavior. The reagents used to impart the desired properties in a reasonable amount of time include octenyl succinic anhydride and alkyl and alkenyl ketene dimers. The method is eas...

  6. Laser surface modification of metallic biomaterials

    NASA Astrophysics Data System (ADS)

    Bandyopadhyay, Amit; Balla, Vamsi Krishna; Roy, Mangal; Bose, Susmita

    2011-06-01

    Load-bearing metal implants often fail prematurely due to inadequate biocompatibility, mechanical/tribological properties, and poor osseointegration. It is well known that biomaterials' surface plays a vital role in the response to these metal implants in the biological environment. The biological effectiveness of artificial implants is determined mainly by their surface characteristics such as surface morphology, microstructure, composition, mechanical properties, wettabilility, and surface free energy. Hence, there is significant interest toward surface modification and effective design of load-bearing metal implants so as to improve their surface properties and thereby elicit a specific, desired, and timely response from the surrounding cells and tissues. In this article, we provide an insight into laser surface modification of Ti/Ti6Al4V alloy with or without functional gradation in composition and their microstructural, in vitro wear and biological properties for various loadbearing orthopedic applications.

  7. Gaseous phase coal surface modification

    SciTech Connect

    Okoh, J.M.; Pinion, J.; Thiensatit, S.

    1992-05-07

    In this report, we present an improved, feasible and potentially cost effective method of cleaning and beneficiating ultrafine coal. Increased mechanization of mining methods and the need towards depyritization, and demineralization have led to an increase in the quantity of coal fines generated in recent times. For example, the amount of {minus}100 mesh coal occurring in coal preparation plant feeds now typically varies from 5 to 25% of the total feed. Environmental constraints coupled with the greatly increased cost of coal have made it increasingly important to recover more of these fines. Our method chemically modifies the surface of such coals by a series of gaseous phase treatments employing Friedel-Crafts reactions. By using olefins (ethene, propene and butene) and hydrogen chloride catalyst at elevated temperature, the surface hydrophobicity of coal is enhanced. This increased hydrophobicity is manifest in surface phenomena which reflect conditions at the solid/liquid interphase (zeta potential) and those which reflect conditions at the solid/liquid/gas interphases (contact angle, wettability and floatability).

  8. Impact of Dental Implant Surface Modifications on Osseointegration.

    PubMed

    Smeets, Ralf; Stadlinger, Bernd; Schwarz, Frank; Beck-Broichsitter, Benedicta; Jung, Ole; Precht, Clarissa; Kloss, Frank; Gröbe, Alexander; Heiland, Max; Ebker, Tobias

    2016-01-01

    Objective. The aim of this paper is to review different surface modifications of dental implants and their effect on osseointegration. Common marketed as well as experimental surface modifications are discussed. Discussion. The major challenge for contemporary dental implantologists is to provide oral rehabilitation to patients with healthy bone conditions asking for rapid loading protocols or to patients with quantitatively or qualitatively compromised bone. These charging conditions require advances in implant surface design. The elucidation of bone healing physiology has driven investigators to engineer implant surfaces that closely mimic natural bone characteristics. This paper provides a comprehensive overview of surface modifications that beneficially alter the topography, hydrophilicity, and outer coating of dental implants in order to enhance osseointegration in healthy as well as in compromised bone. In the first part, this paper discusses dental implants that have been successfully used for a number of years focusing on sandblasting, acid-etching, and hydrophilic surface textures. Hereafter, new techniques like Discrete Crystalline Deposition, laser ablation, and surface coatings with proteins, drugs, or growth factors are presented. Conclusion. Major advancements have been made in developing novel surfaces of dental implants. These innovations set the stage for rehabilitating patients with high success and predictable survival rates even in challenging conditions. PMID:27478833

  9. Impact of Dental Implant Surface Modifications on Osseointegration

    PubMed Central

    Smeets, Ralf; Stadlinger, Bernd; Schwarz, Frank; Beck-Broichsitter, Benedicta; Jung, Ole; Precht, Clarissa; Kloss, Frank; Gröbe, Alexander; Heiland, Max

    2016-01-01

    Objective. The aim of this paper is to review different surface modifications of dental implants and their effect on osseointegration. Common marketed as well as experimental surface modifications are discussed. Discussion. The major challenge for contemporary dental implantologists is to provide oral rehabilitation to patients with healthy bone conditions asking for rapid loading protocols or to patients with quantitatively or qualitatively compromised bone. These charging conditions require advances in implant surface design. The elucidation of bone healing physiology has driven investigators to engineer implant surfaces that closely mimic natural bone characteristics. This paper provides a comprehensive overview of surface modifications that beneficially alter the topography, hydrophilicity, and outer coating of dental implants in order to enhance osseointegration in healthy as well as in compromised bone. In the first part, this paper discusses dental implants that have been successfully used for a number of years focusing on sandblasting, acid-etching, and hydrophilic surface textures. Hereafter, new techniques like Discrete Crystalline Deposition, laser ablation, and surface coatings with proteins, drugs, or growth factors are presented. Conclusion. Major advancements have been made in developing novel surfaces of dental implants. These innovations set the stage for rehabilitating patients with high success and predictable survival rates even in challenging conditions. PMID:27478833

  10. Surface Modification of Nanocellulose Substrates

    NASA Astrophysics Data System (ADS)

    Zoppe, Justin Orazio

    Cellulose fibers constitute an important renewable raw material that is utilized in many commercial applications in non-food, paper, textiles and composite materials. Chemical functionalization is an important approach for improving the properties of cellulose based materials. Different approaches are used to graft polymeric chains onto cellulose substrates, which can be classified by two principal routes, namely 'grafting onto' or 'grafting from' methods. Never-dried cellulose nanocrystals (CNCs) or nanowhiskers produced from sulfuric acid hydrolysis of ramie fibers were used as substrates for surface chemical functionalization with various macromolecules. In addition, the use of cellulose nanocrystals to reinforce poly(epsilon-caprolactone) (PCL) nanofibers was studied. Chemical grafting with low molecular weight polycaprolactone diol onto cellulose nanocrystals was carried out in an attempt to improve the interfacial adhesion with the fiber matrix. Significant improvements in the mechanical properties of the nanofibers after reinforcement with unmodified cellulose nanocrystals were confirmed. Fiber webs from PCL reinforced with 2.5% unmodified CNCs showed ca. 1.5-fold increase in Young's modulus and ultimate strength compared to PCL webs. The CNCs were also grafted with poly(N-isopropylacrylamide) (poly(NiPAAm)) brushes via surface-initiated single-electron transfer living radical polymerization (SI-SETLRP) under various conditions at room temperature. The grafting process depended on the initiator and/or monomer concentrations used. No observable damage occurred to the CNCs after grafting, as determined by X-ray diffraction. Size exclusion chromatography analyses of polymer chains cleaved from the cellulose nanocrystals indicated that a higher degree of polymerization was achieved by increasing initiator or monomer loading, most likely caused by local heterogeneities yielding higher rates of polymerization. In addition, the colloidal stability and thermo

  11. Surface property modification of silicon

    NASA Technical Reports Server (NTRS)

    Danyluk, S.

    1984-01-01

    The main emphasis of this work has been to determine the wear rate of silicon in fluid environments and the parameters that influence wear. Three tests were carried out on single crystal Czochralski silicon wafers: circular and linear multiple-scratch tests in fluids by a pyramidal diamond simulated fixed-particle abrasion; microhardness and three-point bend tests were used to determine the hardness and fracture toughness of abraded silicon and the extent of damage induced by abrasion. The wear rate of (100) and (111) n and p-type single crystal Cz silicon abraded by a pyramidal diamond in ethanol, methanol, acetone and de-ionized water was determined by measuring the cross-sectional areas of grooves of the circular and linear multiple-scratch tests. The wear rate depends on the loads on the diamond and is highest for ethanol and lowest for de-ionized water. The surface morphology of the grooves showed lateral and median cracks as well as a plastically deformed region. The hardness and fracture toughness are critical parameters that influence the wear rate. Microhardness tests were conducted to determine the hardness as influenced by fluids. Median cracks and the damage zone surrounding the indentations were also related to the fluid properties.

  12. Modification of surfaces and surface layers by non equilibrium processes

    NASA Astrophysics Data System (ADS)

    Beamson, G.; Brennan, W. J.; Clark, D. T.; Howard, J.

    1988-01-01

    Methods for using plasma in the synthesis and modification of materials in ways impossible by conventional routes are introduced. The equipment used in these methods is described. The chemical analysis of polymer surfaces undergoing modification by inert gas, hydrogen or oxygen plasmas is shown to give physical information regarding the relative roles of diffusion of active species and direct and radiative energy transfer from the plasma. Surface modification by plasma depositing a new material onto an existing substrate is discussed with particular reference to the deposition of amorphous carbon films. Applications of the unique properties of these films are outlined together with current understanding of these properties based on chemical and physical methods of analysis of both the films and the plasmas producing them. Finally, surface modification by ion beams is briefly illustrated using examples from the electronics and metals industries.

  13. Modification of surface energy in nuclear multifragmentation

    SciTech Connect

    Botvina, A. S.; Buyukcizmeci, N.; Erdogan, M.; Lukasik, J.; Mishustin, I. N.; Ogul, R.; Trautmann, W.

    2006-10-15

    Within the statistical multifragmentation model we study modifications of the surface and symmetry energy of primary fragments in the freeze-out volume. The ALADIN experimental data on multifragmentation obtained in reactions induced by high-energy projectiles with different neutron richness are analyzed. We have extracted the isospin dependence of the surface energy coefficient at different degrees of fragmentation. We conclude that the surface energy of hot fragments produced in multifragmentation reactions differs from the values extracted for isolated nuclei at low excitation. At high fragment multiplicity, it becomes nearly independent of the neutron content of the fragments.

  14. Surface modification: advantages, techniques, and applications

    SciTech Connect

    Natesan, K.

    2000-03-01

    Adequate performance of materials at elevated temperatures is a potential problem in many systems within the chemical, petroleum, process, and power-generating industries. Degradation of materials occurs because of interaction between the structural material and the exposure environment. These interactions are generally undesired chemical reactions that can lead to accelerated wastage and alter the functional requirements and/or structural integrity of the materials. Therefore, material selection for high-temperature applications must be based not only on a material strength properties but also on resistance to the complex environments prevalent in the anticipated exposure environment. As plants become larger, the satisfactory performance and reliability of components play a greater role in plant availability and economics. However, system designers are becoming increasingly concerned with finding the least expensive material that will satisfactorily perform the design function for the desired service life. This present paper addresses the benefits of surface modification and identified several criteria for selection and application of modified surfaces in the power sector. A brief review is presented on potential methods for modification of surfaces, with the emphasis on coatings. In the final section of the paper, several examples address the requirements of different energy systems and surface modification avenues that have been applied to resolve the issues.

  15. Surface modification of magnetic nanoparticles in biomedicine

    NASA Astrophysics Data System (ADS)

    Chu, Xin; Yu, Jing; Hou, Yang-Long

    2015-01-01

    Progress in surface modification of magnetic nanoparticles (MNPs) is summarized with regard to organic molecules, macromolecules and inorganic materials. Many researchers are now devoted to synthesizing new types of multi-functional MNPs, which show great application potential in both diagnosis and treatment of disease. By employing an ever-greater variety of surface modification techniques, MNPs can satisfy more and more of the demands of medical practice in areas like magnetic resonance imaging (MRI), fluorescent marking, cell targeting, and drug delivery. Project supported by the National Natural Science Foundation of China (Grant Nos. 51125001 and 51172005), the Natural Science Foundation of Beijing,China (Grant No. 2122022), the Science Fund for Creative Research Groups of the National Natural Science Foundation of China (Grant No. 81421004), and the Doctoral Program of the Education Ministry of China (Grant No. 20120001110078).

  16. Electrostatic Surface Modifications to Improve Gene Delivery

    PubMed Central

    Shmueli, Ron B.; Anderson, Daniel G.

    2010-01-01

    Importance of the field Gene therapy has the potential to treat a wide variety of diseases including genetic diseases and cancer. Areas covered in this review This review introduces biomaterials used for gene delivery and then focuses on the use of electrostatic surface modifications to improve gene delivery materials. These modifications have been used to stabilize therapeutics in vivo, add cell-specific targeting ligands, and promote controlled release. Coatings of nanoparticles and microparticles as well as non-particulate surface coatings are covered in this review. Electrostatic principles are crucial for the development of multilayer delivery structures fabricated by the layer-by-layer method. What the reader will gain The reader will gain knowledge about the composition of biomaterials used for surface modifications and how these coatings and multilayers can be utilized to improve spatial control and efficiency of delivery. Examples are shown for the delivery of nucleic acids, including DNA and siRNA, to in vitro and in vivo systems. Take home message The versatile and powerful approach of electrostatic coatings and multilayers will lead to the development of enhanced gene therapies. PMID:20201712

  17. Surface modification by plasma immersion ion processing

    NASA Astrophysics Data System (ADS)

    Walter, Kevin C.; Lee, Deok H.; He, X. M.; Baker, N. P.; Nastasi, Michael; Munson, C. P.; Scarborough, W. K.; Tuszewski, M.; Wood, B. P.

    1998-09-01

    Los Alamos National Laboratory is actively researching a surface modification technique called plasma immersion ion processing (PIIP). PIIP is the latest innovation of the plasma source ion implantation (PSII) approach to surface modification. Like PSII, PIIP allows the modification of large areas and non-planar surface geometries, however PIIP is primarily a coating deposition technology rather than solely an ion implantation technology. PIIP utilizes a pulsed-bias on a target to extract ions out of plasma for ion implantation and coating deposition. Plasmas can be made by capacitive or inductive radio frequency sources or by initiating a glow discharge during each pulse of high voltage. Plasmas of hydrocarbon gases have been used to deposit adherent diamond-like carbon (DLC) coating son a variety of ferrous and non-ferrous materials. Instead of sputter depositing interlayers to improve the adhesion of DLC, PIIP uses ion implantation to create a graded interface between the metallic substrate and the DLC coating. Demonstrating the scaleability of PIIP, a 3 m2 area has been simultaneously coated with an adherent DLC coating approximately 7 micrometers thick. Plasmas of diborane and acetylene mixtures are being used to develop deposition processes for boron-carbide coatings. Through the use of organometallics and inorganic gases, other coatings are possible. The PIIP deposition conditions, composition and tribological properties of DLC and boron-carbide coatings will be highlighted.

  18. Surface modifications of some nanocomposites containing starch

    NASA Astrophysics Data System (ADS)

    Pascu, M.-C.; Popescu, M.-C.; Vasile, C.

    2008-09-01

    Polymer-layered silicate nanocomposites have attracted strong interest in today's materials research, due to the possible impressive enhancements of material properties, comparatively with those of pure polymers. Several starch/poly(vinylalcohol)/montmorillonite nanocomposites have been subjected to surface modification by physical treatments such as dielectric barrier discharge (DBD) exposure and coating with proteins (albumin) or polysaccharides (chitosan), for improving their biocompatibility. Untreated and treated surfaces have been comparatively studied by contact angle measurements, FT-IR and 2D-FT-IR spectroscopy and optical microscopy. It has been established that enhancement of the surface characteristics depends on the type and number of incorporated nanoparticles as well as on the treatment applied. Coupling of DBD exposure and coating techniques appears to be highly efficient.

  19. Improved LWR Cladding Performance by EPD Surface Modification Technique

    SciTech Connect

    Corradini, Michael; Sridharan, Kumar

    2012-11-26

    This project will utilize the electro-phoretic deposition technique (EPD) in conjunction with nanofluids to deposit oxide coatings on prototypic zirconium alloy cladding surfaces. After demonstrating that this surface modification is reproducible and robust, the team will subject the modified surface to boiling and corrosion tests to characterize the improved nucleate boiling behavior and superior corrosion performance. The scope of work consists of the following three tasks: The first task will employ the EPD surface modification technique to coat the surface of a prototypic set of zirconium alloy cladding tube materials (e.g. Zircaloy and advanced alloys such as M5) with a micron-thick layer of zirconium oxide nanoparticles. The team will characterize the modified surface for uniformity using optical microscopy and scanning-electron microscopy, and for robustness using standard hardness measurements. After zirconium alloy cladding samples have been prepared and characterized using the EPD technique, the team will begin a set of boiling experiments to measure the heat transfer coefficient and critical heat flux (CHF) limit for each prepared sample and its control sample. This work will provide a relative comparison of the heat transfer performance for each alloy and the surface modification technique employed. As the boiling heat transfer experiments begin, the team will also begin corrosion tests for these zirconium alloy samples using a water corrosion test loop that can mimic light water reactor (LWR) operational environments. They will perform extended corrosion tests on the surface-modified zirconium alloy samples and control samples to examine the robustness of the modified surface, as well as the effect on surface oxidation

  20. Surface modification of polypropylene based particle foams

    NASA Astrophysics Data System (ADS)

    Schreier, P.; Trassl, C.; Altstädt, V.

    2014-05-01

    This paper deals with the modification of the surface properties of expanded polypropylene (EPP). EPP is a semi-hard to soft elastic thermoplastic foam. The characteristic surface of EPP shows process-related steam nozzle imprints and gussets. Therefore EPP does not satisfy the quality requirements for visible automotive applications. In order to meet these demands, plastic surfaces are usually enhanced with functional or decorative coatings, e.g. textiles, plastic films or paint. The coating of plastics with low surface energies such as PP often leads to adhesion problems by reason of the missing polar and functional groups. This paper gives an evaluation of activation and pre-treatment methods of EPP, with the aim to identify the most suitable pre-treatment method. For this purpose five typical surface treatment methods - flame treatment, corona, fluorination, atmospheric and low-pressure plasma - were performed on EPP samples. As a comparison criterion the maximum increase in the adhesion force between a polyurethane-based coating and the modified EPP substrate was selected. Moreover the influence of the selected pre-treatment method on the increase in the total surface energy and its polar component was investigated by the drop shape analysis method. The results showed that the contact angle measurement is a suitable method to determine the polar and disperse fractions of the surface tension of EPP. Furthermore, all performed methods increased the adhesion of EPP.

  1. Surface modification for aluminium pigment inhibition.

    PubMed

    Karlsson, Philip; Palmqvist, Anders E C; Holmberg, Krister

    2006-12-21

    This review concerns surface treatment of aluminium pigments for use in water borne coatings. Aluminium pigments are commonly used in coatings to give a silvery and shiny lustre to the substrate. Such paints and inks have traditionally been solvent borne, since aluminium pigment particles react with water. For environmental and health reasons solvent borne coatings are being replaced by water borne and the aluminium pigments then need to be surface modified in order to stand exposure to water. This process is called inhibition and both organic and inorganic substances are used as inhibiting agents. The organic inhibiting agents range from low molecular weight substances, such as phenols and aromatic acids, via surfactants, in particular alkyl phosphates and other anionic amphiphiles, to high molecular weight compounds, such as polyelectrolytes. A common denominator for them all is that they contain a functional group that interacts specifically with aluminium at the surface. A particularly strong interaction is obtained if the inhibiting agent contains functional groups that form chelating complex with surface Al(III). Encapsulation of the pigment can be made by in situ polymerization at the surface of the pigment and a recent approach is to have the polymerization occur within a double layer of adsorbed surfactant. The inorganic route is dominated by coating with silica, and recent progress has been made using an alkoxide, such as tetraethoxysilane as silica precursor. Such silica coated aluminium pigments are comparable in performance to chromate inhibited pigments and thus offer a possible heavy metal-free alternative. There are obvious connections between surface modifications made to prevent the pigment to react with water and inhibition of corrosion of macroscopic aluminium surfaces. PMID:17239333

  2. Software modifications to the Demonstration Advanced Avionics Systems (DAAS)

    NASA Technical Reports Server (NTRS)

    Nedell, B. F.; Hardy, G. H.

    1984-01-01

    Critical information required for the design of integrated avionics suitable for generation aviation is applied towards software modifications for the Demonstration Advanced Avionics System (DAAS). The program emphasizes the use of data busing, distributed microprocessors, shared electronic displays and data entry devices, and improved functional capability. A demonstration advanced avionics system (DAAS) is designed, built, and flight tested in a Cessna 402, twin engine, general aviation aircraft. Software modifications are made to DAAS at Ames concurrent with the flight test program. The changes are the result of the experience obtained with the system at Ames, and the comments of the pilots who evaluated the system.

  3. Recent developments in PDMS surface modification for microfluidic devices.

    PubMed

    Zhou, Jinwen; Ellis, Amanda Vera; Voelcker, Nicolas Hans

    2010-01-01

    PDMS is enjoying continued and ever increasing popularity as the material of choice for microfluidic devices due to its low cost, ease of fabrication, oxygen permeability and optical transparency. However, PDMS's hydrophobicity and fast hydrophobic recovery after surface hydrophilization, attributed to its low glass transition temperature of less than -120 degrees C, negatively impacts on the performance of PDMS-based microfluidic device components. This issue has spawned a flurry of research to devise longer lasting surface modifications of PDMS, with particular emphasis on microfluidic applications. This review will present recent research on surface modifications of PDMS using techniques ranging from metal layer coatings and layer-by-layer depositions to dynamic surfactant treatments and the adsorption of amphipathic proteins. We will also discuss significant advances that have been made with a broad palette of gas-phase processing methods including plasma processing, sol-gel coatings and chemical vapor deposition. Finally, we will present examples of applications and future prospects of modified PDMS surfaces in microfluidics, in areas such as molecular separations, cell culture in microchannels and biomolecular detection via immunoassays. PMID:20039289

  4. A comparative study of biomolecule and polymer surface modifications by a surface microdischarge

    NASA Astrophysics Data System (ADS)

    Bartis, Elliot A. J.; Luan, Pingshan; Knoll, Andrew J.; Graves, David B.; Seog, Joonil; Oehrlein, Gottlieb S.

    2016-02-01

    Cold atmospheric plasma (CAP) sources are attractive sources of reactive species with promising industrial and biomedical applications, but an understanding of underlying surface mechanisms is lacking. A kHz-powered surface microdischarge (SMD) operating with N2/O2 mixtures was used to study the biological deactivation of two immune-stimulating biomolecules: lipopolysaccharide (LPS) and peptidoglycan (PGN), found in bacteria such as Escherichia coli and Staphylococcus aureus, respectively. Model polymers were also studied to isolate specific functional groups. Changes in the surface chemistry were measured to understand which plasma-generated species and surface modifications are important for biological deactivation. The overall goal of this work is to determine which effects of CAP treatment are generic and which bonds are susceptible to attack. CAP treatment deactivated biomolecules, oxidized surfaces, and introduced surface bound NO3. These effects can be controlled by the N2 fraction in O2 and applied voltage and vary among different target surfaces. The SMD was compared with an Ar/O2/N2-fed kHz-powered atmospheric pressure plasma jet and showed much higher surface modifications and surface chemistry tunability compared to the jet. Possible mechanisms are discussed and findings are compared with recent computational investigations. Our results demonstrate the importance of long-lived plasma-generated species and advance an atomistic understanding of CAP-surface interactions.

  5. Hydrothermal modification of titanium surface in calcium solutions.

    PubMed

    Hamad, Kenichi; Kon, Masayuki; Hanawa, Takao; Yokoyama, Ken'ichi; Miyamoto, Youji; Asaoka, Kenzo

    2002-05-01

    Hydrothermal modification of a titanium surface in calcium solutions was performed. The apatite precipitation on the modified surface in Hanks' solution, as a simulated body fluid, was evaluated and the surface microstructure changes after the modification were characterized by thin-film X-ray diffractometry (TF-XRD) and X-ray photoelectron spectroscopy (XPS). Hydrothermal modification in CaO solution enhanced the precipitation of apatite on the titanium surface. High pH, high pressure and high temperature of the CaO solution increased the thickness of the surface-modified layer and enhanced the synthesis of calcium titanate which possibly promoted the precipitation of apatite in Hanks' solution. Hydrothermal modification in CaCl2 solution, on the other hand, showed reverse effects. The modification of titanium in CaO solution with hydrothermal treatment is expected to result in excellent osteointegration and can be easily performed by using an autoclave, a clinical apparatus widely used. PMID:11962668

  6. Reduction of Glass Surface Reflectance by Ion Beam Surface Modification

    SciTech Connect

    Mark Spitzer

    2011-03-11

    This is the final report for DOE contract DE-EE0000590. The purpose of this work was to determine the feasibility of the reduction of the reflection from the front of solar photovoltaic modules. Reflection accounts for a power loss of approximately 4%. A solar module having an area of one square meter with an energy conversion efficiency of 18% generates approximately 180 watts. If reflection loss can be eliminated, the power output can be increased to 187 watts. Since conventional thin-film anti-reflection coatings do not have sufficient environmental stability, we investigated the feasibility of ion beam modification of the glass surface to obtain reduction of reflectance. Our findings are generally applicable to all solar modules that use glass encapsulation, as well as commercial float glass used in windows and other applications. Ion implantation of argon, fluorine, and xenon into commercial low-iron soda lime float glass, standard float glass, and borosilicate glass was studied by implantation, annealing, and measurement of reflectance. The three ions all affected reflectance. The most significant change was obtained by argon implantation into both low-iron and standard soda-lime glass. In this way samples were formed with reflectance lower than can be obtained with a single-layer coatings of magnesium fluoride. Integrated reflectance was reduced from 4% to 1% in low-iron soda lime glass typical of the glass used in solar modules. The reduction of reflectance of borosilicate glass was not as large; however borosilicate glass is not typically used in flat plate solar modules. Unlike conventional semiconductor ion implantation doping, glass reflectance reduction was found to be tolerant to large variations in implant dose, meaning that the process does not require high dopant uniformity. Additionally, glass implantation does not require mass analysis. Simple, high current ion implantation equipment can be developed for this process; however, before the process

  7. Recent advances in dynamic m6A RNA modification.

    PubMed

    Cao, Guangchao; Li, Hua-Bing; Yin, Zhinan; Flavell, Richard A

    2016-04-01

    The identification of m(6)A demethylases and high-throughput sequencing analysis of methylated transcriptome corroborated m(6)A RNA epigenetic modification as a dynamic regulation process, and reignited its investigation in the past few years. Many basic concepts of cytogenetics have been revolutionized by the growing understanding of the fundamental role of m(6)A in RNA splicing, degradation and translation. In this review, we summarize typical features of methylated transcriptome in mammals, and highlight the 'writers', 'erasers' and 'readers' of m(6)A RNA modification. Moreover, we emphasize recent advances of biological functions of m(6)A and conceive the possible roles of m(6)A in the regulation of immune response and related diseases. PMID:27249342

  8. Recent advances in dynamic m6A RNA modification

    PubMed Central

    Cao, Guangchao; Yin, Zhinan

    2016-01-01

    The identification of m6A demethylases and high-throughput sequencing analysis of methylated transcriptome corroborated m6A RNA epigenetic modification as a dynamic regulation process, and reignited its investigation in the past few years. Many basic concepts of cytogenetics have been revolutionized by the growing understanding of the fundamental role of m6A in RNA splicing, degradation and translation. In this review, we summarize typical features of methylated transcriptome in mammals, and highlight the ‘writers’, ‘erasers’ and ‘readers’ of m6A RNA modification. Moreover, we emphasize recent advances of biological functions of m6A and conceive the possible roles of m6A in the regulation of immune response and related diseases. PMID:27249342

  9. Laser-induced surface modification and metallization of polymers

    NASA Astrophysics Data System (ADS)

    Frerichs, H.; Stricker, J.; Wesner, D. A.; Kreutz, E. W.

    1995-02-01

    Laser-induced surface modification of different polymers is presented as a suitable pretreatment of surfaces in a two-step metallization process. Materials such as polyamide (PA), polypropylene (PP), polystyrene (PS), polycarbonate (PC), acrylbutadienestyrene (ABS), styreneacrylnitrile (SAN), polybutadieneterephthalate (PBT), and polyoxymethylene (POM) were treated by excimer-laser radiation at 248 nm in air. The aim of this study is to investigate different processing regimes of surface modification and ablation to increase surface roughness. Therefore, the laser-processing variables fluence F, repetition rate v and pulse number N are varied and the ablation depth, optical penetration depth, absorption coefficient and ablation threshold are determined. The metallization of pretreated (laser, wet chemical and plasma etching) polymers is investigated for different surface morphologies. The used metallization processes were electroplating and physical vapour deposition (PVD). The adhesion of the deposited films is measured with scratch and tape test methods in order to determine the regimes of suitable surface modification for metallization.

  10. Surface modification of high temperature iron alloys

    DOEpatents

    Park, Jong-Hee

    1995-01-01

    A method and article of manufacture of a coated iron based alloy. The method includes providing an iron based alloy substrate, depositing a silicon containing layer on the alloy surface while maintaining the alloy at a temperature of about 700.degree. C.-1200.degree. C. to diffuse silicon into the alloy surface and exposing the alloy surface to an ammonia atmosphere to form a silicon/oxygen/nitrogen containing protective layer on the iron based alloy.

  11. Surface modification of high temperature iron alloys

    DOEpatents

    Park, J.H.

    1995-06-06

    A method and article of manufacture of a coated iron based alloy are disclosed. The method includes providing an iron based alloy substrate, depositing a silicon containing layer on the alloy surface while maintaining the alloy at a temperature of about 700--1200 C to diffuse silicon into the alloy surface and exposing the alloy surface to an ammonia atmosphere to form a silicon/oxygen/nitrogen containing protective layer on the iron based alloy. 13 figs.

  12. Advanced Space Surface Systems Operations

    NASA Technical Reports Server (NTRS)

    Huffaker, Zachary Lynn; Mueller, Robert P.

    2014-01-01

    The importance of advanced surface systems is becoming increasingly relevant in the modern age of space technology. Specifically, projects pursued by the Granular Mechanics and Regolith Operations (GMRO) Lab are unparalleled in the field of planetary resourcefulness. This internship opportunity involved projects that support properly utilizing natural resources from other celestial bodies. Beginning with the tele-robotic workstation, mechanical upgrades were necessary to consider for specific portions of the workstation consoles and successfully designed in concept. This would provide more means for innovation and creativity concerning advanced robotic operations. Project RASSOR is a regolith excavator robot whose primary objective is to mine, store, and dump regolith efficiently on other planetary surfaces. Mechanical adjustments were made to improve this robot's functionality, although there were some minor system changes left to perform before the opportunity ended. On the topic of excavator robots, the notes taken by the GMRO staff during the 2013 and 2014 Robotic Mining Competitions were effectively organized and analyzed for logistical purposes. Lessons learned from these annual competitions at Kennedy Space Center are greatly influential to the GMRO engineers and roboticists. Another project that GMRO staff support is Project Morpheus. Support for this project included successfully producing mathematical models of the eroded landing pad surface for the vertical testbed vehicle to predict a timeline for pad reparation. And finally, the last project this opportunity made contribution to was Project Neo, a project exterior to GMRO Lab projects, which focuses on rocket propulsion systems. Additions were successfully installed to the support structure of an original vertical testbed rocket engine, thus making progress towards futuristic test firings in which data will be analyzed by students affiliated with Rocket University. Each project will be explained in

  13. Review of surface-modification programs in the DOE-OTM Tribology Program

    SciTech Connect

    Fenske, G.R.; Nichols, F.A.

    1991-02-01

    The use of surface-modification treatments is a widely accepted practice to reduce the wear and modify the friction behavior of surface regions while maintaining desirable bulk properties (e.g., strength, hardness, thermal conductivity, etc.) of the underlying substrate. These treatments range from conventional diffusion processes such as carburizing steels for case-hardening gears, to advanced non-equilibrium processes such as ion implantation or ion plating. The objective of this task area is to develop and investigate new or emerging surface-modification processes that show a potential for improving and controlling the tribological behavior of surfaces and thus permit engineers to design components for advanced heat engines based on desired bulk properties and near-surface tribological properties.

  14. Surface modifications with Lissajous trajectories using atomic force microscopy

    SciTech Connect

    Cai, Wei; Yao, Nan

    2015-09-14

    In this paper, we report a method for atomic force microscopy surface modifications with single-tone and multiple-resolution Lissajous trajectories. The tip mechanical scratching experiments with two series of Lissajous trajectories were carried out on monolayer films. The scratching processes with two scan methods have been illustrated. As an application, the tip-based triboelectrification phenomenon on the silicon dioxide surface with Lissajous trajectories was investigated. The triboelectric charges generated within the tip rubbed area on the surface were characterized in-situ by scanning Kelvin force microscopy. This method would provide a promising and cost-effective approach for surface modifications and nanofabrication.

  15. Surface modifications by field induced diffusion.

    PubMed

    Olsen, Martin; Hummelgård, Magnus; Olin, Håkan

    2012-01-01

    By applying a voltage pulse to a scanning tunneling microscope tip the surface under the tip will be modified. We have in this paper taken a closer look at the model of electric field induced surface diffusion of adatoms including the van der Waals force as a contribution in formations of a mound on a surface. The dipole moment of an adatom is the sum of the surface induced dipole moment (which is constant) and the dipole moment due to electric field polarisation which depends on the strength and polarity of the electric field. The electric field is analytically modelled by a point charge over an infinite conducting flat surface. From this we calculate the force that cause adatoms to migrate. The calculated force is small for voltage used, typical 1 pN, but due to thermal vibration adatoms are hopping on the surface and even a small net force can be significant in the drift of adatoms. In this way we obtain a novel formula for a polarity dependent threshold voltage for mound formation on the surface for positive tip. Knowing the voltage of the pulse we then can calculate the radius of the formed mound. A threshold electric field for mound formation of about 2 V/nm is calculated. In addition, we found that van der Waals force is of importance for shorter distances and its contribution to the radial force on the adatoms has to be considered for distances smaller than 1.5 nm for commonly used voltages. PMID:22253894

  16. Surface Modifications by Field Induced Diffusion

    PubMed Central

    Olsen, Martin; Hummelgård, Magnus; Olin, Håkan

    2012-01-01

    By applying a voltage pulse to a scanning tunneling microscope tip the surface under the tip will be modified. We have in this paper taken a closer look at the model of electric field induced surface diffusion of adatoms including the van der Waals force as a contribution in formations of a mound on a surface. The dipole moment of an adatom is the sum of the surface induced dipole moment (which is constant) and the dipole moment due to electric field polarisation which depends on the strength and polarity of the electric field. The electric field is analytically modelled by a point charge over an infinite conducting flat surface. From this we calculate the force that cause adatoms to migrate. The calculated force is small for voltage used, typical 1 pN, but due to thermal vibration adatoms are hopping on the surface and even a small net force can be significant in the drift of adatoms. In this way we obtain a novel formula for a polarity dependent threshold voltage for mound formation on the surface for positive tip. Knowing the voltage of the pulse we then can calculate the radius of the formed mound. A threshold electric field for mound formation of about 2 V/nm is calculated. In addition, we found that van der Waals force is of importance for shorter distances and its contribution to the radial force on the adatoms has to be considered for distances smaller than 1.5 nm for commonly used voltages. PMID:22253894

  17. Surface modification of YIG by magnet array

    NASA Astrophysics Data System (ADS)

    Atalay, S.; Kolat, V. S.; Bakır, H. G.; Izgi, T.; Kaya, A. O.; Kaya, O. A.; Gencer, H.

    2015-11-01

    In this work, magnetostatic surface spin waves (MSSW) were propagated along the single crystal YIG (Y3Fe5O12) film grown on GGG substrate. In order to obtain magnonic crystals, unlike the conventional methods, the surface of YIG films were magnetically modulated by magnet array in one and two-dimensions. The surface modulated YIG films formed sharp band gaps at approximately 6.55 GHz and 6.58 GHz at 1600 Oe magnetic field for one and two-dimensional magnonic crystals, respectively. It was found that a very small magnetic field change leads a large change in the peak value of band gap frequency.

  18. Surface modification of tribological components in transportation

    SciTech Connect

    Fenske, G.R.

    1992-11-01

    This paper reviews a number of programs funded through the Engineered Tribological Interfaces (ETI) Task area of the Tribology Program that utilize energetic beams of atoms to enhance the mechanical and microstructural properties of near-surface regions to improve the tribological performance of critical components. The processes used in these programs include techniques based on chemical vapor deposition, physical vapor deposition, and ion implantation. A common feature of these techniques is their ability to produce dense and adherent modified surfaces without need for subsequent grinding/polishing treatments. Another feature of these techniques is their ability to introduce a wide range of elements into near-surface regions.

  19. Enzymatic surface modification of acrylonitrile fibers

    NASA Astrophysics Data System (ADS)

    Battistel, Ezio; Morra, Marco; Marinetti, Massimo

    2001-06-01

    The surface of polyacrylonitrile polymer (containing 10% acetate groups) as fibers and finely ground powder have been modified by enzymatic treatment. The enzyme used was a nitrile hydratase, member of the class of nitrile converting enzymes, present in the microorganisms Brevibacterium imperiale and Corynebacterium nitrilophilus. The pendant nitrile groups were selectively converted into the corresponding amides as assessed by XPS analysis. As indicated by the increase of the O/C atomic ratio, the fiber surface showed a significant increase in hydrophilicity. The newly formed amide groups were then able to react with the acid dyes typically used to stain natural fibers, conferring the coloring properties to the otherwise inert polymer surface.

  20. Nanoscale biomaterial interface modification for advanced tissue engineering applications

    NASA Astrophysics Data System (ADS)

    Safonov, V.; Zykova, A.; Smolik, J.; Rogovska, R.; Donkov, N.; Goltsev, A.; Dubrava, T.; Rassokha, I.; Georgieva, V.

    2012-03-01

    Recently, various stem cells, including mesenchymal stem cells (MSCs), have been found to have considerable potential for application in tissue engineering and future advanced therapies due to their biological capability to differentiate into specific lineages. Modified surface properties, such as composition, nano-roughness and wettability, affect the most important processes at the biomaterial interface. The aim of the present is work is to study the stem cells' (MSCs) adhesive potential, morphology, phenotypical characteristics in in vitro tests, and to distinguish betwen the different factors influencing the cell/biomaterial interaction, such as nano-topography, surface chemistry and surface free energy.

  1. Plasma modification of polymethylmethacrylate and polythyleneterephthalate surfaces

    NASA Astrophysics Data System (ADS)

    Groning, P.; Collaud, M.; Dietler, G.; Schlapbach, L.

    1994-07-01

    Noble gas (He, Ar, Xe) and reactive gas (O2, N2) plasma treatments of polymethylmethacrylate (PMMA) and polyethyleneterephthalate (PET) surfaces were performed in an electron-cyclotron-resonance plasma. In situ surface analysis by x-ray photoelectron spectroscopy reveals well-defined surface compositions. From these measurements it is concluded that, independently of the plasma gas, the plasma ions easily decompose the ester group in PMMA in its constituents by an ion-electron recombination process, while in PET the ester decomposition is less pronounced. The difference is ascribed to the presence in PET of a phenyl ring, which protects the ester group by various mechanisms. The study of O2 plasma treatments shows that the equilibrium between the depletion of oxygen and the incorporation of the reactive species in the polymer surface is solely determined by the ion current. The plasma-polymer interactions are qualtitatively explained by simple rules of intermolecular forces and ion-electron recombination phenomena.

  2. Practical applications of plasma surface modification

    SciTech Connect

    Smith, M.D.

    1993-12-01

    Radio frequency activated gas plasma is an environmentally conscious manufacturing process which provides surface treatments for improved product quality. Plasma processing offers significant potential for reducing the use of solvents and other wet processing chemicals now used in surface treatments such as cleaning, activation for bonding, and moisture removal. Plasma treatments are generally accomplished without creating hazardous waste streams to dispose of. Plasma process development and application is ongoing at Allied Signal Inc., Kansas City Division.

  3. Effects of aluminium surface morphology and chemical modification on wettability

    NASA Astrophysics Data System (ADS)

    Rahimi, M.; Fojan, P.; Gurevich, L.; Afshari, A.

    2014-03-01

    Aluminium alloys are some of the predominant metals in industrial applications such as production of heat exchangers, heat pumps. They have high heat conductivity coupled with a low specific weight. In cold working conditions, there is a risk of frost formation on the surface of aluminium in the presence of water vapour, which can lead to the deterioration of equipment performance. This work addresses the methods of surface modification of aluminium and their effect of the underlying surface morphology and wettability, which are the important parameters for frost formation. Three groups of real-life aluminium surfaces of different morphology: unpolished aluminium, polished aluminium, and aluminium foil, were subjected to surface modification procedures which involved the formation of a layer of hydrophilic hyperbranched polyethyleneglycol via in situ polymerization, molecular vapour deposition of a monolayer of fluorinated silane, and a combination of those. The effect of these surface modification techniques on roughness and wettability of the aluminium surfaces was elucidated by ellipsometry, contact angle measurements and atomic force microscopy. We demonstrated that by employing different types of surface modifications the contact angle of water droplets on aluminium samples can be varied from 12° to more than 120°. A crossover from Cassie-Baxter to Wenzel regime upon changing the surface roughness was also observed.

  4. Magellan - Initial analysis of Venus surface modification

    NASA Technical Reports Server (NTRS)

    Arvidson, R. E.; Baker, V. R.; Elachi, Charles; Saunders, R. S.; Wood, J. A.

    1991-01-01

    Images of the Venus surface provided by the Magellan mission make it possible to see the fine-scale features diagnostic of weathering, erosion, and deposition. These include ejecta deposits extending up to 1000 km to the west of several impact craters, windblown deposits, features containing both obstacles and a source of particulate material, and evidence for degradation by atmosphere-surface interactions and mass movements. Initial Magellan observations pertaining to the nature, rate, and history of surficial processes are analyzed. Emphasis is placed on radar imaging, but results from radiometry and altimetry observations are also discussed.

  5. Surface modification by subsurface pressure induced diffusion

    SciTech Connect

    Zimmermann, Claus G.

    2012-01-23

    Polycrystalline Ag, covered with a nm thin siloxane layer, was irradiated with ultraviolet light in vacuum at 500 K. Ag particles of different aspect ratios, 50-1000 nm in size, formed on the surface, including a small fraction of nanorods. Pressurized water vapor bubbles are created in the subsurface region by hydrogen radicals photo-chemically released by the siloxane layer. They provide the driving force for a diffusive material flux along grain boundaries to the surface. This mechanism was modeled and found to agree with the experimental timescale: approximately 300 h are required for a 1000 nm particle to form.

  6. Plasma assisted surface coating/modification processes - An emerging technology

    NASA Technical Reports Server (NTRS)

    Spalvins, T.

    1987-01-01

    A broad understanding of the numerous ion or plasma assisted surface coating/modification processes is sought. An awareness of the principles of these processes is needed before discussing in detail the ion nitriding technology. On the basis of surface modifications arising from ion or plasma energizing and interactions, it can be broadly classified as deposition of distinct overlay coatings (sputtering-dc, radio frequency, magnetron, reactive; ion plating-diode, triode) and surface property modification without forming a discrete coating (ion implantation, ion beam mixing, laser beam irradiation, ion nitriding, ion carburizing, plasma oxidation. These techniques offer a great flexibility and are capable in tailoring desirable chemical and structural surface properties independent of the bulk properties.

  7. Plasma assisted surface coating/modification processes: An emerging technology

    NASA Technical Reports Server (NTRS)

    Spalvins, T.

    1986-01-01

    A broad understanding of the numerous ion or plasma assisted surface coating/modification processes is sought. An awareness of the principles of these processes is needed before discussing in detail the ion nitriding technology. On the basis of surface modifications arising from ion or plasma energizing and interactions, it can be broadly classified as deposition of distinct overlay coatings (sputtering-dc, radio frequency, magnetron, reactive; ion plating-diode, triode) and surface property modification without forming a discrete coating (ion implantation, ion beam mixing, laser beam irradiation, ion nitriding, ion carburizing, plasma oxidation). These techniques offer a great flexibility and are capable in tailoring desirable chemical and structural surface properties independent of the bulk properties.

  8. Advanced Design Mixer Pump Tank 18 Design Modifications Summary Report

    SciTech Connect

    Adkins, B.J.

    2002-12-03

    The Westinghouse Savannah River Company (WSRC) is preparing to retrieve high level waste (HLW) from Tank 18 in early FY03 to provide feed for the Defense Waste Processing Facility (DWPF) and to support tank closure in FY04. As part of the Tank 18 project, WSRC will install a single Advanced Design Mixer Pump (ADMP) in the center riser of Tank 18 to mobilize, suspend, and mix radioactive sludge in preparation for transfer to Tank 7. The use of a single ADMP is a change to the current baseline of four (4) standard slurry pumps used during previous waste retrieval campaigns. The ADMP was originally conceived by Hanford and supported by SRS to provide a more reliable and maintainable mixer pump for use throughout the DOE complex. The ADMP underwent an extensive test program at SRS between 1998 and 2002 to assess reliability and hydraulic performance. The ADMP ran for approximately 4,200 hours over the four-year period. A detailed tear down and inspection of the pump following the 4,2 00-hour run revealed that the gas mechanical seals and anti-friction bearings would need to be refurbished/replaced prior to deployment in Tank 18. Design modifications were also needed to meet current Authorization Basis safety requirements. This report documents the modifications made to the ADMP in support of Tank 18 deployment. This report meets the requirements of Tanks Focus Area (TFA) Milestone 3591.4-1, ''Issue Report on Modifications Made to the ADMP,'' contained in Technical Task Plan (TTP) SR16WT51, ''WSRC Retrieval and Closure.''

  9. Membrane surface modification via polymer grafting and interfacial polymerization

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Membrane separation is an important technology for separating food ingredients and fractionating high-value substances from food processing by-products. Long-term uses of polymeric membranes in food protein processing are impeded by formation of fouled layers on the membrane surface. Surface modif...

  10. The Modification of Ferroelectric Surfaces for Catalysis

    NASA Astrophysics Data System (ADS)

    Herdiech, Matthew William

    Ferroelectrics are a class of materials in which a net dipole can be associated with each repeat unit, resulting in a potentially large electric field through the material. The ability to reversibly switch the polarization direction by applying an external electric field distinguishes ferroelectrics from polar orientations of ordinary materials. Recent studies exploring the reactivity of ferroelectric surfaces toward polar molecules have shown that the heats of adsorption for these molecules are polarization dependent, but the surfaces tend to be unreactive. Despite the inertness of ferroelectric surfaces, their use as supports for catalytically active materials could yield novel reactivity. As even metal oxides that are generally considered inert can influence the catalytic properties of supported layers, a ferroelectric support may offer the opportunity to modulate catalytic activity since charge compensation of the polar surfaces might include chemical and electronic reconstructions of the active layer. In this thesis, the fabrication of active layers with polarization dependent properties was investigated by coating ferroelectric substrates with catalytically active oxides that are likely to grow in a layer-by-layer manner. Two systems in particular were explored: chromium oxide on ferroelectric lithium niobate (Cr2O3/LiNbO3), and ruthenium oxide on ferroelectric lead zirconate titanate (RuO2/Pb(Zr0.2Ti0.8)O 3). The chromium oxide and ruthenium oxide films were characterized with X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED), and reflection high energy electron diffraction (RHEED). Additionally, the chromium oxide films were characterized with X-ray diffraction (XRD) and X-ray reflectivity (XRR) measurements, and the ruthenium oxide films were characterized with ion scattering spectroscopy (ISS) measurements. The reactivity of the films was investigated using temperature programmed desorption (TPD) measurements. In particular

  11. Laser-induced surface modification and metallization of polymers

    NASA Astrophysics Data System (ADS)

    Frerichs, Hartmut; Wesner, David A.; Kreutz, Ernst-Wolfgang

    1995-04-01

    Laser-induced surface modification of various polymers is presented as a suitable pretreatment of surfaces in a two-step metallization process. Materials such as polyamide (PA), polypropylene (PP), polystyrene (PS), polycarbonate (PC), acrylbutadienestyrene (ABS), styreneacrylnitril (SAN), polybutadieneterphtalate (PBT), and polyoxymethylen (POM) were treated by excimer laser radiation ((lambda) equals 248 nm) in air. The aim of this study is to investigate different processing regimes of surface modification. Therefore the laser processing variables fluence F, repetition rate v and pulse number N are varied and the absorption coefficient, optical penetration depth, ablation depth and ablation threshold are determined. The surface morphology and surface roughness are studied by optical surface profilometry and secondary electron microscopy (SEM). The influence of laser treatment on chemical composition of modified and ablated surfaces is analyzed by X-ray photoelectron spectroscopy (XPS). Depending on the processing parameters and materials properties different microstructures and values of surface roughness are generated on the micrometer length scale. Pretreatment for the subsequent metallization is performed with laser radiation, wet chemical and plasma etching. The metallization of polymers is investigated for different surface morphologies. The used metallization processes are electroplating and physical vapor deposition (PVD). Adhesion of the deposited films, measured with scratch and tape test methods, is used as a criterion for determining regimes of suitable surface modification for subsequent metallization.

  12. Surface modification methods for enhanced device efficacy and function.

    PubMed

    Jones, Barbara J; Hayes, Mark A

    2006-01-01

    Currently available microfluidic devices can accomplish a variety of tasks useful in molecular biology. When moving analytical processes to a microenvironment, the properties of the device surface play a larger role in the functioning of the device. Surface modification may become necessary or advantageous for the purpose of control of the functional mechanics of the device, keeping cell components from adsorbing, attaching antibodies to the surface for detection of biological components, and attaching a functional bonding complex. Modification of the surface of microfluidic devices for the control of flow and device function, or for functionalization of the surface to tailor the device to a specific use, can be accomplished in numerous bench-top, postfabrication procedures. The use of polyelectrolyte multilayers, ultraviolet grafting of polymers, and polydimethylsiloxane/surfactant coating to control flow and mitigate adsorption is discussed. In addition, the functionalization of devices through amine termination of surfaces, and immobilization of biotin within a phosphotidylcholine bilayer is detailed. PMID:16790866

  13. Surface modifications of pistons and cylinder liners

    SciTech Connect

    Suzuki, Y. )

    1988-01-01

    With higher brake mean effective pressure (BMEP) of a diesel engine, pistons and cylinder liners suffer from increasing mechanical and thermal loading which causes several problems on these engine parts. The main critical problems are thermally induced cracking on the piston head and scuffing on the cylinder bore. Hard anodizing the piston head is described. It is currently the most effective countermeasure against heat cracking. Another promising method, to reinforce the piston head by means of SiC-whiskers, is also reported. A new process for improving the surface lubrication of the cylinder liner was developed. The bore has numerous finely distributed micropits which act as good oil reservoir. This improves the antiscuffing property of the cylinder liner.

  14. 19 CFR 181.100 - Effect of NAFTA advance ruling letters; modification and revocation.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 19 Customs Duties 2 2011-04-01 2011-04-01 false Effect of NAFTA advance ruling letters... Advance Ruling Procedures § 181.100 Effect of NAFTA advance ruling letters; modification and revocation. (a) Effect of NAFTA advance ruling letters—(1) General. An advance ruling letter issued by...

  15. Environmentally friendly surface modification of PDMS using PEG polymer brush.

    PubMed

    Zhang, Zhaowei; Feng, Xiaojun; Luo, Qingming; Liu, Bi-Feng

    2009-09-01

    A PEG-NH2-based environmentally friendly surface modification strategy was developed for PDMS microchips to prevent protein adsorption and to enhance separation performance. PEG-NH2 was synthesized using a modified synthesis procedure. A two-step grafting method was used for PDMS modification. FTIR absorption by attenuated total reflection and contact angle measurements verified the successful grafting of PEG-NH2 onto the PDMS surface. Subsequent EOF Measurements and protein adsorption studies of PEG-modified PDMS microchips revealed noticeable EOF suppression and resistance to nonspecific protein adsorption for more than 30 days. Separation of four FITC-labeled amino acids was further demonstrated with high repeatability and reproducibility. Comparison of electrophoresis of 3-(2-furoyl)quinoline-2-carboxaldehyde-labeled BSA using PDMS microchips before and after surface modification resulted in significantly improved electrophoretic performance of the PEG-modified PDMS microchips, suggesting that our PEG grafting method successfully modified PDMS surface property and prevented adsorption of proteins. We expect that this environmentally friendly surface modification method will be useful for future protein separations with long-term surface stability. PMID:19722209

  16. Comprehensive characterization of well-defined silk fibroin surfaces: Toward multitechnique studies of surface modification effects.

    PubMed

    Amornsudthiwat, Phakdee; Nitschke, Mirko; Zimmermann, Ralf; Friedrichs, Jens; Grundke, Karina; Pöschel, Kathrin; Damrongsakkul, Siriporn; Werner, Carsten

    2015-01-01

    The study aims at a comprehensive surface characterization of untreated and oxygen plasma-treated silk fibroin with a particular focus on phenomena relevant to biointeraction and cell adhesion. For that purpose, a range of advanced surface diagnostic techniques is employed to thoroughly investigate well-defined and especially clean silk fibroin samples in a comparable setting. This includes surface chemistry and surface charges as factors, which control protein adsorption, but also hydration and swelling of the material as important parameters, which govern the mechanical stiffness at the interface with aqueous media. Oxygen plasma exposure of silk fibroin surfaces reveals that material ablation strongly predominates over the introduction of functional groups even for mild plasma conditions. A substantial increase in mechanical stiffness is identified as the most prominent effect upon this kind of plasma treatment. Regarding the experimental approach and the choice of techniques, the work goes beyond previous studies in this field and paves the way for well-founded investigations of other surface-selective modification procedures that enhance the applicability of silk fibroin in biomedical applications. PMID:25899685

  17. Materials and surface modification for tissue engineered vascular scaffolds.

    PubMed

    Li, Zhong-Kui; Wu, Zhong-Shi; Lu, Ting; Yuan, Hao-Yong; Tang, Hao; Tang, Zhen-Jie; Tan, Ling; Wang, Bin; Yan, Si-Ming

    2016-10-01

    Although vascular implantation has been used as an effective treatment for cardiovascular disease for many years, off-the-shelf and regenerable vascular scaffolds are still not available. Tissue engineers have tested various materials and methods of surface modification in the attempt to develop a scaffold that is more suitable for implantation. Extracellular matrix-based natural materials and biodegradable polymers, which are the focus of this review, are considered to be suitable materials for production of tissue-engineered vascular grafts. Various methods of surface modification that have been developed will also be introduced, their impacts will be summarized and assessed, and challenges for further research will briefly be discussed. PMID:27484610

  18. Polydopamine-Assisted Surface Modification for Bone Biosubstitutes

    PubMed Central

    Zhou, Xin

    2016-01-01

    Polydopamine (PDA) prepared in the form of a layer of polymerized dopamine (DA) in a weak alkaline solution has been used as a versatile biomimetic surface modifier as well as a broadly used immobilizing macromolecule. This review mainly discusses the progress of biomaterial surface modification inspired by the participation of PDA in bone tissue engineering. A comparison between PDA-assisted coating techniques and traditional surface modification applied to bone tissue engineering is first presented. Secondly, the chemical composition and the underlying formation mechanism of PDA coating layer as a unique surface modifier are interpreted and discussed. Furthermore, several typical examples are provided to evidence the importance of PDA-assisted coating techniques in the construction of bone biosubstitutes and the improvement of material biocompatibility. Nowadays, the application of PDA as a superior surface modifier in multifunctional biomaterials is drawing tremendous interests in bone tissue scaffolds to promote the osteointegration for bone regeneration. PMID:27595097

  19. Polydopamine-Assisted Surface Modification for Bone Biosubstitutes.

    PubMed

    Huang, Shishu; Liang, Nuanyi; Hu, Yang; Zhou, Xin; Abidi, Noureddine

    2016-01-01

    Polydopamine (PDA) prepared in the form of a layer of polymerized dopamine (DA) in a weak alkaline solution has been used as a versatile biomimetic surface modifier as well as a broadly used immobilizing macromolecule. This review mainly discusses the progress of biomaterial surface modification inspired by the participation of PDA in bone tissue engineering. A comparison between PDA-assisted coating techniques and traditional surface modification applied to bone tissue engineering is first presented. Secondly, the chemical composition and the underlying formation mechanism of PDA coating layer as a unique surface modifier are interpreted and discussed. Furthermore, several typical examples are provided to evidence the importance of PDA-assisted coating techniques in the construction of bone biosubstitutes and the improvement of material biocompatibility. Nowadays, the application of PDA as a superior surface modifier in multifunctional biomaterials is drawing tremendous interests in bone tissue scaffolds to promote the osteointegration for bone regeneration. PMID:27595097

  20. On the surface modification of microchannels for microcapillary electrophoresis chips.

    PubMed

    Lee, Gwo-Bin; Lin, Che-Hsin; Lee, Kuo-Hoong; Lin, Yue-Feng

    2005-12-01

    This paper presents systematic investigation of the microchannel surface properties in microCE chips. Three popular materials for microCE chips, polydimethylsiloxane (PDMS), quartz, and glass, are used. The zeta potentials of these microchannels are calculated by measuring the EOF velocity to evaluate the surface properties after surface modification. The hydrophobic PDMS is usually plasma-treated for microCE applications. In this study, a new method using a high-throughput atmospheric plasma generator is adopted to treat the PDMS surface under atmospheric conditions. In this approach, the cost and time for surface treatment can be significantly reduced compared with the conventional vacuum plasma generator method. Experimental results indicate that new functional groups could be formed on the PDMS surface after treatment, resulting in a change in the surface property. The time-dependent surface property of the plasma-treated PDMS is then measured in terms of the zeta potential. Results show that the surface property will reach a stable condition after 1 h of plasma treatment. For glass CE chips, two new methods for changing the microchannel surface properties are developed. Instead of using complicated and time-consuming chemical silanization procedures for CE channel surface modification, two simple and reliable methods utilizing organic-based spin-on-glass and water-soluble acrylic resin are reported. The proposed method provides a fast batch process for controlling the surface properties of glass-based CE channels. The proposed methods are evaluated using PhiX-174 DNA maker separation. The experimental data show that the surface property is modified and separation efficiency greatly improved. In addition, the long-term stability of both coatings is verified in this study. The methods proposed in this study show potential as an excellent solution for glass-based microCE chip surface modification. PMID:16358252

  1. Surface modification of magnesium hydroxide using vinyltriethoxysilane by dry process

    NASA Astrophysics Data System (ADS)

    Lan, Shengjie; Li, Lijuan; Xu, Defang; Zhu, Donghai; Liu, Zhiqi; Nie, Feng

    2016-09-01

    In order to improve the compatibility between magnesium hydroxide (MH) and polymer matrix, the surface of MH was modified using vinyltriethoxysilane (VTES) by dry process and the interfacial interaction between MH and VTES was also studied. Zeta potential measurements implied that the MH particles had better dispersion and less aggregation after modification. Sedimentation tests showed that the surface of MH was transformed from hydrophilic to hydrophobic, and the dispersibility and the compatibility of MH particles significantly improved in the organic phase. Scanning electronic microscopy (SEM), Transmission electron microscopy (TEM) and X-ray powder diffraction (XRD) analyses showed that a thin layer had formed on the surface of the modified MH, but did not alter the material's crystalline phase. Fourier transform infrared (FT-IR) spectra, X-ray photoelectron spectra (XPS) and Thermogravimetric analysis (TGA) showed that the VTES molecules bound strongly to the surface of MH after modification. Chemical bonds (Sisbnd Osbnd Mg) formed by the reaction between Si-OC2H5 and hydroxyl group of MH, also there have physical adsorption effect in the interface simultaneously. A modification mechanism of VTES on the MH surface by dry process was proposed, which different from the modification mechanism by wet process.

  2. Surface properties of superfine alumina trihydrate after surface modification with stearic acid

    NASA Astrophysics Data System (ADS)

    Liu, Gui-hua; Zhou, Bo-hao; Li, Yun-feng; Qi, Tian-gui; Li, Xiao-bin

    2015-05-01

    The surface properties of superfine alumina trihydrate (ATH) after surface modification were studied by measuring the contact angle, active ratio, oil adsorption, total organic carbon, adsorption ratio, and Fourier transform infrared (FTIR) spectrum. The contact angle increased initially and then slowly decreased with an increase of the amount of stearic acid. However, the surface free energy decreased initially and then increased. Surface modification with stearic acid or sodium stearate can benefit from elevating temperature. The base surface tension component and the free energy of Lewis acid-base both declined sharply following the surface modification. Excess stearic acid was physically adsorbed in the form of multilayer adsorption, and an interaction between oxygen on the ATH surface and hydroxyl in stearic acid was subsequently determined. Our results further indicated that the contact angle and adsorption ratio can be used as control indicators for surface modification compared with active ratio, oil adsorption and total organic carbon.

  3. Heterogeneous polymer modification: Polyolefin maleation in supercritical carbon dioxide and amorphous fluoropolymer surface modification

    NASA Astrophysics Data System (ADS)

    Hayes, Heather J.

    1999-11-01

    Three distinct heterogeneous polymer modification reactions are explored in this work. The first is a bulk reaction commonly conducted on polyolefins---the free radical addition of maleic anhydride. This reaction was run using supercritical carbon dioxide (SC CO2) as the solvent. The second was the chemical surface modification of an amorphous fluorocopolymer of tetrafluoroethylene and a perfluorodioxole monomer (Teflon AF). Several reactions were explored to reduce the surface of the fluorocopolymer for the enhancement of wettability. The last modification was also on Teflon AF and involved the physical modification of the surface through the transport polymerization of xylylene in order to synthesize a novel bilayer membrane. The bulk maleation of poly-4-methyl-1-pentene (PMP) was the focus of the first project. SC CO2 was utilized as both solvent and swelling agent to promote this heterogeneous reaction and led to successful grafting of anhydride groups on both PMP and linear low density polyethylene. Varying the reaction conditions and reagent concentrations allowed optimization of the reaction. The grafted anhydride units were found to exist as single maleic and succinic grafts, and the PMP became crosslinked upon maleation. The surface of a fluoropolymer can be difficult to alter. An examination of three reactions was made to determine the reactivity of Teflon AF: sodium naphthalenide treatment (Na-Nap), aluminum metal modification through deposition and dissolution, and mercury/ammonia photosensitization. The fluorocopolymer with the lower perfluorodioxole percentage was found to be more reactive towards modification with the Na-Nap treatment. The other modification reactions appeared to be nearly equally reactive toward both fluorocopolymers. The functionality of the Na-Nap-treated surface was examined in detail with the use of several derivatization reactions. In the final project, an asymmetric gas separation membrane was synthesized using Teflon AF as

  4. Surface modification of polymeric materials by cold atmospheric plasma jet

    NASA Astrophysics Data System (ADS)

    Kostov, K. G.; Nishime, T. M. C.; Castro, A. H. R.; Toth, A.; Hein, L. R. O.

    2014-09-01

    In this work we report the surface modification of different engineering polymers, such as, polyethylene terephthalate (PET), polyethylene (PE) and polypropylene (PP) by an atmospheric pressure plasma jet (APPJ). It was operated with Ar gas using 10 kV, 37 kHz, sine wave as an excitation source. The aim of this study is to determine the optimal treatment conditions and also to compare the polymer surface modification induced by plasma jet with the one obtained by another atmospheric pressure plasma source - the dielectric barrier discharge (DBD). The samples were exposed to the plasma jet effluent using a scanning procedure, which allowed achieving a uniform surface modification. The wettability assessments of all polymers reveal that the treatment leads to reduction of more than 40° in the water contact angle (WCA). Changes in surface composition and chemical bonding were analyzed by x-ray photoelectron spectroscopy (XPS) and Fourier-Transformed Infrared spectroscopy (FTIR) that both detected incorporation of oxygen-related functional groups. Surface morphology of polymer samples was investigated by Atomic Force Microscopy (AFM) and an increase of polymer roughness after the APPJ treatment was found. The plasma-treated polymers exhibited hydrophobic recovery expressed in reduction of the O-content of the surface upon rinsing with water. This process was caused by the dissolution of low molecular weight oxidized materials (LMWOMs) formed on the surface as a result of the plasma exposure.

  5. Superhydrophobic surfaces fabricated by surface modification of alumina particles

    NASA Astrophysics Data System (ADS)

    Richard, Edna; Aruna, S. T.; Basu, Bharathibai J.

    2012-10-01

    The fabrication of superhydrophobic surfaces has attracted intense interest because of their widespread potential applications in various industrial fields. Recently, some attempts have been carried out to prepare superhydrophobic surfaces using metal oxide nanoparticles. In the present work, superhydrophobic surfaces were fabricated with low surface energy material on alumina particles with different sizes. It was found that particle size of alumina is an important factor in achieving stable superhydrophobic surface. It was possible to obtain alumina surface with water contact angle (WCA) of 156° and a sliding angle of <2°. Superhydrophobicity of the modified alumina is attributed to the combined effect of the micro-nanostructure and low surface energy of fatty acid on the surface. The surface morphology of the alumina powder and coatings was determined by FESEM. The stability of the coatings was assessed by conducting water immersion test. Effect of heat treatment on WCA of the coating was also studied. The transition of alumina from hydrophilic to superhydrophobic state was explained using Wenzel and Cassie models. The method is shown to have potential application for creating superhydrophobic surface on cotton fabrics.

  6. Modification of Surface Energy via Direct Laser Ablative Surface Patterning

    NASA Technical Reports Server (NTRS)

    Wohl, Christopher J., Jr. (Inventor); Belcher, Marcus A. (Inventor); Connell, John W. (Inventor); Hopkins, John W. (Inventor)

    2015-01-01

    Surface energy of a substrate is changed without the need for any template, mask, or additional coating medium applied to the substrate. At least one beam of energy directly ablates a substrate surface to form a predefined topographical pattern at the surface. Each beam of energy has a width of approximately 25 micrometers and an energy of approximately 1-500 microJoules. Features in the topographical pattern have a width of approximately 1-500 micrometers and a height of approximately 1.4-100 micrometers.

  7. Surface modification using low energy ground state ion beams

    NASA Technical Reports Server (NTRS)

    Chutjian, Ara (Inventor); Hecht, Michael H. (Inventor); Orient, Otto J. (Inventor)

    1990-01-01

    A method of effecting modifications at the surfaces of materials using low energy ion beams of known quantum state, purity, flux, and energy is presented. The ion beam is obtained by bombarding ion-generating molecules with electrons which are also at low energy. The electrons used to bombard the ion generating molecules are separated from the ions thus obtained and the ion beam is directed at the material surface to be modified. Depending on the type of ion generating molecules used, different ions can be obtained for different types of surface modifications such as oxidation and diamond film formation. One area of application is in the manufacture of semiconductor devices from semiconductor wafers.

  8. Disc surface modifications for enhanced performance against friction noise

    NASA Astrophysics Data System (ADS)

    Wang, D. W.; Mo, J. L.; Ge, X. H.; Ouyang, H.; Zhou, Z. R.

    2016-09-01

    Surface modifications of metal discs in the form of parallel and radial grooves are investigated for acquiring enhanced performance against friction-induced noise. Experimental and numerical studies indicate that grooved surfaces are capable of reducing squeal noise, and the groove width significantly affects the squeal noise level. Moreover, a disc sample with parallel grooves distributed on only half of surface well verifies the ability of grooves in reducing squeal noise generation. Numerical analysis is further performed to give an explanation on how the grooves can reduce squeal noise and why the disc samples with different groove widths exhibit different performance in reducing squeal noise.

  9. Chemical surface modification of fluorocarbon polymers by excimer laser processing

    NASA Astrophysics Data System (ADS)

    Niino, Hiroyuki; Yabe, Akira

    1996-04-01

    Surface of poly(tetrafluoroethylene) [PTFE] film was modified chemically by an ArF excimer laser-induced reaction in a hydrazine gas atmosphere. The polymer surface modified upon the irradiation of 1000 pulses at 27 mJ cm -2, which was a fairly lower fluence than the ablation threshold for usual polymer films, showed hydrophilicity (contact angle for water: 30°) enough to be metallized by chemical plating. The mechanism for chemical surface modification was investigated by FTIR, XPS, and SIMS analyses. The laser-treated PTFE film was metallized by a chemical plating process. These processes will be used to fabricate printed wiring boards for high frequency electronics.

  10. Plasma technologies application for building materials surface modification

    NASA Astrophysics Data System (ADS)

    Volokitin, G. G.; Skripnikova, N. K.; Volokitin, O. G.; Shehovtzov, V. V.; Luchkin, A. G.; Kashapov, N. F.

    2016-01-01

    Low temperature arc plasma was used to process building surface materials, such as silicate brick, sand lime brick, concrete and wood. It was shown that building surface materials modification with low temperature plasma positively affects frost resistance, water permeability and chemical resistance with high adhesion strength. Short time plasma processing is rather economical than traditional processing thermic methods. Plasma processing makes wood surface uniquely waterproof and gives high operational properties, dimensional and geometrical stability. It also increases compression resistance and decreases inner tensions level in material.

  11. Surface Modification of Nitinol by Chemical and Electrochemical Etching

    NASA Astrophysics Data System (ADS)

    Yang, Zhendi; Wei, Xiaojin; Cao, Peng; Gao, Wei

    2013-07-01

    In this paper, Nitinol, an equiatomic binary alloy of nickel and titanium, was surface modified for its potential biomedical applications by chemical and electrochemical etching. The main objective of the surface modification is to reduce the nickel content on the surface of Nitinol and simultaneously to a rough surface microstructure. As a result, better biocompatibility and better cell attachment would be achieved. The effect of the etching parameters was investigated, using scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectrometry (EDX) and X-ray photoelectron spectrometry (XPS). The corrosion property of modified Nitinol surfaces was investigated by electrochemical work station. After etching, the Ni content in the surface layer has been reduced and the oxidation of Ti has been enhanced.

  12. Surface modification of biphasic calcium phosphate bioceramic powders

    NASA Astrophysics Data System (ADS)

    Yang, W. Z.; Zhou, D. L.; Yin, G. F.; Li, G. D.

    2008-11-01

    Biphasic calcium phosphate (BCP)/poly L-lactide (PLLA) biocomposite is proven to be a promising bone graft material or scaffold for bone tissue engineering. To improve the interfacial compatibility of BCP bioceramic with biopolymer-PLLA, BCP powders were surface-modified in different condition to graft polymer groups onto the surface of the BCP powders. L-lactide and L-lactic acid (LA) oligomer were used to modify the BCP surface with stannous octanoate (Sn(Oct) 2) and stannous chloride (SnCl 2) as catalyst, respectively. Results show that the surface modification effect is obvious and the amount of grafted organic group is above 6.5 wt.%. Sn(Oct) 2 and SnCl 2 are the optimal catalysts for the surface grafting reaction of L-lactide and L-LA oligomer, respectively. The surface grafting slightly increase the particle size of BCP powders and reduce the tendency for their agglomeration.

  13. Laser surface and subsurface modification of sapphire using femtosecond pulses

    NASA Astrophysics Data System (ADS)

    Eberle, G.; Schmidt, M.; Pude, F.; Wegener, K.

    2016-08-01

    Two methods to process sapphire using femtosecond laser pulses are demonstrated, namely ablation (surface), and in-volume laser modification followed by wet etching (subsurface). Firstly, the single and multipulse ablation threshold is determined and compared with previous literature results. A unique application of ablation is demonstrated by modifying the entrance aperture of water jet orifices. Laser ablation exhibits advantages in terms of geometric flexibility and resolution, however, defects in the form of edge outbreaks and poor surface quality are evident. Secondly, the role of material transformation, polarisation state and formation of multi-focus structures after in-volume laser modification is investigated in order to explain their influence during the wet etching process. Laser scanning and electron microscopy as well as electron backscatter diffraction measurements supported by ion beam polishing are used to better understand quality and laser-material interactions of the two demonstrated methods of processing.

  14. Utilization of waste tires employing novel surface-modification technology

    SciTech Connect

    Bauman, B.D. )

    1989-01-01

    Air Products and Chemicals, Inc. is developing unique technology for the recycle of scrap tires. The approach involves surface-modification of ground tire rubber particles to facilitate their incorporation into novel composites. This form of recycling represents the highest value-added and greatest energy conservation potential of all tire recycle technologies. Furthermore, it is environmentally innocuous. Research and development of this unique technology is partially funded through a cost-shared contract with the US Department of Energy. 4 figs.

  15. Surface Modification of ICF Target Capsules by Pulsed Laser Ablation

    DOE PAGESBeta

    Carlson, Lane C.; Johnson, Michael A.; Bunn, Thomas L.

    2016-06-30

    Topographical modifications of spherical surfaces are imprinted on National Ignition Facility (NIF) target capsules by extending the capabilities of a recently developed full surface (4π) laser ablation and mapping apparatus. The laser ablation method combines the precision, energy density and long reach of a focused laser beam to pre-impose sinusoidal modulations on the outside surface of High Density Carbon (HDC) capsules and the inside surface of Glow Discharge Polymer (GDP) capsules. Sinusoidal modulations described in this paper have sub-micron to 10’s of microns vertical scale and wavelengths as small as 30 μm and as large as 200 μm. The modulatedmore » patterns are created by rastering a focused laser fired at discrete capsule surface locations for a specified number of pulses. The computer program developed to create these raster patterns uses inputs such as laser beam intensity profile, the material removal function, the starting surface figure and the desired surface figure. The patterns are optimized to minimize surface roughness. Lastly, in this paper, simulated surfaces are compared with actual ablated surfaces measured using confocal microscopy.« less

  16. Coal surface control for advanced physical fine coal cleaning technologies

    SciTech Connect

    Morsi, B.I.; Chiang, S.H.; Sharkey, A.; Blachere, J.; Klinzing, G.; Araujo, G.; Cheng, Y.S.; Gray, R.; Streeter, R.; Bi, H.; Campbell, P.; Chiarlli, P.; Ciocco, M.; Hittle, L.; Kim, S.; Kim, Y.; Perez, L.; Venkatadri, R.

    1992-01-01

    This final report presents the research work carried out on the Coal Surface Control for Advanced Physical Fine Coal Cleaning Technologies project, sponsored by the US Department of Energy, Pittsburgh Energy Technology Center (DOE/PETC). The project was to support the engineering development of the selective agglomeration technology in order to reduce the sulfur content of US coals for controlling SO[sub 2] emissions (i.e., acid rain precursors). The overall effort was a part of the DOE/PETCs Acid Rain Control Initiative (ARCI). The overall objective of the project is to develop techniques for coal surface control prior to the advanced physical fine coal cleaning process of selective agglomeration in order to achieve 85% pyrite sulfur rejection at an energy recovery greater than 85% based on run-of-mine coal. The surface control is meant to encompass surface modification during grinding and laboratory beneficiation testing. The project includes the following tasks: Project planning; methods for analysis of samples; development of standard beneficiation test; grinding studies; modification of particle surface; and exploratory R D and support. The coal samples used in this project include three base coals, Upper Freeport - Indiana County, PA, Pittsburgh NO. 8 - Belmont County, OH, and Illinois No. 6 - Randolph County, IL, and three additional coals, Upper Freeport - Grant County- WV, Kentucky No. 9 Hopkins County, KY, and Wyodak - Campbell County, WY. A total of 149 drums of coal were received.

  17. SURFACE MODIFICATION OF ZIRCALOY-4 SUBSTRATES WITH NICKEL ZIRCONIUM INTERMETALLICS

    SciTech Connect

    Luscher, Walter G.; Gilbert, Edgar R.; Pitman, Stan G.; Love, Edward F.

    2013-02-01

    Surfaces of Zircaloy-4 (Zr-4) substrates were modified with nickel-zirconium (NiZr) intermetallics to tailor oxidation performance for specialized applications. Surface modification was achieved by electroplating Zr-4 substrates with nickel (Ni) and then performing thermal treatments to fully react the Ni plating with the substrates, which resulted in a coating of NiZr intermetallics on the substrate surfaces. Both plating thickness and thermal treatment were evaluated to determine the effects of these fabrication parameters on oxidation performance and to identify an optimal surface modification process. Isothermal oxidation tests were performed on surface-modified materials at 290°, 330°, and 370°C under a constant partial pressure of oxidant (i.e., 1 kPa D2O in dry Ar at 101 kPa) for 64 days. Test results revealed an enhanced, transient oxidation rate that decreased asymptotically toward the rate of the Zr-4 substrate. Oxidation kinetics were analyzed from isothermal weight gain data, which were correlated with microstructure, hydrogen pickup, strength, and hardness.

  18. Controlling modulus and morphology of hydrogel tubes through surface modification.

    PubMed

    Enescu, Cristina; Shoichet, Molly S

    2004-01-01

    Crosslinked, porous poly(2-hydroxyethyl methacrylate-co-methyl methacrylate) (PHEMA-MMA) tubes were prepared in cylindrical glass molds using a new centrifugal casting process developed in our group. The resulting hydrogel tubes have a bi-phasic wall structure, with a spongy inner layer and a gel-like outer layer, the latter of which provides mechanical strength to the tube. While many factors influence wall morphology and, thus, mechanical properties, we focused on the effect of the surface properties of the glass mold in which tubes are synthesized. Specifically, we investigated the impact of a diverse set of silane modifications of the glass mold on tube morphology, elastic modulus and mold release. We treated activated glass surfaces with one of three alkoxysilanes having either ethoxy, amine or fluorocarbon end-groups. Silane-modified glass surfaces were found to be more hydrophobic than the unmodified glass mold, with the most hydrophobic surface being that of the fluorocarbon-terminated silane. The presence of the silane layer on the mold was confirmed by X-ray photoelectron spectroscopy and the stability of this modification was confirmed by examining the surface chemistry of the hydrogel tubes. The biphasic hydrogel tube wall structure was observed for all tubes, yet those tubes synthesized in unmodified molds had a cracked outer morphology, whereas those synthesized in silane-modified molds had a smooth outer morphology. This influenced the mechanical properties of the tubes where tubes synthesized in silane-modified molds had a significantly greater elastic modulus than those tubes synthesized in unmodified molds. Release from the molds was easiest with ethoxy- and amine-functionalized silane mold modifications. PMID:15109099

  19. Modification of polymeric substrates using surface-grafted nanoscaffolds

    NASA Astrophysics Data System (ADS)

    Thompson, Kimberlee Fay

    Surface grafting and modification of poly(acrylic acid) (PAA) were performed on nylon 6,6 carpet fibers to achieve permanent stain and soil resistance. PAA was grafted to nylon and modified with 1H, 1H-pentadecafluorooctyl amine (PDFOA) using an amidation agent, 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMTMM). The first goal was to optimize acrylamide modification of PAA in solution. Aqueous reactions with taurine, hydroxyethyl amine, and butyl amine progressed ˜100%, while PDFOA reactions in MeOH progressed ˜80%. Reaction products precipitated at 77% butyl or 52% PDFOA acrylamide contents. The second goal was to optimize the PAA grafting process. First, PAA was adsorbed onto nylon 6,6 films. Next, DMTMM initiated grafting of adsorbed PAA. PAA surface coverage was ˜78%, determined by contact angle analysis of the top 0.1--1 nm and x-ray photoelectron spectroscopy (XPS) analysis of the top 3--10 nm. The third goal was to modify PAA grafted nylon films with butyl amine and PDFOA. Randomly methylated beta-cyclodextrin (RAMEB) solubilized PDFOA in water. Contact angle detected ˜100% surface reaction for each amine, while XPS detected ˜77% butyl amine (H2O) and ˜50% for PDFOA (MeOH or H2O pH = 7) reactions. In H2O pH = 12, the PDFOA reaction progressed ˜89%, perhaps due to greater efficiency, access and solubility. The fourth goal was to perform surface depth profiling via angle-resolved XPS analysis (ARXPS). The PAA surface coverage from contact angle and XPS was confirmed. Further, adsorbed PAA was thicker than grafted PAA, supporting the theory that PAA adsorption occurs in thick layers onto nylon followed by DMTMM-activated spreading and grafting of thinner PAA layers across the surface. The PDFOA reaction in McOH produced a highly fluorinated but thin exterior and an unreacted PAA interior. The PDFOA reaction in H 2O pH = 12 produced a completely fluorinated exterior and highly fluorinated interior. Thus surface modification levels

  20. PREFACE Surface Modifications and Functionalization of Materials for Biomedical Applications

    NASA Astrophysics Data System (ADS)

    Endrino, Jose Luis; Puértolas, Jose A.; Albella, Jose M.

    2010-11-01

    Conference photograph This special issue contains selected papers which were presented as invited and contributed communications at the workshop entitled 'Surface modification and functionalization of materials for biomedical applications' (BIO-COAT 2010) which was held on 24 June 2010 in Zaragoza (Spain). The surface of a material plays a major role in its interaction with the biological medium. Processes related to the mechanical stability of articular devices in contact, osseointegration, thrombogenicity, corrosion and leaching, or the inflammatory response of rejection of a material, are clearly conditioned by the surface properties. Therefore, the modification or functionalization of surfaces can have an important impact on these issues. New techniques for functionalization by thin film deposition or surface treatments help to improve superficial properties, while understanding the interaction of the surface-biological medium is critical for their application in new devices. Jointly organized by the Spanish Materials Research Society, BIO-COAT 2010 provided an open forum to discuss the progress and latest developments in thin film processing and the engineering of biomaterials. Invited lectures were particularly aimed at providing overviews on scientific topics and were given by recognized world-class scientists. Two of them have contributed with a proceedings article to this selected collection (articles 012001 and 012008). The contributed communications were focused on particular cutting-edge aspects of thin film science and functionalization technologies for biomaterials, showing the major scientific push of Spanish research groups in the field. The 2010 BIO-COAT conference was organized along four main topics: (1) functionalization and texture on surfaces, (2) tribology and corrosion, (3) the surface modification of biomaterials, and (4) surface-biological environment interactions. The papers published in this volume were accepted for publication after

  1. How Water Advances on Superhydrophobic Surfaces.

    PubMed

    Schellenberger, Frank; Encinas, Noemí; Vollmer, Doris; Butt, Hans-Jürgen

    2016-03-01

    Superliquid repellency can be achieved by nano- and microstructuring surfaces in such a way that protrusions entrap air underneath the liquid. It is still not known how the three-phase contact line advances on such structured surfaces. In contrast to a smooth surface, where the contact line can advance continuously, on a superliquid-repellent surface, the contact line has to overcome an air gap between protrusions. Here, we apply laser scanning confocal microscopy to get the first microscopic videos of water drops advancing on a superhydrophobic array of micropillars. In contrast to common belief, the liquid surface gradually bends down until it touches the top face of the next micropillars. The apparent advancing contact angle is 180°. On the receding side, pinning to the top faces of the micropillars determines the apparent receding contact angle. Based on these observations, we propose that the apparent receding contact angle should be used for characterizing superliquid-repellent surfaces rather than the apparent advancing contact angle and hysteresis. PMID:26991185

  2. How Water Advances on Superhydrophobic Surfaces

    NASA Astrophysics Data System (ADS)

    Schellenberger, Frank; Encinas, Noemí; Vollmer, Doris; Butt, Hans-Jürgen

    2016-03-01

    Superliquid repellency can be achieved by nano- and microstructuring surfaces in such a way that protrusions entrap air underneath the liquid. It is still not known how the three-phase contact line advances on such structured surfaces. In contrast to a smooth surface, where the contact line can advance continuously, on a superliquid-repellent surface, the contact line has to overcome an air gap between protrusions. Here, we apply laser scanning confocal microscopy to get the first microscopic videos of water drops advancing on a superhydrophobic array of micropillars. In contrast to common belief, the liquid surface gradually bends down until it touches the top face of the next micropillars. The apparent advancing contact angle is 180°. On the receding side, pinning to the top faces of the micropillars determines the apparent receding contact angle. Based on these observations, we propose that the apparent receding contact angle should be used for characterizing superliquid-repellent surfaces rather than the apparent advancing contact angle and hysteresis.

  3. Laser surface modification of boronickelized medium carbon steel

    NASA Astrophysics Data System (ADS)

    Bartkowska, Aneta; Pertek, Aleksandra; Kulka, Michał; Klimek, Leszek

    2015-11-01

    A two-step process was applied to produce the multicomponent boride layers. Boronickelizing consisted of nickel plating and diffusion boriding. Two different methods of heat treatment of boronickelized C45 steel were used: a typical through-hardening, and a laser surface modification with remelting. Microstructure and some mechanical properties of these layers were examined. Microstructural characterization was studied using optical microscope, Scanning Electron Microscope, energy-dispersive X-ray microanalysis, Electron Back-Scatter Diffraction and X-ray diffraction. The laser modification improved wear resistance, cohesion as well as low-cycle fatigue of the boronickelized layer. Compressive stresses, occurring after laser remelting, could be the reason for the advantageous mechanical behavior of the layer.

  4. Silane surface modification for improved bioadhesion of esophageal stents

    NASA Astrophysics Data System (ADS)

    Karakoy, Mert; Gultepe, Evin; Pandey, Shivendra; Khashab, Mouen A.; Gracias, David H.

    2014-08-01

    Stent migration occurs in 10-40% of patients who undergo placement of esophageal stents, with higher migration rates seen in those treated for benign esophageal disorders. This remains a major drawback of esophageal stent therapy. In this paper, we propose a new surface modification method to increase the adhesion between self-expandable metallic stents (SEMS) and tissue while preserving their removability. Taking advantage of the well-known affinity between epoxide and amine terminated silane coupling agents with amine and carboxyl groups that are abundant in proteins and related molecules in the human body; we modified the surfaces of silicone coated esophageal SEMS with these adhesive self-assembled monolayers (SAMs). We utilized vapor phase silanization to modify the surfaces of different substrates including PDMS strips and SEMS, and measured the force required to slide these substrates on a tissue piece. Our results suggest that surface modification of esophageal SEMS via covalent attachment of protein-binding coupling agents improves adhesion to tissue and could offer a solution to reduce SEMS migration while preserving their removability.

  5. Temperature dependent surface modification of silica spheres with methacrylate

    NASA Astrophysics Data System (ADS)

    Kang, Kwang-Sun; Kim, Byoung-Ju; Jo, Dong-Hyun; Lim, Sae-Han; Park, Jin-Young; Kim, Do-gyun

    2014-09-01

    Surface modification of silica spheres with 3-(Trimethoxysilyl)propylmethacrylate (TMSPM) has been performed at ambient condition. However, the FTIR spectra and field emission scanning electron microscope (FESEM) images show no evidence of the surface modification. The reaction temperatures were varied from 60 to 80 °C with various reaction periods. Small absorption shoulder of the C=O stretching vibration was at 1700 cm-1, and slightly increased with the increase of the reaction time at 60 °C. The clear absorption peak appeared at 1698 cm-1 for the spheres reacted for 80 min at 70 °C and shifted toward 1720 cm-1 with the increase the reaction time. Strong absorption peak showed at 1698 cm-1 and shifted toward 1725 cm-1 with the increase of the reaction time at 80 °C. The spheres were dispersed to methanol and added photoinitiator (Irgacure-184). The solution was poured to a patterned glass substrate and exposed to the 254 nm UV-light during a self-assembly process. A large area and crack-free silica sphere film was formed. To increase the mechanical stability, a cellulose acetate solution was spin-coated to the film. The film was lift-off from the glass substrate to analyze the surface nanostructures. The surface nanostructures were maintained, and the film is stable enough to use as a mold to duplicate the nanopattern and flexible.

  6. Silane surface modification for improved bioadhesion of esophageal stents

    PubMed Central

    Karakoy, Mert; Gultepe, Evin; Pandey, Shivendra; Khashab, Mouen A.; Gracias, David H.

    2014-01-01

    Stent migration occurs in 10-40% of patients who undergo placement of esophageal stents, with higher migration rates seen in those treated for benign esophageal disorders. This remains a major drawback of esophageal stent therapy. In this paper, we propose a new surface modification method to increase the adhesion between self-expandable metallic stents (SEMS) and tissue while preserving their removability. Taking advantage of the well-known affinity between epoxide and amine terminated silane coupling agents with amine and carboxyl groups that are abundant in proteins and related molecules in the human body; we modified the surfaces of silicone coated esophageal SEMS with these adhesive self-assembled monolayers (SAMs). We utilized vapor phase silanization to modify the surfaces of different substrates including PDMS strips and SEMS, and measured the force required to slide these substrates on a tissue piece. Our results suggest that surface modification of esophageal SEMS via covalent attachment of protein-binding coupling agents improves adhesion to tissue and could offer a solution to reduce SEMS migration while preserving their removability. PMID:25663731

  7. Enhancing surface free energy and hydrophilicity through chemical modification of microstructured titanium implant surfaces.

    PubMed

    Rupp, F; Scheideler, L; Olshanska, N; de Wild, M; Wieland, M; Geis-Gerstorfer, J

    2006-02-01

    Roughness-induced hydrophobicity, well-known from natural plant surfaces and intensively studied toward superhydrophobic surfaces, has currently been identified on microstructured titanium implant surfaces. Studies indicate that microstructuring by sandblasting and acid etching (SLA) enhances the osteogenic properties of titanium. The undesired initial hydrophobicity, however, presumably decelerates primary interactions with the aqueous biosystem. To improve the initial wettability and to retain SLA microstructure, a novel surface modification was tested. This modification differs from SLA by its preparation after acid etching, which was done under protective gas conditions following liquid instead of dry storage. We hypothesized that this modification should have increased wettability due to the prevention of contaminations that occurs during air contact. The main outcome of dynamic wettability measurements was that the novel modification shows increased surface free energy (SFE) and increased hydrophilicity with initial water contact angles of 0 degrees compared to 139.9 degrees for SLA. This hydrophilization was kept even after any drying. Reduced hydrocarbon contaminations were identified to play a possible role in altered surface thermodynamics. Such surfaces aim to retain the hydrophilicity and natural high surface energy of the Ti dioxide surface until surgical implants' insertion and are compared in this in vitro study with structural surface variants of titanium to compare roughness and chemically induced wettability. PMID:16270344

  8. Surface chemical modification for exceptional wear life of MEMS materials

    NASA Astrophysics Data System (ADS)

    Singh, R. Arvind; Satyanarayana, N.; Sinha, Sujeet Kumar

    2011-12-01

    Micro-Electro-Mechanical-Systems (MEMS) are built at micro/nano-scales. At these scales, the interfacial forces are extremely strong. These forces adversely affect the smooth operation and cause wear resulting in the drastic reduction in wear life (useful operating lifetime) of actuator-based devices. In this paper, we present a surface chemical modification method that reduces friction and significantly extends the wear life of the two most popular MEMS structural materials namely, silicon and SU-8 polymer. The method includes surface chemical treatment using ethanolamine-sodium phosphate buffer, followed by coating of perfluoropolyether (PFPE) nanolubricant on (i) silicon coated with SU-8 thin films (500 nm) and (ii) MEMS process treated SU-8 thick films (50 μm). After the surface chemical modification, it was observed that the steady-state coefficient of friction of the materials reduced by 4 to 5 times and simultaneously their wear durability increased by more than three orders of magnitude (> 1000 times). The significant reduction in the friction coefficients is due to the lubrication effect of PFPE nanolubricant, while the exceptional increase in their wear life is attributed to the bonding between the -OH functional group of ethanolamine treated SU-8 thin/thick films and the -OH functional group of PFPE. The surface chemical modification method acts as a common route to enhance the performance of both silicon and SU-8 polymer. It is time-effective (process time ≤ 11 min), cost-effective and can be readily integrated into MEMS fabrication/assembly processes. It can also work for any kind of structural material from which the miniaturized devices are/can be made.

  9. Towards Enhanced Performance Thin-film Composite Membranes via Surface Plasma Modification

    PubMed Central

    Reis, Rackel; Dumée, Ludovic F.; Tardy, Blaise L.; Dagastine, Raymond; Orbell, John D.; Schutz, Jürg A.; Duke, Mikel C.

    2016-01-01

    Advancing the design of thin-film composite membrane surfaces is one of the most promising pathways to deal with treating varying water qualities and increase their long-term stability and permeability. Although plasma technologies have been explored for surface modification of bulk micro and ultrafiltration membrane materials, the modification of thin film composite membranes is yet to be systematically investigated. Here, the performance of commercial thin-film composite desalination membranes has been significantly enhanced by rapid and facile, low pressure, argon plasma activation. Pressure driven water desalination tests showed that at low power density, flux was improved by 22% without compromising salt rejection. Various plasma durations and excitation powers have been systematically evaluated to assess the impact of plasma glow reactions on the physico-chemical properties of these materials associated with permeability. With increasing power density, plasma treatment enhanced the hydrophilicity of the surfaces, where water contact angles decreasing by 70% were strongly correlated with increased negative charge and smooth uniform surface morphology. These results highlight a versatile chemical modification technique for post-treatment of commercial membrane products that provides uniform morphology and chemically altered surface properties. PMID:27363670

  10. Towards Enhanced Performance Thin-film Composite Membranes via Surface Plasma Modification.

    PubMed

    Reis, Rackel; Dumée, Ludovic F; Tardy, Blaise L; Dagastine, Raymond; Orbell, John D; Schutz, Jürg A; Duke, Mikel C

    2016-01-01

    Advancing the design of thin-film composite membrane surfaces is one of the most promising pathways to deal with treating varying water qualities and increase their long-term stability and permeability. Although plasma technologies have been explored for surface modification of bulk micro and ultrafiltration membrane materials, the modification of thin film composite membranes is yet to be systematically investigated. Here, the performance of commercial thin-film composite desalination membranes has been significantly enhanced by rapid and facile, low pressure, argon plasma activation. Pressure driven water desalination tests showed that at low power density, flux was improved by 22% without compromising salt rejection. Various plasma durations and excitation powers have been systematically evaluated to assess the impact of plasma glow reactions on the physico-chemical properties of these materials associated with permeability. With increasing power density, plasma treatment enhanced the hydrophilicity of the surfaces, where water contact angles decreasing by 70% were strongly correlated with increased negative charge and smooth uniform surface morphology. These results highlight a versatile chemical modification technique for post-treatment of commercial membrane products that provides uniform morphology and chemically altered surface properties. PMID:27363670

  11. Towards Enhanced Performance Thin-film Composite Membranes via Surface Plasma Modification

    NASA Astrophysics Data System (ADS)

    Reis, Rackel; Dumée, Ludovic F.; Tardy, Blaise L.; Dagastine, Raymond; Orbell, John D.; Schutz, Jürg A.; Duke, Mikel C.

    2016-07-01

    Advancing the design of thin-film composite membrane surfaces is one of the most promising pathways to deal with treating varying water qualities and increase their long-term stability and permeability. Although plasma technologies have been explored for surface modification of bulk micro and ultrafiltration membrane materials, the modification of thin film composite membranes is yet to be systematically investigated. Here, the performance of commercial thin-film composite desalination membranes has been significantly enhanced by rapid and facile, low pressure, argon plasma activation. Pressure driven water desalination tests showed that at low power density, flux was improved by 22% without compromising salt rejection. Various plasma durations and excitation powers have been systematically evaluated to assess the impact of plasma glow reactions on the physico-chemical properties of these materials associated with permeability. With increasing power density, plasma treatment enhanced the hydrophilicity of the surfaces, where water contact angles decreasing by 70% were strongly correlated with increased negative charge and smooth uniform surface morphology. These results highlight a versatile chemical modification technique for post-treatment of commercial membrane products that provides uniform morphology and chemically altered surface properties.

  12. ADVANCED UTILITY SIMULATION MODEL DESCRIPTION OF MODIFICATIONS TO THE STATE LEVEL MODEL (VERSION 3.0)

    EPA Science Inventory

    The report documents modifications to the state level model portion of the Advanced Utility Simulation Model (AUSM), one of four stationary source emission and control cost forecasting models developed for the National Acid Precipitation Assessment Program (NAPAP). The AUSM model...

  13. 76 FR 8330 - Hawaii Bottomfish and Seamount Groundfish Fisheries; Modification to Advance Notification Period...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-14

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration 50 CFR Part 665 RIN 0648-BA58 Hawaii Bottomfish and Seamount Groundfish Fisheries; Modification to Advance Notification Period for Fishery Closures...

  14. Recent advances in the chemical modification of unsaturated polymers

    NASA Technical Reports Server (NTRS)

    Schulz, D. N.; Turner, S. R.; Golub, M. A.

    1982-01-01

    The present discussion has the objective to update the most comprehensive reviews on the considered subject and to fill in the gaps of less complete, but more modern treatments. Only simple chemical functionalization or structural modification of unsaturated polymers are covered, and the literature of diene polymer modification since 1974 is emphasized. Attention is given to hydrogenation, halogenation and hydrohalogenation, cyclization, cis-trans isomerization, epoxidation, ene and other cycloaddition reactions, sulfonation, carboxylation, phosphonylation, sulfenyl chloride addition, carbene addition, metalation, and silylation. It is pointed out that modern synthetic reagents and catalysts have been advantageously employed to improve process and/or product quality. Synthetic techniques have been refined to allow the selective modification of specific polymer microstructures or blocks.

  15. Surface modification of zirconia-alumina composite ceramics

    SciTech Connect

    Ghosh, S.K.; Chatterjee, D.K.

    1994-12-31

    Surface modification of tetragonal zirconia and {alpha}-alumina composite was accomplished by diffusion of MgO during sintering at 1500{degrees}C. {alpha}-Al{sub 2}O{sub 3} powder, 2 to 60 wt%, was thoroughly mixed with 5 wt% yttria-alloyed zirconia powder, cold pressed and sintered in contact with fine MgO powder. In the diffusion zone, {alpha}-Al{sub 2}O{sub 3} was transformed to spinel, MgAl{sub 2}O{sub 4}, and transformation of tetragonal zirconia to cubic phase depended primarily on alumina concentration. The modified surface was, therefore, a composite of spinel, tetragonal (t) and/or cubic zirconia as distinguished from the core, comprised of {alpha}-Al{sub 2}O{sub 3} and t-ZrO{sub 2}. Tribological characteristics of the modified outer surface are also reported.

  16. Surface modification of multilayer graphene using Ga ion irradiation

    SciTech Connect

    Wang, Quan; Shao, Ying; Ge, Daohan; Ren, Naifei; Yang, Qizhi

    2015-04-28

    The effect of Ga ion irradiation intensity on the surface of multilayer graphene was examined. Using Raman spectroscopy, we determined that the irradiation caused defects in the crystal structure of graphene. The density of defects increased with the increase in dwell times. Furthermore, the strain induced by the irradiation changed the crystallite size and the distance between defects. These defects had the effect of doping the multilayer graphene and increasing its work function. The increase in work function was determined using contact potential difference measurements. The surface morphology of the multilayer graphene changed following irradiation as determined by atomic force microscopy. Additionally, the adhesion between the atomic force microscopy tip and sample increased further indicating that the irradiation had caused surface modification, important for devices that incorporate graphene.

  17. Rational surface silane modification for immobilizing glucose oxidase.

    PubMed

    Tian, Feibao; Guo, Yi; Lin, Feifei; Zhang, Yumei; Yuan, Qipeng; Liang, Hao

    2016-06-01

    Glucose oxidase (GOx) has many significant applications in biosensor and biocatalysis. In this study, we firstly quantitatively analyzed the binding efficiency of (3-aminopropyl) trimethoxysilane (APTES) modified onto the surface of GOx. It was found that the contents of the grafted silane did not significantly influence the relative activities and tertiary structures of all surface modified GOxs. Immobilization ratio and relative activity of all instances of APTES modified GOx increased, compared with those of native enzyme. However, good stability of immobilized GOx at extreme pH and high temperature could only be obtained when modified protein with low binding silane content. At pH 2.0, the immobilized GOx with low binding content showed a more than 600% activity, compared to the free enzyme. Therefore, rational surface modification would be beneficial to improving the activity and stability of immobilized enzyme as well as increasing loading amount. PMID:26921503

  18. Laser surface modification of stainless steels for cavitation erosion resistance

    NASA Astrophysics Data System (ADS)

    Kwok, Chi Tat

    1999-12-01

    Austenitic stainless steel UNS S31603 (Fe -17.6Cr -11.2Ni -2.5Mo -1.4Mn -0.4Si -0.03C) has higher pitting corrosion resistance but lower cavitation erosion resistance than that of UNS S30400. This is because of its lower tendency for strain induced martensitic transformation and higher stacking fault energy as compared with those of UNS S30400. In order to improve its cavitation erosion resistance, surface modification of S31603 was performed by laser surface melting and laser surface alloying using a 2-kW CW Nd-YAG laser and a 3-kW CW CO2 laser. For laser surface melting, austenitic stainless steel UNS S30400, super duplex stainless steel UNS S32760 and martensitic stainless steel UNS S42000 were also investigated for comparison purpose. For laser surface alloying, alloying materials including various elements (Co, Cr, Ni, Mo, Mn, Si & C), alloys (AlSiFe & NiCrSiB), ceramics (Si3N 4, SiC, Cr3C2, TiC, CrB & Cr2O 3) and alloys-ceramics (Co-WC, Ni-WC, Ni-Al2O3, Ni-Cr2C3) were used to modify the surface of S31603. The alloyed surface was achieved first by flame spraying or pre-placing of the alloy powder on the S31603 surface and then followed by laser surface remelting. The cavitation erosion characteristics of laser surface modified specimens in 3.5% NaCl solution at 23°C were studied by means of a 20-kHz ultrasonic vibrator at a peak-to-peak amplitude of 30 mum. In addition, their pitting corrosion behaviour was evaluated by electrochemical techniques. The microstructures, compositions, phase changes and damage mechanisms under cavitation erosion were investigated by optical microscopy, SEM, EDAX and X-ray diffractometry. Mechanical properties such as microhardness profile were also examined. The cavitation erosion resistance Re (reciprocal of the mean depth of penetration rate) of laser surface melted S31603 was found to be improved by 22% and was attributed to the existence of tensile residual stress. Improvement on the Re of S42000 was found to be 8.5 times

  19. Nanotubular surface modification of metallic implants via electrochemical anodization technique

    PubMed Central

    Wang, Lu-Ning; Jin, Ming; Zheng, Yudong; Guan, Yueping; Lu, Xin; Luo, Jing-Li

    2014-01-01

    Due to increased awareness and interest in the biomedical implant field as a result of an aging population, research in the field of implantable devices has grown rapidly in the last few decades. Among the biomedical implants, metallic implant materials have been widely used to replace disordered bony tissues in orthopedic and orthodontic surgeries. The clinical success of implants is closely related to their early osseointegration (ie, the direct structural and functional connection between living bone and the surface of a load-bearing artificial implant), which relies heavily on the surface condition of the implant. Electrochemical techniques for modifying biomedical implants are relatively simple, cost-effective, and appropriate for implants with complex shapes. Recently, metal oxide nanotubular arrays via electrochemical anodization have become an attractive technique to build up on metallic implants to enhance the biocompatibility and bioactivity. This article will thoroughly review the relevance of electrochemical anodization techniques for the modification of metallic implant surfaces in nanoscale, and cover the electrochemical anodization techniques used in the development of the types of nanotubular/nanoporous modification achievable via electrochemical approaches, which hold tremendous potential for bio-implant applications. In vitro and in vivo studies using metallic oxide nanotubes are also presented, revealing the potential of nanotubes in biomedical applications. Finally, an outlook of future growth of research in metallic oxide nanotubular arrays is provided. This article will therefore provide researchers with an in-depth understanding of electrochemical anodization modification and provide guidance regarding the design and tuning of new materials to achieve a desired performance and reliable biocompatibility. PMID:25258532

  20. Surface modification using MeV ion beams

    NASA Technical Reports Server (NTRS)

    Tombrello, T. A.

    1983-01-01

    Electronic excitation induced by MeV/amu ion beams in a variety of materials has been employed successfully for a number of applications. The examples that will be presented are: modification of the surface reflectivities of optical materials; sputter-erosion of dielectrics; and enhancement of the adhesion of thin film coatings. All of these effects arise from the loss of energy by the ion beam to electrons in the target material; the mechanisms involved are at best qualitatively understood. This paper will stress not only the exploitation of such high energy bombardment techniques but will also briefly review attempts to expose the underlying causes.

  1. Surface assessment and modification of concrete using abrasive blasting

    NASA Astrophysics Data System (ADS)

    Millman, Lauren R.

    Composite systems are applied to concrete substrates to strengthen and extend the service life. Successful restoration or rehabilitation requires surface preparation prior to the application of the overlay. Surface coatings, waterproofing systems, and other external surface applications also require surface preparation prior to application. Abrasive blast media is often used to clean and uniformly roughen the substrate. The appropriate surface roughness is necessary to facilitate a strong bond between the existing substrate and overlay. Thus, surface modification using abrasive blast media (sand and dry ice), their respective environmental effects, surface roughness characterization prior to and after blasting, and the adhesion between the substrate and overlay are the focus of this dissertation. This dissertation is comprised of an introduction, a literature review, and four chapters, the first of which addresses the environmental effects due to abrasive blasting using sand, water, and dry ice. The assessment considered four response variables: carbon dioxide (CO2) emissions, fuel and energy consumption, and project duration. The results indicated that for sand blasting and water jetting, the primary factor contributing to environmental detriment was CO22 emissions from vehicular traffic near the construction site. The second chapter is an analysis of the International Concrete Repair Institute's (ICRI) concrete surface profiles (CSPs) using 3-D optical profilometry. The primary objective was to evaluate the suitability of approximating the 3-D surface (areal) parameters with those extracted from 2-D (linear) profiles. Four profile directions were considered: two diagonals, and lines parallel and transverse to the longitudinal direction of the mold. For any CSP mold, the estimation of the 3-D surface roughness using a 2-D linear profile resulted in underestimation and overestimation errors exceeding 50%, demonstrating the inadequacy of 2-D linear profiles to

  2. Directly thiolated modification onto the surface of detonation nanodiamonds.

    PubMed

    Hsu, Ming-Hua; Chuang, Hong; Cheng, Fong-Yu; Huang, Ying-Pei; Han, Chien-Chung; Chen, Jiun-Yu; Huang, Su-Chin; Chen, Jen-Kun; Wu, Dian-Syue; Chu, Hsueh-Liang; Chang, Chia-Ching

    2014-05-28

    An efficient method for modifying the surface of detonation nanodiamonds (5 and 100 nm) with thiol groups (-SH) by using an organic chemistry strategy is presented herein. Thiolated nanodiamonds were characterized by spectroscopic techniques, and the atomic percentage of sulfur was analyzed by elemental analysis and X-ray photoelectron spectroscopy. The conjugation between thiolated nanodiamonds and gold nanoparticles was elucidated by transmission electron microscopy and UV-vis spectrometry. Moreover, the material did not show significant cytotoxicity to the human lung carcinoma cell line and may prospectively be applied in bioconjugated technology. The new method that we elucidated may significantly improve the approach to surface modification of detonation nanodiamonds and build up a new platform for the application of nanodiamonds. PMID:24766528

  3. Biocompatible benzocyclobutene-based intracortical neural implant with surface modification

    NASA Astrophysics Data System (ADS)

    Lee, Keekeun; Massia, Stephen; He, Jiping

    2005-11-01

    This paper presents the fabrication of a benzocyclobutene (BCB) polymer-based intracortical neural implant for reliable and stable long-term implant function. BCB polymer has many attractive features for chronic implant application: flexibility, biocompatibility, low moisture uptake, low dielectric constant and easy surface modification. A 2 µm thick silicon backbone layer was attached underneath a flexible BCB electrode to improve mechanical stiffness. No insertion trauma was observed during penetrating into the dura of a rat. In vitro cytotoxicity tests of the completed BCB electrode revealed no toxic effects on cultured cells. The modified BCB surface with a dextran coating showed a significant reduction in 3T3 cell adhesion and spreading, indicating that this coating has the potential for lowering protein adsorption, minimizing inflammatory cell adhesion and glial scar formation in vivo, and thereby enhancing long-term implant performance.

  4. Hydrophilic surface modification of acrylate-based biomaterials.

    PubMed

    Arnal-Pastor, M; Comín-Cebrián, S; Martínez-Ramos, C; Monleón Pradas, M; Vallés-Lluch, A

    2016-04-01

    Acrylic polymers have proved to be excellent with regard to cell adhesion, colonization and survival, in vitro and in vivo. Highly ordered and regular pore structures thereof can be produced with the help of polyamide templates, which are removed with nitric acid. This treatment converts a fraction of the ethyl acrylate side groups into acrylic acid, turning poly(ethyl acrylate) scaffolds into a more hydrophilic and pH-sensitive substrate, while its good biological performance remains intact. To quantify the extent of such a modification, and be able to characterize the degree of hydrophilicity of poly(ethyl acrylate), poly(ethyl acrylate) was treated with acid for different times (four, nine and 17 days), and compared with poly(acrylic acid) and a 90/10%wt. EA/AAc copolymer (P(EA-co-AAc)). The biological performance was also assessed for samples immersed in acid up to four days and the copolymer, and it was found that the incorporation of acidic units on the material surface was not prejudicial for cells. This surface modification of 3D porous hydrophobic scaffolds makes easier the wetting with culture medium and aqueous solutions in general, and thus represents an advantage in the manageability of the scaffolds. PMID:26767395

  5. The surface modification of stainless steel and the correlation between the surface properties and protein adsorption.

    PubMed

    Kang, Chan-Koo; Lee, Yoon-Sik

    2007-07-01

    Protein adsorption on a biomaterial surface is of great importance as it usually induces unfavorable biological cascades, with the result that much surface modification research has had to be performed in an effort to prevent this. In this study, we developed surface modification methods for stainless steel, which is a representative metal for biomedical device. The stainless steels were first smoothened to different extents by electropolishing, in order to obtain a rough or smooth surface. On these two kinds of substrates, we introduced epoxide groups to the metal surface by silanization with 3-glycidoxypropyltrimethoxysilane (GPTS). Then, various polymers such as poly(ethylene glycol) (PEG), poly(tetrahydrofuran glycol) (PTG), poly(propylene glycol) (PPG) and poly(dimethylsiloxane) (PDMS) were grafted on the silanized stainless steels. Each surface modification step was confirmed by various analytical methods. Contact angle measurement revealed that the surface hydrophilicity was controllable by polymer grafting. Root-mean-square (RMS) data of atomic force microscopy showed that surface roughness was dramatically changed by electropolishing. Based on these results, the correlation between surface properties and protein adsorption was investigated. In the protein adsorption study, we observed that all of the polymer-grafted stainless steels exhibited lower protein adsorption, when compared with bare stainless steel. Moreover, a hydrophilic and smooth surface was found to be the best of choice for decreasing the protein adsorption. PMID:17277988

  6. Atmospheric Microplasma Application for Surface Modification of Biomaterials

    NASA Astrophysics Data System (ADS)

    Shimizu, Kazuo; Fukunaga, Hodaka; Tatematsu, Shigeki; Blajan, Marius

    2012-11-01

    Atmospheric microplasma has been intensively studied for applications in various fields, since in this technology the generated field is only 1 kV (approx) under atmospheric pressure and a dielectric barrier discharge gap of 10 to 100 µm. A low discharge voltage atmospheric plasma process is an economical and effective solution for various applications such as indoor air control including sterilization, odor removal, and surface treatment, and would be suitable for medical applications in the field of plasma life sciences. In this paper, we present the application of microplasma for the surface treatment of materials used in medical fields. Moreover, a biomaterial composed of L-lactic acid is used in experiments, which can be biodecomposed in the human body after medical operations. The surface modification process was carried out with active species generated between the microplasma electrodes, which were observed by emission spectrometry. Microplasma treatment of a polymer sheet using Ar as the process gas decreased the contact angle of a water droplet at the surface of the polymer from 78.3 to 45.6° in 10 s, indicating improved surface adhesive characteristics.

  7. Surface modifications of W divertor components for EAST during exposure to high heat loads with He

    NASA Astrophysics Data System (ADS)

    Li, C.; Greuner, H.; Yuan, Y.; Zhao, S. X.; Luo, G. N.; Böswirth, B.; Fu, B. Q.; Jia, Y. Z.; Liu, X.; Liu, W.

    2015-08-01

    Flat-type W/Cu plasma-facing components have been developed for the new generation divertor of the Chinese Experimental Advanced Superconducting Tokamak. Surface modifications of such actively water-cooled W components following short and long pulse high heat loading coupled with He particle loads with fluence of 3 × 1022 m-2 have been investigated. An adiabatically loaded W block was investigated as a comparison and exposed to short pulse loads. Blistering was observed on all sample surfaces, but was less pronounced on the components than on the W block, due to the significant lower surface temperature caused by active cooling. For components, longer pulse loads gave rise to a rougher surface. Furthermore, most blisters on components are found to be less than 1 μm in diameter, with just a very few blisters larger than 1 μm, observed only in some near <1 1 1> grains.

  8. Surface charging, discharging and chemical modification at a sliding contact

    SciTech Connect

    Singh, S. V.; Kusano, Y.; Morgen, P.; Michelsen, P. K.

    2012-04-15

    Electrostatic charging, discharging, and consequent surface modification induced by sliding dissimilar surfaces have been studied. The surface-charge related phenomena were monitored by using a home-built capacitive, non-contact electrical probe, and the surface chemistry was studied by X-ray photoelectron spectroscopy (XPS). The experiments were performed on the disk surface of a ball-on-rotating-disk apparatus; using a glass disk and a Teflon (polytetrafluoroethylene) ball arrangement, and a polyester disks and a diamondlike carbon (DLC) coated steel ball arrangement. The capacitive probe is designed to perform highly resolved measurements, which is sensitive to relative change in charge density on the probed surface. For glass and Teflon arrangement, electrical measurements show that the ball track acquires non-uniform charging. Here not only the increase in charge density, but interestingly, increase in number of highly charged regions on the ball track was resolved. Threefold increase in the number of such highly charged regions per cycle was detected immediately before the gas breakdown-like incidences compared to that of other charge/discharge incidences at a fixed disk rotation speed. We are also able to comment on the behavior and the charge decay time in the ambient air-like condition, once the sliding contact is discontinued. XPS analysis showed a marginal deoxidation effect on the polyester disks due to the charging and discharging of the surfaces. Moreover, these XPS results clearly indicate that the wear and friction (sliding without charging) on the surface can be discarded from inducing such a deoxidation effect.

  9. Surface charging, discharging and chemical modification at a sliding contact

    NASA Astrophysics Data System (ADS)

    Singh, S. V.; Kusano, Y.; Morgen, P.; Michelsen, P. K.

    2012-04-01

    Electrostatic charging, discharging, and consequent surface modification induced by sliding dissimilar surfaces have been studied. The surface-charge related phenomena were monitored by using a home-built capacitive, non-contact electrical probe, and the surface chemistry was studied by X-ray photoelectron spectroscopy (XPS). The experiments were performed on the disk surface of a ball-on-rotating-disk apparatus; using a glass disk and a Teflon (polytetrafluoroethylene) ball arrangement, and a polyester disks and a diamondlike carbon (DLC) coated steel ball arrangement. The capacitive probe is designed to perform highly resolved measurements, which is sensitive to relative change in charge density on the probed surface. For glass and Teflon arrangement, electrical measurements show that the ball track acquires non-uniform charging. Here not only the increase in charge density, but interestingly, increase in number of highly charged regions on the ball track was resolved. Threefold increase in the number of such highly charged regions per cycle was detected immediately before the gas breakdown-like incidences compared to that of other charge/discharge incidences at a fixed disk rotation speed. We are also able to comment on the behavior and the charge decay time in the ambient air-like condition, once the sliding contact is discontinued. XPS analysis showed a marginal deoxidation effect on the polyester disks due to the charging and discharging of the surfaces. Moreover, these XPS results clearly indicate that the wear and friction (sliding without charging) on the surface can be discarded from inducing such a deoxidation effect.

  10. Regolith Advanced Surface Systems Operations Robot Excavator

    NASA Technical Reports Server (NTRS)

    Mueller, Robert P.; Smith, Jonathan D.; Ebert, Thomas; Cox, Rachel; Rahmatian, Laila; Wood, James; Schuler, Jason; Nick, Andrew

    2013-01-01

    The Regolith Advanced Surface Systems Operations Robot (RASSOR) excavator robot is a teleoperated mobility platform with a space regolith excavation capability. This more compact, lightweight design (<50 kg) has counterrotating bucket drums, which results in a net-zero reaction horizontal force due to the self-cancellation of the symmetrical, equal but opposing, digging forces.

  11. Roles of the reproductive tract in modifications of the sperm membrane surface

    PubMed Central

    KUO, Yu-Wen; LI, Sheng-Hsiang; MAEDA, Kei-Ichiro; GADELLA, Bart M.; TSAI, Pei Shiue J.

    2016-01-01

    Successful fertilization requires viable and functional spermatozoa to recognize and fuse with the oocyte. In most mammalian species, mature spermatozoa are not capable of fertilizing the oocytes immediately after ejaculation. However, unlike somatic cells, spermatozoa, after leaving the testis, are transcriptionally and translationally silent; therefore, upon completion of spermiogenesis, spermatozoa carry only a minimal amount of essential proteins on their membranes as well as within their restricted volume of cytoplasm. To develop into a fully functional and competent sperm that is capable of successful fertilization, modifications of the sperm membrane surface during its transit in the reproductive tracts is critical. These post-spermatogenesis modifications advance the maturation of epididymal spermatozoa. In addition, components secreted into the lumen of the reproductive tracts that are later added onto the sperm membrane surface also regulate (inhibit or activate) the functions of the spermatozoa. This acquisition of additional proteins from the reproductive tracts may compensate for the inactivity of morphologically mature spermatozoa. In this review, we discuss the contributions of the male and female genital tracts to modifications of the sperm membrane surface at different stages of fertilization. PMID:27009019

  12. Surface modification of closed plastic bags for adherent cell cultivation

    NASA Astrophysics Data System (ADS)

    Lachmann, K.; Dohse, A.; Thomas, M.; Pohl, S.; Meyring, W.; Dittmar, K. E. J.; Lindenmeier, W.; Klages, C.-P.

    2011-07-01

    In modern medicine human mesenchymal stem cells are becoming increasingly important. However, a successful cultivation of this type of cells is only possible under very specific conditions. Of great importance, for instance, are the absence of contaminants such as foreign microbiological organisms, i.e., sterility, and the chemical functionalization of the ground on which the cells are grown. As cultivation of these cells makes high demands, a new procedure for cell cultivation has been developed in which closed plastic bags are used. For adherent cell growth chemical functional groups have to be introduced on the inner surface of the plastic bag. This can be achieved by a new, atmospheric-pressure plasma-based method presented in this paper. The method which was developed jointly by the Fraunhofer IST and the Helmholtz HZI can be implemented in automated equipment as is also shown in this contribution. Plasma process gases used include helium or helium-based gas mixtures (He + N2 + H2) and vapors of suitable film-forming agents or precursors such as APTMS, DACH, and TMOS in helium. The effect of plasma treatment is investigated by FTIR-ATR spectroscopy as well as surface tension determination based on contact angle measurements and XPS. Plasma treatment in nominally pure helium increases the surface tension of the polymer foil due to the presence of oxygen traces in the gas and oxygen diffusing through the gas-permeable foil, respectively, reacting with surface radical centers formed during contact with the discharge. Primary amino groups are obtained on the inner surface by treatment in mixtures with nitrogen and hydrogen albeit their amount is comparably small due to diffusion of oxygen through the gas-permeable bag, interfering with the plasma-amination process. Surface modifications introducing amino groups on the inner surface turned out to be most efficient in the promotion of cell growth.

  13. Direct modification of silicon surface by nanosecond laser interference lithography

    NASA Astrophysics Data System (ADS)

    Wang, Dapeng; Wang, Zuobin; Zhang, Ziang; Yue, Yong; Li, Dayou; Maple, Carsten

    2013-10-01

    Periodic and quasi-periodic structures on silicon surface have numerous significant applications in photoelectronics and surface engineering. A number of technologies have been developed to fabricate the structures in various research fields. In this work, we take the strategy of direct nanosecond laser interference lithography technology, and focus on the silicon material to create different well-defined surface structures based on theoretical analysis of the formation of laser interference patterns. Two, three and four-beam laser interference systems were set up to fabricate the grating, regular triangle and square structures on silicon surfaces, respectively. From the AFM micrographs, the critical features of structures have a dependence on laser fluences. For a relative low laser fluence, grating and dot structures formed with bumps due to the Marangoni Effect. With the increase of laser fluences, melt and evaporation behaviors can be responsible for the laser modification. By properly selecting the process parameters, well-defined grating and dot structures can been achieved. It can be demonstrated that direct laser interference lithography is a facile and efficient technology with the advantage of a single process procedure over macroscale areas for the fabrication of micro and nano structures.

  14. Surface modification of multiwall carbon nanotubes by sulfonitric treatment

    NASA Astrophysics Data System (ADS)

    Gómez, Sofía; Rendtorff, Nicolás M.; Aglietti, Esteban F.; Sakka, Yoshio; Suárez, Gustavo

    2016-08-01

    Carbon nanotubes are widely used for electronic, mechanical, and optical devices due to their unique structural and quantum characteristics. The species generated by oxidation on the surface of these materials permit binding new reaction chains, which improves the dispersibility, processing and compatibility with other materials. Even though different acid treatments and applications of these CNT have been reported, relatively few research studies have focused on the relationship between the acid treatment and the formation of nanodefects, specific oxidized species or CNT surface defects. In this work, multiwall carbon nanotube (MWCNT) oxidation at 90 °C was characterized in order to determine the acid treatment effect on the surface. It was found that oxidized species are already present in MWCNT without an acid treatment, but there are not enough to cause water-based dispersion. The species were identified and quantified by infrared spectroscopy and X-ray photoelectron spectroscopy. Also, transmission electron microscopy observations showed not only modifications of the oxidized species, but also morphological damage on the surfaces of MWCNT after being subjected to the acid treatment. This effect was also confirmed by Raman spectroscopy. The acid treatment generates higher oxidized species, decreasing the zeta potential in the whole pH range.

  15. The Effect of Titanium Surface Modifications on Dental Implant Osseointegration.

    PubMed

    Annunziata, Marco; Guida, Luigi

    2015-01-01

    The use of titanium dental implants has consistently changed the way of rehabilitating patients in modern dentistry and can count on high long-term survival and success rates. With respect to its introduction in the late 1960s, clinical indications for implant therapy have been significantly extended and optimal results have been achieved, even in clinical conditions formerly considered as unfavourable. Such evolution owes a lot to the significant progress made in the field of titanium surfaces. The topographical and chemical modification of traditional titanium surfaces has led to a real epochal shift in implant dentistry. Depending on the type and characteristics of the surface treatment applied, a wide range of implants has been produced, which have contributed to the success but also increased the risk of confusion in implant selection criteria for the clinician. This chapter, which provides an updated analysis of the relevant literature, the characteristics of modern implant surfaces, the biological principles underlying their role in promoting osseointegration and the scientific evidence about their clinical use are analyzed and presented. PMID:26201277

  16. Surface Modification of Polymer Substrates by Oxygen Ion Irradiation

    SciTech Connect

    Takaoka, G. H.; Ryuto, H.; Araki, R.; Yakushiji, T.

    2008-11-03

    Oxygen cluster ions and/or monomer ions were used for the sputtering and the surface modification of polymers such as polycarbonate (PC) and polyethylene terephthalate (PET). For the case of oxygen cluster ion irradiation, the sputtered depth increased with increase of the acceleration voltage, and the sputtering yield was much larger than that by the monomer ion irradiation. The sputtered particles represented the polymer structure, which indicated that the bond scission by the cluster ion irradiation resulted in an ejection of monomer molecule through the intermolecular collision. On the other hand, for the oxygen monomer ion irradiation, the implanted depth increased with increase of the acceleration voltage, and the bond scission occurred at the deep region through the binary collision with the high energetic ions. Therefore, the sputtering yield for the polymer surfaces decreased, and the sputtering effect became very small. Furthermore, the simultaneous use of oxygen cluster and monomer ions was more effective for oxidation of the PET surfaces rather than the monomer ion irradiation or the cluster ion irradiation. As a result, the contact angle measurement showed that the wettability of the PET surfaces irradiated by the simultaneous use of oxygen cluster and monomer ions was much enhanced.

  17. A bioinspired strategy for surface modification of silica nanoparticles

    NASA Astrophysics Data System (ADS)

    Tian, Jianwen; Zhang, Haoxuan; Liu, Meiying; Deng, Fengjie; Huang, Hongye; Wan, Qing; Li, Zhen; Wang, Ke; He, Xiaohui; Zhang, Xiaoyong; Wei, Yen

    2015-12-01

    Silica nanoparticles have become one of the most promising nanomaterials for a vast of applications. In this work, a novel strategy for surface modification of silica nanoparticles has been developed for the first time via combination of mussel inspired chemistry and Michael addition reaction. In this procedure, thin polydopamine (PDA) films were first coated on the bare silica nanoparticles via self-polymerization of dopamine in alkaline condition. And then amino-containing polymers were introduced onto the PDA coated silica nanoparticles through Michael addition reaction, that are synthesized from free radical polymerization using poly(ethylene glycol) methyl methacrylate (PEGMA) and N-(3-aminopropyl) methacrylamide (NAPAM) as monomers and ammonium persulfate as the initiator. The successful modification of silica nanoparticles was evidenced by a series of characterization techniques. As compared with the bare silica nanoparticles, the polymers modified silica nanoparticles showed remarkable enhanced dispersibility in both aqueous and organic solution. This strategy is rather simple, effective and versatile. Therefore, it should be of specific importance for further applications of silica nanoparticles and will spark great research attention of scientists from different fields.

  18. Laser surface modification of ultra-high-molecular-weight polyethylene (UHMWPE) for biomedical applications

    NASA Astrophysics Data System (ADS)

    Riveiro, A.; Soto, R.; del Val, J.; Comesaña, R.; Boutinguiza, M.; Quintero, F.; Lusquiños, F.; Pou, J.

    2014-05-01

    Ultra-high-molecular-weight polyethylene (UHMWPE) is a synthetic polymer used for biomedical applications because of its high impact resistance, ductility and stability in contact with physiological fluids. Therefore, this material is being used in human orthopedic implants such as total hip or knee replacements. Surface modification of this material relates to changes on its chemistry, microstructure, roughness, and topography, all influencing its biological response. Surface treatment of UHMWPE is very difficult due to its high melt viscosity. This work presents a systematic approach to discern the role of different laser wavelengths (λ = 1064, 532, and 355 nm) on the surface modification of carbon coated UHMWPE samples. Influence of laser processing conditions (irradiance, pulse frequency, scanning speed, and spot overlapping) on the surface properties of this material was determined using an advanced statistical planning of experiments. A full factorial design of experiments was used to find the main effects of the processing parameters. The obtained results indicate the way to maximize surface properties which largely influence cell-material interaction.

  19. CARBOSURF™ Surface Modification Technology for Charge Dissipative and Radio-Transparent GEO Durable Space Polymers

    NASA Astrophysics Data System (ADS)

    Iskanderova, Zelina; Kleiman, Jacob I.; Issoupov, Vitali; Bussieres, François

    2009-01-01

    A new surface modification technology has been developed to make the surface of a number of advanced thin polymer films charge dissipative and, at the same time, RF transmissive, with or without influence on the thermal optical properties, as required for specific applications. This ion beam treatment for surface carbonization technology, tentatively named CARBOSURF™, has been successfully applied to hydrocarbon thin space polymer films, Kapton HN polyimide and Upilex S, as well as tried for space-related partially fluorinated polymers CP-1, clear and filled with white pigment. Ground-based simulation testing has been conducted on selected pristine and surface-modified space-related thin polymer film specimens to estimate the space life of those materials in GEO space conditions. Combined proton, electron, and UV exposure has been used for GEO simulating testing. The performed GEO simulated testing has shown high stability of the CARBOSURF™-treated polymer films for multi-year applications in GEO environment. The treatment was achieved using moderate-energy and low-energy intensive technological ion beam sources of noble gases and was shown to be transferrable for industrial implementation and scale-up. The developed ion beam treatment surface modification technology has a number of strong innovative components, and the treated space polymer films may be used in many space applications.

  20. Recent advances in maize nuclear proteomic studies reveal histone modifications.

    PubMed

    Casati, Paula

    2012-01-01

    The nucleus of eukaryotic organisms is highly dynamic and complex, containing different types of macromolecules including DNA, RNA, and a wide range of proteins. Novel proteomic applications have led to a better overall determination of nucleus protein content. Although nuclear plant proteomics is only at the initial phase, several studies have been reported and are summarized in this review using different plants species, such as Arabidopsis thaliana, rice, cowpea, onion, garden cress, and barrel clover. These include the description of the total nuclear or phospho-proteome (i.e., Arabidopsis, cowpea, onion), or the analysis of the differential nuclear proteome under different growth environments (i.e., Arabidopsis, rice, cowpea, onion, garden cress, and barrel clover). However, only few reports exist on the analysis of the maize nuclear proteome or its changes under various conditions. This review will present recent data on the study of the nuclear maize proteome, including the analysis of changes in posttranslational modifications in histone proteins. PMID:23248634

  1. Upconversion Nanoparticles: Synthesis, Surface Modification, and Biological Applications

    PubMed Central

    Wang, Meng; Abbineni, Gopal; Clevenger, April; Mao, Chuanbin; Xu, Shukun

    2011-01-01

    New generation fluorophores, also termed upconversion nanoparticles (UCNPs), have the ability to convert near infrared radiations with lower energy into visible radiations with higher energy via a non-linear optical process. Recently, these UCNPs have evolved as alternative fluorescent labels to traditional fluorophores, showing great potential for imaging and biodetection assays in both in vitro and in vivo applications. UCNPs exhibit unique luminescent properties, including high penetration depth into tissues, low background signals, large Stokes shifts, sharp emission bands, and high resistance to photo-bleaching, making UCNPs an attractive alternative source for overcoming current limitations in traditional fluorescent probes. In this review, we discuss the recent progress in the synthesis and surface modification of rare earth doped UCNPs with a specific focus on their biological applications. PMID:21419877

  2. Surface modification of silicon nitride powder with aluminum

    SciTech Connect

    Han, K.R.; Lim, C.S.; Hong, M.J.; Choi, S.K.; Kwon, S.H.

    1996-02-01

    Surface modification of Si{sub 3}N{sub 4} with alumina was tried. It was achieved by simply mixing Si{sub 3}N{sub 4} powder with an alumina sol up to {approximately}2 wt% as alumina in an aqueous medium, dried, and followed by calcination at 400 C for 1 h. A TEM micrograph showed a coating layer of {approximately} 15 nm thickness. The isoelectric point of the modified Si{sub 3}N{sub 4} powder with porous alumina was at 0H 7.8, which is different from 5.8 and 8.6 for Si{sub 3}N{sub 4} and amorphous alumina, respectively.

  3. Effective modification of particle surface properties using ultrasonic water mist.

    PubMed

    Genina, Natalja; Räikkönen, Heikki; Heinämäki, Jyrki; Antikainen, Osmo; Siiriä, Simo; Veski, Peep; Yliruusi, Jouko

    2009-01-01

    The goal of the present study was to design a new technique to modify particle surface properties and, through that, to improve flowability of poorly flowing drug thiamine hydrochloride and pharmaceutical sugar lactose monohydrate of two different grades. The powdered particles were supplied by a vibratory feeder and exposed to an instantaneous effect of water mist generated from an ultrasound nebulizer. The processed and original powders were evaluated with respect to morphology (scanning electron microscopy, atomic force microscopy, and spatial filtering technique), flow, and solid state properties. It was found that rapid exposition of pharmaceutical materials by water mist resulted in the improvement of powder technical properties. The evident changes in flowability of coarser lactose were obviously due to smoothing of particle surface and decreasing in the level of fines with very slight increment in particle size. The changes in thiamine powder flow were mainly due to narrowing in particle size distribution where the tendency for better flow of finer lactose was related to surface and size modifications. The aqueous mist application did not cause any alteration of the crystal structures of the studied materials. The proposed water mist treatment technique appears to be a robust, rapid, and promising tool for the improvement of the technological properties of pharmaceutical powders. PMID:19288203

  4. Gold coated magnetic nanoparticles: from preparation to surface modification for analytical and biomedical applications.

    PubMed

    Moraes Silva, Saimon; Tavallaie, Roya; Sandiford, Lydia; Tilley, Richard D; Gooding, J Justin

    2016-06-18

    Gold coated magnetic nanoparticles (Au@MNPs) have become increasingly interesting to nanomaterial scientists due to their multifunctional properties and their potential in both analytical chemistry and nanomedicine. The past decade has seen significant progress in the synthesis and surface modification of Au@MNPs. This progress is based on advances in the preparation and characterization of iron/iron oxide nanocrystals with the required surface functional groups. In this critical review, we summarize recent developments in the methods of preparing Au@MNPs, surface functionalization and their application in analytical sensing and biomedicine. We highlight some of the remaining major challenges, as well as the lessons learnt when working with Au@MNPs. PMID:27182032

  5. Nanoparticle-Based Surface Modifications for Microtribology Control and Superhydrophobicity

    NASA Astrophysics Data System (ADS)

    Hurst, Kendall Matthew

    2010-11-01

    contact" between two contacting surfaces. The studies found that AuNP thin films produced using the lowest initial concentrations of nanoparticles in solution produced estimated real contact areas of around 1%, reducing the adhesion of oxidized Si (100) surfaces from about 37 mJ/m2 down to 0.02 mJ/m 2. In addition, the reducing in real contact area effectively reduced the coefficient of static friction between silicon-based surfaces due to the extremely high dependence of stiction on friction and wear at the microscale. This work also investigated methods of permanently immobilizing AuNP-based films on the silicon surfaces of microstructures in order to create more mechanically robust coatings. The use of organic self-assembled monolayers (SAMs) functionalized with tail-groups known to bond to metallic surfaces were effective in producing much more durable coatings as opposed to non-immobilized AuNP films. Chemical vapor deposition (CVD) techniques were also used to coat rough AuNP films with very thin films of silica (SiO2) to create a robust, rough surface. This method was also very effective in creating a durable coating which is capable of reducing the adhesion energy and friction between two microscale surfaces for extended periods of time. Similar CVD techniques were also used to begin investigating the production of alumina nanoparticle-based superhydrophobic films for use in consumer electronics. Overall, the work presented in this dissertation illustrates that engineered nanoparticle-based surface modifications can be extremely effective in the reduction of the inherent interfacial phenomena that exist on microfabricated systems. This work is can potentially lead us into a new age of the miniaturization of mechanical and electronic devices.

  6. Plasma surface modification and hydrophobic barrier coating of paper

    NASA Astrophysics Data System (ADS)

    Sahin, Halil Turgut

    2001-07-01

    Development of new technologies for production of alternative paper properties with minimal environmental hazards was the goal of this project. In this study, the utilization of various chemicals under radio frequency (RF) plasma environments was investigated for creation of hydrophobic barrier properties and deposition of electrically conductive conjugated thin layers on the surface of paper. Four basic approaches have been utilized to impart hydrophobic barriers to the paper without affecting bulk properties; argon plasma treatment after Teflon-like chemical; 1,1,1,2 tetrafluoroethane (TFE) predeposition, carbon tetrafluoride (CF4) plasma treatment after TFE pre-deposition, carbon tetrafluoride plasma treatment alone and octamethylcyclotetrasiloxane (OMCTSO) plasma treatment of paper under an RF-glow discharge. The chosen chemicals were found to enhance the properties of the paper substrates and surface analysis aided explanation of the mechanism of hydrophobic barrier improvements on paper. An attempt was also made to prepare oriented thin films of pi-conjugated polymers on paper surfaces with a pulsed plasma technique for incorporation of electrically conductive layers. Progressive changes in composition, with varying plasma duty cycles during the plasma polymerization, were observed with thiophene. The results of this study provide additional support for the unusually good control of film chemistry available via the pulsed plasma technique. Electrical conductivity measurements indicated that fragmented thiophene films were obtained under mild plasma conditions, but the discontinuous thiophene film was found to be oriented. The electrical behavior of the thiophene derived deposited layer was dramatically improved with chemical doping. Correlation of the changes of paper surface properties with changes in plasma parameters are partially explained by based on surface chemistry, although other structural features of the paper morphology were also affected to some

  7. Advanced oxidation process sanitization of eggshell surfaces.

    PubMed

    Gottselig, Steven M; Dunn-Horrocks, Sadie L; Woodring, Kristy S; Coufal, Craig D; Duong, Tri

    2016-06-01

    The microbial quality of eggs entering the hatchery represents an important critical control point for biosecurity and pathogen reduction programs in integrated poultry production. The development of safe and effective interventions to reduce microbial contamination on the surface of eggs will be important to improve the overall productivity and microbial food safety of poultry and poultry products. The hydrogen peroxide (H2O2) and ultraviolet (UV) light advanced oxidation process is a potentially important alternative to traditional sanitizers and disinfectants for egg sanitation. The H2O2/UV advanced oxidation process was demonstrated previously to be effective in reducing surface microbial contamination on eggs. In this study, we evaluated treatment conditions affecting the efficacy of H2O2/UV advanced oxidation in order to identify operational parameters for the practical application of this technology in egg sanitation. The effect of the number of application cycles, UV intensity, duration of UV exposure, and egg rotation on the recovery of total aerobic bacteria from the surface of eggs was evaluated. Of the conditions evaluated, we determined that reduction of total aerobic bacteria from naturally contaminated eggs was optimized when eggs were sanitized using 2 repeated application cycles with 5 s exposure to 14 mW cm(-2) UV light, and that rotation of the eggs between application cycles was unnecessary. Additionally, using these optimized conditions, the H2O2/UV process reduced Salmonella by greater than 5 log10 cfu egg(-1) on the surface of experimentally contaminated eggs. This study demonstrates the potential for practical application of the H2O2/UV advanced oxidation process in egg sanitation and its effectiveness in reducing Salmonella on eggshell surfaces. PMID:27030693

  8. An overview of advanced surface engineering technologies for protection against wear

    SciTech Connect

    Seitzman, L.E.

    1995-12-31

    Advanced engineering processes used to produce wear-resistant surfaces are reviewed. These include coating techniques, such as thermal spray, sol-gel, physical vapor deposition, and plasma-assisted chemical vapor deposition. Surface modification treatments such as ion implantation, ion beam mixing, and centrifugal casting, are also considered. The coating techniques of evaporation, plasma-assisted deposition, and ion-beam-assisted deposition are used to examine the optimization of process complexity and control. Examples of commercial facilities and applications for advanced surface engineering are also described. Two issues affecting the expansion of commercial opportunities for surface engineering -- quality control and meaningful surface engineering properties -- are discussed. 67 refs., 5 figs.

  9. Nanoscale surface modification of Mt. Etna volcanic ashes

    NASA Astrophysics Data System (ADS)

    Barone, G.; Mazzoleni, P.; Corsaro, R. A.; Costagliola, P.; Di Benedetto, F.; Ciliberto, E.; Gimeno, D.; Bongiorno, C.; Spinella, C.

    2016-02-01

    Ashes emitted during volcanic explosive activity present peculiar surface chemical and mineralogical features related in literature to the interaction in the plume of solid particles with gases and aerosols. The compositional differences of magmas and gases, the magnitude, intensity and duration of the emission and the physical condition during the eruption, strongly influence the results of the modification processes. Here we report the characterization of the products emitted during the 2013 paroxysmal activity of Mt. Etna. The surface features of the ash particles were investigated through X-ray photoelectron spectroscopy (XPS) and Transmission electron microscopy (TEM) allowing the analysis at nanometer scale. TEM images showed on the surface the presence of composite structures formed by Ca, Mg and Na sulphates and halides and of droplets and crystals of chlorides; nanometric magnesioferrite and metallic iron dendrites are observable directly below the surface. From the chemical point of view, the most external layer of the volcanic glassy particles (<5 nm), analysed by XPS, presents depletion in Si, Mg, Ca, Na and K and strong enrichment in volatile elements especially F and S, with respect to the inner zone, which represents the unaltered counterpart. Below this external layer, a transition glassy shell (thick 50-100 nm) is characterized by Fe, Mg and Ca enrichments with respect to the inner zone. We propose that the ash particle surface composition is the result of a sequence of events which start at shallow depth, above the exsolution surface, where gas bubbles nucleate and the interfaces between bubbles and melt represent proto-surfaces of future ash particles. Enrichment of Ca, Mg and Fe and halides may be due to the early partition of F and Cl in the gas phase and their interaction with the melt layer located close to the bubbles. Furthermore the formation of volatile SiF4 and KF explain the observed depletion of Si and K. The F enrichment in the

  10. Self-assembling triblock proteins for biofunctional surface modification

    NASA Astrophysics Data System (ADS)

    Fischer, Stephen E.

    of the triblock protein hydrogels, and the ease of introducing multiple functionalities to a substrate surface, a surface coating is tailored for neural stem cell culture in order to improve proliferation on the scaffold, while maintaining the stem cell phenotype. These studies demonstrate the unique advantages of genetic engineering over traditional techniques for surface modification. In addition to their unmatched sequence fidelity, recombinant proteins can easily be modified with bioactive ligands and their organization into coherent, supramolecular structures mimics natural self-assembly processes.

  11. Automatic braking system modification for the Advanced Transport Operating Systems (ATOPS) Transportation Systems Research Vehicle (TSRV)

    NASA Technical Reports Server (NTRS)

    Coogan, J. J.

    1986-01-01

    Modifications were designed for the B-737-100 Research Aircraft autobrake system hardware of the Advanced Transport Operating Systems (ATOPS) Program at Langley Research Center. These modifications will allow the on-board flight control computer to control the aircraft deceleration after landing to a continuously variable level for the purpose of executing automatic high speed turn-offs from the runway. A bread board version of the proposed modifications was built and tested in simulated stopping conditions. Test results, for various aircraft weights, turnoff speed, winds, and runway conditions show that the turnoff speeds are achieved generally with errors less than 1 ft/sec.

  12. Advanced Materials for Neural Surface Electrodes

    PubMed Central

    Schendel, Amelia A.; Eliceiri, Kevin W.; Williams, Justin C.

    2015-01-01

    Designing electrodes for neural interfacing applications requires deep consideration of a multitude of materials factors. These factors include, but are not limited to, the stiffness, biocompatibility, biostability, dielectric, and conductivity properties of the materials involved. The combination of materials properties chosen not only determines the ability of the device to perform its intended function, but also the extent to which the body reacts to the presence of the device after implantation. Advances in the field of materials science continue to yield new and improved materials with properties well-suited for neural applications. Although many of these materials have been well-established for non-biological applications, their use in medical devices is still relatively novel. The intention of this review is to outline new material advances for neural electrode arrays, in particular those that interface with the surface of the nervous tissue, as well as to propose future directions for neural surface electrode development. PMID:26392802

  13. Surface-defect induced modifications in the optical properties of α-MnO2 nanorods

    NASA Astrophysics Data System (ADS)

    John, Reenu Elizabeth; Chandran, Anoop; Thomas, Marykutty; Jose, Joshy; George, K. C.

    2016-03-01

    The science of defect engineering via surface tuning opens a new route to modify the inherent properties of nanomaterials for advanced functional and practical applications. In this work, two independent synthesis methods (hydrothermal and co-precipitation) are adopted to fabricate α-MnO2 nanorods with different defect structures so as to understand the effect of surface modifications on their optical properties. The crystal structure and morphology of samples are investigated with the aid of X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). Atomic composition calculated from energy dispersive spectroscopy (EDS) confirms non-stoichiometry of the samples. The surface properties and chemical environment are thoroughly studied using X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) analysis. Bond angle variance and bond valence sum are determined to validate distortions in the basic MnO6 octahedron. The surface studies indicate that the concentration of Jahn-Teller manganese (III) (Mn3+) ion in the samples differ from each other which results in their distinct properties. Band structure modifications due to Jahn-Teller distortion are examined with the aid of ultraviolet-visible (UV) reflectance and photoluminescence (PL) studies. The dual peaks obtained in derivative spectrum conflict the current concept on the bandgap energy of MnO2. These studies suggest that emission lines from the samples can be strongly modified by selectively varying their defect density.

  14. Designing Pulse Laser Surface Modification of H13 Steel Using Response Surface Method

    NASA Astrophysics Data System (ADS)

    Aqida, S. N.; Brabazon, D.; Naher, S.

    2011-01-01

    This paper presents a design of experiment (DOE) for laser surface modification process of AISI H13 tool steel in achieving the maximum hardness and minimum surface roughness at a range of modified layer depth. A Rofin DC-015 diffusion-cooled CO2 slab laser was used to process AISI H13 tool steel samples. Samples of 10 mm diameter were sectioned to 100 mm length in order to process a predefined circumferential area. The parameters selected for examination were laser peak power, overlap percentage and pulse repetition frequency (PRF). The response surface method with Box-Behnken design approach in Design Expert 7 software was used to design the H13 laser surface modification process. Metallographic study and image analysis were done to measure the modified layer depth. The modified surface roughness was measured using two-dimensional surface profilometer. The correlation of the three laser processing parameters and the modified surface properties was specified by plotting three-dimensional graph. The hardness properties were tested at 981 mN force. From metallographic study, the laser modified surface depth was between 37 μm and 150 μm. The average surface roughness recorded from the 2D profilometry was at a minimum value of 1.8 μm. The maximum hardness achieved was between 728 and 905 HV0.1. These findings are significant to modern development of hard coatings for wear resistant applications.

  15. Designing Pulse Laser Surface Modification of H13 Steel Using Response Surface Method

    SciTech Connect

    Aqida, S. N.; Brabazon, D.; Naher, S.

    2011-01-17

    This paper presents a design of experiment (DOE) for laser surface modification process of AISI H13 tool steel in achieving the maximum hardness and minimum surface roughness at a range of modified layer depth. A Rofin DC-015 diffusion-cooled CO{sub 2} slab laser was used to process AISI H13 tool steel samples. Samples of 10 mm diameter were sectioned to 100 mm length in order to process a predefined circumferential area. The parameters selected for examination were laser peak power, overlap percentage and pulse repetition frequency (PRF). The response surface method with Box-Behnken design approach in Design Expert 7 software was used to design the H13 laser surface modification process. Metallographic study and image analysis were done to measure the modified layer depth. The modified surface roughness was measured using two-dimensional surface profilometer. The correlation of the three laser processing parameters and the modified surface properties was specified by plotting three-dimensional graph. The hardness properties were tested at 981 mN force. From metallographic study, the laser modified surface depth was between 37 {mu}m and 150 {mu}m. The average surface roughness recorded from the 2D profilometry was at a minimum value of 1.8 {mu}m. The maximum hardness achieved was between 728 and 905 HV{sub 0.1}. These findings are significant to modern development of hard coatings for wear resistant applications.

  16. Surface modification of nickel based alloys for improved oxidation resistance

    SciTech Connect

    Jablonski, Paul D.; Alman, David E.

    2005-02-01

    The present research is aimed at the evaluation of a surface modification treatment to enhance the high temperature stability of nickel-base superalloys. A low Coefficient Thermal Expansion (CTE ~12.5x10-6/°C) alloy based on the composition (in weight %) of Ni-22Mo-12.5Cr was produced by Vacuum Induction Melting and Vacuum Arc Melting and reduced to sheet by conventional thermal-mechanical processing. A surface treatment was devised to enhance the oxidation resistance of the alloys at high temperature. Oxidation tests (in dry and wet air; treated and untreated) were conducted 800°C to evaluate the oxidation resistance of the alloys. The results were compared to the behavior of Haynes 230 (Ni-22Cr) in the treated and untreated conditions. The treatment was not very effective for Haynes 230, as this alloy had similar oxidation behavior in both the treated and untreated conditions. However, the treatment had a significant effect on the behavior of the low CTE alloy. At 800°C, the untreated Ni-12.5Cr alloy was 5 times less oxidation resistant than Haynes 230. However, in the treated condition, the Ni-12.5Cr alloy had comparable oxidation resistance to the Haynes 230 alloy.

  17. Climate change due to anthropogenic surface albedo modification

    SciTech Connect

    Potter, G.L.; Ellsaesser, H.W.; MacCracken, M.C.; Ellis, J.S.; Luther, F.M.

    1980-02-01

    Using a statistical dynamic climate model with more realistic surface albedo changes than used in previous experiments, we have conducted a numerical experiment combining desertification of the Sahara and deforestation of the tropical rain forest. Over an area of 9 x 10/sup 6/ km/sup 2/ at 20/sup 0/N the desert albedo was increased from 0.16 to 0.35 and over 7 x 10/sup 6/ km/sup 2/ at the equator and 10/sup 0/S the rain forest albedo was increased from 0.07 to 0.16. While the most significant direct climatic responses were observed in the modified zones, high northern latitudes exhibited the greatest cooling through activation of the ice-albedo feedback process. In contrast to Sagan et al., this experiment suggests that anthropogenic modification of surface albedo over the past few thousand years has had an impact on global climate which is likely quite small and probably undetectable.

  18. Design of surface modifications for nanoscale sensor applications.

    PubMed

    Reimhult, Erik; Höök, Fredrik

    2015-01-01

    Nanoscale biosensors provide the possibility to miniaturize optic, acoustic and electric sensors to the dimensions of biomolecules. This enables approaching single-molecule detection and new sensing modalities that probe molecular conformation. Nanoscale sensors are predominantly surface-based and label-free to exploit inherent advantages of physical phenomena allowing high sensitivity without distortive labeling. There are three main criteria to be optimized in the design of surface-based and label-free biosensors: (i) the biomolecules of interest must bind with high affinity and selectively to the sensitive area; (ii) the biomolecules must be efficiently transported from the bulk solution to the sensor; and (iii) the transducer concept must be sufficiently sensitive to detect low coverage of captured biomolecules within reasonable time scales. The majority of literature on nanoscale biosensors deals with the third criterion while implicitly assuming that solutions developed for macroscale biosensors to the first two, equally important, criteria are applicable also to nanoscale sensors. We focus on providing an introduction to and perspectives on the advanced concepts for surface functionalization of biosensors with nanosized sensor elements that have been developed over the past decades (criterion (iii)). We review in detail how patterning of molecular films designed to control interactions of biomolecules with nanoscale biosensor surfaces creates new possibilities as well as new challenges. PMID:25594599

  19. Design of Surface Modifications for Nanoscale Sensor Applications

    PubMed Central

    Reimhult, Erik; Höök, Fredrik

    2015-01-01

    Nanoscale biosensors provide the possibility to miniaturize optic, acoustic and electric sensors to the dimensions of biomolecules. This enables approaching single-molecule detection and new sensing modalities that probe molecular conformation. Nanoscale sensors are predominantly surface-based and label-free to exploit inherent advantages of physical phenomena allowing high sensitivity without distortive labeling. There are three main criteria to be optimized in the design of surface-based and label-free biosensors: (i) the biomolecules of interest must bind with high affinity and selectively to the sensitive area; (ii) the biomolecules must be efficiently transported from the bulk solution to the sensor; and (iii) the transducer concept must be sufficiently sensitive to detect low coverage of captured biomolecules within reasonable time scales. The majority of literature on nanoscale biosensors deals with the third criterion while implicitly assuming that solutions developed for macroscale biosensors to the first two, equally important, criteria are applicable also to nanoscale sensors. We focus on providing an introduction to and perspectives on the advanced concepts for surface functionalization of biosensors with nanosized sensor elements that have been developed over the past decades (criterion (iii)). We review in detail how patterning of molecular films designed to control interactions of biomolecules with nanoscale biosensor surfaces creates new possibilities as well as new challenges. PMID:25594599

  20. X-ray assisted chemical modification of silicon surfaces

    NASA Astrophysics Data System (ADS)

    Pinhero, Patrick Joseph

    Interest in surface photochemistry induced by x-irradiation has received a renaissance with the construction of new synchrotron radiation facilities worldwide. There are three general pathways that a x-ray excited gas-surface system can follow that will lead to reaction. These are: (1) direct excitation, (2) excitation by emitted secondary electrons, and (3) reactions induced by hot electrons at the surface. Two chemical systems are studied in a modified x-ray photoelectron spectrometer (XPS) that allows for reactions to be studied in situ. The systems studied were (1) Nsb2/Si(100) and (2) the SFsb6/Si system. The motivation for studying these two compounds is: they are both relatively inert, i.e. no spontaneous reactions; they both are technologically interesting, possible silicon nitride formation in the case of Nsb2, and SFsb6 is a popular etchant gas in the semiconductor industry; and these two compounds have the potential to exhibit contrasting behavior. Besides its etching qualities, SFsb6 possesses a large x-ray absorption cross section and it has a large electron capture cross section. Both systems are primarily studied by XPS. XPS has the quality of providing quantifiable information about the composition of the surface and details about the chemical environment of each constituent element present. Atomic force microscopy (AFM) is used with the SFsb6 system to observe any structural changes that may occur after reaction. In the Nsb2/Si(100) system, a silicon nitride is formed at very long exposures. This is first observed after 24 hours of simultaneous exposure to Nsb2 and x-irradiation. In the SFsb6 experiments, several subsystems are examined: (1) simultaneous exposure of a Si(100) surface to SFsb6 and x-irradiation at 298K; (2) x-irradiation of a SFsb6 film adsorbed on Si(100) at 100K; (3) simultaneous exposure of a natively oxidized Si surface to SFsb6 and x-rays at 298K; and (4) x-irradiation of a SFsb6 film adsorbed on natively oxidized Si at 100K

  1. Advances in mechanisms and modifications for rendering yeast thermotolerance.

    PubMed

    Gao, Liman; Liu, Yueqin; Sun, Hun; Li, Chun; Zhao, Zhiping; Liu, Guiyan

    2016-06-01

    Thermotolerant Saccharomyces cerevisiae is widely regarded as an attractive strain with which to accomplish the coupling of enzyme saccharification, ethanol fermentation and ethanol distillation in non-grain fuel bioethanol fermentation systems, and it has many advantages for increasing the ethanol yield and reducing production costs. This review provided an overview of the yeast heat-resistant mechanisms from six aspects, including gene expression responses, heat shock proteins, trehalose, ATPase, the ubiquitin-proteasome pathway and heat-induced antioxidant defenses. Innovative methods, such as random and rational strategies for improving yeast thermotolerance, were further discussed, and several special cases were provided. To rationally engineer thermotolerance in yeast, the advances in employing heat-resistant mechanisms of thermophiles were particularly discussed. By designing and constructing heat-resistant devices consists of heat-resistant parts from thermophiles to yeast, a superior thermotolerance of S. cerevisiae has been achieved, providing a new system with important applications for research regarding the improvement of the robustness of microbes. PMID:26685013

  2. Charged particle modification of surfaces in the outer solar system

    NASA Technical Reports Server (NTRS)

    Johnson, R. E.

    1987-01-01

    Voyager reflectance spectra data have indicated clear leading/trailing differences in the albedo of the icy Galilean and Saturian satellites. For the Galilean satellites, these have been analyzed by Nelson, et al. and, more recently, by McEwen. They have described the longitudinal dependence of this data and attempted to interpret this in terms of plasma and meteorite modification of the surface. Primary attention has been paid to Europa at which the leading/trailing differences are the largest. This data was reanalyzed extracting the single grain albedo (w) and constructing the Espat-function, W = (1-w)/w from this. Because w is near unity, W is approximately 2(alpha)D where alpha is the absorption coefficient and D is the grain size. In doing so, a direct comparison to the longitudinal plasma bombardment flux was found for the first time. This occurs primarily in the UV and is probably due to an absorption associated with implanted S, as the UV band of Voyager overlaps the IUE data of Lane et al. The relative importance of grain size effects and implant impurity effects can now be studied.

  3. Top down nano technologies in surface modification of materials

    NASA Astrophysics Data System (ADS)

    Radjenović, Branislav; Radmilović-Radjenović, Marija

    2011-04-01

    This article contains a broad overview of etch process as one of the most important top-down technologies widely used in semiconductor manufacturing and surface modification of nanostructures. In plasma etching process, the complexity comes from the introduction of new materials and from the constant reduction in dimensions of the structures in microelectronics. The emphasis was made on two types of etching processes: dry etching and wet etching illustrated by three dimensional (3D) simulation results for the etching profile evolution based on the level set method. The etching of low-k dielectrics has been demonstrated via modelling the porous materials. Finally, simulation results for the roughness formation during isotropic etching of nanocomposite materials as well as smoothing of the homogeneous materials have also been shown and analyzed. Simulation results, presented here, indicate that with shrinking microelectronic devices, plasma and wet etching interpretative and predictive modeling and simulation have become increasingly more attractive as a tool for design, control and optimization of plasma reactors.

  4. Toxicity of nanocrystal quantum dots: the relevance of surface modifications.

    PubMed

    Hoshino, Akiyoshi; Hanada, Sanshiro; Yamamoto, Kenji

    2011-07-01

    With the development of nanotechnology, nanometer-sized products smaller than several 100 nm have been applied for all areas of science and technology. The nanometer-sized products, including carbon nanotubes, fullerene derivatives, and nanocrystals made of various materials, are widely employed as novel tools in various fields, not only in material engineering, electronics, plastics, automobile, aviation, and aerospace industries, but also even in cellular biology, molecular biology, and basic and clinical medical fields. In particular, nanocrystal quantum dots (QDs) have been widely used in biological and medical studies because of their far brighter photoemission and photostability. The physical and chemical properties of QDs have been circumstantially investigated, but little is known about the potential harmful effects of QDs on human health. In addition to the physical and chemical properties of the QDs, their toxicity and biological behavior are generally regulated by three other conditions: (1) the QD core material itself, (2) the surface modifications of the QD, and (3) the external environmental condition of the QDs. We herein report on the in vitro and in vivo toxicity and biological behavior of nanocrystals such as QDs. Accumulating evidence suggests that the QD-capping material, rather than the core metalloid complex, is responsible for the majority of their toxicity and biological activity. For example, molecules covered with a toxic agent showed cytotoxicity, whereas QDs conjugated with biomolecules retained the biological effects of the conjugate. PMID:21445587

  5. 78 FR 49079 - Lease Modifications, Lease and Logical Mining Unit Diligence, Advance Royalty, Royalty Rates, and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-08-12

    ... published in final form, following public comment, in the Federal Register on August 29, 1985 (50 FR 35145... August 30, 1982, must be revised to comply with the rules as modified as of August 30, 1982 (47 FR 33154..., et al. Lease Modifications, Lease and Logical Mining Unit Diligence, Advance Royalty, Royalty...

  6. Surface modifications of the Sima de los Huesos fossil humans.

    PubMed

    Andrews, P; Fernandez Jalvo, Y

    1997-01-01

    The sample of fossil human bones from the Sima de los Huesos, Atapuerca, has been analysed to trace parts of its taphonomic history. The work reported here is restricted to analysis of the skeletal elements preserved and their surface modifications. Preliminary plans of specimen distribution published 6 years ago indicate that the skeletal elements are dispersed within the cave, but more recent data are not yet available. Most of the fossils are broken, with some breakage when the bone was fresh and some when already partly mineralized, both types showing some rounding. There are few longitudinal breaks on shafts of long bones and so very few bone splinters. All skeletal elements are preserved but in unequal proportions, with elements like femora, humeri and mandibles and teeth with greater structural density being best represented. There is no evidence of weathering or of human damage such as cut marks on any of the human assemblage, but trampling damage is present on most bones. Carnivore damage is also common, with some present on more than half the sample, but it is mostly superficial, either on the surfaces of shafts and articular ends or on the edges of spiral breaks. The sizes and distribution of the carnivore pits indicate extensive canid activity, and this is interpreted as scavenging of the bones in place in the cave. Indications of tooth marks from a larger carnivore indicate the activity possibly of a large felid: the marks are too large to be produced by small canids, with the larger marks concentrated on spiral breaks on the more robust bones, and there is no evidence of bone crushing and splintering in the manner of hyaenas. The nature of the SH human assemblage is also consistent with accumulation by humans, the evidence for this being the lack of other animals, especially the lack of herbivorous animals, associated with the humans, and the high number of individuals preserved. PMID:9300342

  7. Surface modification for titanium implants by hydroxyapatite nanocomposite

    PubMed Central

    Family, Roxana; Solati-Hashjin, Mehran; Namjoy Nik, Shahram; Nemati, Ali

    2012-01-01

    Background: Titanium (Ti) implants are commonly coated with hydroxyapatite (HA). However, HA has some disadvantages such as brittleness, low tensile strength and fracture toughness. It is desirable to combine the excellent mechanical properties of ZrO2 and the chemical inertness of Al2O3 with respect to the purpose of this project which was coating Ti implants with HA-ZrO2-Al2O3 to modify the surface of these implants by adding ZrO2 and Al2O3 to HA. The purpose of this study was to evaluate the efficacy of hydroxyapatite coating nonocomposite. Methods: From September 2009 to January2011, functionally graded HA-Al2O3-ZrO2 and HA coatings were applied on Ti samples. HA-Al2O3-ZrO2 and HA sols were orderly dip coated on the substrates and calcined. Scanning electron microscopy and EDS were used to estimate the particle size of the surfaces and for morphological analysis. The morphology of non-coated HA-coated HA-Al2O3-ZrO2 (composite-coated) and double-layer composite coated samples were compared with one other. Mechanical test (heat & quench) was also done for comparing single-phase (HA), composite and double-layer composite samples. Results: The morphology of HA-Al2O3-ZrO2 coating is more homogenous than HA-coated and uncoated samples. Furthermore, single-layer coating is more homogenous than double-layer coating. EDS analysis was done on HA-coated sample and showed that the Ca/P ratio in the film was similar to the theoretical value 1.67 in HA. Conclusion: Surface modification of Ti implants can be done by coating them with single-layer of HA-Al2O3-ZrO2. Single-layer hydroxyapatite-alumina-zirconia coated sample has the most homogenous morphology on the surface. PMID:24009915

  8. Advanced surface design for logistics analysis

    NASA Astrophysics Data System (ADS)

    Brown, Tim R.; Hansen, Scott D.

    The development of anthropometric arm/hand and tool models and their manipulation in a large system model for maintenance simulation are discussed. The use of Advanced Surface Design and s-fig technology in anthropometrics, and three-dimensional graphics simulation tools, are found to achieve a good balance between model manipulation speed and model accuracy. The present second generation models are shown to be twice as fast to manipulate as the first generation b-surf models, to be easier to manipulate into various configurations, and to more closely approximate human contours.

  9. PREFACE Surface Modifications of Diamond and Related Materials (Session D, E-MRS Spring Meeting)

    NASA Astrophysics Data System (ADS)

    Nebel, Christoph E.

    2010-11-01

    This special issue contains selected papers which were presented at the E-MRS Symposium BIOMATERIALS, SENSORS & SURFACES, D: 'Surface modifications of diamond and related materials' which was held on 7-9 June 2010 in Strasbourg (France). With about 54 oral and poster presentations given from teams all over the world it was a very interesting, dense and lively meeting. The symposium focused on chemical modifications applied to graft surfaces of diamond, nano-diamond particles, diamond-like carbon, graphene, graphite and carbon nano-tubes with linker molecular layers for realization of bio-sensors, bio-markers, separation techniques, and switchable chemical links. Presented techniques span spontaneous bonding to photo-chemical attachment, electrochemical modifications, to Suzuki-coupling of aryl molecules. Special attention was drawn to mechanisms driving bonding kinetics such as electron transfer reactions, hydrogen cleavage reactions by nucleophilic molecules and growths schemas which vary from correlated two-dimensional chain reactions to three-dimensional cross polymerization. Hydrogen terminations, surface defects, surface roughness and atomic arrangements of surface carbon atoms were of interest to elucidate bonding mechanisms. In addition, bonding stability, either of linker molecules or of complex functionalized surfaces with DNA, proteins and enzymes was discussed by several speakers as well as details of the electronic interfaces between solid transducers and bio-layers. Here the characterization of surface and interface defect densities, of Fermi level pinning and of electron transfer rates was a major topic. Miniaturization of sensor area and application of new detection schemas was discussed. Diamond nano-particles which are increasingly used as biomarkers in drug delivery experiments also attracted attention. The organizers express our gratitude to the international members of the scientific committee who actively contributed to ensure an attractive

  10. Stability studies of plasma modification effects of polylactide and polycaprolactone surface layers

    NASA Astrophysics Data System (ADS)

    Moraczewski, Krzysztof; Stepczyńska, Magdalena; Malinowski, Rafał; Rytlewski, Piotr; Jagodziński, Bartłomiej; Żenkiewicz, Marian

    2016-07-01

    The article presents results of research on the stability of oxygen plasma modification effects of polylactide and polycaprolactone surface layers. The modified samples were aged for three, six or nine weeks. The studies were carried out using scanning electron microscopy, goniometry and Fourier transform infrared spectroscopy. Studies have shown that the plasma modification has significant impact on the geometric structure and chemical composition of the surface, wettability and surface energy of tested polymers. The modification effects are not permanent. It has been observed that over time the effects of plasma modification fade. Studies have shown that modifying effect lasts longer in the case of polycaprolactone.

  11. Studies on polyurethane adhesives and surface modification of hydrophobic substrates

    NASA Astrophysics Data System (ADS)

    Krishnamoorthy, Jayaraman

    studies involved making functionalized, thickness-controlled, wettability-controlled multilayers on hydrophobic substrates and the adsorption of carboxylic acid-terminated poly(styrene-b-isoprene) on alumina/silica substrates. Poly(vinyl alcohol) has been shown to adsorb onto hydrophobic surfaces irreversibly due to hydrophobic interactions. This thin semicrystalline coating is chemically modified using acid chlorides, butyl isocyanate and butanal to form thicker and hydrophobic coatings. The products of the modification reactions allow adsorption of a subsequent layer of poly(vinyl alcohol) that could subsequently be hydrophobized. This 2-step (adsorption/chemical modification) allows layer-by-layer deposition to prepare coatings with thickness, chemical structure and wettability control on any hydrophobic surface. Research on adsorption characteristics of carboxylic acid-terminated poly(styrene-b-isoprene) involved syntheses of block copolymers with the functional group present at specific ends. Comparative adsorption studies for carboxylic acid-terminated and hydrogen-terminated block copolymers was carried out on alumina and silica substrates.

  12. Surface modification and antimicrobial properties of cellulose nanocrystals

    NASA Astrophysics Data System (ADS)

    Bespalova, Yulia A.

    Surface modification of cellulose nanocrystals (CNC) was performed by acetylation and subsequent reaction with various tertiary amines with different lengths of alkyl groups. Chloroacetic anhydride (95%) was used for acetylation. The acetylation of CNC was confirmed using IR spectroscopy. The bands associated with C=0 stretching (1740 cm-1) and C-Cl stretching (793 cm -1) was present in the acetylated CNC but they were absent in the neat CNC. It has been suggested that the primary hydroxyl groups of CNC are substituted by chloro acetyl groups during acetylation reaction. Subsequent reaction of chloro acetylated CNC with N, N - Dimethyl ethylamine, N, N - Dimethyl hexylamine, N, N - Dimethyl dodecylamine, N, N - Dimethyl hexadecylamine and N, N - Dimethyl decylamine formed quaternary ammonium salts. These quaternary ammonium salts were characterized by FTIR and solid state13C NMR spectroscopy. FTIR spectra of five types of quaternary ammonium salts of CNC are similar and they showed infrared bands at 2905 -1 and 2850 cm-1, attributed to symmetrical and unsymmetrical C-H stretching vibration. The absence of C-Cl band at 793 cm-1 proves that quaternary salt formation was successful. The 13C NMR spectrum of quaternary ammonium modified CNC with N, N - Dimethyl dodecylamine shows several additional resonances ranging from 14.5 ppm to 58.0 ppm when compared to 13C NMR spectrum of pure CNC. This evidence proves that long alkyl chains have been added to the pure CNC. The disc diffusion method confirmed that quaternary ammonium modified CNCs with a chain longer than ten carbons are effective antimicrobial agents against Staphylococcus aureus and E. coli bacteria. Pure CNC and quaternary ammonium modified CNCs with an alkyl chain length of ten or less were not able to inhibit bacteria growth.

  13. Metal ion implantation for large scale surface modification

    SciTech Connect

    Brown, I.G.

    1992-10-01

    Intense energetic beams of metal ions can be produced by using a metal vapor vacuum arc as the plasma discharge from which the ion beam is formed. We have developed a number of ion sources of this kind and have built a metal ion implantation facility which can produce repetitively pulsed ion beams with mean ion energy up to several hundred key, pulsed beam current of more than an ampere, and time averaged current of several tens of milliamperes delivered onto a downstream target. We've also done some preliminary work on scaling up this technology to very large size. For example, a 50-cm diameter (2000 cm[sup 2]) set of beam formation electrodes was used to produce a pulsed titanium beam with ion current over 7 amperes at a mean ion energy of 100 key. Separately, a dc embodiment has been used to produce a dc titanium ion beam with current over 600 mA, power supply limited in this work, and up to 6 amperes of dc plasma ion current was maintained for over an hour. In a related program we've developed a plasma immersion method for applying thin metallic and compound films in which the added species is atomically mixed to the substrate. By adding a gas flow to the process, well-bonded compound films can also be formed; metallic films and multilayers as well as oxides and nitrides with mixed transition zones some hundreds of angstroms thick have been synthesized. Here we outline these parallel metal-plasma-based research programs and describe the hardware that we've developed and some of the surface modification research that we've done with it.

  14. Surface modification of biomaterials using plasma immersion ion implantation and deposition

    PubMed Central

    Lu, Tao; Qiao, Yuqin; Liu, Xuanyong

    2012-01-01

    Although remarkable progress has been made on biomaterial research, the ideal biomaterial that satisfies all the technical requirements and biological functions is not available up to now. Surface modification seems to be a more economic and efficient way to adjust existing conventional biomaterials to meet the current and ever-evolving clinical needs. From an industrial perspective, plasma immersion ion implantation and deposition (PIII&D) is an attractive method for biomaterials owing to its capability of treating objects with irregular shapes, as well as the control of coating composition. It is well acknowledged that the physico-chemical characteristics of biomaterials are the decisive factors greatly affecting the biological responses of biomaterials including bioactivity, haemocompatibility and antibacterial activity. Here, we mainly review the recent advances in surface modification of biomaterials via PIII&D technology, especially titanium alloys and polymers used for orthopaedic, dental and cardiovascular implants. Moreover, the variations of biological performances depending on the physico-chemical properties of modified biomaterials will be discussed. PMID:23741609

  15. Unique carbon nanotube architectures via surface modification and capillary effects

    NASA Astrophysics Data System (ADS)

    Chakrapani, Nirupama

    dimensions. Pattern formation could also be tailored by prefabricating nanotube arrays by simple lithographic techniques. This study is on the fundamental understanding of capillary effects in dense arrays of ordered nanotubes and the effect of surface modification of nanotubes. This simple self-assembly process is a novel way of creating different macroscopic morphologies and architectures with nanotubes.

  16. Chemoselective modification of viral surfaces via bioorthogonal click chemistry.

    PubMed

    Rubino, Frederick A; Oum, Yoon Hyeun; Rajaram, Lakshmi; Chu, Yanjie; Carrico, Isaac S

    2012-01-01

    The modification of virus particles has received a significant amount of attention for its tremendous potential for impacting gene therapy, oncolytic applications and vaccine development. Current approaches to modifying viral surfaces, which are mostly genetics-based, often suffer from attenuation of virus production, infectivity and cellular transduction. Using chemoselective click chemistry, we have developed a straightforward alternative approach which sidesteps these issues while remaining both highly flexible and accessible. The goal of this protocol is to demonstrate the effectiveness of using bioorthogonal click chemistry to modify the surface of adenovirus type 5 particles. This two-step process can be used both therapeutically or analytically, as it allows for chemoselective ligation of targeting molecules, dyes or other molecules of interest onto proteins pre-labeled with azide tags. The three major advantages of this method are that (1) metabolic labeling demonstrates little to no impact on viral fitness, (2) a wide array of effector ligands can be utilized, and (3) it is remarkably fast, reliable and easy to access. In the first step of this procedure, adenovirus particles are produced bearing either azidohomoalanine (Aha, a methionine surrogate) or the unnatural sugar O-linked N-azidoacetylglucosamine (O-GlcNAz), both of which contain the azide (-N3) functional group. After purification of the azide-modified virus particles, an alkyne probe containing the fluorescent TAMRA moiety is ligated in a chemoselective manner to the pre-labeled proteins or glycoproteins. Finally, an SDS-PAGE analysis is performed to demonstrate the successful ligation of the probe onto the viral capsid proteins. Aha incorporation is shown to label all viral capsid proteins (Hexon, Penton and Fiber), while O-GlcNAz incorporation results in labeling of Fiber only. In this evolving field, multiple methods for azide-alkyne ligation have been successfully developed; however only the

  17. Statistical modification analysis of helical planetary gears based on response surface method and Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Zhang, Jun; Guo, Fan

    2015-11-01

    Tooth modification technique is widely used in gear industry to improve the meshing performance of gearings. However, few of the present studies on tooth modification considers the influence of inevitable random errors on gear modification effects. In order to investigate the uncertainties of tooth modification amount variations on system's dynamic behaviors of a helical planetary gears, an analytical dynamic model including tooth modification parameters is proposed to carry out a deterministic analysis on the dynamics of a helical planetary gear. The dynamic meshing forces as well as the dynamic transmission errors of the sun-planet 1 gear pair with and without tooth modifications are computed and compared to show the effectiveness of tooth modifications on gear dynamics enhancement. By using response surface method, a fitted regression model for the dynamic transmission error(DTE) fluctuations is established to quantify the relationship between modification amounts and DTE fluctuations. By shifting the inevitable random errors arousing from manufacturing and installing process to tooth modification amount variations, a statistical tooth modification model is developed and a methodology combining Monte Carlo simulation and response surface method is presented for uncertainty analysis of tooth modifications. The uncertainly analysis reveals that the system's dynamic behaviors do not obey the normal distribution rule even though the design variables are normally distributed. In addition, a deterministic modification amount will not definitely achieve an optimal result for both static and dynamic transmission error fluctuation reduction simultaneously.

  18. Surface modification of thermoplastics--towards the plastic biochip for high throughput screening devices.

    PubMed

    Diaz-Quijada, Gerardo A; Peytavi, Régis; Nantel, André; Roy, Emmanuel; Bergeron, Michel G; Dumoulin, Michel M; Veres, Teodor

    2007-07-01

    Microarrays have become one of the most convenient tools for high throughput screening, supporting major advances in genomics and proteomics. Other important applications can be found in medical diagnostics, detection of biothreats, drug discovery, etc. Integration of microarrays with microfluidic devices can be highly advantageous in terms of portability, shorter analysis time and lower consumption of expensive biological analytes. Since fabrication of microfluidic devices using traditional materials such as glass is rather expensive, there is great interest in employing polymeric materials as a low cost alternative that is suitable for mass production. A number of commercially available plastic materials were reviewed for this purpose and poly(methylmethacrylate) Zeonor 1060R and Zeonex E48R were identified as promising candidates, for which methods for surface modification and covalent immobilization of DNA oligonucleotides were developed. In addition, we present proof-of-concept plastic-based microarrays with and without integration with microfluidics. PMID:17594004

  19. Surface modification of biomaterials by pulsed laser ablation deposition and plasma/gamma polymerization

    NASA Astrophysics Data System (ADS)

    Rau, Kaustubh R.

    Surface modification of stainless-steel was carried out by two different methods: pulsed laser ablation deposition (PLAD) and a combined plasma/gamma process. A potential application was the surface modification of endovascular stents, to enhance biocompatibility. The pulsed laser ablation deposition process, had not been previously reported for modifying stents and represented a unique and potentially important method for surface modification of biomaterials. Polydimethylsiloxane (PDMS) elatomer was studied using the PLAD technique. Cross- linked PDMS was deemed important because of its general use for biomedical implants and devices as well as in other fields. Furthermore, PDMS deposition using PLAD had not been previously studied and any information gained on its ablation characteristics could be important scientifically and technologically. The studies reported here showed that the deposited silicone film properties had a dependence on the laser energy density incident on the target. Smooth, hydrophobic, silicone-like films were deposited at low energy densities (100-150 mJ/cm2). At high energy densities (>200 mJ/cm2), the films had an higher oxygen content than PDMS, were hydrophilic and tended to show a more particulate morphology. It was also determined that (1)the deposited films were stable and extremely adherent to the substrate, (2)silicone deposition exhibited an `incubation effect' which led to the film properties changing with laser pulse number and (3)films deposited under high vacuum were similar to films deposited at low vacuum levels. The mechanical properties of the PLAD films were determined by nanomechanical measurements which are based on the Atomic Force Microscope (AFM). From these measurements, it was possible to determine the modulus of the films and also study their scratch resistance. Such measurement techniques represent a significant advance over current state-of-the-art thin film characterization methods. An empirical model for

  20. Advanced Bayesian Method for Planetary Surface Navigation

    NASA Technical Reports Server (NTRS)

    Center, Julian

    2015-01-01

    Autonomous Exploration, Inc., has developed an advanced Bayesian statistical inference method that leverages current computing technology to produce a highly accurate surface navigation system. The method combines dense stereo vision and high-speed optical flow to implement visual odometry (VO) to track faster rover movements. The Bayesian VO technique improves performance by using all image information rather than corner features only. The method determines what can be learned from each image pixel and weighs the information accordingly. This capability improves performance in shadowed areas that yield only low-contrast images. The error characteristics of the visual processing are complementary to those of a low-cost inertial measurement unit (IMU), so the combination of the two capabilities provides highly accurate navigation. The method increases NASA mission productivity by enabling faster rover speed and accuracy. On Earth, the technology will permit operation of robots and autonomous vehicles in areas where the Global Positioning System (GPS) is degraded or unavailable.

  1. Surface modification of PVDF membrane via AGET ATRP directly from the membrane surface

    NASA Astrophysics Data System (ADS)

    Meng, Jian-Qiang; Chen, Chun-Lin; Huang, Li-Ping; Du, Qi-Yun; Zhang, Yu-Feng

    2011-05-01

    This contribution demonstrates a method for PVDF microporous membrane modification via surface-initiated activators generated by electron transfer atom transfer radical polymerization (AGET ATRP) directly from the membrane surface. Three hydrophilic polymers, poly(2-(N,N-dimethylamino) ethyl methacrylate) (PDMAEMA), poly(2-oligo (ethylene glycol) monomethyl ether methacrylate) (POEGMA), and poly(2-hydroxyethyl methacrylate) (PHEMA), were grafted from the PVDF membrane surface in aqueous solution at room temperature. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) confirmed the successful covalent tethering of the polymer chains onto the PVDF membrane surface. The gravimetry results indicated an approximately linear increase of the graft yields, up to about 330 μg/cm 2 for DMAEMA and 470 μg/cm 2 for both HEMA and OEGMA, with the polymerization time. Block copolymer brushes were prepared by chain extension. Water contact angle decreased over 50% for high yields, indicating improved surface hydrophilicity. The effects of the graft polymerization on membrane surface morphology, pore structure and permeability were investigated. It was found that the surface roughness was decreased and the pore size distribution was narrowed. The membrane permeability increased at low graft yields due to the enhanced hydrophilicity and decreased at high graft yields due to the overall reduction of the pore diameters.

  2. Polymer Thin Films and Surface Modification by Chemical Vapor Deposition: Recent Progress.

    PubMed

    Chen, Nan; Kim, Do Han; Kovacik, Peter; Sojoudi, Hossein; Wang, Minghui; Gleason, Karen K

    2016-06-01

    Chemical vapor deposition (CVD) polymerization uses vapor phase monomeric reactants to synthesize organic thin films directly on substrates. These thin films are desirable as conformal surface engineering materials and functional layers. The facile tunability of the films and their surface properties allow successful integration of CVD thin films into prototypes for applications in surface modification, device fabrication, and protective films. CVD polymers also bridge microfabrication technology with chemical and biological systems. Robust coatings can be achieved via CVD methods as antifouling, anti-icing, and antihydrate surfaces, as well as stimuli-responsive or biocompatible polymers and novel nanostructures. Use of low-energy input, modest vacuum, and room-temperature substrates renders CVD polymerization compatible with thermally sensitive substrates and devices. Compared with solution-based methods, CVD is particularly useful for insoluble materials, such as electrically conductive polymers and controllably crosslinked networks, and has the potential to reduce environmental, health, and safety impacts associated with solvents. This review discusses the relevant background and selected applications of recent advances by two methods that display and use the high retention of the organic functional groups from their respective monomers, initiated CVD (iCVD) and oxidative CVD (oCVD) polymerization. PMID:27276550

  3. Bio-inspired dual surface modification to improve tribological properties at small-scale

    NASA Astrophysics Data System (ADS)

    Singh, R. Arvind; Pham, Duc-Cuong; Kim, Jinseok; Yang, Sungwook; Yoon, Eui-Sung

    2009-02-01

    In miniaturized devices like micro/nano-electro-mechanical systems (MEMS/NEMS), the critical forces, namely adhesion and friction restrict the smooth operation of the elements that are in relative motion. MEMS/NEMS are traditionally made of silicon, whose tribological properties are not good. In this paper, we present an investigation on the approach of dual surface modification of silicon surfaces and their tribological properties at micro-scale. The dual surface modification is a combination of topographical and chemical modifications. As the topographical modification, micro-patterns with varying shapes of pillars and channels were fabricated on Si(1 0 0) wafer surfaces using photolithography method. Chemical modification included the coating of micro-patterns with diamond-like carbon (DLC) and Z-DOL (perfluoropolyether, PFPE) thin films. The surfaces with combined modification were evaluated for their micro-friction behavior in comparison with those of bare Si(1 0 0) flat surfaces and the topographically/chemically modified silicon surfaces. Results showed that the surfaces with dual modification exhibited superior tribological properties. These results indicate that a combination of topographical and chemical modification is very effective in enhancing tribological properties at small-scale. The combined surface treatments such as the ones investigated in the current work could be useful for tribological applications in small-scale devices such as MEMS/NEMS. The motivation for undertaking the dual modification approach comes from an earlier observation made on the significant influence of the surface characteristics of lotus leaf on its micro-friction behavior.

  4. i3DP, a robust 3D printing approach enabling genetic post-printing surface modification.

    PubMed

    Wang, Xiaolong; Cai, Xiaobing; Guo, Qiuquan; Zhang, Tengyuan; Kobe, Brad; Yang, Jun

    2013-10-01

    Initiator integrated 3D printing, namely i3DP, was developed by incorporating a vinyl-terminated initiator into UV curable resin to make functional structural materials that enable genetic post-printing surface-initiated modification. Taking advantage of 3D printing and surface-initiated ATRP, the feasible i3DP makes 3D printed complex architectures possible for nearly any desired surface modification for various applications, for example, even pouring water into a sieve was readily achieved. PMID:24002351

  5. Resistive Memory for Harsh Electronics: Immunity to Surface Effect and High Corrosion Resistance via Surface Modification

    PubMed Central

    Huang, Teng-Han; Yang, Po-Kang; Lien, Der-Hsien; Kang, Chen-Fang; Tsai, Meng-Lin; Chueh, Yu-Lun; He, Jr-Hau

    2014-01-01

    The tolerance/resistance of the electronic devices to extremely harsh environments is of supreme interest. Surface effects and chemical corrosion adversely affect stability and operation uniformity of metal oxide resistive memories. To achieve the surrounding-independent behavior, the surface modification is introduced into the ZnO memristors via incorporating fluorine to replace the oxygen sites. F-Zn bonds is formed to prevent oxygen chemisorption and ZnO dissolution upon corrosive atmospheric exposure, which effectively improves switching characteristics against harmful surroundings. In addition, the fluorine doping stabilizes the cycling endurance and narrows the distribution of switching parameters. The outcomes provide valuable insights for future nonvolatile memory developments in harsh electronics. PMID:24638086

  6. Interaction of soft x-ray laser pulse radiation with aluminum surface: Nano-meter size surface modification

    SciTech Connect

    Ishino, Masahiko; Faenov, Anatoly; Tanaka, Momoko; Hasegawa, Noboru; Nishikino, Masaharu; Tamotsu, Satoshi; Pikuz, Tatiana; Inogamov, Nail; Zhakhovsky, Vasily; Skobelev, Igor; Fortov, Vladimir; Khohlov, Viktor; Shepelev, Vadim; Ohba, Toshiyuki; Kaihori, Takeshi; Ochi, Yoshihiro; Imazono, Takashi; Kawachi, Tetsuya

    2012-07-11

    Interaction of soft x-ray laser radiation with material and caused modification of the exposed surface has both physical and practical interests. We irradiated the focusing soft x-ray laser (SXRL) pulses having a wavelength of 13.9 nm and the duration of 7 ps to aluminum (Al) surface. After the SXRL irradiation process, the irradiated Al surface was observed with a scanning electron microscope. The surface modifications caused by SXRL single pulse exposure were clearly seen. In addition, it was found that the conical structures having around 100 nm in diameters were formed in the shallow features. The nano-meter size modified structures at Al surface induced by SXRL pulse is interesting as the newly surface structure. Hence, the SXRL beam would be a candidate for a tool of micromachining. We also provide a thermomechanical modeling of SXRL interaction with Al briefly to explain the surface modification.

  7. Coal surface control for advanced fine coal flotation

    SciTech Connect

    Fuerstenau, D.W.; Sastry, K.V.S.; Hanson, J.S.; Narayanan, K.S.; Urbina, R.H.; Diao, J.; Yin, Y.; Harris, G.; Hu, Weibei; Zou, Y.; Chen, W.; Somasundaran, P.; Harris, C.C.; Vasudevan, T.; Xhong, K.; Xiao, L.; Choudhry, V.; Shea, S.; Ghosh, A.; Sehgal, R.; Utah Univ., Salt Lake City, UT; Columbia Univ., New York, NY; Praxis Engineers, Inc., Milpitas, CA )

    1989-08-15

    The primary goal of this project is to develop advanced flotation methods for coal cleaning in order to achieve 90% pyritic sulfur removal at 90% Btu yield, using coal samples procured from six major US coal seams. Concomitantly, the ash content of these coals is to be reduced to 6% or less. Investigation of mechanisms for the control of coal and pyrite surfaces prior to fine coal flotation is an important aspect of the project objectives. Large quantities of coal samples have been procured from six major seams. Samples of the same coals are also to be supplied to the University of Pittsburgh for selective agglomeration research. A second objective is to investigate factors involved in the progressive weathering and oxidation of coal stored in three storage modes, namely, open, covered and in an argon-inerted atmosphere, over a period of twelve months. After regular intervals of weathering, samples of the three base coals are to be collected and shipped to both the University of Pittsburgh and the University of California at Berkeley for characterization studies of the weathered coals. Work is divided into 8 tasks: (1) project work plan; (2) coal procurement and weathering; (3) coal characterization; (4) standard beneficiation test; (5) grinding studies; (6) surface modification studies; (7) exploratory R D and support; and (8) task integration and project management. 8 refs., 50 figs., 38 tabs.

  8. Coal surface control for advanced fine coal flotation

    SciTech Connect

    Fuerstenau, D.W.; Sastry, K.V.S.; Hanson, J.S.; Harris, G.; Sotillo, F.; Diao, J.; Yin, Y. ); Somasundaran, P.; Harris, C.C.; Vasudevan, T.; Liu, D.; Li, C. ); Hu, Weibai; Zou, Y.; Chen, W. ); Choudhry, V.; Sehgal, R.; Ghosh, A. )

    1990-05-31

    The primary objective in the scope of this research project is to develop advanced flotation methods for coal cleaning in order to achieve near total pyritic sulfur removal at 90% Btu recovery, using coal samples procured from six major US coal seams. The ash content of these coals is to be reduced to 6% or less. Investigation of mechanisms for the control of coal and pyrite surfaces prior to fine coal flotation is an important aspect of the project objectives. A second major objective is to investigate factors involved in the progressive weathering and oxidation of coal that had been exposed to varying weathered degrees, namely, open, covered and in an argon-inerted'' atmosphere, over a period of twelve months. After regular intervals of weathering, samples of the three base coals (Illinois No. 6, Pittsburgh No. 8 and Upper Freeport PA) were collected and shipped to both the University of Pittsburgh and the University of California at Berkeley for characterization studies of the weathered material. Progress is described on weathering, washability studies (calorific value, ash analysis, pyritic sulfur rejection, variability analysis), coal grinding and flotation, pH effects and modification of surfaces on flotation. 26 figs., 20 tabs.

  9. Coal surface control for advanced fine coal flotation

    SciTech Connect

    Fuerstenau, D.W.; Sastry, K.V.S.; Hanson, J.S.; Harris, G.; Sotillo, F.; Diao, J. ); Somasundaran, P.; Harris, C.C.; Vasudevan, T.; Liu, D.; Li, C. ); Hu, Weibai; Zou, Y.; Chen, W. ); Choudhry, V.; Sehgal, R.; Ghosh, A. )

    1990-08-15

    The primary objective of this research project is to develop advanced flotation methods for coal cleaning in order to achieve near total pyritic-sulfur removal at 90% Btu recovery, using coal samples procured from six major US coal seams. Concomitantly, the ash content of these coals is to be reduced to 6% or less. Work this quarter concentrated on the following: washability studies, which included particle size distribution of the washability samples, and chemical analysis of washability test samples; characterization studies of induction time measurements, correlation between yield, combustible-material recovery (CMR), and heating-value recovery (HVR), and QA/QC for standard flotation tests and coal analyses; surface modification and control including testing of surface-modifying reagents, restoration of hydrophobicity to lab-oxidized coals, pH effects on coal flotation, and depression of pyritic sulfur in which pyrite depression with calcium cyanide and pyrite depression with xanthated reagents was investigated; flotation optimization and circuitry included staged reagent addition, cleaning and scavenging, and scavenging and middling recycling. Weathering studies are also discussed. 19 figs., 28 tabs.

  10. RASSOR - Regolith Advanced Surface Systems Operations Robot

    NASA Technical Reports Server (NTRS)

    Gill, Tracy R.; Mueller, Rob

    2015-01-01

    The Regolith Advanced Surface Systems Operations Robot (RASSOR) is a lightweight excavator for mining in reduced gravity. RASSOR addresses the need for a lightweight (<100 kg) robot that is able to overcome excavation reaction forces while operating in reduced gravity environments such as the moon or Mars. A nominal mission would send RASSOR to the moon to operate for five years delivering regolith feedstock to a separate chemical plant, which extracts oxygen from the regolith using H2 reduction methods. RASSOR would make 35 trips of 20 kg loads every 24 hours. With four RASSORs operating at one time, the mission would achieve 10 tonnes of oxygen per year (8 t for rocket propellant and 2 t for life support). Accessing craters in space environments may be extremely hard and harsh due to volatile resources - survival is challenging. New technologies and methods are required. RASSOR is a product of KSC Swamp Works which establishes rapid, innovative and cost effective exploration mission solutions by leveraging partnerships across NASA, industry and academia.

  11. 10 CFR 830 Major Modification Determination for Advanced Test Reactor LEU Fuel Conversion

    SciTech Connect

    Boyd D. Christensen; Michael A. Lehto; Noel R. Duckwitz

    2012-05-01

    The Advanced Test Reactor (ATR), located in the ATR Complex of the Idaho National Laboratory (INL), was constructed in the 1960s for the purpose of irradiating reactor fuels and materials. Other irradiation services, such as radioisotope production, are also performed at ATR. The ATR is fueled with high-enriched uranium (HEU) matrix (UAlx) in an aluminum sandwich plate cladding. The National Nuclear Security Administration Global Threat Reduction Initiative (GTRI) strategic mission includes efforts to reduce and protect vulnerable nuclear and radiological material at civilian sites around the world. Converting research reactors from using HEU to low-enriched uranium (LEU) was originally started in 1978 as the Reduced Enrichment for Research and Test Reactors (RERTR) Program under the U.S. Department of Energy (DOE) Office of Science. Within this strategic mission, GTRI has three goals that provide a comprehensive approach to achieving this mission: The first goal, the driver for the modification that is the subject of this determination, is to convert research reactors from using HEU to LEU. Thus the mission of the ATR LEU Fuel Conversion Project is to convert the ATR and Advanced Test Reactor Critical facility (ATRC) (two of the six U.S. High-Performance Research Reactors [HPRR]) to LEU fuel by 2017. The major modification criteria evaluation of the project pre-conceptual design identified several issues that lead to the conclusion that the project is a major modification.

  12. Chemical modification of graphite surfaces using chitosan as a mediator

    SciTech Connect

    Hatley, M.E.; Albahadily, F.N.

    1995-12-01

    Several techniques for modifying graphite surfaces have been utilized the last two decades. Some of these techniques have a few limitations which include monolayer coverage and nonspecific binding to the graphite surfaces. In this report, we describe a novel approach to modify graphite surfaces using chitosan. The graphite is coated with an acidic chitosan solution. After drying, a chitosan film is formed on the graphite surfaces. Glutaraldehyde is attached to the chitosan through an amide linkage. The desired modifiers which contain amine groups are then attached to the free end of the glutaraldehyde. Utilization of the modified graphite surfaces in paste electrodes will be discussed.

  13. Simultaneous Sterilization With Surface Modification Of Plastic Bottle By Plasma-Based Ion Implantation

    SciTech Connect

    Sakudo, N.; Ikenaga, N.; Ikeda, F.; Nakayama, Y.; Kishi, Y.; Yajima, Z.

    2011-01-07

    Dry sterilization of polymeric material is developed. The technique utilizes the plasma-based ion implantation which is same as for surface modification of polymers. Experimental data for sterilization are obtained by using spores of Bacillus subtilis as samples. On the other hand we previously showed that the surface modification enhanced the gas barrier characteristics of plastic bottles. Comparing the implantation conditions for the sterilization experiment with those for the surface modification, we find that both sterilization and surface modification are simultaneously performed in a certain range of implantation conditions. This implies that the present bottling system for plastic vessels will be simplified and streamlined by excluding the toxic peroxide water that has been used in the traditional sterilization processes.

  14. Simultaneous Sterilization With Surface Modification Of Plastic Bottle By Plasma-Based Ion Implantation

    NASA Astrophysics Data System (ADS)

    Sakudo, N.; Ikenaga, N.; Ikeda, F.; Nakayama, Y.; Kishi, Y.; Yajima, Z.

    2011-01-01

    Dry sterilization of polymeric material is developed. The technique utilizes the plasma-based ion implantation which is same as for surface modification of polymers. Experimental data for sterilization are obtained by using spores of Bacillus subtilis as samples. On the other hand we previously showed that the surface modification enhanced the gas barrier characteristics of plastic bottles. Comparing the implantation conditions for the sterilization experiment with those for the surface modification, we find that both sterilization and surface modification are simultaneously performed in a certain range of implantation conditions. This implies that the present bottling system for plastic vessels will be simplified and streamlined by excluding the toxic peroxide water that has been used in the traditional sterilization processes.

  15. Surface modification of polymer nanofibres by plasma treatment

    NASA Astrophysics Data System (ADS)

    Wei, Q. F.; Gao, W. D.; Hou, D. Y.; Wang, X. Q.

    2005-05-01

    Polymer nanofibres have great potential for technical applications in biomaterials, filtration, composites and electronics. The surface properties of nanofibres are of importance in these applications. In this study, cold gas plasma treatment was used to modify the surface of polyamide 6 nanofibres prepared by electrospinning. The chemical nature of the nanofibre surfaces was examined by X-ray photoelectron spectroscopy (XPS). Atomic force microscopy (AFM) was employed to study the surface characteristics of the fibres. The AFM results indicate a significant change in the morphology of the fibre surface before and after plasma treatment. A Philips Environmental Scanning Electron Microscopy (ESEM) was also used to study the wetting behaviour of the fibres. In the ESEM, relative humidity was raised to 100% to facilitate the water condensation onto fibre surfaces for wetting observation. The ESEM observation revealed that the plasma treatment significantly altered the surface wettability of the polyamide 6 nanofibres

  16. Surface Modifications and Their Effects on Titanium Dental Implants

    PubMed Central

    Jemat, A.; Ghazali, M. J.; Razali, M.; Otsuka, Y.

    2015-01-01

    This review covers several basic methodologies of surface treatment and their effects on titanium (Ti) implants. The importance of each treatment and its effects will be discussed in detail in order to compare their effectiveness in promoting osseointegration. Published literature for the last 18 years was selected with the use of keywords like titanium dental implant, surface roughness, coating, and osseointegration. Significant surface roughness played an important role in providing effective surface for bone implant contact, cell proliferation, and removal torque, despite having good mechanical properties. Overall, published studies indicated that an acid etched surface-modified and a coating application on commercial pure titanium implant was most preferable in producing the good surface roughness. Thus, a combination of a good surface roughness and mechanical properties of titanium could lead to successful dental implants. PMID:26436097

  17. Surface modification of active material structures in battery electrodes

    DOEpatents

    Erickson, Michael; Tikhonov, Konstantin

    2016-02-02

    Provided herein are methods of processing electrode active material structures for use in electrochemical cells or, more specifically, methods of forming surface layers on these structures. The structures are combined with a liquid to form a mixture. The mixture includes a surface reagent that chemically reacts and forms a surface layer covalently bound to the structures. The surface reagent may be a part of the initial liquid or added to the mixture after the liquid is combined with the structures. In some embodiments, the mixture may be processed to form a powder containing the structures with the surface layer thereon. Alternatively, the mixture may be deposited onto a current collecting substrate and dried to form an electrode layer. Furthermore, the liquid may be an electrolyte containing the surface reagent and a salt. The liquid soaks the previously arranged electrodes in order to contact the structures with the surface reagent.

  18. Modification of fracture surfaces by dissolution. Part II

    SciTech Connect

    Johnson, B.

    1983-01-01

    This study focuses upon how and to what extent dissolution related fluid/rock interactions modify the morphology and roughness of surfaces on Sioux Quartzite. Dissolution experiments consisted of reacting small discs of Sioux Quartzite in sealed gold capsules containing either distilled water or 0.05 N to 4.0 N aqueous solutions of Na/sub 2/CO/sub 3/. Samples were reacted at 200/sup 0/C and 20 to 30 MPa fluid pressures for 2 to 5 days. Two markedly different starting surface textures were used: polished, optically flat surfaces and tensile fracture surfaces. An exploratory experiment also was performed to assess the occurrence of a pressure solution phenomenon on a polished quartzite surface at contact regions of indenting quartz sand grains. Scanning electron microscopy studies indicate progressive increases in the amount of dissolution produced significant changes of surface roughness for both initial surface textures. Surface roughness increased measurably, with the initially polished surfaces exhibiting the more dramatic changes. The pressure solution experiments did not produce definite results, but several surface features are suggestive of dissolution enhancement at load carrying contacts. 9 refs., 10 figs.

  19. [Research on surface modification and bio-tribological properties of artificial joint].

    PubMed

    Pan, Yusong; Wang, Jing; Ding, Guoxin

    2012-06-01

    The bio-tribological properties of an artificial joint can be obviously improved by surface modification technologies. In this paper, the benefits and disadvantages of various surface modification methods-such as surface coating, plasma treatment, surface texture and surface grafting modification-are discussed. The aim of surface coating and/or plasma treatment is to improve the surface hardness of the materials, thus enhancing the wear resistance of artificial joints. However, these technologies do not effectively alleviate stress concentration of material in the short times in which artificial joints bear physiological impact load, resulting in easy fracture. Surface texture serves mainly to improve the lubrication properties through micro-concavities on the material surface for storage lubricant. Surface texturing can realize improvements in bio-tribological properties, but it does not enhance the impact resistance of the joint. Surface grafting modification is implemented mainly by grafting hydrophilic or other specific functional groups to improve the surface hydrophilicity and wetability, thus enhancing lubricating performance and reducing the coefficient of friction. PMID:22772408

  20. Enzymatic synthesis and modification of structured phospholipids: recent advances in enzyme preparation and biocatalytic processes.

    PubMed

    Hama, Shinji; Ogino, Chiaki; Kondo, Akihiko

    2015-10-01

    Phospholipids (PLs) containing specific polar head groups and fatty acids, artificially synthesized from a complex mixture of natural PLs, have considerable industrial applications. The biocatalytic approaches to synthesizing structured PLs are of great interest because the enzymes used show high selectivity and performance under mild conditions, leading to the generation of products that cannot easily be obtained by chemical catalysis. Although the limited supply of phospholipases (e.g., phospholipase D) has thus far been an obstacle to the widespread use of enzymatic processing, recent advances in enzyme preparation have opened up various applications for PL modification. In this review, attempts to increase the productivity and utility of microbial phospholipases and lipases are presented. We also summarize recent developments in enzyme-catalyzed modification of PLs, focusing particularly on the relevant reactions, bioreactor design, and novel proof-of-concept experiments. PMID:26245679

  1. Surface modification of sapphire for enhanced infrared window performance

    SciTech Connect

    McHargue, C.J.; Joslin, D.L.; Williams, J.M.; O`Hern, M.E.

    1993-09-01

    Two ion implantation conditions were evaluated for improving the mechanical performance of sapphire IR window material. Both increased the average strength as measured by 4-point bend tests and were effective in preventing the propagation of surface flaws. Ion implantation that produced a damaged crystalline surface improved the reliability at lower stresses more than the implantation that produced an amorphous surface. Neither process significantly affected the IR transmission.

  2. Modification of surface properties of copper-refractory metal alloys

    DOEpatents

    Verhoeven, John D.; Gibson, Edwin D.

    1993-10-12

    The surface properties of copper-refractory metal (CU-RF) alloy bodies are modified by heat treatments which cause the refractory metal to form a coating on the exterior surfaces of the alloy body. The alloys have a copper matrix with particles or dendrites of the refractory metal dispersed therein, which may be niobium, vanadium, tantalum, chromium, molybdenum, or tungsten. The surface properties of the bodies are changed from those of copper to that of the refractory metal.

  3. Ammonia modification of oxide-free Si(111) surfaces

    NASA Astrophysics Data System (ADS)

    Chopra, Tatiana Peixoto; Longo, Roberto C.; Cho, Kyeongjae; Chabal, Yves J.

    2016-08-01

    Amination of surfaces is useful in a variety of fields, ranging from device manufacturing to biological applications. Previous studies of ammonia reaction on silicon surfaces have concentrated on vapor phase rather than wet chemical processes, and mostly on clean Si surfaces. In this work, the interaction of liquid and vapor-phase ammonia is examined on three types of oxide-free surfaces - passivated by hydrogen, fluorine (1/3 monolayer) or chlorine - combining infrared absorption spectroscopy, X-ray photoelectron spectroscopy, and first-principles calculations. The resulting chemical composition highly depends on the starting surface; there is a stronger reaction on both F- and Cl-terminated than on the H-terminated Si surfaces, as evidenced by the formation of Si-NH2. Side reactions can also occur, such as solvent reaction with surfaces, formation of ammonium salt by-products (in the case of 0.2 M ammonia in dioxane solution), and nitridation of silicon (in the case of neat and gas-phase ammonia reactions for instance). Unexpectedly, there is formation of Si-H bonds on hydrogen-free Cl-terminated Si(111) surfaces in all cases, whether vapor phase of neat liquid ammonia is used. The first-principles modeling of this complex system suggests that step-edge surface defects may play a key role in enabling the reaction under certain circumstances, despite the endothermic nature for Si-H bond formation.

  4. Analysis of the Effect of Surface Modification on Polyimide Composites Coated with Erosion Resistant Materials

    NASA Technical Reports Server (NTRS)

    Ndalama, Tchinga; Hirschfeld, Deidre; Sutter, James K. (Technical Monitor)

    2003-01-01

    The aim of this research is to enhance performance of composite coatings through modification of graphite-reinforced polyimide composite surfaces prior to metal bond coat/ hard topcoat application for use in the erosive and/or oxidative environments of advanced engines. Graphite reinforced polyimide composites, PMR-15 and PMR-II-50, formed by sheet molding and pre-pregging will be surface treated, overlaid with a bond coat and then coated with WC-Co. The surface treatment will include cleaning, RF plasma or ultraviolet light- ozone etching, and deposition of SiO(x) groups. These surface treatments will be studied in order to investigate and improve adhesion and oxidation resistance. The following panels were provided by NASA-Glenn Research Center(NASA-GRC): Eight compression molded PMR-II-50; 6 x 6 x 0.125 in. Two vacuum-bagged PMR-II-50; 12 x 12 x 0.125 in. Eight compression molded PMR-15; 6 x 6 x 0.125 in. One vacuum-bagged PMR-15; 12 x 12 x 0.125 in. All panels were made using a 12 x 12 in. T650-35 8HS (3K-tow) graphite fabric. A diamond-wafering blade, with deionized water as a cutting fluid, was used to cut PMR-II-50 and PMR-15 panels into 1 x 1 in. pieces for surface tests. The panel edges exhibiting delamination were used for the preliminary surface preparation tests as these would be unsuitable for strength and erosion testing. PMR-15 neat resin samples were also provided by NASA GRC. Surface profiles of the as-received samples were determined using a Dektak III Surface profile measuring system. Two samples of compression molded PMR-II-50 and PMR-15, vacuum-bagged PMR-II-50 and PMR-15 were randomly chosen for surface profile measurement according to ANSI/ASME B46.1. Prior to each measurement, the samples were blasted with compressed air to remove any artifacts. Five 10 mm-long scans were made on each sample. The short and long wavelength cutoff filter values were set at 100 and 1000 m, diamond stylus radius was 12.5 microns. Table 1 is a summary of the

  5. Surface chemical deposition of advanced electronic materials

    NASA Astrophysics Data System (ADS)

    Bjelkevig, Cameron

    The focus of this work was to examine the direct plating of Cu on Ru diffusion barriers for use in interconnect technology and the substrate mediated growth of graphene on boron nitride for use in advanced electronic applications. The electrodeposition of Cu on Ru(0001) and polycrystalline substrates (with and without pretreatment in an iodine containing solution) has been studied by cyclic voltammetry (CV), current--time transient measurements (CTT), in situ electrochemical atomic force microscopy (EC-AFM), and X-ray photoelectron spectroscopy (XPS). The EC-AFM data show that at potentials near the OPD/UPD threshold, Cu crystallites exhibit pronounced growth anisotropy, with lateral dimensions greatly exceeding vertical dimensions. XPS measurements confirmed the presence and stability of adsorbed I on the Ru surface following pre-treatment in a KI/H2SO4 solution and following polarization to at least -200 mV vs. Ag/AgCl. CV data of samples pre-reduced in I-containing electrolyte exhibited a narrow Cu deposition peak in the overpotential region and a UPD peak. The kinetics of the electrodeposited Cu films was investigated by CTT measurements and applied to theoretical models of nucleation. The data indicated that a protective I adlayer may be deposited on an airexposed Ru electrode as the oxide surface is electrochemically reduced, and that this layer will inhibit reformation of an oxide during the Cu electroplating process. A novel method for epitaxial graphene growth directly on a dielectric substrate of systematically variable thickness was studied. Mono/multilayers of BN(111) were grown on Ru(0001) by atomic layer deposition (ALD), exhibiting a flat (non-nanomesh) R30(✓3x✓3) structure. BN(111) was used as a template for growth of graphene by chemical vapor deposition (CVD) of C2H4 at 1000 K. Characterization by LEED, Auger, STM/STS and Raman indicate the graphene is in registry with the BN substrate, and exhibits a HOPG-like 0 eV bandgap density

  6. Surface modification of silver nanofilms for improved perchlorate detection by surface-enhanced Raman scattering.

    PubMed

    Hao, Jumin; Han, Mei-Juan; Li, Jinwei; Meng, Xiaoguang

    2012-07-01

    Surface-enhanced Raman scattering (SERS), as one of the most sensitive spectroscopic analysis methods, has been investigated extensively for the detection of environmental contaminants in recent years. In this work, we reported the new development of robust SERS substrates for rapid and sensitive sensing of aqueous perchlorate, a widespread environmental contaminant. The fabrication of the substrates consisted of two simple steps: (a) formation of Ag nanofilms on Cu and surface-roughened Cu foils (Ag/Cu and Ag/rCu nanofilms) using a controllable and inexpensive one-step electroless plating process, and (b) surface modification of the Ag nanofilms with cysteamine (Cys) self-assembly monolayer (SAM) (Cys-Ag/Cu and Cys-Ag/rCu substrates). Due to the strong affinity of -NH(3)(+) groups of the Cys molecules for perchlorate ions, the rapid SERS detection of perchlorate has been realized with a limit of detection (LOD) down to 5 μg L(-1) (ppb) for aqueous samples without need for drying. Various calibration curves with good linear relationships were obtained, indicating the quantification potential of SERS analysis of perchlorate using these new substrates. It was found that the neutral pH yielded the maximum SERS signals, and 85% of original sensitivity was remained in 5 days of storage time in the air, indicating the substrates are fairly stable. Within 10 regeneration-reuse cycles, the SERS signals of perchlorate kept in the range of 85-105% of the original value, verifying its reusability. PMID:22494687

  7. Surface modification of fibers by conducting polymers and their use in composites

    NASA Astrophysics Data System (ADS)

    Yavuz, Hande; Girard, Gregory; Bai, Jinbo; Lab. PPSM, CNRS UMR 8531, ENS Cachan, 94235, Cachan Cedex Collaboration; Acxys Technologies France Collaboration

    2013-09-01

    Due to the discovery of their incredible functional properties, carbon nanotubes (CNTs) have drawn a great deal of interest from both academic and industrial research teams in the past few years. Since novel materials are to be integrated in structural and functional applications in several fields, inclusion of CNTs as a reinforcement component in polymer matrix composites (PMC) could bring new solutions. However, in order to obtain more advanced CNTs composites, the amount of strong bonding between CNTs and matrix must be realized to ensure the effective stress transfer in a PMC. This research aims to establish an efficient dielectric barrier discharge technique for the surface modification of CNTs grafted carbon fibers (CNTs-CF) with plasma polypyrrole (PPPy) in order to be used in PMC. It is found that response surface methodology can be applicable in modeling to evaluate the effects of important process variables on electrical resistivity of CNTs-CF. From low to high plasma powers, X-ray Photoelectron Spectroscopy studies revealed the loss of α- and β-carbons in pyrrole ring. The higher the plasma power the lower the electrical conductivity and the higher the mechanical properties. This research was supported under ANR PROCOM Project (EADS-IW). The financial support from French Government and Ecole Centrale Paris are gratefully acknowledged.

  8. Surface modification of CaF 2 in atomic layer scale by electron beam exposure

    NASA Astrophysics Data System (ADS)

    Hwang, S. M.; Izumi, A.; Tsutsui, K.; Furukawa, S.

    1994-12-01

    Surface modification of CaF 2/Si(111) was studied for the purpose of 1 ML adsorption of group-V atoms on a fluoride surface which is applicable to heteroepitaxy of III—V compound semiconductors on CaF 2. By using Rutherford backscattering (RBS) and X-ray photoelectron spectroscopy (XPS), it was found that 1 ML of As and P were successfully adsorbed on a CaF 2 surface, and that a 1 ML self-limiting adsorption of As for the electron beam exposure was realized. Also, we propose a model for the adsorption conditions depending on the substrate temperature during surface modification.

  9. Identification of Posttranslational Modification-Dependent Protein Interactions Using Yeast Surface Displayed Human Proteome Libraries.

    PubMed

    Bidlingmaier, Scott; Liu, Bin

    2015-01-01

    The identification of proteins that interact specifically with posttranslational modifications such as phosphorylation is often necessary to understand cellular signaling pathways. Numerous methods for identifying proteins that interact with posttranslational modifications have been utilized, including affinity-based purification and analysis, protein microarrays, phage display, and tethered catalysis. Although these techniques have been used successfully, each has limitations. Recently, yeast surface-displayed human proteome libraries have been utilized to identify protein fragments with affinity for various target molecules, including phosphorylated peptides. When coupled with fluorescently activated cell sorting and high throughput methods for the analysis of selection outputs, yeast surface-displayed human proteome libraries can rapidly and efficiently identify protein fragments with affinity for any soluble ligand that can be fluorescently detected, including posttranslational modifications. In this review we compare the use of yeast surface display libraries to other methods for the identification of interactions between proteins and posttranslational modifications and discuss future applications of the technology. PMID:26060076

  10. Identification of Posttranslational Modification-Dependent Protein Interactions Using Yeast Surface Displayed Human Proteome Libraries

    PubMed Central

    Bidlingmaier, Scott; Liu, Bin

    2016-01-01

    The identification of proteins that interact specifically with posttranslational modifications such as phosphorylation is often necessary to understand cellular signaling pathways. Numerous methods for identifying proteins that interact with posttranslational modifications have been utilized, including affinity-based purification and analysis, protein microarrays, phage display, and tethered catalysis. Although these techniques have been used successfully, each has limitations. Recently, yeast surface-displayed human proteome libraries have been utilized to identify protein fragments with affinity for various target molecules, including phosphorylated peptides. When coupled with fluorescently activated cell sorting and high throughput methods for the analysis of selection outputs, yeast surface-displayed human proteome libraries can rapidly and efficiently identify protein fragments with affinity for any soluble ligand that can be fluorescently detected, including posttranslational modifications. In this review we compare the use of yeast surface display libraries to other methods for the identification of interactions between proteins and posttranslational modifications and discuss future applications of the technology. PMID:26060076

  11. Surface modification of implanted cardiovascular metal stents: from antithrombosis and antirestenosis to endothelialization.

    PubMed

    Zhang, Kun; Liu, Tao; Li, Jing-An; Chen, Jun-Ying; Wang, Jian; Huang, Nan

    2014-02-01

    Driven by the complications occurring with bare metal stents and drug-eluting stents, concerns have been raised over strategies for long-term safety, with respect to preventing or inhibiting stent thrombosis, restenosis, and in-stent restenosis in particularly. Surface modification is very important in constructing a buffer layer at the interface of the organic and inorganic materials and in ultimately obtaining long-term biocompatibility. In this review, we summarize the developments in surface modification of implanted cardiovascular metal stents. This review focuses on the modification of metal stents via coating drugs or biomolecules to enhance antithrombosis, antirestenosis, and/or endothelialization. In addition, we indicate the probable future work involving the modification of the metallic blood-contacting surfaces of stents and other cardiovascular devices that are under development. PMID:23520056

  12. Electron beam surface modifications in reinforcing and recycling of polymers

    NASA Astrophysics Data System (ADS)

    Czvikovszky, T.; Hargitai, H.

    1997-08-01

    Thermoplastic polymers can be fiber-reinforced in the recycling step through a reactive modification of the interface between the polymer matrix and fiber. Recollected automobile bumpers made of polypropylene copolymers have been reinforced during the reprocessing with eight different types of high-strength fibers, with waste cord-yarns of the tire industry. A thin layer reactive interface of acrylic oligomers has been applied and activated through low energy (175 keV) electron beam (EB). The upcycling (upgrading recycling) resulted in a series of extrudable and injection-mouldable, fiber-reinforced thermoplastic of enhanced bending strength, increased modulus of elasticity and acceptable impact strength. EB treatment has been compared with conventional methods.

  13. Effect of plasma surface modification on the biocompatibility of UHMWPE.

    PubMed

    Kaklamani, G; Mehrban, N; Chen, J; Bowen, J; Dong, H; Grover, L; Stamboulis, A

    2010-10-01

    In this paper active screen plasma nitriding (ASPN) is used to chemically modify the surface of UHMWPE. This is an unexplored and new area of research. ASPN allows the homogeneous treatment of any shape or surface at low temperature; therefore, it was thought that ASPN would be an effective technique to modify organic polymer surfaces. ASPN experiments were carried out at 120 °C using a dc plasma nitriding unit with a 25% N(2) and 75% H(2) atmosphere at 2.5 mbar of pressure. UHMWPE samples treated for different time periods were characterized by nanoindentation, FTIR, XPS, interferometry and SEM. A 3T3 fibroblast cell line was used for in vitro cell culture experiments. Nanoindentation of UHMWPE showed that hardness and elastic modulus increased with ASPN treatment compared to the untreated material. FTIR spectra did not show significant differences between the untreated and treated samples; however, some changes were observed at 30 min of treatment in the range of 1500-1700 cm(-1) associated mainly with the presence of N-H groups. XPS studies showed that nitrogen was present on the surface and its amount increased with treatment time. Interferometry showed that no significant changes were observed on the surfaces after the treatment. Finally, cell culture experiments and SEM showed that fibroblasts attached and proliferated to a greater extent on the plasma-treated surfaces leading to the conclusion that ASPN surface treatment can potentially significantly improve the biocompatibility behaviour of polymeric materials. PMID:20876959

  14. Enhanced cell adhesion on silk fibroin via lectin surface modification.

    PubMed

    Teuschl, Andreas H; Neutsch, Lukas; Monforte, Xavier; Rünzler, Dominik; van Griensven, Martijn; Gabor, Franz; Redl, Heinz

    2014-06-01

    Various tissue engineering (TE) approaches are based on silk fibroin (SF) as scaffold material because of its superior mechanical and biological properties compared to other materials. The translation of one-step TE approaches to clinical application has generally failed so far due to the requirement of a prolonged cell seeding step before implantation. Here, we propose that the plant lectin WGA (wheat germ agglutinin), covalently bound to SF, will mediate cell adhesion in a time frame acceptable to be part of a one-step surgical intervention. After the establishment of a modification protocol utilizing carbodiimide chemistry, we examined the attachment of cells, with a special focus on adipose-derived stromal cells (ASC), on WGA-SF compared to pure native SF. After a limited time frame of 20min the attachment of ASCs to WGA-SF showed an increase of about 17-fold, as compared to pure native SF. The lectin-mediated cell adhesion further showed an enhanced resistance to trypsin (as a protease model) and to applied fluid shear stress (mechanical stability). Moreover, we could demonstrate that the adhesion of ASCs on the WGA-SF does not negatively influence proliferation or differentiation potential into the osteogenic lineage. To test for in vitro immune response, the proliferation of peripheral blood mononuclear cells in contact with the WGA-SF was determined, showing no alterations compared to plain SF. All these findings suggest that the WGA modification of SF offers important benefits for translation of SF scaffolds into clinical applications. PMID:24530561

  15. Chemical modification of near-surface charge trapping in polymers

    NASA Astrophysics Data System (ADS)

    Haridoss, S.; Perlman, M. M.

    1984-03-01

    The surfaces of three polyolefin films, low-density polyethylene, high-density polyethylene, and polypropylene, were chemically modified by etching with permanganic acid, and low-density polyethylene by etching with chromic acid and by staining with chlorosulphonic acid. Polytetrafluoroethylene (Teflon) was treated with a sodium naphthalene complex in glycol ether. The surfaces were examined with a scanning electron microscope, and chemical groups identified by attenuated total reflectance infrared measurements. The surfaces were then corona charged, and the charge stability and trap distributions determined by the methods of thermally stimulated charge decay and thermally stimulated current, respectively. Scanning electron micrographs revealed a nodular surface structure in polyolefins etched with permanganic acid, a rough surface without nodules in low-density polyethylene etched with chromic acid, isolated corroded surface spots in low-density polyethylene stained with chlorosulphonic acid, and a web-like surface in etched Teflon. Permanganic acid removed amorphous and defective regions of the polymer surfaces, exposing more crystalline regions and crystalline-amorphous boundaries, both of which provided trapping sites, producing better charge storers than the virgin equivalents. Lifetimes, and hence usable temperatures in device application, were increased for both negative and positive charge. The other acids reduced the lifetimes in low-density polyethylene. Etching made Teflon as good a positive charge storer as the virgin negatively charged material, a result important to practical applications. While attenuated total reflectance measurements showed the presence of various chemical groups, charge stability seemed to depend more on surface morphology than on which active groups were added to the polymers by the etchants and staining agent.

  16. Method for chemical surface modification of fumed silica particles

    DOEpatents

    Grabbe, Alexis; Michalske, Terry Arthur; Smith, William Larry

    1999-01-01

    Dehydroxylated, silica-containing, glass surfaces are known to be at least partially terminated by strained siloxane rings. According to the invention, a surface of this kind is exposed to a selected silane compound or mixture of silane compounds under reaction-promoting conditions. The ensuing reaction results in opening of the strained siloxane rings, and termination of surface atoms by chemical species, such as organic or organosilicon species, having desirable properties. These species can be chosen to provide qualities such as hydrophobicity, or improved coupling to a polymeric coating.

  17. Method for chemical surface modification of fumed silica particles

    DOEpatents

    Grabbe, A.; Michalske, T.A.; Smith, W.L.

    1999-05-11

    Dehydroxylated, silica-containing, glass surfaces are known to be at least partially terminated by strained siloxane rings. According to the invention, a surface of this kind is exposed to a selected silane compound or mixture of silane compounds under reaction-promoting conditions. The ensuing reaction results in opening of the strained siloxane rings, and termination of surface atoms by chemical species, such as organic or organosilicon species, having desirable properties. These species can be chosen to provide qualities such as hydrophobicity, or improved coupling to a polymeric coating. 11 figs.

  18. Surface modification and characterization of aramid fibers with hybrid coating

    NASA Astrophysics Data System (ADS)

    Chen, Jianrui; Zhu, Yaofeng; Ni, Qingqing; Fu, Yaqin; Fu, Xiang

    2014-12-01

    Aramid fibers were modified through solution dip-coating and interfacial in situ polymerization using a newly synthesized SiO2/shape memory polyurethane (SiO2/SMPU) hybrid. Fourier transform infrared and X-ray photoelectron spectroscopy indicated that the synthesized SiO2/SMPU hybrid successfully coated the fiber surface. The surface morphology of the aramid fibers and the single fiber tensile strength and interfacial shear strength (IFSS) of the composites were determined. The IFSS of the fiber coated with the hybrid improved by 45%, which benefited from a special "pizza-like" structure on the fiber surface.

  19. Comparison of surface modification chemistries in mouse, porcine, and human islets.

    PubMed

    SoRelle, Jeffrey A; Kanak, Mazhar A; Itoh, Takeshi; Horton, Joshua M; Naziruddin, Bashoo; Kane, Robert R

    2015-03-01

    Beta cell replacement therapy, the transplantation of isolated pancreatic islets by intraportal infusion, offers patients with brittle type 1 diabetes blood glucose regulation with a minimally invasive technique. Chemical modification of islets prior to transplantation, providing a nanothin barrier that potentially includes active protective compounds, has been proposed as a strategy to minimize the inflammatory and immune reactions that often significantly limit graft function and duration. Chemical modification also has the potential to allow the use of alternative sources of islets, such as porcine islets, for transplantation. This investigation compared three orthogonal covalent islet modification techniques across three species (human, porcine, and murine), using multiple measures to determine biocompatibility and effectiveness. All three conjugation chemistries were well tolerated, and the overall efficiency, gross uniformity, and stability of the surface modifications were dependent upon the conjugation chemistry as well as the islet source (human, porcine, or murine). Notably, the reductive modification of surface disulfides was shown to afford intense and long-lasting modification of human islets. This study demonstrates that murine, human, and porcine islets tolerate a variety of covalent modifications, that these modifications are relatively stable, and that the murine islet model may not be predictive for some chemical contexts. PMID:24829144

  20. Modification of surface properties of polyethylene by Ar plasma discharge

    NASA Astrophysics Data System (ADS)

    Švorčík, V.; Kotál, V.; Slepička, P.; Bláhová, O.; Špírková, M.; Sajdl, P.; Hnatowicz, V.

    2006-03-01

    Polyethylene (PE) surface was modified by Ar plasma discharge. The changes of surface morphology and surface wettability (characterized by contact angle) were followed using AFM microscopy and standard goniometry, respectively. The changes of chemical structure of PE polymeric chain were characterized by FTIR and XPS techniques. A nanoindenter was used to study mechanical properties (microhardness, elasticity module and microscratch test) of modified PE. After exposition to the plasma discharge a fast decline of the contact angle is observed. The decline depends on the discharge power and the time elapsed from the plasma exposition. FTIR and XPS measurements indicate an oxidation of degraded polymeric chains and creation of hydroxyl, carbonyl, ether, ester and carboxyl groups. Surface morphology of modified PE depends on the plasma discharge power and exposure time. Maximum microhardness and elastic module, observed on PE specimens exposed to plasma discharge for 240 s, may be connected with PE crosslinking initiated by plasma discharge.

  1. Ionic-charge modification at the surface of polar crystals

    SciTech Connect

    Watson, R.E.; Davenport, J.W.

    1983-05-15

    A simple variational principle has been applied to obtain a bound on the change in ionic charge of a polar crystal between the surface and the interior. Central to the estimate is the assumption that the energy involves terms analytic in the ionic charge q and that these may be treated as a sum of Madelung, intra-atomic, and interatomic (overlap and hybridization) contributions. The Madelung terms are calculated explicitly, the intra-atomic contributions are obtained from the following paper (Phys. Rev. B 27, 6428 (1983)), and the change in interatomic terms on going from the bulk to the surface is estimated by scaling with coordination number. The results do not replace detailed quantum-mechanical calculations but they are simple computationally, and they suggest trends in the competition between the Madelung potential, which encourages ion charging, and hybridization, which discourages ionic charging, both at the surface and in the interior of a crystal. Nonpolar surfaces are of principal concern but one polar surface is considered indicating that the charge disturbance penetrates much further in from the surface than it does in nonpolar cases where the effect is largely limited to the first layer of atoms.

  2. Atomic and molecular layer deposition for surface modification

    SciTech Connect

    Vähä-Nissi, Mika; Sievänen, Jenni; Salo, Erkki; Heikkilä, Pirjo; Kenttä, Eija; Johansson, Leena-Sisko; Koskinen, Jorma T.; Harlin, Ali

    2014-06-01

    Atomic and molecular layer deposition (ALD and MLD, respectively) techniques are based on repeated cycles of gas–solid surface reactions. A partial monolayer of atoms or molecules is deposited to the surface during a single deposition cycle, enabling tailored film composition in principle down to molecular resolution on ideal surfaces. Typically ALD/MLD has been used for applications where uniform and pinhole free thin film is a necessity even on 3D surfaces. However, thin – even non-uniform – atomic and molecular deposited layers can also be used to tailor the surface characteristics of different non-ideal substrates. For example, print quality of inkjet printing on polymer films and penetration of water into porous nonwovens can be adjusted with low-temperature deposited metal oxide. In addition, adhesion of extrusion coated biopolymer to inorganic oxides can be improved with a hybrid layer based on lactic acid. - Graphical abstract: Print quality of a polylactide film surface modified with atomic layer deposition prior to inkjet printing (360 dpi) with an aqueous ink. Number of printed dots illustrated as a function of 0, 5, 15 and 25 deposition cycles of trimethylaluminum and water. - Highlights: • ALD/MLD can be used to adjust surface characteristics of films and fiber materials. • Hydrophobicity after few deposition cycles of Al{sub 2}O{sub 3} due to e.g. complex formation. • Same effect on cellulosic fabrics observed with low temperature deposited TiO{sub 2}. • Different film growth and oxidation potential with different precursors. • Hybrid layer on inorganic layer can be used to improve adhesion of polymer melt.

  3. Effects of Weak Surface Modification on Co/SiO2 Catalyst for Fischer-Tropsch Reaction

    PubMed Central

    Ning, Wensheng; Shen, Hehong; Jin, Yangfu; Yang, Xiazhen

    2015-01-01

    A weak surface modification is applied to Co/SiO2 catalyst by hydrothermal treatment at 180°C for 5 h. Aluminum is introduced to Co/SiO2 catalysts during the surface modification. The effects of surface modification on Co/SiO2 catalyst are studied by changing the operating sequences of surface modification and cobalt impregnation in the catalyst preparation. Surface modification before cobalt impregnation makes Co3O4 particle small and dispersed into the deep part of enlarged pore in SiO2, while surface modification after cobalt impregnation does not obviously change the particle size of Co3O4. The improved amplitude of catalytic activity is similar for the two kinds of catalysts, but they are benefited from different factors. The content of iso-hydrocarbons in the products is increased by the surface modifications. PMID:25938725

  4. Effects of Weak Surface Modification on Co/SiO2 Catalyst for Fischer-Tropsch Reaction.

    PubMed

    Ning, Wensheng; Shen, Hehong; Jin, Yangfu; Yang, Xiazhen

    2015-01-01

    A weak surface modification is applied to Co/SiO2 catalyst by hydrothermal treatment at 180°C for 5 h. Aluminum is introduced to Co/SiO2 catalysts during the surface modification. The effects of surface modification on Co/SiO2 catalyst are studied by changing the operating sequences of surface modification and cobalt impregnation in the catalyst preparation. Surface modification before cobalt impregnation makes Co3O4 particle small and dispersed into the deep part of enlarged pore in SiO2, while surface modification after cobalt impregnation does not obviously change the particle size of Co3O4. The improved amplitude of catalytic activity is similar for the two kinds of catalysts, but they are benefited from different factors. The content of iso-hydrocarbons in the products is increased by the surface modifications. PMID:25938725

  5. Study on Glow Discharge Plasma Used in Polyester Surface Modification

    NASA Astrophysics Data System (ADS)

    Liu, Wenzheng; Lei, Xiao; Zhao, Qiang

    2016-01-01

    To achieve an atmospheric pressure glow discharge (APGD) in air and modify the surface of polyester thread using plasma, the electric field distribution and discharge characteristics under different conditions were studied. We found that the region with a strong electric field, which was formed in a tiny gap between two electrodes constituting a line-line contact electrode structure, provided the initial electron for the entire discharge process. Thus, the discharge voltage was reduced. The dielectric barrier of the line-line contact electrodes can inhibit the generation of secondary electrons. Thus, the transient current pulse discharge was reduced significantly, and an APGD in air was achieved. We designed double layer line-line contact electrodes, which can generate the APGD on the surface of a material under treatment directly. A noticeable change in the surface morphology of polyester fiber was visualized with the aid of a scanning electron microscope (SEM). Two electrode structures - the multi-row line-line and double-helix line-line contact electrodes - were designed. A large area of the APGD plasma with flat and curved surfaces can be formed in air using these contact electrodes. This can improve the efficiency of surface treatment and is significant for the application of the APGD plasma in industries.

  6. Plasma modification of HEMA and EOEMA surface properties

    NASA Astrophysics Data System (ADS)

    Svorcik, V.; Kolarova, K.; Dvorankova, B.; Michalek, J.; Krumbholcova, E.; Hnatowicz, V.

    2006-01-01

    Process of plasma etching of poly(2-hydroxyethylmethacrylate) (HEMA) and poly(2-ethyloxyethyl methacrylate) (EOEMA) in Ar atmosphere at room temperature was studied. Ablation of the samples exposed to the plasma was determined by gravimetry, surface wettability by goniometry, chemical structure by FTIR spectroscopy and surface morphology by Scanning Electron (SEM) microscopy. Adhesion and proliferation of 3T3 mouse fibroblasts was studied in vitro in order to determine biological activity of plasma-modified HEMA and EOEMA substrates. It was demonstrated that the plasma etching leads to oxidation of HEMA and to an increase of its wettability. More estheric structures are produced in EOEMA. For both polymers, a surface layer similar to 2 mu m thick is ablated after plasma etching for 400 s. The etching changes the sample surface morphology and its biological activity. The surface becomes smoother after etching. The results obtained after 3T3 cells cultivation show that the plasma etching decreases cell adhesion and increases cell proliferation in comparison with pristine polymers.

  7. Femtosecond laser modification of titanium surfaces: direct imprinting of hydroxylapatite nanopowder and wettability tuning via surface microstructuring

    NASA Astrophysics Data System (ADS)

    Ionin, Andrey A.; Kudryashov, Sergey I.; Makarov, Sergey V.; Saltuganov, Pavel N.; Seleznev, Leonid V.; Sinitsyn, Dmitry V.; Golosov, Evgene V.; Goryainov, Artem A.; Kolobov, Yury R.; Kornieieva, Kateryna A.; Skomorokhov, Andrei N.; Ligachev, Alexander E.

    2013-04-01

    Femtosecond laser modification of titanium surfaces was performed to produce microstructured hydrophilic and biocompatible surface layers. Biocompatible nano/microcoatings were prepared for the first time by dry femtosecond laser imprinting of hydroxylapatite nano/micropowder onto VT6 titanium surfaces. In these experiments HAP was first deposited onto the titanium surfaces and then softly imprinted by multiple femtosecond laser pulses into the laser-melted surface metal layer. The surface relief was modified at the nano- and microscales depending on the incident laser fluence and sample scanning speed. Wetting tests demonstrated that the wetting properties of the pristine Ti surface can be tuned through its laser modification in both the hydrophobic and hydrophilic directions.

  8. Surface Modification of Polymers by Reaction of Alkyl Radicals.

    PubMed

    Hetemi, Dardan; Médard, Jérôme; Kanoufi, Frédéric; Combellas, Catherine; Pinson, Jean; Podvorica, Fetah I

    2016-01-19

    The surfaces of poly(methyl methacrylate) and polyethylene are modified either (i) by a two-step process including the thermal reaction of alkyl radicals derived from bromohexanoic acid in a mixture of 2,6-dimethylbenzene diazonium salt and neat isopentyl nitrite at 60 °C, followed by reaction with p-nitroaniline, anthraquinone, neutral red, and polyethylene glycol moieties, or (ii) by reaction of a previously anthraquinone-modified bromohexanoic acid. The modified surfaces are characterized by IR, XPS, UV, and water contact angles. A mechanism is proposed to rationalize the results. This approach is an efficient way to modify and pattern polymer surfaces with different organic groups and chemical functionalities under mild conditions. PMID:26653398

  9. Laser produced coatings and surface modifications for medical implants

    NASA Astrophysics Data System (ADS)

    León, B.

    2010-11-01

    Lasers can be an effective tool for tailoring the surface of medical implants. Laser irradiation can modify the surface wettability, bioactivity and its capacity to absorb proteins. By using appropriate energies and wavelengths, also the topographical features at macro, micro and nano level can be shaped in order to adapt to cells, extracellular matrices and orientation of ligand molecules. Pulsed laser deposition can produce nanometer thick, dense and well adhering CaP coatings with extremely fine control of chemistry and crystallinity. No further thermal annealing is needed. In-vitro and in-vivo experiments with different cells and animals models have demonstrated similar or better osseointegration of laser deposited coatings compared to the commercial available plasma sprayed ones. Ultraviolet lasers can successfully chemically functionalize the surface of implants, and femtosecond laser can drill polymer plates or meshes for tissue engineering applications.

  10. Controlled mechnical modification of manganite surface with nanoscale resolution.

    PubMed

    Kelly, Simon J; Kim, Yunseok; Eliseev, Eugene; Morozovska, Anna; Jesse, Stephen; Biegalski, Michael D; Mitchell, J F; Zheng, H; Aarts, J; Hwang, Inrok; Oh, Sungtaek; Choi, Jin Sik; Choi, Taekjib; Park, Bae Ho; Kalinin, Sergei V; Maksymovych, Peter

    2014-11-28

    We investigated the surfaces of magnetoresistive manganites, La(1-x)Ca(x)MnO3 and La(2-2x)Sr(1+2x)Mn2O7, using a combination of ultrahigh vacuum conductive, electrostatic and magnetic force microscopy methods. Scanning as-grown film with a metal tip, even with zero applied bias, was found to modify the surface electronic properties such that in subsequent scans, the conductivity is reduced below the noise level of conductive probe microscopy. Scanned areas also reveal a reduced contact potential difference relative to the pristine surface by ∼0.3 eV. We propose that contact-pressure of the tip modifies the electrochemical potential of oxygen vacancies via the Vegard effect, causing vacancy motion and concomitant changes of the electronic properties. PMID:25380080

  11. Modification of polytetrafluoroethylene surfaces using H2S plasma treatment

    NASA Astrophysics Data System (ADS)

    Vesel, Alenka; Kovac, Janez; Zaplotnik, Rok; Modic, Martina; Mozetic, Miran

    2015-12-01

    A process for modifying the surface properties of polytetrafluoroethylene (PTFE) polymer using sulfur-containing gaseous plasma is presented in this paper. Samples of PTFE foils were treated in pure H2S gaseous plasma sustained by an electrode-less radio-frequency discharge in the E-mode. The samples were kept at a floating potential. X-ray photoelectron spectroscopy, secondary ion mass spectrometry and atomic force microscopy were used to determine the evolution of the surface functionalities and morphology. An extremely thin film of chemically bonded sulfur was formed on the surface after a few seconds of plasma treatment, whereas a treatment duration of more than a minute resulted in the deposition of pure sulfur. The deposited film remained as thin as a few nanometers, even after half an hour of treatment.

  12. Effects of cementation surface modifications on fracture resistance of zirconia

    PubMed Central

    Srikanth, Ramanathan; Kosmac, Tomaz; Bona, Alvaro Della; Yin, Ling; Zhang, Yu

    2015-01-01

    Objectives To examine the effects of glass infiltration (GI) and alumina coating (AC) on the indentation flexural load and four-point bending strength of monolithic zirconia. Methods Plate-shaped (12 mm × 12 mm × 1.0 mm or 1.5 mm or 2.0 mm) and bar-shaped (4 mm × 3 mm × 25 mm) monolithic zirconia specimens were fabricated. In addition to monolithic zirconia (group Z), zirconia monoliths were glass-infiltrated or alumina-coated on their tensile surfaces to form groups ZGI and ZAC, respectively. They were also glass-infiltrated on their upper surfaces, and glass-infiltrated or alumina-coated on their lower (tensile) surfaces to make groups ZGI2 and ZAC2, respectively. For comparison, porcelain-veneered zirconia (group PVZ) and monolithic lithium disilicate glass-ceramic (group LiDi) specimens were also fabricated. The plate-shaped specimens were cemented onto a restorative composite base for Hertzian indentation using a tungsten carbide spherical indenter with a radius of 3.2 mm. Critical loads for indentation flexural fracture at the zirconia cementation surface were measured. Strengths of bar-shaped specimens were evaluated in four-point bending. Results Glass infiltration on zirconia tensile surfaces increased indentation flexural loads by 32% in Hertzian contact and flexural strength by 24% in four-point bending. Alumina coating showed no significant effect on resistance to flexural damage of zirconia. Monolithic zirconia outperformed porcelain-veneered zirconia and monolithic lithium disilicate glass-ceramics in terms of both indentation flexural load and flexural strength. Significance While both alumina coating and glass infiltration can be used to effectively modify the cementation surface of zirconia, glass infiltration can further increase the flexural fracture resistance of zirconia. PMID:25687628

  13. Surface erosion and modification by highly charged ions.

    SciTech Connect

    Insepov, Z.; Terasawa, M.; Takayama, K.; Mathematics and Computer Science; KEK, Japan; Univ. of Hyogo

    2008-06-01

    Analyses were conducted of various models and mechanisms of highly charged ion (HCI) and swift-heavy ion energy transfer into a solid target, such as hollow atom formation, charge screening, neutralization, shock wave generation, crater formation, and sputtering. A plasma model of space charge neutralization based on impact ionization of semiconductors at high electric fields was developed and applied to analyze HCI impacts on Si and W. Surface erosions of semiconductor and metal surfaces caused by HCI bombardments were studied by using a molecular dynamics simulation method, and the results were compared with experimental sputtering data.

  14. Surface Modification by Atmospheric Pressure Plasma for Improved Bonding

    NASA Astrophysics Data System (ADS)

    Williams, Thomas Scott

    An atmospheric pressure plasma source operating at temperatures below 150?C and fed with 1.0-3.0 volume% oxygen in helium was used to activate the surfaces of the native oxide on silicon, carbon-fiber reinforced epoxy composite, stainless steel type 410, and aluminum alloy 2024. Helium and oxygen were passed through the plasma source, whereby ionization occurred and ˜10 16 cm-3 oxygen atoms, ˜1015 cm -3 ozone molecules and ˜1016 cm-3 metastable oxygen molecules (O21Deltag) were generated. The plasma afterglow was directed onto the substrate material located 4 mm downstream. Surface properties of the plasma treated materials have been investigated using water contact angle (WCA), atomic force microscopy (AFM), infrared spectroscopy (IR), and x-ray photoelectron spectroscopy (XPS). The work presented herein establishes atmospheric-pressure plasma as a surface preparation technique that is well suited for surface activation and enhanced adhesive bond strength in a variety of materials. Atmospheric plasma activation presents an environmentally friendly alternative to wet chemical and abrasive methods of surface preparation. Attenuated total internal reflection infrared spectroscopy was used to study the aging mechanism of the native oxide on silicon. During storage at ambient conditions, the water contact angle of a clean surface increased from <5° to 40° over a period of 12 hours. When stored under a nitrogen purge, the water contact angle of a clean surface increased from <5° to 30° over a period of 40-60 hours. The change in contact angle resulted from the adsorption of nonanal onto the exposed surface hydroxyl groups. The rate of adsorption of nonanal under a nitrogen purged atmosphere ranged from 0.378+/-0.011 hr-1 to 0.182+/-0.008 hr -1 molecules/(cm2•s), decreasing as the fraction of hydrogen-bonded hydroxyl groups increased from 49% to 96% on the SiO 2 surface. The adsorption of the organic contaminant could be suppressed indefinitely by storing the

  15. Surface modification of nonviral nanocarriers for enhanced gene delivery.

    PubMed

    Fortier, Charles; Durocher, Yves; De Crescenzo, Gregory

    2014-01-01

    Biomedical nanotechnology has given a new lease of life to gene therapy with the ever-developing and ever-diversifying nonviral gene delivery nanocarriers. These are designed to pass a series of barriers in order to bring their nucleic acid cargo to the right subcellular location of particular cells. For a given application, each barrier has its dedicated strategy, which translates into a physicochemical, biological and temporal identity of the nanocarrier surface. Different strategies have thus been explored to implement adequate surface identities on nanocarriers over time for systemic delivery. In that context, this review will mainly focus on organic nanocarriers, for which these strategies will be described and discussed. PMID:24354815

  16. Reducing ZnO nanoparticle cytotoxicity by surface modification

    NASA Astrophysics Data System (ADS)

    Luo, Mingdeng; Shen, Cenchao; Feltis, Bryce N.; Martin, Lisandra L.; Hughes, Anthony E.; Wright, Paul F. A.; Turney, Terence W.

    2014-05-01

    Nanoparticulate zinc oxide (ZnO) is one of the most widely used engineered nanomaterials and its toxicology has gained considerable recent attention. A key aspect for controlling biological interactions at the nanoscale is understanding the relevant nanoparticle surface chemistry. In this study, we have determined the disposition of ZnO nanoparticles within human immune cells by measurement of total Zn, as well as the proportions of extra- and intracellular dissolved Zn as a function of dose and surface coating. From this mass balance, the intracellular soluble Zn levels showed little difference in regard to dose above a certain minimal level or to different surface coatings. PEGylation of ZnO NPs reduced their cytotoxicity as a result of decreased cellular uptake arising from a minimal protein corona. We conclude that the key role of the surface properties of ZnO NPs in controlling cytotoxicity is to regulate cellular nanoparticle uptake rather than altering either intracellular or extracellular Zn dissolution.Nanoparticulate zinc oxide (ZnO) is one of the most widely used engineered nanomaterials and its toxicology has gained considerable recent attention. A key aspect for controlling biological interactions at the nanoscale is understanding the relevant nanoparticle surface chemistry. In this study, we have determined the disposition of ZnO nanoparticles within human immune cells by measurement of total Zn, as well as the proportions of extra- and intracellular dissolved Zn as a function of dose and surface coating. From this mass balance, the intracellular soluble Zn levels showed little difference in regard to dose above a certain minimal level or to different surface coatings. PEGylation of ZnO NPs reduced their cytotoxicity as a result of decreased cellular uptake arising from a minimal protein corona. We conclude that the key role of the surface properties of ZnO NPs in controlling cytotoxicity is to regulate cellular nanoparticle uptake rather than

  17. Laser surface modification of Ti implants to improve osseointegration

    NASA Astrophysics Data System (ADS)

    Marticorena, M.; Corti, G.; Olmedo, D.; Guglielmotti, M. B.; Duhalde, S.

    2007-04-01

    Commercially Pure Titanium foils, were irradiated using a pulsed Nd:YAG laser under ambient air, in order to produce and characterize a well controlled surface texture (roughness and waviness) that enhances osseointegration. To study the 'peri-implant' reparative process response, the laser treated Ti foils were implanted in the tibia of 10 male Wistar rats. At 14 days post-implantation, the histological analysis showed a tendency to more bone formation compared to the untreated control implants. The formation of a layer of TiN on the surface and the obtained roughness, have been demonstrated to improve bone response.

  18. Plasma treatment induces internal surface modifications of electrospun poly(L-lactic) acid scaffold to enhance protein coating

    NASA Astrophysics Data System (ADS)

    Jin Seo, Hyok; Hee Lee, Mi; Kwon, Byeong-Ju; Kim, Hye-Lee; Jin Lee, Seung; Kim, Bong-Jin; Wang, Kang-Kyun; Kim, Yong-Rok; Park, Jong-Chul

    2013-08-01

    Advanced biomaterials should also be bioactive with regard to desirable cellular responses, such as selective protein adsorption and cell attachment, proliferation, and differentiation. To enhance cell-material interactions, surface modifications have commonly been performed. Among the various surface modification approaches, atmospheric pressure glow discharge plasma has been used to change a hydrophobic polymer surface to a hydrophilic surface. Poly(L-lactic acid) (PLLA)-derived scaffolds lack cell recognition signals and the hydrophobic nature of PLLA hinders cell seeding. To make PLLA surfaces more conducive to cell attachment and spreading, surface modifications may be used to create cell-biomaterial interfaces that elicit controlled cell adhesion and maintain differentiated phenotypes. In this study, (He) gaseous atmospheric plasma glow discharge was used to change the characteristics of a 3D-type polymeric scaffold from hydrophobic to hydrophilic on both the outer and inner surfaces of the scaffold and the penetration efficiency with fibronectin was investigated. Field-emission scanning electron microscope images showed that some grooves were formed on the PLLA fibers after plasma treatment. X-ray photoelectron spectroscopy data also showed chemical changes in the PLLA structure. After plasma treatment, -CN (285.76 eV) was increased in C1s and -NH2 (399.70 eV) was increased significantly and -N=CH (400.80 eV) and -NH3+ (402.05 eV) were newly appeared in N1s. These changes allowed fibronectin to penetrate into the PLLA scaffold; this could be observed by confocal microscopy. In conclusion, helium atmospheric pressure plasma treatment was effective in modifying the polymeric scaffold, making it hydrophilic, and this treatment can also be used in tissue engineering research as needed to make polymers hydrophilic.

  19. Plasma treatment induces internal surface modifications of electrospun poly(L-lactic) acid scaffold to enhance protein coating

    SciTech Connect

    Jin Seo, Hyok; Hee Lee, Mi; Kwon, Byeong-Ju; Kim, Hye-Lee; Park, Jong-Chul; Jin Lee, Seung; Kim, Bong-Jin; Wang, Kang-Kyun; Kim, Yong-Rok

    2013-08-21

    Advanced biomaterials should also be bioactive with regard to desirable cellular responses, such as selective protein adsorption and cell attachment, proliferation, and differentiation. To enhance cell-material interactions, surface modifications have commonly been performed. Among the various surface modification approaches, atmospheric pressure glow discharge plasma has been used to change a hydrophobic polymer surface to a hydrophilic surface. Poly(L-lactic acid) (PLLA)-derived scaffolds lack cell recognition signals and the hydrophobic nature of PLLA hinders cell seeding. To make PLLA surfaces more conducive to cell attachment and spreading, surface modifications may be used to create cell-biomaterial interfaces that elicit controlled cell adhesion and maintain differentiated phenotypes. In this study, (He) gaseous atmospheric plasma glow discharge was used to change the characteristics of a 3D-type polymeric scaffold from hydrophobic to hydrophilic on both the outer and inner surfaces of the scaffold and the penetration efficiency with fibronectin was investigated. Field-emission scanning electron microscope images showed that some grooves were formed on the PLLA fibers after plasma treatment. X-ray photoelectron spectroscopy data also showed chemical changes in the PLLA structure. After plasma treatment, -CN (285.76 eV) was increased in C1s and -NH{sub 2} (399.70 eV) was increased significantly and –N=CH (400.80 eV) and –NH{sub 3}{sup +} (402.05 eV) were newly appeared in N1s. These changes allowed fibronectin to penetrate into the PLLA scaffold; this could be observed by confocal microscopy. In conclusion, helium atmospheric pressure plasma treatment was effective in modifying the polymeric scaffold, making it hydrophilic, and this treatment can also be used in tissue engineering research as needed to make polymers hydrophilic.

  20. Friction Surface Modification by Nanodiamonds of Denotational Synthesis

    NASA Astrophysics Data System (ADS)

    Davidov, S. V.; Gorlenko, A. O.

    2016-04-01

    The paper deals with the technology and equipment for making a hardened antifriction surface layer of machine elements on the basis of using carbon nanomaterials in order to improve wear resistance. The paper presents the results of tribotechnical tests of pins according to standard techniques using an automated system for research.

  1. Ion beam induced optical and surface modification in plasmonic nanostructures

    NASA Astrophysics Data System (ADS)

    Singh, Udai B.; Gautam, Subodh K.; Kumar, Sunil; Hooda, Sonu; Ojha, Sunil; Singh, Fouran

    2016-07-01

    In present work, ion irradiation induced nanostructuring has been exploited as an efficient and effective tool for synthesis of coupled plasmonics nanostructures by using 1.2 MeV Xe ions on Au/ZnO/Au system deposited on glass substrate. The results are correlated on the basis of their optical absorption, surface morphologies and enhanced sensitivity of evolved phonon modes by using UV Visible spectroscopy, scanning electron microscopy (SEM), and Raman spectroscopy (RS), respectively. Optical absorbance spectra of plasmonic nanostructures (NSs) show a decrease in band gap, which may be ascribed to the formation of defects with ion irradiation. The surface morphology reveals the formation of percolated NSs upon ion irradiation and Rutherford backscattering spectrometry (RBS) study clearly shows the formation of multilayer system. Furthermore, RS measurements on samples are studied to understand the enhanced sensitivity of ion irradiation induced phonon mode at 573 cm-1 along with other modes. As compared to pristine sample, a stronger and pronounced evolution of these phonon modes is observed with further ion irradiation, which indicates localized surface plasmon results with enhanced intensity of phonon modes of Zinc oxide (ZnO) material. Thus, such plasmonic NSs can be used as surface enhanced Raman scattering (SERS) substrates.

  2. Oxygen plasma surface modification enhances immobilization of simvastatin acid.

    PubMed

    Yoshinari, Masao; Hayakawa, Tohru; Matsuzaka, Kenichi; Inoue, Takashi; Oda, Yutaka; Shimono, Masaki; Ide, Takaharu; Tanaka, Teruo

    2006-02-01

    Simvastatin acid (SVA) has been reported to stimulate bone formation with increased expression of BMP-2. Therefore, immobilization of SVA onto dental implants is expected to promote osteogenesis at the bone tissue/implant interface. The aim of this study was to evaluate the immobilization behavior of SVA onto titanium (Ti), O(2)-plasma treated titanium (Ti + O(2)), thin-film coatings of hexamethyldisiloxane (HMDSO), and O(2)-plasma treated HMDSO (HMDSO + O(2)) by using the quartz crystal microbalance-dissipation (QCM-D) technique. HMDSO surfaces were activated by the introduction of an OH group and/or O(2)-functional groups by O(2)-plasma treatment. In contrast, titanium surfaces showed no appreciable compositional changes by O(2)-plasma treatment. The QCM-D technique enabled evaluation even at the adsorption behavior of a substance with a low molecular weight such as simvastatin. The largest amount of SVA was adsorbed on O(2)-plasma treated HMDSO surfaces compared to untreated titanium, HMDSO-coated titanium, and O(2)-plasma treated titanium. These findings suggested that the adsorption of SVA was enhanced on more hydrophilic surfaces concomitant with the presence of an OH group and/or O(2)-functional group resulting from the O(2)-plasma treatment, and that an organic film of HMDSO followed by O(2)-plasma treatment is a promising method for the adsorption of SVA in dental implant systems. PMID:16543663

  3. Surface parameters modification by multilayer coatings deposition for biomedical applications

    NASA Astrophysics Data System (ADS)

    Zykova, A.; Safonov, V.; Virva, O.; Luk'yanchenko, V.; Walkowich, J.; Rogowska, R.; Yakovin, S.

    2008-05-01

    Studies are presented of the surface parameters of various multilayer coatings, namely, TiN, CrN, (Ti, Cr)N, TiN/TiC10N90, TiN/TiC20N80 deposited by means of Arc-PVD on stainless steel (1H18N9), as well as of the same coatings with an additional Al2O3 film deposited by reactive magnetron sputtering (RMS). The surface thickness, roughness and topography are estimated. Other parameters, such as the surface free energy (SFE) and fractional polarity are determined by means of the Wu and the Owens-Wendt-Rabel-Kaelble methods. Experiments are carried out on the in vitro cell/material interaction (in a fibroblasts culture) in order to determine the materials biomedical response. The results show some correlation between the surface properties and cell adhesion. The best biological response parameters (cell number, proliferation function, morphology) are obtained in the case of coatings with the highest values of the polar part component of the SFE and the fractional polarity, such as TiN, TiN/TiC10N90 and oxide coatings.

  4. Surface modification of layered zirconium phosphate with PNIPAM.

    PubMed

    Wang, Xuezhen; Zhao, Di; Medina, Ilse B Nava; Diaz, Agustin; Wang, Huiliang; Clearfield, Abraham; Mannan, M Sam; Cheng, Zhengdong

    2016-04-01

    A new method was reported to modify layered zirconium phosphate (ZrP) with thermoresponsive polymer PNIPAM (poly N-isopropylacrylamide). PNIPAM was proved to be covalently grafted onto ZrP. (60)Co γ-rays irradiation produced peroxide groups on the surface which, upon heating, initiated free radical polymerization and subsequent attachment of PNIPAM. PMID:26966882

  5. Surface Modification by Atmospheric Pressure Plasma for Improved Bonding

    NASA Astrophysics Data System (ADS)

    Williams, Thomas Scott

    An atmospheric pressure plasma source operating at temperatures below 150?C and fed with 1.0-3.0 volume% oxygen in helium was used to activate the surfaces of the native oxide on silicon, carbon-fiber reinforced epoxy composite, stainless steel type 410, and aluminum alloy 2024. Helium and oxygen were passed through the plasma source, whereby ionization occurred and ˜10 16 cm-3 oxygen atoms, ˜1015 cm -3 ozone molecules and ˜1016 cm-3 metastable oxygen molecules (O21Deltag) were generated. The plasma afterglow was directed onto the substrate material located 4 mm downstream. Surface properties of the plasma treated materials have been investigated using water contact angle (WCA), atomic force microscopy (AFM), infrared spectroscopy (IR), and x-ray photoelectron spectroscopy (XPS). The work presented herein establishes atmospheric-pressure plasma as a surface preparation technique that is well suited for surface activation and enhanced adhesive bond strength in a variety of materials. Atmospheric plasma activation presents an environmentally friendly alternative to wet chemical and abrasive methods of surface preparation. Attenuated total internal reflection infrared spectroscopy was used to study the aging mechanism of the native oxide on silicon. During storage at ambient conditions, the water contact angle of a clean surface increased from <5° to 40° over a period of 12 hours. When stored under a nitrogen purge, the water contact angle of a clean surface increased from <5° to 30° over a period of 40-60 hours. The change in contact angle resulted from the adsorption of nonanal onto the exposed surface hydroxyl groups. The rate of adsorption of nonanal under a nitrogen purged atmosphere ranged from 0.378+/-0.011 hr-1 to 0.182+/-0.008 hr -1 molecules/(cm2•s), decreasing as the fraction of hydrogen-bonded hydroxyl groups increased from 49% to 96% on the SiO 2 surface. The adsorption of the organic contaminant could be suppressed indefinitely by storing the

  6. On-line monitoring of poly dimethylsiloxane surface modification using the photothermal deflection technique

    NASA Astrophysics Data System (ADS)

    Najmoddin, Najmeh; Khosroshahi, Mohammad. E.

    2015-02-01

    Over the last decade, there has been particular interest in surface modification of biomaterials with regard to understanding the importance of surface characterization. This paper reports the use of photothermal deflection (PTD) technique to monitor modifications in poly dimethylsiloxane (PDMS) surface induced following laser treatments. The FTIR results are in agreement with PTD results, indicating that no structural changes occurred using Argon laser up to 180 s and 200 mW at 454, 488 and 514 nm wavelengths. However, with CO2 laser some physical and chemical changes occurred which are monitored by PTD technique and proved by SEM images.

  7. Some environmental problems and their satellite monitoring. [anthropogenic modifications of earth surface

    NASA Technical Reports Server (NTRS)

    Otterman, J.

    1975-01-01

    Anthropogenic modification of the earth's surface is discussed in two problem areas: (1) land use changes and overgrazing, and how it affects albedo and land surface-atmosphere interactions, and (2) water and land surface pollution, especially oil slicks. A literature survey evidences the importance of these problems. The need for monitoring is stressed, and it is suggested that with some modifications to the sensors, ERTS (Landsat) series satellites can provide approximate monitoring information. The European Landsat receiving station in Italy will facilitate data collection for the tasks described.

  8. Biofouling behavior and performance of forward osmosis membranes with bioinspired surface modification in osmotic membrane bioreactor.

    PubMed

    Li, Fang; Cheng, Qianxun; Tian, Qing; Yang, Bo; Chen, Qianyuan

    2016-07-01

    Forward osmosis (FO) has received considerable interest for water and energy related applications in recent years. Biofouling behavior and performance of cellulose triacetate (CTA) forward osmosis membranes with bioinspired surface modification via polydopamine (PD) coating and poly (ethylene glycol) (PEG) grafting (PD-g-PEG) in a submerged osmotic membrane bioreactor (OMBR) were investigated in this work. The modified membranes exhibited lower flux decline than the pristine one in OMBR, confirming that the bioinspired surface modification improved the antifouling ability of the CTA FO membrane. The result showed that the decline of membrane flux related to the increase of the salinity and MLSS concentration of the mixed liquid. It was concluded that the antifouling ability of modified membranes ascribed to the change of surface morphology in addition to the improvement of membrane hydrophilicity. The bioinspired surface modifications might improve the anti-adhesion for the biopolymers and biocake. PMID:27089532

  9. Electronic structure modification of graphene on d-band metal surfaces and its Raman signature

    NASA Astrophysics Data System (ADS)

    Coh, Sinisa; Zhou, Qin; Zettl, Alex; Cohen, Marvin L.; Louie, Steven G.

    2014-03-01

    We find strong modifications of the graphene electronic structure when it is placed on a platinum surface. Additionally, these modifications strongly depend on the relative orientation of the graphene and platinum lattices. We expect that the same will occur whenever graphene is brought in contact with a surface of a material that has d-orbital close to the Fermi level. We demonstrate experimentally and theoretically that these modifications leave a distinct signature in the Raman spectrum of graphene. Out of two prominent graphene Raman peaks, one is unaffected (the G peak) while the other (the 2D peak) is severely affected, in proportion with the modification of the graphene electronic structure. This work was supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Computational resources have been provided by the DOE at Lawrence Berkeley National Laboratory's NERSC facility.

  10. Boronic acid as an efficient anchor group for surface modification of solid polyvinyl alcohol.

    PubMed

    Nishiyabu, Ryuhei; Shimizu, Ai

    2016-07-28

    We report the use of boronic acid as an anchor group for surface modification of solid polyvinyl alcohol (PVA); the surfaces of PVA microparticles, films, and nanofibers were chemically modified with boronic acid-appended fluorescent dyes through boronate esterification using a simple soaking technique in a short time under ambient conditions. PMID:27311634

  11. Effect of polymer surface modification on polymer-protein interaction via hydrophilic polymer grafting

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Surface modification of flat sheet ultrafiltration membranes, polyethersulfone (PES) was investigated to improve the hydrophilicity of the membrane surface thereby reducing adsorption of the proteins onto the membrane. Grafting of hydrophilic polymers onto UV/ozone treated PES was used to improve t...

  12. Modification of silicon nitride surfaces with GOPES and APTES for antibody immobilization: computational and experimental studies

    NASA Astrophysics Data System (ADS)

    Dien To, Thien; Nguyen, Anh Tuan; Nhat Thanh Phan, Khoa; Thu Thi Truong, An; Doan, Tin Chanh Duc; Mau Dang, Chien

    2015-12-01

    Chemical modification of silicon nitride (SiN) surfaces by silanization has been widely studied especially with 3-(aminopropyl)triethoxysilane (APTES) and 3-(glycidyloxypropyl) dimethylethoxysilane (GOPES). However few reports performed the experimental and computational studies together. In this study, surface modification of SiN surfaces with GOPES and APTES covalently bound with glutaraldehyde (GTA) was investigated for antibody immobilization. The monoclonal anti-cytokeratin-FITC (MACF) antibody was immobilized on the modified SiN surfaces. The modified surfaces were characterized by water contact angle measurements, atomic force microscopy and fluorescence microscopy. The FITC-fluorescent label indicated the existence of MACF antibody on the SiN surfaces and the efficiency of the silanization reaction. Absorption of APTES and GOPES on the oxidized SiN surfaces was computationally modeled and calculated by Materials Studio software. The computational and experimental results showed that modification of the SiN surfaces with APTES and GTA was more effective than the modification with GOPES.

  13. Surface modification of nanoparticles for radiation curable acrylate clear coatings

    NASA Astrophysics Data System (ADS)

    Bauer, F.; Gläsel, H.-J.; Hartmann, E.; Bilz, E.; Mehnert, R.

    2003-08-01

    To obtain transparent, scratch and abrasion resistant coatings a high content of nanosized silica and alumina filler was embedded in radiation-curable acrylate formulations by acid catalyzed silylation using trialkoxysilanes. 29SiMAS NMR and MALDI-TOF mass spectrometry were employed to elucidate the structure of the surface-grafted methacryloxypropyl-, vinyl- and n-propyl-trimethoxysilane. In accordance with NMR findings, MALDI-TOF MS showed highly condensed oligomeric siloxanes of more than 20 monomeric silane units. A ladder-like structure of bound polysiloxanes is proposed rather than a simplified picture of tridentate silane bonding. Hence, silane coupling agents do not only modify the chemical nature of the filler surface but also strongly effect the rheological properties of the acrylate nanodispersions.

  14. Surface modification of ZnO nanorods with Hamilton receptors.

    PubMed

    Zeininger, Lukas; Klaumünzer, Martin; Peukert, Wolfgang; Hirsch, Andreas

    2015-01-01

    A new prototype of a Hamilton receptor suitable for the functionalization of inorganic nanoparticles was synthesized and characterized. The hydrogen bonding receptor was coupled to a catechol moiety, which served as anchor group for the functionalization of metal oxides, in particular zinc oxide. Synthesized zinc oxide nanorods [ZnO] were used for surface functionalization. The wet-chemical functionalization procedure towards monolayer-grafted particles [ZnO-HR] is described and a detailed characterization study is presented. In addition, the detection of specific cyanurate molecules is demonstrated. The hybrid structures [ZnO-HR-CA] were stable towards agglomeration and exhibited enhanced dispersability in apolar solvents. This observation, in combination with several spectroscopic experiments gave evidence of the highly directional supramolecular recognition at the surface of nanoparticles. PMID:25872141

  15. Surface Modifications of Polyester Films by Ammonia Plasma

    NASA Astrophysics Data System (ADS)

    Narushima, Kazuo; Yamashita, Nanami; Fukuoka, Megumi; Inagaki, Norihiro; Isono, Yoshihiro; Islam, Mohammed Rafiqul

    2007-07-01

    Effects of treatment using ammonia plasma on poly(lactic acid) (PLA), poly(ethylene terephthalate) (PET), and liquid-crystal polymer (LCP) were investigated to elucidate differences related to polymer structures and the mode of introduction of nitrogen functional groups onto the polyester surfaces. Nitrogen functional groups were introduced into PET and LCP, but were not introduced into PLA. Those results indicate reductions in the contact angle for PET and LCP. No decrease in the contact angle was observed for PLA. Reasons for differences in attachment of nitrogen functional groups by ammonia plasma processing on polyester surfaces were discussed. The respective actions of active species were investigated for radicals, electrons, and ions in plasma.

  16. Surface Modification of ZnO Nanorods with Hamilton Receptors

    PubMed Central

    Zeininger, Lukas; Klaumünzer, Martin; Peukert, Wolfgang; Hirsch, Andreas

    2015-01-01

    A new prototype of a Hamilton receptor suitable for the functionalization of inorganic nanoparticles was synthesized and characterized. The hydrogen bonding receptor was coupled to a catechol moiety, which served as anchor group for the functionalization of metal oxides, in particular zinc oxide. Synthesized zinc oxide nanorods [ZnO] were used for surface functionalization. The wet-chemical functionalization procedure towards monolayer-grafted particles [ZnO-HR] is described and a detailed characterization study is presented. In addition, the detection of specific cyanurate molecules is demonstrated. The hybrid structures [ZnO-HR-CA] were stable towards agglomeration and exhibited enhanced dispersability in apolar solvents. This observation, in combination with several spectroscopic experiments gave evidence of the highly directional supramolecular recognition at the surface of nanoparticles. PMID:25872141

  17. The surface modification of clay particles by RF plasma technique

    NASA Astrophysics Data System (ADS)

    Lee, Sang-Keol

    In this study, the surface coatings of ball clay, organoclay and exfoliated clay prepared by sol-gel process were done by RF plasma polymerization to improve the surface activity of the clay filler. Characterization of the above plasma-treated clays has been carried out by various techniques. The effects of plasma-treated clays as substitute of carbon black in styrene-butadiene rubber (SBR) and ethylene-propylene-diene monomer (EPDM) on the curing and mechanical properties were investigated. After plasma treatment, the tensile properties of organo and exfoliated clay were not unsatisfactory to that of carbon black filler system. Moreover, only 10 phr filler loading of plasma-treated organoclay in EPDM vulcanizates showed better results than 40 phr filler loading of carbon black in EPDM vulcanizates. The main objective of this study was to verify the applicability of the plasma technique for modifying clay surfaces for their use in the tire manufacturing industry. Another purpose was to reveal the advantage of the plasma technique used to obtain modified-clay and improved properties that those materials can display.

  18. Biomimetic surface modification of polyurethane with phospholipids grafted carbon nanotubes.

    PubMed

    Tan, Dongsheng; Liu, Liuxu; Li, Zhen; Fu, Qiang

    2015-08-01

    To improve blood compatibility of polyurethane (PU), phospholipids grafted carbon nanotubes (CNTs) were prepared through zwitterion-mediated cycloaddition reaction and amide condensation, and then were added to the PU as fillers via solution mixing to form biomimetic surface. The properties of phospholipids grafted CNTs (CNT-PC) were investigated by thermal gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and proton nuclear magnetic resonance ((1) H NMR). The results indicated that the phospholipids were grafted onto CNTs in high efficiency, and the hydrophilicity and dispersibility of the modified CNTs were improved effectively. The structures and properties of composites containing CNT-PC were investigated by optical microscope, XPS, and water contact angles. The results indicated that phospholipids were enriched on the surface with addition of 0.1 wt % of CNT-PC, which significantly reduced protein adsorption and platelet adhesion. The method of carrying phospholipids on the nanofiller to modify polymers has provided a promising way of constructing biomimetic phospholipid membrane on the surface to improve blood compatibility. PMID:25630300

  19. Surface modification of nanoporous alumina membranes by plasma polymerization

    NASA Astrophysics Data System (ADS)

    Losic, Dusan; Cole, Martin A.; Dollmann, Björn; Vasilev, Krasimir; Griesser, Hans J.

    2008-06-01

    The deposition of plasma polymer coatings onto porous alumina (PA) membranes was investigated with the aim of adjusting the surface chemistry and the pore size of the membranes. PA membranes from commercial sources with a range of pore diameters (20, 100 and 200 nm) were used and modified by plasma polymerization using n-heptylamine (HA) monomer, which resulted in a chemically reactive polymer surface with amino groups. Heptylamine plasma polymer (HAPP) layers with a thickness less than the pore diameter do not span the pores but reduce their diameter. Accordingly, by adjusting the deposition time and thus the thickness of the plasma polymer coating, it is feasible to produce any desired pore diameter. The structural and chemical properties of modified membranes were studied by scanning electron microscopy (SEM), atomic force microscopy (AFM) and x-ray electron spectroscopy (XPS). The resultant PA membranes with specific surface chemistry and controlled pore size are applicable for molecular separation, cell culture, bioreactors, biosensing, drug delivery, and engineering complex composite membranes.

  20. Controlling solid lipid nanoparticle adhesion by polyelectrolyte multilayer surface modifications.

    PubMed

    Finke, Jan Henrik; Schmolke, Hannah; Klages, C-P; Müller-Goymann, Christel C

    2013-06-01

    This study addresses the tunability of polyelectrolyte multilayers (PEM) toward adsorption of solid lipid nanoparticles (SLN). In SLN production for pharmaceutical applications, repellence from production equipment is desired while targeted adsorption is necessary for the functionalization of surfaces. SLN containing triglyceride/phospholipid or wax matrices were exposed to different PEM (consisting of poly(allylamine hydrochloride) (PAH), poly(diallyldimethylammonium chloride), and poly(acrylic acid)). PEM varied regarding layer architecture and surface properties by means of deposition pH, top layer variation, PEGylation with poly(acrylic acid)-graft-poly(ethylene glycol) copolymer, and thermal crosslinking. FTIR-ATR and SEM revealed SLN adhesion depending on PEM composition. Particle adsorption was tunable toward attraction as well as repellence: PEGylated PEM displayed lowest adsorption while PEM capped with PAH provided the strongest attraction of particles. Examinations at elevated temperatures resembled production conditions of SLN where these are processed as emulsions. Crystalline triglyceride SLN displayed high anisometry and, consequently, a large specific surface area. These platelets were more adherend than spherical droplets from the same formulation as an emulsion. Wax-based nanoparticles showed spherical shape, both in crystalline and molten state. However, adsorption was fostered as the fluidity of the disperse phase increased upon melting. Additionally, coalescence of adsorbed droplets took place, further increasing adsorption. PMID:23591009

  1. Gaseous phase coal surface modification. Final technical report

    SciTech Connect

    Okoh, J.M.; Pinion, J.; Thiensatit, S.

    1992-05-07

    In this report, we present an improved, feasible and potentially cost effective method of cleaning and beneficiating ultrafine coal. Increased mechanization of mining methods and the need towards depyritization, and demineralization have led to an increase in the quantity of coal fines generated in recent times. For example, the amount of {minus}100 mesh coal occurring in coal preparation plant feeds now typically varies from 5 to 25% of the total feed. Environmental constraints coupled with the greatly increased cost of coal have made it increasingly important to recover more of these fines. Our method chemically modifies the surface of such coals by a series of gaseous phase treatments employing Friedel-Crafts reactions. By using olefins (ethene, propene and butene) and hydrogen chloride catalyst at elevated temperature, the surface hydrophobicity of coal is enhanced. This increased hydrophobicity is manifest in surface phenomena which reflect conditions at the solid/liquid interphase (zeta potential) and those which reflect conditions at the solid/liquid/gas interphases (contact angle, wettability and floatability).

  2. Highly efficient industrial large-area black silicon solar cells achieved by surface nanostructured modification

    NASA Astrophysics Data System (ADS)

    Li, Ping; Wei, Yi; Zhao, Zengchao; Tan, Xin; Bian, Jiming; Wang, Yuxuan; Lu, Chunxi; Liu, Aimin

    2015-12-01

    Traditional black silicon solar cells show relatively low efficiencies due to the high surface recombination occurring at the front surfaces. In this paper, we present a surface modification process to suppress surface recombination and fabricate highly efficient industrial black silicon solar cells. The Ag-nanoparticle-assisted etching is applied to realize front surface nanostructures on silicon wafers in order to reduce the surface reflectance. Through a further tetramethylammonium hydroxide (TMAH) treatment, the carrier recombination at and near the surface is greatly suppressed, due to a lower surface dopant concentration after the surface modification. This modified surface presents a low reflectivity in a range of 350-1100 nm. Large-area solar cells with an average conversion efficiency of 19.03% are achieved by using the TMAH treatment of 30 s. This efficiency is 0.18% higher than that of standard silicon solar cells with pyramidal surfaces, and also a remarkable improvement compared with black silicon solar cells without TMAH modifications.

  3. PES Surface Modification Using Green Chemistry: New Generation of Antifouling Membranes.

    PubMed

    Nady, Norhan

    2016-01-01

    A major limitation in using membrane-based separation processes is the loss of performance due to membrane fouling. This drawback can be addressed thanks to surface modification treatments. A new and promising surface modification using green chemistry has been recently investigated. This modification is carried out at room temperature and in aqueous medium using green catalyst (enzyme) and nontoxic modifier, which can be safely labelled "green surface modification". This modification can be considered as a nucleus of new generation of antifouling membranes and surfaces. In the current research, ferulic acid modifier and laccase bio-catalyst were used to make poly(ethersulfone) (PES) membrane less vulnerable to protein adsorption. The blank and modified PES membranes are evaluated based on e.g., their flux and protein repellence. Both the blank and the modified PES membranes (or laminated PES on silicon dioxide surface) are characterized using many techniques e.g., SEM, EDX, XPS and SPM, etc. The pure water flux of the most modified membranes was reduced by 10% on average relative to the blank membrane, and around a 94% reduction in protein adsorption was determined. In the conclusions section, a comparison between three modifiers-ferulic acid, and two other previously used modifiers (4-hydroxybenzoic acid and gallic acid)-is presented. PMID:27096873

  4. Fabrication and surface-modification of implantable microprobes for neuroscience studies

    NASA Astrophysics Data System (ADS)

    Cao, H.; Nguyen, C. M.; Chiao, J. C.

    2012-06-01

    In this work implantable micro-probes for central nervous system (CNS) studies were developed on silicon and polyimide substrates. The probes which contained micro-electrode arrays with different surface modifications were designed for implantation in the CNS. The electrode surfaces were modified with nano-scale structures that could greatly increase the active surface area in order to enhance the electrochemical current outputs while maintaining micro-scale dimensions of the electrodes and probes. The electrodes were made of gold or platinum, and designed with different sizes. The silicon probes were modified by silicon nanowires fabricated with the vapor–liquid–solid mechanism at high temperatures. With polyimide substrates, the nanostructure modification was carried out by applying concentrated gold or silver colloid solutions onto the micro-electrodes at room temperature. The surfaces of electrodes before and after modification were observed by scanning electron microscopy. The silicon nanowire-modified surface was characterized by cyclic voltammetry. Experiments were carried out to investigate the improvement in sensing performance. The modified electrodes were tested with H2O2, electrochemical L-glutamate and dopamine. Comparisons between electrodes with and without nanostructure modification were conducted showing that the modifications have enhanced the signal outputs of the electrochemical neurotransmitter sensors.

  5. Improvement of β-TCP/PLLA biodegradable material by surface modification with stearic acid.

    PubMed

    Ma, Fengcang; Chen, Sai; Liu, Ping; Geng, Fang; Li, Wei; Liu, Xinkuan; He, Daihua; Pan, Deng

    2016-05-01

    Poly-l-lactide (PLLA) is a biodegradable polymer and used widely. Incorporation of beta tricalcium phosphate (β-TCP) into PLLA can enhance its osteoinductive properties. But the interfacial layer between β-TCP particles with PLLA matrix is easy to be destroyed due to inferior interfacial compatibility of the organic/inorganic material. In this work, a method of β-TCP surface modification with stearic acid was investigated to improve the β-TCP/PLLA biomaterial. The effects of surface modification on the β-TCP were investigated by FTIR, XPS, TGA and CA. It was found that the stearic acid reacted with β-TCP and oxhydryl was formed during the surface modification. Hydrophilicity of untreated or modified β-TCP/PLLA composite was increased by the addition of 10wt.% β-TCP, but it decreased as the addition amount increased from 10wt.% to 20wt.%. Two models were suggested to describe the effect of β-TCP concentration on CA of the composites. Mechanical properties of β-TCP/PLLA composites were tested by bending and tensile tests. Fractures of the composites after mechanical test were observed by SEM. It was found that surface modification with stearic acid improved bending and tensile strengths of the β-TCP/PLLA composites obviously. The SEM results indicated that surface modification decreased the probability of interface debonding between fillers and matrix under load. PMID:26952440

  6. Root Surface Bio-modification with Erbium Lasers- A Myth or a Reality??

    PubMed Central

    Lavu, Vamsi; Sundaram, Subramoniam; Sabarish, Ram; Rao, Suresh Ranga

    2015-01-01

    The objective of this literature review was to critically review the evidence available in the literature regarding the expediency of erbium family of lasers for root bio modification as a part of periodontal therapy. The literature search was performed on the Pubmed using MeSH words such as "lasers/therapeutic use, scaling, dental calculus, tooth root/anatomy and histology, ultrasonic therapy". The studies were screened and were grouped as follows: those evaluating a) efficacy for calculus removal with the Erbium family of laser b) root surface changes following Er YAG and Er Cr YSGG application c) comparative studies of the Er YAG, Er Cr YSGG lasers versus conventional methods of root surface modification d) Bio compatibility of root surface following Erbium laser treatment e) Studies on the combined efficacy of laser root modification with conventional methods towards root surface bio-modification f) Studies on effectiveness of root surface bio-modification prior to root coverage procedures. In conclusion, the erbium family has a proven anti-bacterial action, predictable calculus removal, minimal root substance removal, and appears to favor cell attachment. The Erbium family of lasers appears to be a useful adjunct for the management of periodontal disease. PMID:25713635

  7. Plasma Surface Modification of Polyaramid Fibers for Protective Clothing

    NASA Astrophysics Data System (ADS)

    Widodo, Mohamad

    2011-12-01

    The purpose of this research was to develop a novel process that would achieve biocidal properties on Kevlar fabric via atmospheric pressure plasma jet (APPJ) induced-graft polymerization of monomers. In the course of the study, experiments were carried out to understand plasma-monomer-substrate interactions, particularly, how each of the main parameters in the plasma processing affects the formation of surface radicals and eventually the degree of graft polymerization of monomers. The study also served to explore the possibility of developing plasma-initiated and plasma-controlled graft polymerization for continuous operation. In this regards, three methods of processing were studied, which included two-step plasma graft-polymerization with immersion, two-step and one-step plasma graft-polymerization with pad-dry. In general, plasma treatment did not cause visible damage to the surface of Kevlar fibers, except for the appearance of tiny globules distributed almost uniformly indicating a minor effect of plasma treatment to the surface morphology of the polymer. From the examination of SEM images, however, it was found that a very localized surface etching seemed to have taken place, especially at high RF power (800 W) and long time of exposure (60 s), even in plasma downstream mode of operation. It was suggested that a small amount of charged particles might have escaped and reached the substrate surface. High density of surface radicals, which is the prerequisite for high graft density and high antimicrobial activity, was achieved by the combination of high RF power and short exposure time or low RF power and long time of exposure. This was a clear indication that the formation of surface radicals is a function of amount of the dissipated energy, which also explained the two-factor interaction between the two process parameters. XPS results showed that hydrolysis of the anilide bond of PPTA chains took place to some extent on the surface of Kevlar, leading to the

  8. The effect of polymer surface modification on polymer-protein interaction via interfacial polymerization and hydrophilic polymer grafting

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Protein membrane separation is prone to fouling on the membrane surface resulting from protein adsorption onto the surface. Surface modification of synthetic membranes is one way to reduce fouling. We investigated surface modification of polyethersulfone (PES) as a way of improving hydrophilicity ...

  9. Advancing contact angles on large structured surfaces

    NASA Astrophysics Data System (ADS)

    Yoshitake, Yumiko; Itakura, Yoshinori; Gobo, Junichi; Takahashi, Tsutomu

    2014-11-01

    To understand wetting phenomena on complex surfaces, simple modeling experiments in two-dimension system would be one of the most efficient approaches. We develop a new experimental method for wetting dynamics using a large pseudo two- dimensional droplet. This method is useful to examine theoretical studies developed in two dimensional systems. In this study, we examine a pinning and depinning phenomena on millimeter-size structured surface to explain the origin of contact angle hysteresis. Contact lines of the droplet are pinned and deppined at the edge of surface texture. The contact lines can move when the contact angle is equal to the Young's contact angle which are determined by the balance of the surface and interfacial tension immediate vicinity of the contact lines, which is different from the Wenzel's low. Our approach enables to realize a macroscopic modelling experiment of wetting on complex surfaces, which opens a path to design functional surfaces with chemical and physical structure.

  10. Nanostructured silicon surface modifications for as a selective matrix-free laser desorption/ionization mass spectrometry.

    PubMed

    Tsao, C W; Lin, C H; Cheng, Y C; Chien, C C; Chang, C C; Chen, W Y

    2012-06-01

    Matrix-assisted laser desorption/ionization mass spectrometry is an established soft ionization method that is widely applied to analyze biomolecules. The UV-absorbing organic matrix is essential for biomolecule ionization; however, it also creates matrix background interference, which results in problematic analyses of biomolecules of less than 700 Da. Therefore, this study investigates hydrophilic, hydrophobic cationic, anionic and immobilized metal ion surface chemical modifications to advance nanostructured silicon mass spectrometry performance (nSi-MS). This investigation provides information required for a possible novel mass spectroscopy that combines surface-enhanced and nanostructured silicon surface-assisted laser desorption/ionization mass spectrometry for the selective detection of specific compounds of a mixture. PMID:22531330

  11. 3-dimensional microscope analysis of bone and tooth surface modifications: comparisons of fossil specimens and replicas.

    PubMed

    Bello, Silvia M; Verveniotou, Efstratia; Cornish, Lorraine; Parfitt, Simon A

    2011-01-01

    Cut-marks on fossil bones and teeth are an important source of evidence in the reconstruction of ancient butchery practices. The analysis of butchery marks has allowed archaeologists to interpret aspects of past subsistence strategies and the behavior of early humans. Recent advances in optical scanning microscopy allow detailed measurements of cut-mark morphology to be undertaken. An example of this technology is the Alicona 3D InfiniteFocus imaging microscope, which has been applied recently to the study of surface modifications on bones and teeth. Three-dimensional models generated by the Alicona microscope have been used to identify cross-sectional features of experimental cut-marks that are characteristic for specific cutting actions (e.g., slicing, chopping, scraping) and different tool types (e.g., metal versus stone tools). More recently, this technology has been applied successfully to the analysis of ∼500,000 year-old cut-marked animal bones from Boxgrove (U.K.), as well as cannibalized 14,700 cal BP year-old human bones from Gough's Cave (U.K.). This article describes molding methods used to replicate fragile prehistoric bones and teeth, where image quality was adversely affected by specimen translucency and reflectivity. Alicona images generated from molds and casts are often of better quality than those of the original specimen. PMID:21660994

  12. Photoluminescence of CuInS2 nanocrystals: effect of surface modification

    NASA Astrophysics Data System (ADS)

    Kim, Young-Kuk; Cho, Young-Sang; Chung, Kookchae; Choi, Chul-Jin

    2011-09-01

    We have synthesized highly luminescent Cu-In-S(CIS) nanocrystals (NCs) by heating the mixture of metal carboxylates and alkylthiol under inert atmosphere. We modified the surface of CIS NCs with zinc carboxylate and subsequent injection of alkylthiol. As a result of the surface modification, highly luminescent CIS@ZnS core/shell nanocrystals were synthesized. The luminescence quantum yield (QY) of best CIS@ZnS NCs was above 50%, which is 10 times higher than the initial QY of CIS NCs before surface modification (QY=3%). Detailed study on the luminescence mechanism implies that etching of the surface of NCs by dissociated carboxylate group (CH3COO-) and formation of epitaxial shell by Zn with sulfur from alkylthiol efficiently removed the surface defects which are known to be major non-radiative recombination sites in semiconductor nanocrystals. In this study, we developed a novel surface modification route for monodispersed highly luminescent Cu-In-S NCs with less toxic and highly stable precursors. Investigation with the timeand the temperature-dependent photoluminescence showed that the trap related emission was minimized by surface modification and the donor-acceptor pair recombination was enhanced by controlling copper stoichiometry.xb

  13. Nanoscale surface modifications to control capillary flow characteristics in PMMA microfluidic devices.

    PubMed

    Mukhopadhyay, Subhadeep; Roy, Susanta S; D'Sa, Raechelle A; Mathur, Ashish; Holmes, Richard J; McLaughlin, James A

    2011-01-01

    Polymethylmethacrylate (PMMA) microfluidic devices have been fabricated using a hot embossing technique to incorporate micro-pillar features on the bottom wall of the device which when combined with either a plasma treatment or the coating of a diamond-like carbon (DLC) film presents a range of surface modification profiles. Experimental results presented in detail the surface modifications in the form of distinct changes in the static water contact angle across a range from 44.3 to 81.2 when compared to pristine PMMA surfaces. Additionally, capillary flow of water (dyed to aid visualization) through the microfluidic devices was recorded and analyzed to provide comparison data between filling time of a microfluidic chamber and surface modification characteristics, including the effects of surface energy and surface roughness on the microfluidic flow. We have experimentally demonstrated that fluid flow and thus filling time for the microfluidic device was significantly faster for the device with surface modifications that resulted in a lower static contact angle, and also that the incorporation of micro-pillars into a fluidic device increases the filling time when compared to comparative devices. PMID:21711936

  14. Electron beam enhanced surface modification for making highly resolved structures

    DOEpatents

    Pitts, John R.

    1986-01-01

    A method for forming high resolution submicron structures on a substrate is provided by direct writing with a submicron electron beam in a partial pressure of a selected gas phase characterized by the ability to dissociate under the beam into a stable gaseous leaving group and a reactant fragment that combines with the substrate material under beam energy to form at least a surface compound. Variations of the method provide semiconductor device regions on doped silicon substrates, interconnect lines between active sites, three dimensional electronic chip structures, electron beam and optical read mass storage devices that may include color differentiated data areas, and resist areas for use with selective etching techniques.

  15. Surface modification of polytetrafluoroethylene by excimer-laser radiation

    SciTech Connect

    Nishii, M.; Sugimoto, S.; Shimizu, Y.; Suzuki, N.; Kewanishi, S.; Nagese, T.; Endo, M.; Eguchi, Y.

    1993-12-31

    The adhesive strength of polytetrafluoroethylene (PTFE) films was enhanced remarkably by KrF-laser irradiation in air when a small amount of aromatic polymers such as aromatic polyester, polyetheretherketone and polyimide were blended with PTFE. From the surface analysis of the laser-irradiated PTFE by an X-ray photoelectron spectroscopy and a scanning electron microscopy, it was found that the enhancement in the adhesive properties was attributable to both the chemical effect owing to the formation of the polar groups such as carbonyl group and ethylene linkage and the physical one owing to the formation of the uneveness by the KrF-laser irradiation.

  16. Preparation of high porosity xerogels by chemical surface modification.

    DOEpatents

    Deshpande, Ravindra; Smith, Douglas M.; Brinker, C. Jeffrey

    1996-01-01

    This invention provides an extremely porous xerogel dried at vacuum-to-below supercritical pressures but having the properties of aerogels which are typically dried at supercritical pressures. This is done by reacting the internal pore surface of the wet gel with organic substances in order to change the contact angle of the fluid meniscus in the pores during drying. Shrinkage of the gel (which is normally prevented by use of high autoclave pressures, such that the pore fluid is at temperature and pressure above its critical values) is avoided even at vacuum or ambient pressures.

  17. Surface property modification of coatings via self-stratification

    NASA Astrophysics Data System (ADS)

    Pieper, Robert Joseph

    Biological fouling occurs everywhere in the marine environment and is a significant problem for marine vessels. Anti-fouling coatings have been used effectively to prevent fouling; however, these coatings harm non-targeted sea-life. Fouling-release coatings (FRC) appear to be an alternative way to combat fouling. FRC do not necessarily prevent the settlement of marine organisms but rather allow their easy removal with application of shear to the coatings surface. These coatings must be non-toxic, non-leaching, have low surface energy, low modulus, and durability to provide easy removal of marine organisms. Here the goal is to develop FRC based on thermosetting siloxane-polyurethane, amphiphilic polyurethane, and zwitterionic/amphiphilic polyurethane systems. A combinatorial high-throughput approach has been taken in order to explore the variables that may affect the performance of the final coatings. Libraries of acrylic polyols were synthesized using combinatorial high-throughput techniques by either batch or semi-batch processes. The design of the experiments for the batch and semi-batch processes were done combinatorially to explore a range of compositions and various reaction process variables that cannot be accomplished or are not suitable for single reaction experiments. Characterization of Rapid-GPC, high-throughput DSC, and gravimetrically calculated percent solids verified the effects of different reaction conditions on the MW, glass transition temperatures, and percent conversion of the different compositions of acrylic polyols. Coatings were characterized for their surface energy, pseudobarnacle pull-off adhesion, and were subjected to bioassays including marine bacteria, algae, and barnacles. From the performance properties results the acrylic polyol containing 20% hydroxyethyl acrylate and 80% butyl acrylate was selected for further siloxane-polyurethane formulations and were subjected to the same physical, mechanical, and performance testing

  18. Surface Modification of Metallic Glass Composites Through Severe Plastic Deformation

    NASA Astrophysics Data System (ADS)

    Mukherjee, Sundeep; Arora, Harpreet Singh; Mridha, Sanghita

    2015-03-01

    Refinement of crystalline dendrites in a metallic glass composite, Zr56.2Ti13.8Nb5.0Cu6.9Ni5.6Be12.5, was demonstrated by friction stir processing. The surface hardness of the amorphous matrix as well as the crystalline dendritic phase was found to increase by nearly a factor of two for the processed specimens. Higher hardness for the amorphous matrix was explained by the interaction of shear bands, while that for the crystalline dendrite was explained by grain refinement.

  19. Electron beam enhanced surface modification for making highly resolved structures

    DOEpatents

    Pitts, J.R.

    1984-10-10

    A method for forming high resolution submicron structures on a substrate is provided by direct writing with a submicron electron beam in a partial pressure of a selected gas phase characterized by the ability to dissociate under the beam into a stable gaseous leaving group and a reactant fragment that combines with the substrate material under beam energy to form at least a surface compound. Variations of the method provide semiconductor device regions on doped silicon substrates, interconnect lines between active sites, three dimensional electronic chip structures, electron beam and optical read mass storage devices that may include color differentiated data areas, and resist areas for use with selective etching techniques.

  20. Surface modification of investment cast-316L implants: microstructure effects.

    PubMed

    El-Hadad, Shimaa; Khalifa, Waleed; Nofal, Adel

    2015-03-01

    Artificial femur stem of 316L stainless steel was fabricated by investment casting using vacuum induction melting. Different surface treatments: mechanical polishing, thermal oxidation and immersion in alkaline solution were applied. Thicker hydroxyapatite (HAP) layer was formed in the furnace-oxidized samples as compared to the mechanically polished ones. The alkaline treatment enhanced the precipitation of HAP on the samples. It was also observed that the HAP precipitation responded differently to the different phases of the microstructure. The austenite phase was observed to have more homogeneous and smoother layer of HAP. In addition, the growth of HAP was sometimes favored on the austenite phase rather than on ferrite phase. PMID:25579929

  1. Inexpensive laser-induced surface modification in bismuth thin films

    NASA Astrophysics Data System (ADS)

    Contreras, A. Reyes; Hautefeuille, M.; García, A. Esparza; Mejia, O. Olea; López, M. A. Camacho

    2015-05-01

    In this work, we present results on texturing a 500 nm thick bismuth film, deposited by sputtering onto a glass slide using a low-cost homemade, near-infrared pulsed laser platform. A 785 nm laser diode of a CD-DVD pickup head was precisely focused on the sample mounted on a motorized two-axis translation stage to generate localized surface microbumps on the bismuth films. This simple method successfully transferred desired micropatterns on the films in a computer-numerical control fashion. Irradiated zones were characterized by atomic force microscopy and scanning electron microscopy. It was observed that final results are strongly dependent on irradiation parameters.

  2. Methods of preparation and modification of advanced zero-valent iron nanoparticles, their properties and application in water treatment technologies

    NASA Astrophysics Data System (ADS)

    Filip, Jan; Kašlík, Josef; Medřík, Ivo; Petala, Eleni; Zbořil, Radek; Slunský, Jan; Černík, Miroslav; Stavělová, Monika

    2014-05-01

    Zero-valent iron nanoparticles are commonly used in modern water treatment technologies. Compared to conventionally-used macroscopic iron or iron microparticles, the using of nanoparticles has the advantages given mainly by their generally large specific surface area (it drives their high reactivity and/or sorption capacity), small dimensions (it allows their migration e.g. in ground water), and particular physical and chemical properties. Following the applications of zero-valent iron particles in various pilot tests, there arose several critical suggestions for improvements of used nanomaterials and for development of new generation of reactive nanomaterials. In the presentation, the methods of zero-valent iron nanoparticles synthesis will be summarized with a special attention paid to the thermally-induced solid-state reaction allowing preparation of zero-valent iron nanoparticles in an industrial scale. Moreover, the method of thermal reduction of iron-oxide precursors enables to finely tune the critical parameters (mainly particle size and morphology, specific surface area, surface chemistry of nanoparticles etc.) of resulting zero-valet iron nanoparticles. The most important trends of advanced nanoparticles development will be discussed: (i) surface modification of nanomaterilas, (ii) development of nanocomposites and (iii) development of materials for combined reductive-sorption technologies. Laboratory testing of zero-valent iron nanoparticles reactivity and migration will be presented and compared with the field observations: the advanced zero-valent iron nanoparticles were used for groundwater treatment at the locality contaminated by chlorinated hydrocarbons (VC, DCE, TCE and PCE) and reacted nanoparticles were extracted from the sediments for their fate assessment. The authors gratefully acknowledge the support by the Technology Agency of the Czech Republic "Competence Centres" (project No. TE01020218) and the EU FP7 (project NANOREM).

  3. Surface modification of silicon dioxide, silicon nitride and titanium oxynitride for lactate dehydrogenase immobilization.

    PubMed

    Saengdee, Pawasuth; Chaisriratanakul, Woraphan; Bunjongpru, Win; Sripumkhai, Witsaroot; Srisuwan, Awirut; Jeamsaksiri, Wutthinan; Hruanun, Charndet; Poyai, Amporn; Promptmas, Chamras

    2015-05-15

    Three different types of surface, silicon dioxide (SiO2), silicon nitride (Si3N4), and titanium oxynitride (TiON) were modified for lactate dehydrogenase (LDH) immobilization using (3-aminopropyl)triethoxysilane (APTES) to obtain an amino layer on each surface. The APTES modified surfaces can directly react with LDH via physical attachment. LDH can be chemically immobilized on those surfaces after incorporation with glutaraldehyde (GA) to obtain aldehyde layers of APTES-GA modified surfaces. The wetting properties, chemical bonding composition, and morphology of the modified surface were determined by contact angle (CA) measurement, Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM), respectively. In this experiment, the immobilized protein content and LDH activity on each modified surface was used as an indicator of surface modification achievement. The results revealed that both the APTES and APTES-GA treatments successfully link the LDH molecule to those surfaces while retaining its activity. All types of tested surfaces modified with APTES-GA gave better LDH immobilizing efficiency than APTES, especially the SiO2 surface. In addition, the SiO2 surface offered the highest LDH immobilization among tested surfaces, with both APTES and APTES-GA modification. However, TiON and Si3N4 surfaces could be used as alternative candidate materials in the preparation of ion-sensitive field-effect transistor (ISFET) based biosensors, including lactate sensors using immobilized LDH on the ISFET surface. PMID:25108848

  4. Modification of wool surface by liposomes for dyeing with weld.

    PubMed

    Montazer, Majid; Zolfaghari, Alireza; Toliat, Taibeh; Moghadam, Mohammad Bameni

    2009-01-01

    In this research work, wool surface has been modified by liposome to investigate its effects on dyeing with weld, a yellow natural dye. To do this, samples were first treated with aluminium sulphate and afterward with different concentrations of liposomes at various temperatures for 30 minutes and, finally, dyed with weld at 75, 85, and 95 degrees C for 30, 45, and 60 minutes. K/S values of fabric samples were calculated and washing, light and rub fastness properties of the samples were indicated. The results proposed that the sample treated with 1% liposomes and dyed at 75 degrees C for 60 min has the highest K/S value. The central composite design (CCD) used for the experimental plan with three variables on the results of color strength and statistical analysis confirms the optimum conditions obtained by the experimental results. It was also found that washing, light, wet, and dry rub fastness properties of samples dyed with weld, including liposomes, have not significantly changed. The results of water drop absorption indicated that the hydrophobicity is higher for the samples pretreated with liposomes. The SEM picture of wool sample treated with mordant and liposomes and finally dyed with weld shows a coated layer on the fiber surface. PMID:19552578

  5. Modeling of metallic surface topography modification by high-frequency vibration

    NASA Astrophysics Data System (ADS)

    Yao, Zhehe; Mei, Deqing; Chen, Zichen

    2016-02-01

    High-frequency vibration is capable of modifying metallic surface topography significantly, while the underlying mechanisms are still unclear. In this study, the acoustic softening effect is considered to explain and model the effects of high-frequency normal vibration on surface topography. The surface asperities can be softened by the high-frequency vibration due to acoustic softening, leading to the enhancement of surface topography modification. A theoretical model for metallic surface topography modification by high-frequency vibration is proposed based on the acoustic plasticity. Numerical predictions of surface roughness evolution were conducted under various working conditions based on the model developed. It was found that the reduction of surface roughness (RSR) after vibration-assisted forming was affected by static stress, vibration amplitude, material properties and initial specimen surface roughness. The predictions using the developed model were compared with experimental data. Results showed that the predicted RSR agreed well with the experimental results, indicating that the analytical model is able to accurately capture surface topography evolution during vibration-assisted metal forming. This study provides a basis for understanding the underlying mechanisms of surface topography modification in vibration-assisted manufacturing.

  6. Laser surface modification of AZ31B Mg alloy for bio-wettability.

    PubMed

    Ho, Yee-Hsien; Vora, Hitesh D; Dahotre, Narendra B

    2015-02-01

    Magnesium alloys are the potential degradable materials for load-bearing implant application due to their comparable mechanical properties to human bone, excellent bioactivity, and in vivo non-toxicity. However, for a successful load-bearing implant, the surface of bio-implant must allow protein absorption and layer formation under physiological environment that can assist the cell/osteoblast growth. In this regard, surface wettability of bio-implant plays a key role to dictate the quantity of protein absorption. In light of this, the main objective of the present study was to produce favorable bio-wettability condition of AZ31B Mg alloy bio-implant surface via laser surface modification technique under various laser processing conditions. In the present efforts, the influence of laser surface modification on AZ31B Mg alloy surface on resultant bio-wettability was investigated via contact-angle measurements and the co-relationships among microstructure (grain size), surface roughness, surface energy, and surface chemical composition were established. In addition, the laser surface modification technique was simulated by computational (thermal) model to facilitate the prediction of temperature and its resultant cooling/solidification rates under various laser processing conditions for correlating with their corresponding composition and phase evolution. These predicted thermal properties were later used to correlate with the corresponding microstructure, chemical composition, and phase evolution via experimental analyses (X-ray diffractometer, scanning electron microscope, energy-dispersive spectroscopy). PMID:25201909

  7. Quantitative DEMS study of ethanol oxidation: effect of surface structure and Sn surface modification.

    PubMed

    Mostafa, Ehab; Abd-El-Latif, Abd-El-Aziz A; Ilsley, Richard; Attard, Gary; Baltruschat, Helmut

    2012-12-14

    Using the dual thin layer flow through cell, a semi-quantitative analysis of the volatile products during the electrooxidation of adsorbed and bulk solution of 0.01 M ethanol at polycrystalline platinum, smooth, roughened and Sn modified Pt(11,1,1), Pt(311) electrodes has been done by on-line differential electrochemical mass spectroscopy (DEMS). In addition to the current efficiency of CO(2), that of acetaldehyde was determined as a function of the flow rate. At polycrystalline platinum, ethanol oxidation produces only acetaldehyde; the amount of acetaldehyde further oxidized to acetic acid is negligible due to convection conditions. For comparison and for calibration purposes, i-propanol oxidation was examined for which acetone is the only oxidation product. At Pt(11,1,1), the main oxidation product is acetaldehyde. At Pt(311), in addition to acetaldehyde, acetic acid was also formed. Surface modification with Sn did not increase the reactivity of Pt(11,1,1) instead it led to inhibition of the ethanol oxidation. In the case of Pt(311), the onset potential of oxidation was shifted negatively by 0.2 V in the presence of Sn. The results of the potentiostatic measurements showed that this shift is not associated with the production of CO(2); rather acetic acid and acetaldehyde are the main oxidation products. PMID:23108295

  8. Interfacing biomembrane mimetic polymer surfaces with living cells Surface modification for reliable bioartificial liver

    NASA Astrophysics Data System (ADS)

    Iwasaki, Yasuhiko; Takami, Utae; Sawada, Shin-ichi; Akiyoshi, Kazunari

    2008-11-01

    The surface design used for reducing nonspecific biofouling is one of the most important issues for the fabrication of medical devices. We present here a newly synthesized a carbohydrate-immobilized phosphorylcholine polymer for surface modification of medical devices to control the interface with living cells. A random copolymer composed of 2-methacryloyloxyethyl phosphorylcholine (MPC), n-butyl methacrylate (BMA), and 2-lactobionamidoethyl methacrylate (LAMA) was synthesized by conventional radical polymerization. The monomer feeding ratio in the copolymer was adjusted to 24/75/1 (MPC/BMA/LAMA). The copolymer (PMBL1.0) could be coated by solvent evaporation from an ethanol solution. Cells of the human hepatocellular liver carcinoma cell line (HepG2) having asialoglycoprotein receptors (ASGPRs) were seeded on PMBL1.0 or poly(BMA) (PBMA)-coated PET plates. On PBMA, many adherent cells were observed and were well spread with monolayer adhesion. HepG2 adhesion was observed on PMBL1.0 because the cell has ASGPRs. Furthermore, some of the cells adhering to PMBL1.0 had a spheroid formation and similarly shaped spheroids were scattered on the surface. According to confocal laser microscopic observation after 96 h cultivation, it was found that albumin production preferentially occurred in the center of the spheroid. The albumin production of the cells that adhered to PBMA was sparse. The amount of albumin production per unit cell that adhered to PMBL1.0 was determined by ELISA and was significantly higher than that which adhered to PBMA. Long-term cultivation of HepG2 was also performed using hollow fiber mini-modules coated with PMBL1.0. The concentration of albumin produced from HepG2 increased continuously for one month. In the mini-module, the function of HepG2 was effectively preserved for that period. On the hollow fiber membrane, spheroid formation of HepG2 cells was also observed. In conclusion, PMBL1.0 can provide a suitable surface for the cultivation of

  9. Ultraviolet curing for surface modification of textile fabrics.

    PubMed

    Ferrero, Franco; Periolatto, Monica

    2011-10-01

    In this study, cotton, polyester and polyamide fabrics were treated by radical or cationic ultraviolet curing of different commercial products conferring water and oil repellency. Moreover, radical ultraviolet curing of chitosan was applied to confer antimicrobial properties. The advantages of this technology are well known making it very interesting for industrial applications: energy savings, low environmental impact, simple, cheap and small equipment, high treatment speed. The polymerization was controlled through weight gain and gel content measurements, while the properties of hydro and oil repellency were determined in terms of contact angle, moisture adsorption and water vapor permeability. The polymer distribution on fabric surfaces was investigated by scanning electron microscopy and atomic force microscopy. However the fabrics treated with chitosan were subjected to the standard test for determining the antimicrobial activity. Finally the finished cotton samples were subjected to washing fastness tests. PMID:22400240

  10. Synthesis and surface modification of birefringent vaterite microspheres.

    PubMed

    Vogel, Robert; Persson, Martin; Feng, Chao; Parkin, Simon J; Nieminen, Timo A; Wood, Barry; Heckenberg, Norman R; Rubinsztein-Dunlop, Halina

    2009-10-01

    This paper reports on the synthesis of birefringent vaterite microspheres with narrow size distribution using a seeded growth method. In a post-treatment the microspheres were stabilized and functionalized through coating with a combination of organosilica and silica. The coating vastly enhanced the stability of the vaterite microspheres in biological buffers and allowed the attachment of biomolecules such as DNA or proteins. As an example, streptavidin was attached to the surface of the functionalized microspheres. These results pave the way for the use of birefringent vaterite particles for the micromanipulation of single biological molecules such as DNA or specific proteins in an optical trap capable of exerting and measuring torques. The stabilized birefringent microspheres may also find use for biosensor and biological screening applications. PMID:19788220

  11. Surface Modifications with Laser Synthesized Mo Modified Coating

    NASA Astrophysics Data System (ADS)

    Sun, Lu; Chen, Hao; Liu, Bo

    2013-02-01

    Mg-Cu-Al was first used to improve the surface performance of TA15 titanium alloys by means of laser cladding technique. The synthesis of hard composite coating on TA15 titanium alloy by laser cladding of Mg-Cu-Al-B4C/Mo pre-placed powders was investigated by means of scanning electron microscope, energy dispersive spectrometer and high resolution transmission electron microscope. Experimental results indicated that such composite coating mainly consisted of TiB2, TiB, TiC, Ti3Al and AlCuMg. Compared with TA15 alloy substrate, an improvement of wear resistance was observed for this composite coating due to the actions of fine grain, amorphous and hard phase strengthening.

  12. Effects of different substrate surface modifications on the epitaxial ZnO/Si

    NASA Astrophysics Data System (ADS)

    Wang, Peng; Jin, Changlian; Zhan, Huahan; Chen, Xiaohang; Xu, Fuchun; Zhou, Yinghui; Wang, Huiqiong; Kang, Junyong

    2013-09-01

    To produce high quality ZnO/Si for the applications in short wavelength optoelectronic devices, the effects of different silicon surface modifications on the overgrown ZnO thin film were investigated. Samples were grown by a plasma assistant molecular beam epitaxy at room temperature, avoiding the oxidation of the Si surface and the thermal stress caused by difference of the thermal expansion coefficients between ZnO and silicon. Different modifications on the Si(100) substrate surface including nitridation, oxidation, and depositions of Mg and Zn, were employed. The effects on the overgrown ZnO layers and the interlayer SiOx were investigated by atomic force microscopy, photoluminescence, X-ray diffraction and auger depth electron spectroscopy. All the modifications were effective in different degrees at reducing the SiOx amorphous layer. However, different mechanisms resulted in distinct performance in crystal structure and optical property.

  13. Synthesis and surface modification of polyurethanes with chitosan for antibacterial properties.

    PubMed

    Kara, Filiz; Aksoy, Eda Ayse; Yuksekdag, Zehranur; Hasirci, Nesrin; Aksoy, Serpil

    2014-11-01

    Surface modification and providing antibacterial properties to the materials or devices are getting great attention especially in the last decades. In this study, polyurethane (PU) films were prepared by synthesizing them in medical purity from toluene diisocyanate and polypropylene ethylene glycol without using any other ingredients and then the film surfaces were modified by covalent immobilization of chitosan (CH) which has antibacterial activity. CH immobilized PU films (PU-CH) were found to be more hydrophilic than control PU films. Electron Spectroscopy for Chemical Analysis (ESCA) and Atomic Force Microscopy (AFM) analyses showed higher nitrogen contents and rougher surface topography for PU-CH compared to PU films. Modification with CH significantly increased antibacterial activity against Gram positive (Staphylococcus aureus) and Gram negative (Pseudomonas aeruginosa) bacteria. It was observed that the number of bacteria colonies were less about 10(2)-10(5) CFU/mL and number of attached viable bacteria decreased significantly after CH modification of PU films. PMID:25129714

  14. Modification of surface oxide layers of titanium targets for increasing lifetime of neutron tubes

    SciTech Connect

    Zakharov, A. M. Dvoichenkova, O. A.; Evsin, A. E.

    2015-12-15

    The peculiarities of interaction of hydrogen ions with a titanium target and its surface oxide layer were studied. Two ways of modification of the surface oxide layers of titanium targets for increasing the lifetime of neutron tubes were proposed: (1) deposition of an yttrium oxide barrier layer on the target surface; (2) implementation of neutron tube work regime in which the target is irradiated with ions with energies lower than 1000 eV between high-energy ion irradiation pulses.

  15. Modification of surface oxide layers of titanium targets for increasing lifetime of neutron tubes

    NASA Astrophysics Data System (ADS)

    Zakharov, A. M.; Dvoichenkova, O. A.; Evsin, A. E.

    2015-12-01

    The peculiarities of interaction of hydrogen ions with a titanium target and its surface oxide layer were studied. Two ways of modification of the surface oxide layers of titanium targets for increasing the lifetime of neutron tubes were proposed: (1) deposition of an yttrium oxide barrier layer on the target surface; (2) implementation of neutron tube work regime in which the target is irradiated with ions with energies lower than 1000 eV between high-energy ion irradiation pulses.

  16. Recent Advances in Modeling of the Atmospheric Boundary Layer and Land Surface in the Coupled WRF-CMAQ Model

    EPA Science Inventory

    Advances in the land surface model (LSM) and planetary boundary layer (PBL) components of the WRF-CMAQ coupled meteorology and air quality modeling system are described. The aim of these modifications was primarily to improve the modeling of ground level concentrations of trace c...

  17. Surface modification of biodegradable magnesium and its alloys for biomedical applications.

    PubMed

    Tian, Peng; Liu, Xuanyong

    2015-06-01

    Magnesium and its alloys are being paid much attention recently as temporary implants, such as orthopedic implants and cardiovascular stents. However, the rapid degradation of them in physiological environment is a major obstacle preventing their wide applications to date, which will result in rapid mechanical integrity loss or even collapse of magnesium-based implants before injured tissues heal. Moreover, rapid degradation of the magnesium-based implants will also cause some adverse effects to their surrounding environment, such as local gas cavity around the implant, local alkalization and magnesium ion enrichment, which will reduce the integration between implant and tissue. So, in order to obtain better performance of magnesium-based implants in clinical trials, special alloy designs and surface modifications are prerequisite. Actually, when a magnesium-based implant is inserted in vivo, corrosion firstly happens at the implant-tissue interface and the biological response to implant is also determined by the interaction at this interface. So the surface properties, such as corrosion resistance, hemocompatibility and cytocompatibility of the implant, are critical for their in vivo performance. Compared with alloy designs, surface modification is less costly, flexible to construct multi-functional surface and can prevent addition of toxic alloying elements. In this review, we would like to summarize the current investigations of surface modifications of magnesium and its alloys for biomedical application. The advantages/disadvantages of different surface modification methods are also discussed as a suggestion for their utilization. PMID:26816637

  18. Glass surface modification using Nd:YAG laser in SF6 atmospheres

    NASA Astrophysics Data System (ADS)

    Dehghanpour, H. R.; Parvin, P.

    2015-02-01

    Glass surface modification is one of the processes which changes its physical properties. Changing optical property is a significant effect of surface modification. Among the surface modification methods, laser surface modification is attractive for researchers. Here, SiO2 glass target was irradiated by Q-switched Nd:YAG laser (1064 nm) in SF6 atmospheres as well as vacuum. In this process, an Nd:YAG laser beam was focused near the glass target while the target was inserted in a chamber containing SF6 atmosphere or at vacuum condition. The surface morphology changes were investigated by scanning electron microscopy (SEM). Noticeable surface changes were observed due to laser irradiation in SF6 atmosphere. Although the absorption lines of SF6 molecule are not near the Nd:YAG laser wavelength, laser-induced breakdown spectroscopy (LIBS) showed decomposition of SF6 molecules near a glass target. The ablated fragments from the target impacted on gas molecules and decomposed them. In this work, LIBS showed that there were several fluorine ions when the target was irradiated in an SF6 atmosphere. This demonstrates SF6 molecule decomposition near the glass target by laser irradiation. The plasma temperature was ~2000 K. This temperature is much less than metallic or other gaseous materials' plasma temperatures.

  19. Surface modification of biodegradable magnesium and its alloys for biomedical applications

    PubMed Central

    Tian, Peng; Liu, Xuanyong

    2015-01-01

    Magnesium and its alloys are being paid much attention recently as temporary implants, such as orthopedic implants and cardiovascular stents. However, the rapid degradation of them in physiological environment is a major obstacle preventing their wide applications to date, which will result in rapid mechanical integrity loss or even collapse of magnesium-based implants before injured tissues heal. Moreover, rapid degradation of the magnesium-based implants will also cause some adverse effects to their surrounding environment, such as local gas cavity around the implant, local alkalization and magnesium ion enrichment, which will reduce the integration between implant and tissue. So, in order to obtain better performance of magnesium-based implants in clinical trials, special alloy designs and surface modifications are prerequisite. Actually, when a magnesium-based implant is inserted in vivo, corrosion firstly happens at the implant-tissue interface and the biological response to implant is also determined by the interaction at this interface. So the surface properties, such as corrosion resistance, hemocompatibility and cytocompatibility of the implant, are critical for their in vivo performance. Compared with alloy designs, surface modification is less costly, flexible to construct multi-functional surface and can prevent addition of toxic alloying elements. In this review, we would like to summarize the current investigations of surface modifications of magnesium and its alloys for biomedical application. The advantages/disadvantages of different surface modification methods are also discussed as a suggestion for their utilization. PMID:26816637

  20. Surface modification of silicon-containing fluorocarbon films prepared by plasma-enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Jin, Yoonyoung; Desta, Yohannes; Goettert, Jost; Lee, G. S.; Ajmera, P. K.

    2005-07-01

    Surface modification of silicon-containing fluorocarbon (SiCF) films achieved by wet chemical treatments and through x-ray irradiation is examined. The SiCF films were prepared by plasma-enhanced chemical vapor deposition, using gas precursors of tetrafluoromethane and disilane. As-deposited SiCF film composition was analyzed by x-ray photoelectron spectroscopy. Surface modification of SiCF films utilizing n-lithiodiaminoethane wet chemical treatment is discussed. Sessile water-drop contact angle changed from 95°+/-2° before treatment to 32°+/-2° after treatment, indicating a change in the film surface characteristics from hydrophobic to hydrophilic. For x-ray irradiation on the SiCF film with a dose of 27.4 kJ/cm3, the contact angle of the sessile water drop changed from 95°+/-2° before radiation to 39°+/-3° after x-ray exposure. The effect of x-ray exposure on chemical bond structure of SiCF films is studied using Fourier transform infrared measurements. Electroless Cu deposition was performed to test the applicability of the surface modified films. The x-ray irradiation method offers a unique advantage in making possible surface modification in a localized area of high-aspect-ratio microstructures. Fabrication of a Ti-membrane x-ray mask is introduced here for selective surface modification using x-ray irradiation.

  1. Spine interbody implants: material selection and modification, functionalization and bioactivation of surfaces to improve osseointegration.

    PubMed

    Rao, Prashanth J; Pelletier, Matthew H; Walsh, William R; Mobbs, Ralph J

    2014-05-01

    The clinical outcome of lumbar spinal fusion is correlated with achievement of bony fusion. Improving interbody implant bone on-growth and in-growth may enhance fusion, limiting pseudoarthrosis, stress shielding, subsidence and implant failure. Polyetheretherketone (PEEK) and titanium (Ti) are commonly selected for interbody spacer construction. Although these materials have desirable biocompatibility and mechanical properties, they require further modification to support osseointegration. Reports of extensive research on this topic are available in biomaterial-centric published reports; however, there are few clinical studies concerning surface modification of interbody spinal implants. The current article focuses on surface modifications aimed at fostering osseointegration from a clinician's point of view. Surface modification of Ti by creating rougher surfaces, modifying its surface topography (macro and nano), physical and chemical treatment and creating a porous material with high interconnectivity can improve its osseointegrative potential and bioactivity. Coating the surface with osteoconductive materials like hydroxyapatite (HA) can improve osseointegration. Because PEEK spacers are relatively inert, creating a composite by adding Ti or osteoconductive materials like HA can improve osseointegration. In addition, PEEK may be coated with Ti, effectively bio-activating the coating. PMID:24890288

  2. Study on the mechanism of surface modification of magnesium oxysulfate whisker

    NASA Astrophysics Data System (ADS)

    Dang, Li; Nai, Xueying; Zhu, Donghai; Jing, Yanwei; Liu, Xin; Dong, Yaping; Li, Wu

    2014-10-01

    Hydrophobic-lipophilic magnesium oxysulfate whisker (MOSw) was prepared by surface modification with lauric acid and the surface morphology of MOSw was examined with field emission scanning electron microscope (FESEM). X-ray powder diffraction (XRD) was used to characterize the crystalline degree of MOSw and modified MOSw (MOSw-LA). Both FESEM and XRD suggested that modification occurred on the surface of MOSw exclusively. The inexistence of physisorbed lauric acid was proved by Fouier transform infrared (FT-IR) spectroscopy. Thermogravimetric analyses ruled out the possibility that magnesium laurate (LA-Mg) physisorbed on the surface of MOSw-LA. Solid state 13C nuclear magnetic resonance (13C NMR) further verified the formation of COO-Mg< bonds based on the significant changes of chemical shift and decrease in intensity. Hence, we confirmed that the type of surface modification of MOSw with lauric acid was chemical adsorption taken place between lauric acid and Mg<. In order to study the dynamic state approach of this reaction, a pH meter was employed to monitor the reaction process synchronously, and then we proposed a reaction mechanism which was similar to the "acid-base neutralization". This research provides a detailed explanation for a kind of surface modification, which may be further used in the performance of whisker/polymer matrix composites.

  3. Surface modification of graphene nanopores for protein translocation

    PubMed Central

    Shan, Y. P.; Tiwari, P. B.; Krishnakumar, P.; Vlassiouk, I.; Li, W.Z.; Wang, X.W.; Darici, Y.; Lindsay, S.M.; Wang, H. D.; Smirnov, S.; He, J.

    2014-01-01

    Studies of DNA translocation through graphene nanopores have revealed their potential for DNA sequencing. Here we report a study of protein translocation through chemically modified graphene nanopores. A transmission electron microscope (TEM) was used to cut nanopores with diameters between 5-20 nm in multilayer graphene prepared by chemical vapor deposition (CVD). After oxygen plasma treatment, the dependence of the measured ionic current on salt concentration and pH was consistent with a small surface charge induced by the formation of carboxyl groups. While translocation of gold nanoparticles (10 nm) was readily detected through such treated pores of a larger diameter, translocation of protein ferritin was not observed either for oxygen plasma treated pores, or for pores modified with mercaptohexadecanoic acid. Ferritin translocation events were reliably observed after the pores were modified with the phospholipid-PEG (DPPE-PEG750) amphiphile. The ion current signature of translocation events was complex, suggesting that a series of interactions between the protein and pore occur during the process. PMID:24231385

  4. Surface Modification of Nickel Foams by a Slurry Aluminizing Process

    SciTech Connect

    Omar, H.; Papanastasiou, N.; Psyllaki, P.; Stergioudi, F.; Tsipas, D. N.; Tsipas, S. A.; Michailidis, N.

    2010-01-21

    A novel slurry-based process for aluminizing nickel foams while improving the mechanical properties and conserving the excellent ductility is reported. Cellular unalloyed nickel foams with 92% porosity and uniform pore size and distribution were used as a starting material. Several slurries of different compositions were examined to investigate the possibility of developing an aluminide-nickel intermetallic coating on a Ni foam without considerably degrading the original ductile properties of the foam. The process temperature was varying from 400 to 850 deg. C and the process holding time was ranging between 2h to 6h. Scanning electron microscopy with an energy dispersive X-ray spectrometry and X-Ray diffraction were applied to assess the effectiveness of the aluminizing process and determine both the optimum parameters of the procedure (slurry composition, holding temperature and time) and the concentration profiles across the coating cross-section. The mechanical behavior of the aluminized Ni-foams was evaluated by the conduction of micro-tension tests. The resulting Ni-foams after aluminization retain the pore structure of original Ni-foams and present a thick outer surface layer which consists of a range of aluminide phases. The mechanical properties of the Ni-foams aluminized in low process temperature were insignificantly affected.

  5. Surface Modification of Block Copolymer Through Sulfur Containing Plasma Treatment.

    PubMed

    Choi, Sang Wook; Shin, Jae Hee; Jeon, Min Hwan; Mun, Jeong Ho; Kim, Sang Ouk; Yeom, Geun Young; Kim, Kyong Nam

    2015-10-01

    Some of the important issues of block copolymer (BCP) as an application to the potential low cost next generation lithography are thermal stability and deformation during pattern transfer process in addition to defect density, line edge/width roughness, etc. In this study, sulfur containing plasma treatment was used to modify the BCP and the effects of the plasma on the properties of plasma treated BCP were investigated. The polystyrene hole pattern obtained from polystyrene polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) was initially degraded when the polystyrene hole was annealed at 190 °C for 15 min. However, when the hole pattern was treated using sulfur containing plasmas using H2S or SF6 up to 2 min, possibly due to the sulfurization of the polystyrene hole surface, no change in the hole pattern was observed after the annealing even though there is a slight change in hole shapes during the plasma treatment. The optimized plasma treated polystyrene pattern showed the superior characteristics as the mask layer by showing better thermal stability, higher chemical inertness, and higher etch selectivity during plasma etching. PMID:26726468

  6. Surface modification of graphene nanopores for protein translocation.

    PubMed

    Shan, Y P; Tiwari, P B; Krishnakumar, P; Vlassiouk, I; Li, W Z; Wang, X W; Darici, Y; Lindsay, S M; Wang, H D; Smirnov, S; He, J

    2013-12-13

    Studies of DNA translocation through graphene nanopores have revealed their potential for DNA sequencing. Here we report a study of protein translocation through chemically modified graphene nanopores. A transmission electron microscope (TEM) was used to cut nanopores with diameters between 5 and 20 nm in multilayer graphene prepared by chemical vapor deposition (CVD). After oxygen plasma treatment, the dependence of the measured ionic current on salt concentration and pH was consistent with a small surface charge induced by the formation of carboxyl groups. While translocation of gold nanoparticles (10 nm) was readily detected through such treated pores of a larger diameter, translocation of the protein ferritin was not observed either for oxygen plasma treated pores, or for pores modified with mercaptohexadecanoic acid. Ferritin translocation events were reliably observed after the pores were modified with the phospholipid-PEG (DPPE-PEG750) amphiphile. The ion current signature of translocation events was complex, suggesting that a series of interactions between the protein and pores occurs during the process. PMID:24231385

  7. Ion beam modification of surface for improved high temperature performance

    NASA Astrophysics Data System (ADS)

    Was, Gary S.; Cavasin, Daniel

    1990-07-01

    A novel experimental technique, Thin Film Calorimetry (TFC), has been developed to determine the enthalpy of transformation from metastable to stable equilibrium structures in thin films. This technique has been applied to investigate metastable stable transformations occurring in thin films of nominal composition NiAl3. Elemental Ni and Al are codeposited directly onto the surface of a pure Al calorimeter sample pan to form a 0.75 solid solution of NiAl3. The as-deposited microstructure in this case is a metastable configuration, and the reaction heat accompanying its transformation to the stable, equilibrium NiAl3 phase is measured directly in the calorimeter. The mean change in enthalpy, DeltaH, for a series of such measurements, is -4.16 kcal/mole. A second approach involves annealing the as-deposited film to form the epsilon phase, then irradiating the as-annealed film, using 1.5 MeV Ni++ ions, to form an amorphous structure. The enthalpy associated with the transformation of this structure to the equilibrium is then measured in the DSC. The mean DeltaH found for this reaction is -5.02 kcal/mole.

  8. Plasma-implantation-based surface modification of metals with single-implantation mode

    NASA Astrophysics Data System (ADS)

    Tian, X. B.; Cui, J. T.; Yang, S. Q.; Fu, Ricky K. Y.; Chu, Paul K.

    2004-12-01

    Plasma ion implantation has proven to be an effective surface modification technique. Its biggest advantage is the capability to treat the objects with irregular shapes without complex manipulation of target holder. Many metal materials such as aluminum, stainless steel, tool steel, titanium, magnesium etc, has been treated using this technique to improve their wear-resistance, corrosion-resistance, fatigue-resistance, oxidation-resistance, bio-compatiblity etc. However in order to achieve thicker modified layers, hybrid processes combining plasma ion implantation with other techniques have been frequently employed. In this paper plasma implantation based surface modification of metals using single-implantation mode is reviewed.

  9. Surface modification for corrosion protection of steel pipes

    NASA Astrophysics Data System (ADS)

    Morshed, Ali

    Corrosion of carbon steel oil pipelines in the sweet environments has been a well- known problem in the oil industry all over the world and corrosion inhibitors of the film forming type have been widely used to combat this type of corrosion. In this project numerous effort has been made to devise a similar way of corrosion mitigation by producing an impermeable and protective coating made of precipitated iron carbonate scale. Based on the previous works it was suggested that iron carbonate scale as the corrosion product (of carbon steel and CO2) could to some extent offer protection to its substrate and reduce the corrosion rate effectively. However, precipitating an adherent and protective iron carbonate scale has not been an easy job. Our main objectives during this work have been firstly to define the favourable conditions under which an iron carbonate scale would precipitate in the system and then to investigate how the protective characteristics of the scale could be improved. The effects of several environmental variables like solution pH, solution temperature, additives (scale inhibitors), stirring and solution composition on the scale properties such as adhesion, surface coverage, stability and porosity (scale density) have been investigated. Simultaneously, the adverse effects of certain conditions or variables that tended to reduce the scale protectiveness or prevent its precipitation have been investigated and discussed. Some of the presented results are rather qualitative; nevertheless it is believed that they have contributed in the better understanding of the iron carbonate scale properties and its precipitation process. Based on the results and conclusions of this project few suggestions have been made at the end for the possible continuation of this work.

  10. Selective Area Modification of Silicon Surface Wettability by Pulsed UV Laser Irradiation in Liquid Environment.

    PubMed

    Liu, Neng; Moumanis, Khalid; Dubowski, Jan J

    2015-01-01

    The wettability of silicon (Si) is one of the important parameters in the technology of surface functionalization of this material and fabrication of biosensing devices. We report on a protocol of using KrF and ArF lasers irradiating Si (001) samples immersed in a liquid environment with low number of pulses and operating at moderately low pulse fluences to induce Si wettability modification. Wafers immersed for up to 4 hr in a 0.01% H2O2/H2O solution did not show measurable change in their initial contact angle (CA) ~75°. However, the 500-pulse KrF and ArF lasers irradiation of such wafers in a microchamber filled with 0.01% H2O2/H2O solution at 250 and 65 mJ/cm(2), respectively, has decreased the CA to near 15°, indicating the formation of a superhydrophilic surface. The formation of OH-terminated Si (001), with no measurable change of the wafer's surface morphology, has been confirmed by X-ray photoelectron spectroscopy and atomic force microscopy measurements. The selective area irradiated samples were then immersed in a biotin-conjugated fluorescein-stained nanospheres solution for 2 hr, resulting in a successful immobilization of the nanospheres in the non-irradiated area. This illustrates the potential of the method for selective area biofunctionalization and fabrication of advanced Si-based biosensing architectures. We also describe a similar protocol of irradiation of wafers immersed in methanol (CH3OH) using ArF laser operating at pulse fluence of 65 mJ/cm(2) and in situ formation of a strongly hydrophobic surface of Si (001) with the CA of 103°. The XPS results indicate ArF laser induced formation of Si-(OCH3)x compounds responsible for the observed hydrophobicity. However, no such compounds were found by XPS on the Si surface irradiated by KrF laser in methanol, demonstrating the inability of the KrF laser to photodissociate methanol and create -OCH3 radicals. PMID:26575362

  11. An experimental study of USB flap noise reduction through mean flow modification. [Upper Surface Blown

    NASA Technical Reports Server (NTRS)

    Joshi, M. C.; Yu, J. C.

    1979-01-01

    The effect of mean flow modification on the noise production of upper surface blown flaps has been studied experimentally. Mean velocity profile at the nozzle exit was modified from the usual 'top-hat' shape to 'Gamma' and 'L'-shaped profiles. The 'L'-modification caused noise reduction around and above the peak frequency of the 'top-hat' spectrum when compared on an equal thrust per exit area basis. Modification to 'Gamma'-shaped profile resulted in a shift of the spectrum to lower frequencies and a lower overall noise reduction. These modifications alter the development of the large scale disturbances in the upper shear layer and trailing edge wake of the wall jet geometry.

  12. Modification of surface properties of polyamide 6 films with atmospheric pressure plasma

    NASA Astrophysics Data System (ADS)

    Gao, Zhiqiang

    2011-05-01

    To investigate the effect of the different plasma gases treatment on the surface modification of atmospheric pressure plasma, polyamide 6 films were treated using pure helium (He), He/O 2 and He/CF 4, respectively. Atomic force microscopy (AFM) showed rougher surface, while X-ray photoelectron spectroscopy (XPS) revealed increased oxygen and fluorine contents after the plasma treatments. The plasma treated samples had lower water contact angles and higher T-peel strength than that of the control. The addition of small amount of O 2 or CF 4 to He plasma increases the effectiveness of the plasma treatment in polymer surface modification in terms of surface roughness, surface hydrophilic groups, etching rate, water contact angle and bonding strength.

  13. Surface modification of magnetic recording media by filtered cathodic vacuum arc

    NASA Astrophysics Data System (ADS)

    Zhang, H.-S.; Komvopoulos, K.

    2009-11-01

    Surface modification of a magnetic recording medium was accomplished by filtered cathodic vacuum arc (FCVA). The carbon overcoat of thin-film disks was removed by Ar+ ion sputter etching in vacuum to prevent oxidation of the exposed magnetic medium, which was then modified by FCVA carbon plasma under conditions of zero and -100 V pulsed substrate bias. Monte Carlo simulations performed with the T-DYN code, x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and surface force microscopy (SFM) provided insight into carbon implantation profiles, surface chemical composition, roughness, and nanomechanical properties of the surface-treated magnetic medium. The dependence of surface modification on the FCVA treatment conditions is discussed in the context of T-DYN, XPS, AFM, and SFM results. The findings of this study demonstrate the potential of FCVA to provide overcoat-free magnetic recording media exhibiting oxidation resistance and enhanced nanomechanical properties.

  14. Surface Modifications Induced by High Fluxes of Low Energy Helium Ions

    PubMed Central

    Tanyeli, İrem; Marot, Laurent; Mathys, Daniel; van de Sanden, Mauritius C. M.; De Temmerman, Gregory

    2015-01-01

    Several metal surfaces, such as titanium, aluminum and copper, were exposed to high fluxes (in the range of 1023 m−2s−1) of low energy (<100 eV) Helium (He) ions. The surfaces were analyzed by scanning electron microscopy and to get a better understanding on morphology changes both top view and cross sectional images were taken. Different surface modifications, such as voids and nano pillars, are observed on these metals. The differences and similarities in the development of surface morphologies are discussed in terms of the material properties and compared with the results of similar experimental studies. The results show that He ions induced void growth and physical sputtering play a significant role in surface modification using high fluxes of low energy He ions. PMID:25919912

  15. Chemical modification of glass surface with a monolayer of nonchromophoric and chromophoric methacrylate terpolymer

    NASA Astrophysics Data System (ADS)

    Janik, Ryszard; Kucharski, Stanisław; Sobolewska, Anna; Barille, Regis

    2010-11-01

    The methacrylate terpolymers, a nonchromophoric and chromophoric one, containing 2-hydroxyethyl groups were reacted with 3-isocyanatopropyltriethoxysilane to obtain reactive polymers able to form covalent bonding with -SiOH groups of the glass surface via triethoxysilane group condensation. Chemical modification of the Corning 2949 glass plates treated in this way resulted in increase of wetting angle from 11° to ca. 70-73°. Determination of ellipsometric parameters revealed low value of the substrate refractive index as compared with that of bulk Corning 2949 glass suggesting roughness of the surface. The AFM image of the bare glass surface and that modified with terpolymer monolayer confirmed this phenomenon. Modification of the glass with the terpolymer monolayer made it possible to create the substrate surface well suited for deposition of familiar chromophore film by spin-coating. The chromophore polymer film deposited onto the modified glass surface was found to be resistant to come unstuck in aqueous solution.

  16. Surface modification of poly(ethylene terephthalate) fibers induced by radio frequency air plasma treatment

    NASA Astrophysics Data System (ADS)

    Riccardi, Claudia; Barni, Ruggero; Selli, Elena; Mazzone, Giovanni; Massafra, Maria Rosaria; Marcandalli, Bruno; Poletti, Giulio

    2003-04-01

    The surface chemical and physical modifications of poly(ethylene terephthalate) (PET) fibers induced by radiofrequency air plasma treatments were correlated with the characteristics of the discharge parameters and the chemical composition of the plasma itself, to identify the plasma-induced surface processes prevailing under different operating conditions. Treated polymer surfaces were characterized by water droplet absorption time measurements and XPS analysis, as a function of the aging time in different media, and by AFM analysis. They exhibited a remarkable increase in hydrophilicity, accompanied by extensive etching and by the implantation of both oxygen- and nitrogen-containing polar groups. Etching was mainly a consequence of ion bombardment, yielding low molecular weight, water soluble oxidation products, while surface chemical modifications were mainly due to the action of neutral species on the plasma-activated polymer surface.

  17. Surface modification of magnetic recording media by filtered cathodic vacuum arc

    SciTech Connect

    Zhang, H.-S.; Komvopoulos, K.

    2009-11-01

    Surface modification of a magnetic recording medium was accomplished by filtered cathodic vacuum arc (FCVA). The carbon overcoat of thin-film disks was removed by Ar{sup +} ion sputter etching in vacuum to prevent oxidation of the exposed magnetic medium, which was then modified by FCVA carbon plasma under conditions of zero and -100 V pulsed substrate bias. Monte Carlo simulations performed with the T-DYN code, x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and surface force microscopy (SFM) provided insight into carbon implantation profiles, surface chemical composition, roughness, and nanomechanical properties of the surface-treated magnetic medium. The dependence of surface modification on the FCVA treatment conditions is discussed in the context of T-DYN, XPS, AFM, and SFM results. The findings of this study demonstrate the potential of FCVA to provide overcoat-free magnetic recording media exhibiting oxidation resistance and enhanced nanomechanical properties.

  18. Advanced glycation end products induce differential structural modifications and fibrillation of albumin

    NASA Astrophysics Data System (ADS)

    Awasthi, Saurabh; Sankaranarayanan, Kamatchi; Saraswathi, N. T.

    2016-06-01

    Glycation induced amyloid fibrillation is fundamental to the development of many neurodegenerative and cardiovascular complications. Excessive non-enzymatic glycation in conditions such as hyperglycaemia results in the increased accumulation of advanced glycation end products (AGEs). AGEs are highly reactive pro-oxidants, which can lead to the activation of inflammatory pathways and development of oxidative stress. Recently, the effect of non-enzymatic glycation on protein structure has been the major research area, but the role of specific AGEs in such structural alteration and induction of fibrillation remains undefined. In this study, we determined the specific AGEs mediated structural modifications in albumin mainly considering carboxymethyllysine (CML), carboxyethyllysine (CEL), and argpyrimidine (Arg-P) which are the major AGEs formed in the body. We studied the secondary structural changes based on circular dichroism (CD) and spectroscopic analysis. The AGEs induced fibrillation was determined by Congo red binding and examination of scanning and transmission electron micrographs. The amyloidogenic regions in the sequence of BSA were determined using FoldAmyloid. It was observed that CEL modification of BSA leads to the development of fibrillar structures, which was evident from both secondary structure changes and TEM analysis.

  19. Advanced glycation end products induce differential structural modifications and fibrillation of albumin.

    PubMed

    Awasthi, Saurabh; Sankaranarayanan, Kamatchi; Saraswathi, N T

    2016-06-15

    Glycation induced amyloid fibrillation is fundamental to the development of many neurodegenerative and cardiovascular complications. Excessive non-enzymatic glycation in conditions such as hyperglycaemia results in the increased accumulation of advanced glycation end products (AGEs). AGEs are highly reactive pro-oxidants, which can lead to the activation of inflammatory pathways and development of oxidative stress. Recently, the effect of non-enzymatic glycation on protein structure has been the major research area, but the role of specific AGEs in such structural alteration and induction of fibrillation remains undefined. In this study, we determined the specific AGEs mediated structural modifications in albumin mainly considering carboxymethyllysine (CML), carboxyethyllysine (CEL), and argpyrimidine (Arg-P) which are the major AGEs formed in the body. We studied the secondary structural changes based on circular dichroism (CD) and spectroscopic analysis. The AGEs induced fibrillation was determined by Congo red binding and examination of scanning and transmission electron micrographs. The amyloidogenic regions in the sequence of BSA were determined using FoldAmyloid. It was observed that CEL modification of BSA leads to the development of fibrillar structures, which was evident from both secondary structure changes and TEM analysis. PMID:27037764

  20. Advances in surfaces and osseointegration in implantology. Biomimetic surfaces

    PubMed Central

    Albertini, Matteo; Fernandez-Yague, Marc; Lázaro, Pedro; Herrero-Climent, Mariano; Bullon, Pedro; Gil, Francisco-Javier

    2015-01-01

    The present work is a revision of the processes occurring in osseointegration of titanium dental implants according to different types of surfaces -namely, polished surfaces, rough surfaces obtained from subtraction methods, as well as the new hydroxyapatite biomimetic surfaces obtained from thermochemical processes. Hydroxyapatite’s high plasma-projection temperatures have proven to prevent the formation of crystalline apatite on the titanium dental implant, but lead to the formation of amorphous calcium phosphate (i.e., with no crystal structure) instead. This layer produce some osseointegration yet the calcium phosphate layer will eventually dissolve and leave a gap between the bone and the dental implant, thus leading to osseointegration failure due to bacterial colonization. A new surface -recently obtained by thermochemical processes- produces, by crystallization, a layer of apatite with the same mineral content as human bone that is chemically bonded to the titanium surface. Osseointegration speed was tested by means of minipigs, showing bone formation after 3 to 4 weeks, with the security that a dental implant can be loaded. This surface can be an excellent candidate for immediate or early loading procedures. Key words:Dental implants, implants surfaces, osseointegration, biomimetics surfaces. PMID:25662555

  1. Surface modification and metallization of fluorocarbon polymers by excimer laser processing

    NASA Astrophysics Data System (ADS)

    Niino, Hiroyuki; Yabe, Akira

    1993-12-01

    The surface chemical modification of poly(tetrafluoroethylene) and poly(tetrafluoroethylene- co-hexafluoropropylene) films was carried out in hydrazine gas photolyzed with ArF excimer laser irradiation. The contact angle of the modified surfaces with water changed from 130° to 30° due to the reaction with hydrazine. Nitrogen on the surface was detected with x-ray photoelectron spectroscopy, suggesting that amino groups were introduced onto the surface. In addition, on the basis of hydrophilic behavior, we succeeded in selective-area electroless plating of nickel metal on the chemically modified surface.

  2. Modification of the Surface Properties of Polyimide Films using POSS Deposition and Oxygen Plasma Exposure

    NASA Technical Reports Server (NTRS)

    Wohl, Christopher J.; Belcher, Marcus A.; Ghose, Sayata; Connell, John W.

    2008-01-01

    Topographically rich surfaces were generated by spray-coating organic solutions of a polyhedral oligomeric silsesquioxane, octakis (dimethylsilyloxy) silsesquioxane (POSS), on Kapton HN films and exposing them to radio frequency generated oxygen plasma. Changes in both surface chemistry and topography were observed. High-resolution scanning electron microscopy indicated substantial modification of the POSS-coated polyimide surface topographies as a result of oxygen plasma exposure. Water contact angles varied from 104 deg for unexposed POSS-coated surfaces to approximately 5 deg, for samples exposed for 5 h. Modulation of the dispersive and polar contributions to the surface energy was determined using van Oss Good Chaudhury theory.

  3. Permanent modification in electrothermal atomic absorption spectrometry — advances, anticipations and reality

    NASA Astrophysics Data System (ADS)

    Tsalev, Dimiter L.; Slaveykova, Vera I.; Lampugnani, Leonardo; D'Ulivo, Alessandro; Georgieva, Rositsa

    2000-05-01

    Permanent modification is an important recent development in chemical modification techniques which is promising in view of increasing sample throughput with 'fast' programs, reducing reagent blanks, preliminary elimination of unwanted modifier components, compatibility with on-line and in situ enrichment, etc. An overview of this approach based on the authors' recent research and scarce literature data is given, revealing both success and failure in studies with permanently modified surfaces (carbides, non-volatile noble metals, noble metals on carbide coatings, etc.), as demonstrated in examples of direct electrothermal atomic absorption spectrometric (ETAAS) applications to biological and environmental matrices and vapor generation (VG)-ETAAS coupling with in-atomizer trapping of hydrides and other analyte vapors. Permanent modifiers exhibit certain drawbacks and limitations such as: poorly reproducible treatment technologies — eventually resulting in poor tube-to-tube repeatability and double or multiple peaks; impaired efficiency compared with modifier addition to each sample aliquot; relatively short lifetimes; limitations imposed on temperature programs, the pyrolysis, atomization and cleaning temperatures being set somewhat lower to avoid excessive loss of modifier; applicability to relatively simple sample solutions rather than to high-salt matrices and acidic digests; side effects of overstabilization, etc. The most important niches of application appear to be the utilization of permanently modified surfaces in coupled VG-ETAAS techniques, analysis of organic solvents and extracts, concentrates and fractions obtained after enrichment and/or speciation separations and direct ETAAS determinations of highly volatile analytes in relatively simple sample matrices.

  4. Surface morphological modification of crosslinked hydrophilic co-polymers by nanosecond pulsed laser irradiation

    NASA Astrophysics Data System (ADS)

    Primo, Gastón A.; Alvarez Igarzabal, Cecilia I.; Pino, Gustavo A.; Ferrero, Juan C.; Rossa, Maximiliano

    2016-04-01

    This work reports an investigation of the surface modifications induced by irradiation with nanosecond laser pulses of ultraviolet and visible wavelengths on crosslinked hydrophilic co-polymeric materials, which have been functionalized with 1-vinylimidazole as a co-monomer. A comparison is made between hydrogels differing in the base co-monomer (N,N-dimethylaminoethyl methacrylate and N-[3-(dimethylamino)propyl] methacrylamide) and in hydration state (both swollen and dried states). Formation of craters is the dominant morphological change observed by ablation in the visible at 532 nm, whereas additional, less aggressive surface modifications, chiefly microfoams and roughness, are developed in the ultraviolet at 266 nm. At both irradiation wavelengths, threshold values of the incident laser fluence for the observation of the various surface modifications are determined under single-pulse laser irradiation conditions. It is shown that multiple-pulse irradiation at 266 nm with a limited number of laser shots can be used alternatively for generating a regular microfoam layer at the surface of dried hydrogels based on N,N-dimethylaminoethyl methacrylate. The observations are rationalized on the basis of currently accepted mechanisms for laser-induced polymer surface modification, with a significant contribution of the laser foaming mechanism. Prospective applications of the laser-foamed hydrogel matrices in biomolecule immobilization are suggested.

  5. Flotation separation of polyvinyl chloride and polyethylene terephthalate plastics combined with surface modification for recycling.

    PubMed

    Wang, Chongqing; Wang, Hui; Fu, Jiangang; Zhang, Lingling; Luo, Chengcheng; Liu, Younian

    2015-11-01

    Surface modification with potassium permanganate (KMnO4) solution was developed for separation of polyvinyl chloride (PVC) and polyethylene terephthalate (PET) waste plastics. The floatability of PVC decreases with increasing of KMnO4 concentration, treatment time, temperature and stirring rate, while that of PET is unaffected. Fourier transform infrared (FT-IR) analysis confirms that mechanism of surface modification may be due to oxidization reactions occurred on PVC surface. The optimum conditions are KMnO4 concentration 1.25 mM/L, treatment time 50 min, temperature 60°C, stirring rate 300 r/min, frother concentration 17.5 g/L and flotation time 1 min. PVC and PET with different particle sizes were separated efficiently through two-stage flotation. Additionally, after ultrasonic assisted surface modification, separation of PVC and PET with different mass ratios was obtained efficiently through one-stage flotation. The purity and the recovery of the obtained products after flotation separation are up to 99.30% and 99.73%, respectively. A flotation process was designed for flotation separation of PVC and PET plastics combined with surface modification. This study provides technical insights into physical separation of plastic wastes for recycling industry. PMID:26253330

  6. Surface modification and endothelialization of biomaterials as potential scaffolds for vascular tissue engineering applications.

    PubMed

    Ren, Xiangkui; Feng, Yakai; Guo, Jintang; Wang, Haixia; Li, Qian; Yang, Jing; Hao, Xuefang; Lv, Juan; Ma, Nan; Li, Wenzhong

    2015-08-01

    Surface modification and endothelialization of vascular biomaterials are common approaches that are used to both resist the nonspecific adhesion of proteins and improve the hemocompatibility and long-term patency of artificial vascular grafts. Surface modification of vascular grafts using hydrophilic poly(ethylene glycol), zwitterionic polymers, heparin or other bioactive molecules can efficiently enhance hemocompatibility, and consequently prevent thrombosis on artificial vascular grafts. However, these modified surfaces may be excessively hydrophilic, which limits initial vascular endothelial cell adhesion and formation of a confluent endothelial lining. Therefore, the improvement of endothelialization on these grafts by chemical modification with specific peptides and genes is now arousing more and more interest. Several active peptides, such as RGD, CAG, REDV and YIGSR, can be specifically recognized by endothelial cells. Consequently, graft surfaces that are modified by these peptides can exhibit targeting selectivity for the adhesion of endothelial cells, and genes can be delivered by targeting carriers to specific tissues to enhance the promotion and regeneration of blood vessels. These methods could effectively accelerate selective endothelial cell recruitment and functional endothelialization. In this review, recent developments in the surface modification and endothelialization of biomaterials in vascular tissue engineering are summarized. Both gene engineering and targeting ligand immobilization are promising methods to improve the clinical outcome of artificial vascular grafts. PMID:26023741

  7. PES Surface Modification Using Green Chemistry: New Generation of Antifouling Membranes

    PubMed Central

    Nady, Norhan

    2016-01-01

    A major limitation in using membrane-based separation processes is the loss of performance due to membrane fouling. This drawback can be addressed thanks to surface modification treatments. A new and promising surface modification using green chemistry has been recently investigated. This modification is carried out at room temperature and in aqueous medium using green catalyst (enzyme) and nontoxic modifier, which can be safely labelled “green surface modification”. This modification can be considered as a nucleus of new generation of antifouling membranes and surfaces. In the current research, ferulic acid modifier and laccase bio-catalyst were used to make poly(ethersulfone) (PES) membrane less vulnerable to protein adsorption. The blank and modified PES membranes are evaluated based on e.g., their flux and protein repellence. Both the blank and the modified PES membranes (or laminated PES on silicon dioxide surface) are characterized using many techniques e.g., SEM, EDX, XPS and SPM, etc. The pure water flux of the most modified membranes was reduced by 10% on average relative to the blank membrane, and around a 94% reduction in protein adsorption was determined. In the conclusions section, a comparison between three modifiers—ferulic acid, and two other previously used modifiers (4-hydroxybenzoic acid and gallic acid)—is presented. PMID:27096873

  8. Protein surface topology-probing by selective chemical modification and mass spectrometric peptide mapping.

    PubMed Central

    Suckau, D; Mak, M; Przybylski, M

    1992-01-01

    Aminoacetylation of lysine residues and the modification of arginine by 1,2-cyclohexanedione to N7,N8-(dihydroxy-1,2-cyclohexylidene)arginine were used for probing the surface topology of hen-eggwhite lysozyme as a model protein. The molecular identification of lysine and arginine modification sites was provided by molecular weight determinations of modified and unmodified tryptic peptide mixtures (peptide mapping) using 252Cf plasma desorption mass spectrometry. At conditions of limited chemical modification, mass-spectrometric peptide-mapping analyses of lysozyme derivatives enabled the direct assignment of relative reactivities of lysine and arginine residues at different reaction times and reagent concentrations. The relative reactivities of lysine residues showed a direct correlation with their surface accessibilities from x-ray structure data. For the reaction with 1,2-cyclohexanedione, a selective modification at Arg-5, -125, -112, and -73 was identified, and an inverse correlation of relative reactivities with the surface accessibility ratios of the N7- and the N8-guanidino functions was obtained. By examination of the x-ray structural data of lysozyme, this selective modification was attributed to intramolecular catalysis because of the presence of neighboring proton acceptor groups, such as the Asp-119 carboxylate group for Arg-125 and the Trp-123 and Arg-125 carbonyl groups for Arg-5. PMID:1608973

  9. Novel Surface Modification Method for Ultrasupercritical Coal-Fired Boilers

    SciTech Connect

    Xiao, T. Danny

    2013-05-22

    US Department of Energy seeks an innovative coating technology for energy production to reduce the emission of SOx, NOx, and CO2 toxic gaseous species. To realize this need, Inframat Corporation (IMC) proposed an SPS thermal spray coating technique to produce ultrafine/nanocoatings that can be deposited onto the surfaces of high temperature boiler tubes, so that higher temperatures of boiler operation becomes possible, leading to significantly reduced emission of toxic gaseous species. It should be noted that the original PI was Dr. Xinqing Ma, who after 1.5 year conducting this project left Inframat in December, 2008. Thus, the PI was transferred to Dr. Danny Xiao, who originally co-authored the proposal with Dr. Ma, in order to carry the project into a completion. Phase II Objectives: The proposed technology has the following attributes, including: (1). Dispersion of a nanoparticle or alloyed particle in a solvent to form a uniform slurry feedstock; (2). Feeding of the slurry feedstock into a thermal spray flame, followed by deposition of the slurry feedstock onto substrates to form tenacious nanocoatings; (3). High coating performance: including high bonding strength, and high temperature service life in the temperature range of 760oC/1400oF. Following the above premises, our past Phase I project has demonstrated the feasibility in small scale coatings on boiler substrates. The objective of this Phase II project was to focus on scale-up the already demonstrated Phase I work for the fabrication of SPS coatings that can satisfy DOE's emission reduction goals for energy production operations. Specifically, they are: (1). Solving engineering problems to scale-up the SPS-HVOF delivery system to a prototype production sub-delivery system; (2). Produce ultrafine/nanocoatings using the scale-up prototype system; (3). Demonstrate the coated components using the scale-up device having superior properties. Proposed Phase II Tasks: In the original Phase II proposal, we have

  10. Surface modification on polydimethylsiloxane-based microchannels with fragmented poly(l-lactic acid) nanosheets.

    PubMed

    Yang, Lu; Okamura, Yosuke; Kimura, Hiroshi

    2015-11-01

    Surface modification is a critical issue in various applications of polydimethylsiloxane (PDMS)-based microfluidic devices. Here, we describe a novel method through which PDMS-based microchannels were successfully modified with fragmented poly(l-lactic acid) (PLLA) nanosheets through a simple patchwork technique that exploited the high level of adhesiveness of PLLA nanosheets. Compared with other surface modification methods, our method required neither complicated chemical modifications nor the use of organic solvents that tend to cause PDMS swelling. The experimental results indicated that the modified PDMS exhibited excellent capacity for preventing the adhesion and activation of platelets. This simple yet efficient method can be used to fabricate the special PDMS microfluidic devices for biological, medical, and even hematological purposes. PMID:26634016

  11. Influence of surface modifications to titanium on antibacterial activity in vitro.

    PubMed

    Yoshinari, M; Oda, Y; Kato, T; Okuda, K

    2001-07-01

    The antibacterial effect of surface modifications to titanium on Porphyromonas gingivalis ATCC 33277 and Actinobacillus actinomycetemcomitans ATCC 43718 was evaluated. Surface modifications were performed with dry processes including ion implantation (Ca+, N+, F+), oxidation (anode oxidation, titania spraying), ion plating (TiN, alumina), and ion beam mixing (Ag, Sn, Zn, Pt) with Ar+ on polished pure titanium plates. F+-implanted specimens significantly inhibited the growth of both P. gingivalis and A. actinomycetemcomitans than the polished titanium. The other surface-modified specimens did not exhibit effective antibacterial activity against both bacteria. No release of the fluorine ion was detected from F-implanted specimens under dissolution testing. This result and the characterization of the F+-implanted surfaces suggested that the possible antibacterial mechanism of the F+-implanted specimen was caused by the formation of a metal fluoride complex on the surfaces. In addition, F+-implanted surfaces did not inhibit the proliferation of fibroblast L929-cells. These findings indicate that surface modification by means of a dry process is useful in providing antibacterial activity of oral bacteria to titanium implants exposed to the oral cavity. PMID:11426884

  12. Regolith Advanced Surface Systems Operations Robot (RASSOR)

    NASA Astrophysics Data System (ADS)

    Mueller, Robert P.; Cox, Rachel E.; Ebert, Tom; Smith, Jonathan D.; Schuler, Jason M.; Nick, Andrew J.

    Regolith is abundant on extra-terrestrial surfaces and is the source of many resources such as oxygen, hydrogen, titanium, aluminum, iron, silica and other valuable materials, which can be used to make rocket propellant, consumables for life support, radiation protection barrier shields, landing pads, blast protection berms, roads, habitats and other structures and devices. Recent data from the Moon also indicates that there are substantial deposits of water ice in permanently shadowed crater regions and possibly under an over burden of regolith. The key to being able to use this regolith and acquire the resources, is being able to manipulate it with robotic excavation and hauling machinery that can survive and operate in these very extreme extra-terrestrial surface environments.

  13. Regolith Advanced Surface Systems Operations Robot (RASSOR)

    NASA Technical Reports Server (NTRS)

    Mueller, Robert P.; Smith, Jonathan D.; Cox, Rachel E.; Schuler, Jason M.; Ebert, Tom; Nick, Andrew J.

    2012-01-01

    Regolith is abundant on extra-terrestrial surfaces and is the source of many resources such as oxygen, hydrogen, titanium, aluminum, iron, silica and other valuable materials, which can be used to make rocket propellant, consumables for life support, radiation protection barrier shields, landing pads, blast protection berms, roads, habitats and other structures and devices. Recent data from the Moon also indicates that there are substantial deposits of water ice in permanently shadowed crater regions and possibly under an over burden of regolith. The key to being able to use this regolith and acquire the resources, is being able to manipulate it with robotic excavation and hauling machinery that can survive and operate in these very extreme extra-terrestrial surface environments. In addition, the reduced gravity on the Moon, Mars, comets and asteroids poses a significant challenge in that the necessary reaction force for digging cannot be provided by the robot's weight as is typically done on Earth. Space transportation is expensive and limited in capacity, so small, lightweight payloads are desirable, which means large traditional excavation machines are not a viable option. A novel, compact and lightweight excavation robot prototype for manipulating, excavating, acquiring, hauling and dumping regolith on extra-terrestrial surfaces has been developed and tested. Lessons learned and test results will be presented including digging in a variety of lunar regolith simulant conditions including frozen regolith mixed with water ice.

  14. Biophysical bases of human plasma lipoprotein polydispersity: role of surface modification

    SciTech Connect

    Shahrokh, Z.

    1984-11-01

    Metabolic depletion of the core of the triglyceride-rich lipoproteins via lipolysis results in the production of polydisperse species of particles within the density range of low density lipoproteins (LDL). Modifications of surface properties of plasma LDL may further contribute to LDL polydispersity. In this dissertation, we study the interactions with LDL of models of lipolysis-related surface products (i.e., phosphatidylcholine vesicles (PCV) and discoidal complexes (DC) of apoprotein AI and phosphatidylcholine) and examine the influence on such interactions of high density lipoproteins (HDL) and other relevant plasma components (lecithin:cholesterol acyltransferase (LCAT), lipid transfer proteins (LTPs), albumin, lysolecithin (LPC)). Based on the studies obtained in this dissertation LDL surface modification may contribute to LDL polydispersity. Since HDL is a major acceptor of PL, formation of surface-modified LDL (e.g., PL-enriched, larged LDL) in vivo would depend on LDL/HDL weight ratio in plasma. 140 references, 50 figures, 15 tables.

  15. Surface modification via wet chemical etching of single-crystalline silicon for photovoltaic application.

    PubMed

    Reshak, A H; Shahimin, M M; Shaari, S; Johan, N

    2013-11-01

    The potential of solar cells have not been fully tapped due to the lack of energy conversion efficiency. There are three important mechanisms in producing high efficiency cells to harvest solar energy; reduction of light reflectance, enhancement of light trapping in the cell and increment of light absorption. The current work represent studies conducted in surface modification of single-crystalline silicon solar cells using wet chemical etching techniques. Two etching types are applied; alkaline etching (KOH:IPA:DI) and acidic etching (HF:HNO3:DI). The alkaline solution resulted in anisotropic profile that leads to the formation of inverted pyramids. While acidic solution formed circular craters along the front surface of silicon wafer. This surface modification will leads to the reduction of light reflectance via texturizing the surface and thereby increases the short circuit current and conversion rate of the solar cells. PMID:24139943

  16. Electrochemical behavior of nano and femtosecond laser textured titanium alloy for implant surface modification.

    PubMed

    Jeong, Yong-Hoon; Kim, Won-Gi; Choe, Han-Cheol

    2011-02-01

    In this study, the electrochemical behavior of nano and femtosecond laser textured titanium alloy for implant surface modification has been researched using the potentiostat equipment. Cp-Ti and Ti-6Al-4V alloy, located on X-Y motorized stage, were irradiated using femtosecond laser. The corrosion properties were examined by a potentiodynamic and AC impedance test. PMID:21456241

  17. Atmospheric Pressure Glow Discharge Plasma and Surface Modification of PET Textile by APGDP

    NASA Astrophysics Data System (ADS)

    Gu, Biao; Chen, Ru; Xu, Yin; Deng, Xiang; Shi, Qingjun

    2002-11-01

    Comparing with traditional chemistry method, surface modification of Polyethylene terephthalate (PET) fabrics by using of Atmospheric Pressure Glow Discharge Plasma (APGDP) has many advantages, such as low cost, low pollution and low energy consumption. So it has huge application in textile industry due to no requirement for vacuum system. In this paper, the generation and the characteristics of APGDP on a homemade device were investigated experimentally. The volt-ampere characteristic and the Lissajous figure demonstrated that, different from dielectric barrier discharge (DBD), there is no filaments appeared between electrodes. It is a glow discharge in one atmospheric pressure. Furthermore we investigated the surface modification of PET by APGDP. The relationship between PET characteristics (wettability, critical surface tension, timing-effect, dyeablity etc.) and various discharge parameters are discussed. At last, the measurements of ATR-FTIR (Attenuated Total Refraction-Fourier Transform Infarared Spectroscopy) and dyeing properties are demonstrated, and the mechanism of modification is analyzed basically. Key words: APGDP£¬Surface modification , PET

  18. Proceedings of the 10th international symposium on polymer surface modification

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Contamination of meats, seafood, poultry, eggs, and fresh and fresh-cut fruits and vegetables is an ongoing concern. Although well-established in non-food applications for surface treatment and modification, cold plasma is a relatively new food safety intervention. As a nonthermal food processing te...

  19. Surface modification of porous poly(tetrafluoroethylene) film via cold plasma treatment

    NASA Astrophysics Data System (ADS)

    Shi, Tongna; Shao, Meiling; Zhang, Hongrui; Yang, Qing; Shen, Xinyuan

    2011-12-01

    In this study, cold plasma technology was applied for the surface modification of porous polytetrafluoroethylene (PTFE) film to improve the hydrophilicity. The surface properties of PTFE, modified by air, helium (He) or acrylic acid (AAc), were investigated with scanning electron microscopy (SEM), scanning probe microscope (SPM), in situ X-ray photoelectron spectroscopy (XPS) and water contact angle measurements. The changes of the surface property before and after plasma treatment were discussed. According to SEM and SPM measurements, the surface roughness increased at different levels after plasma treatment. Compared to air and AAc plasma treatment, the He plasma treatment introduced large amounts of oxygen into the surface, as known from XPS results. Contact angle measurements revealed that the hydrophilicity of the PTFE film surface was greatly improved due to the surface roughness and changes of chemical elements on the PTFE surface.

  20. Realization of Dirac Cones in Few Bilayer Sb(111) Films by Surface Modification.

    PubMed

    Pan, Hui; Wang, Xue-Sen

    2015-12-01

    We report the first-principle study on the recovery and linearization of Dirac cones in the electronic band structures of a few bilayer Sb(111) films (n-BL Sb) by surface modification. Due to the interaction between the surface states on the two surfaces of a free-standing film, the distorted Dirac cone in n-BL Sb(111) (n < 5) disappears. We demonstrate that the Dirac cone can be restored by functionalizing one surface with certain atoms including H, Ag, and Au, to reduce the inter-surface interaction. We further show that an ideal Dirac cone with linear dispersion of topological surface states near the zone center can be realized by functionalizing both surfaces of the film with oxygen, which enhances spin-orbital coupling. The realization of Dirac cone by surface functionalization shows promise for applications of topologic materials to spintronic devices and their operation in complicated conditions. PMID:26293493

  1. Surface Modification of Polypropylene Membrane by RF Methane/Oxygen Mixture Plasma Treatment

    NASA Astrophysics Data System (ADS)

    Tsai, Ching-Yuan; Juang, Ruey-Shin; Huang, Chun

    2011-08-01

    The hydrophilic surface modification of micro-porous polypropylene (PP) membranes is achieved by low-pressure 13.56 MHz RF methane (CH4)/oxygen (O2) gas mixture plasma treatment. The changes in surface wettability and surface free energy were examined by static contact angle analysis. The static water contact angle of the plasma modified membrane notably decreased with increases in treatment time and plasma power. The obvious increase in the surface energy of polypropylene membranes due to CH4/O2 mixture gas plasma treatments was also observed. Optical emission spectroscopy (OES) was used to analyze the chemical species of CH4/O2 mixture gas plasma treatment. The variations in the surface morphology and chemical structure of the micro-porous PP membranes were confirmed by confocal laser scanning microscopy (CLSM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) measurements. XPS analysis showed significantly higher surface concentrations of oxygen functional groups for CH4/O2 mixture gas plasma-modified polypropylene membrane surfaces than for the originally unmodified polypropylene membrane surface. The experimental results show the important role of chemical species in the interaction between a CH4/O2 mixture gas plasma and a membrane surface, which can be controlled by surface modification to tailor the hydrophilicity of the membrane to the requirements of various applications.

  2. Advanced Face Gear Surface Durability Evaluations

    NASA Technical Reports Server (NTRS)

    Lewicki, David G.; Heath, Gregory F.

    2016-01-01

    The surface durability life of helical face gears and isotropic super-finished (ISF) face gears was investigated. Experimental fatigue tests were performed at the NASA Glenn Research Center. Endurance tests were performed on 10 sets of helical face gears in mesh with tapered involute helical pinions, and 10 sets of ISF-enhanced straight face gears in mesh with tapered involute spur pinions. The results were compared to previous tests on straight face gears. The life of the ISF configuration was slightly less than that of previous tests on straight face gears. The life of the ISF configuration was slightly greater than that of the helical configuration.

  3. Effect of Hybrid Surface Modifications on Tensile Properties of Polyacrylonitrile- and Pitch-Based Carbon Fibers

    NASA Astrophysics Data System (ADS)

    Naito, Kimiyoshi

    2016-05-01

    Recent interest has emerged in techniques that modify the surfaces of carbon fibers, such as carbon nanotube (CNT) grafting or polymer coating. Hybridization of these surface modifications has the potential to generate highly tunable, high-performance materials. In this study, the mechanical properties of surface-modified polyacrylonitrile (PAN)-based and pitch-based carbon fibers were investigated. Single-filament tensile tests were performed for fibers modified by CNT grafting, dipped polyimide coating, high-temperature vapor deposition polymerized polyimide coating, grafting-dipping hybridization, and grafting-vapor deposition hybridization. The Weibull statistical distributions of the tensile strengths of the surface-modified PAN- and pitch-based carbon fibers were examined. All surface modifications, especially hybrid modifications, improved the tensile strengths and Weibull moduli of the carbon fibers. The results exhibited a linear relationship between the Weibull modulus and average tensile strength on a log-log scale for all surface-modified PAN- and pitch-based carbon fibers.

  4. Surface Structure Modification of ZnO and the Impact on Electronic Properties.

    PubMed

    Hewlett, Robert M; McLachlan, Martyn A

    2016-05-01

    Zinc oxide (ZnO) is a widely utilized, versatile material implemented in a diverse range of technological applications, particularly in optoelectronic devices, where its inherent transparency, tunable electronic properties, and accessible nanostructures can be combined to confer superior device properties. ZnO is a complex material with a rich and intricate defect chemistry, and its properties can be extremely sensitive to processing methods and conditions; consequently, surface modification of ZnO using both inorganic and organic species has been explored to control and regulate its surface properties, particularly at heterointerfaces in electronic devices. Here, the properties of ZnO are described in detail, particularly its surface chemistry, along with the role of defects in governing its electronic properties, and methods employed to modulate the behavior of as-grown ZnO. An outline is also given on how the native and modified oxide interact with molecular materials. To illustrate the diverse range of surface modification methods and their subsequent influence on electronic properties, a comprehensive review of the modification of ZnO surfaces at molecular interfaces in hybrid photovoltaic (hPV) and organic photovoltaic (OPV) devices is presented. This is a case study rather than a progress report, aiming to highlight the progress made toward controlling and altering the surface properties of ZnO, and to bring attention to the ways in which this may be achieved by using various interfacial modifiers (IMs). PMID:26936217

  5. Surface modification and properties of Bombyx mori silk fibroin films by antimicrobial peptide

    NASA Astrophysics Data System (ADS)

    Bai, Liqiang; Zhu, Liangjun; Min, Sijia; Liu, Lin; Cai, Yurong; Yao, Juming

    2008-03-01

    The Bombyx mori silk fibroin films (SFFs) were modified by a Cecropin B ( CB) antimicrobial peptide, (NH 2)-NGIVKAGPAIAVLGEAAL-CONH 2, using the carbodiimide chemistry method. In order to avoid the dissolution of films during the modification procedure, the SFFs were first treated with 60% (v/v) ethanol aqueous solution, resulting a structural transition from unstable silk I to silk II. The investigation of modification conditions showed that the surface-modified SFFs had the satisfied antimicrobial activity and durability when they were activated by EDC·HCl/NHS solution followed by a treatment in CB peptide/PBS buffer (pH 6.5 or 8) solution at ambient temperature for 2 h. Moreover, the surface-modified SFFs showed the smaller contact angle due to the hydrophilic antimicrobial peptides coupled on the film surface, which is essential for the cell adhesion and proliferation. AFM results indicated that the surface roughness of SFFs was considerably increased after the modification by the peptides. The elemental composition analysis results also suggested that the peptides were tightly coupled to the surface of SFFs. This approach may provide a new option to engineer the surface-modified implanted materials preventing the biomaterial-centered infection (BCI).

  6. Nanomaterial surface chemistry design for advancements in capillary electrophoresis modes.

    PubMed

    Ivanov, Michael R; Haes, Amanda J

    2011-01-01

    Tailored surface chemistry impacts nanomaterial function and stability in applications including in various capillary electrophoresis (CE) modes. Although colloidal nanoparticles were first integrated as colouring agents in artwork and pottery over 2000 years ago, recent developments in nanoparticle synthesis and surface modification increased their usefulness and incorporation in separation science. For instance, precise control of surface chemistry is critically important in modulating nanoparticle functionality and stability in dynamic environments. Herein, recent developments in nanomaterial pseudostationary and stationary phases will be summarized. First, nanomaterial core and surface chemistry compositions will be classified. Next, characterization methods will be described and related to nanomaterial function in various CE modes. Third, methods and implications of nanomaterial incorporation into CE will be discussed. Finally, nanoparticle-specific mechanisms likely involved in CE will be related to nanomaterial surface chemistry. Better understanding of surface chemistry will improve nanoparticle design for the integration into separation techniques. PMID:20967383

  7. Modification of Surface Properties of Biomaterials Influences the Ability of Candida albicans To Form Biofilms

    PubMed Central

    Chandra, Jyotsna; Patel, Jasmine D.; Li, Jian; Zhou, Guangyin; Mukherjee, Pranab K.; McCormick, Thomas S.; Anderson, James M.; Ghannoum, Mahmoud A.

    2005-01-01

    Candida albicans biofilms form on indwelling medical devices (e.g., denture acrylic or intravenous catheters) and are associated with both oral and invasive candidiasis. Here, we determined whether surface modifications of polyetherurethane (Elasthane 80A [E80A]), polycarbonateurethane, and poly(ethyleneterephthalate) (PET) can influence fungal biofilm formation. Polyurethanes were modified by adding 6% polyethylene oxide (6PEO), 6% fluorocarbon, or silicone, while the PET surface was modified to generate hydrophilic, hydrophobic, cationic, or anionic surfaces. Formation of biofilm was quantified by determining metabolic activity and total biomass (dry weight), while its architecture was analyzed by confocal scanning laser microscopy (CSLM). The metabolic activity of biofilm formed by C. albicans on 6PEO-E80A was significantly reduced (by 78%) compared to that of biofilm formed on the nonmodified E80A (optical densities of 0.054 ± 0.020 and 0.24 ± 0.10, respectively; P = 0.037). The total biomass of Candida biofilm formed on 6PEO-E80A was 74% lower than that on the nonmodified E80A surface (0.46 ± 0.15 versus 1.76 ± 0.32 mg, respectively; P = 0.003). Fungal cells were easily detached from the 6PEO-E80A surface, and we were unable to detect C. albicans biofilm on this surface by CSLM. All other surface modifications allowed formation of C. albicans biofilm, with some differences in thearchitecture. Correlation between contact angle and biofilm formation was observed for polyetherurethane substrates (r = 0.88) but not for PET biomaterials (r = −0.40). This study illustrates that surface modification is a viable approach for identifying surfaces that have antibiofilm characteristics. Investigations into the clinical utility of the identified surfaces are warranted. PMID:16332875

  8. Surface modification of ferritic steels using MEVVA and duoplasmatron ion sources.

    PubMed

    Kulevoy, Timur V; Chalyhk, Boris B; Fedin, Petr A; Sitnikov, Alexey L; Kozlov, Alexander V; Kuibeda, Rostislav P; Andrianov, Stanislav L; Orlov, Nikolay N; Kravchuk, Konstantin S; Rogozhkin, Sergey V; Useinov, Alexey S; Oks, Efim M; Bogachev, Alexey A; Nikitin, Alexander A; Iskandarov, Nasib A; Golubev, Alexander A

    2016-02-01

    Metal Vapor Vacuum Arc (MEVVA) ion source (IS) is a unique tool for production of high intensity metal ion beam that can be used for material surface modification. From the other hand, the duoplasmatron ion source provides the high intensity gas ion beams. The MEVVA and duoplasmatron IS developed in Institute for Theoretical and Experimental Physics were used for the reactor steel surface modification experiments. Response of ferritic-martensitic steel specimens on titanium and nitrogen ions implantation and consequent vacuum annealing was investigated. Increase in microhardness of near surface region of irradiated specimens was observed. Local chemical analysis shows atom mixing and redistribution in the implanted layer followed with formation of ultrafine precipitates after annealing. PMID:26932112

  9. Surface modification on microfluidic devices with 2-methacryloyloxyethyl phosphorylcholine polymers for reducing unfavorable protein adsorption.

    PubMed

    Sibarani, James; Takai, Madoka; Ishihara, Kazuhiko

    2007-01-15

    Surface modification of polymer materials for preparing microfluidic devices including poly(dimethyl siloxane) (PDMS) was investigated with phospholipids polymers such as poly(2-methacryloyloxylethyl phosphorylcholine(MPC)-co-n-butyl methacrylate) (PMB) and poly(MPC-co-2-ethylhexyl methacrylate-co-2-(N,N-dimethylamino)ethyl methacrylate) (PMED). The hydrophilicity of every surface on the polymer materials modified with these MPC polymers increased and the value of zeta-potential became close to zero. The protein adsorption on the polymer materials with and without the surface modification was evaluated using a protein mixture of human plasma fibrinogen and serum albumin. Amount of proteins adsorbed on these polymeric materials showed significant reduction by the surface modification with the MPC polymers compared to the uncoated surfaces ranging from 56 to 90%. Furthermore, we successfully prepared PDMS-based microchannel which was modified by simple coating with the PMB and PMED. The modified microchannel also revealed a significant reduction of adsorption of serum albumin. We conclude that the MPC polymers are useful for reducing unfavorable protein adsorption on microfluidic devices. PMID:17112710

  10. Cell adhesive and antifouling polyvinyl chloride surfaces via wet chemical modification.

    PubMed

    Gabriel, Matthias; Strand, Dennis; Vahl, Christian-Friedrich

    2012-09-01

    Polyvinyl chloride (PVC) is one of the most frequently used polymers for the manufacturing of medical devices. Limitations for its usage are based upon unfavorable surface properties of the polymer including its hydrophobicity and lack of functionalities in order to increase its versatility. To address this issue, wet chemical modification of PVC was performed through surface amination using the bifunctional compound ethylene diamine. The reaction was conducted in order to achieve maximum surface amination while leaving the bulk material unaffected. The initial activation step was characterized by means of various methods including contact angle measurements, colorimetric amine quantification, infrared spectroscopy, and gel permeation chromatography. Depth profiles were obtained by a confocal microscopic method using fluorescence labeling. Exclusive surface modification was thus confirmed. To demonstrate biological applications of the presented technique, two examples were chosen: The covalent immobilization of the cell adhesive Asp-Gly-Asp-Ser-peptide (RGD) onto PVC samples yielded a surface that strongly supported cellular adhesion and proliferation of fibroblasts. In contrast, the decoration of PVC with the hydrophilic polymer polyethylene glycol prevented cellular adhesion to a large extent. The impact of these modifications was demonstrated by cell culture experiments. PMID:22747750

  11. Surface modification of plasmonic nanostructured materials with thiolated oligonucleotides in 10 seconds using selective microwave heating.

    PubMed

    Abel, Biebele; Aslan, Kadir

    2012-11-01

    This study demonstrates the proof-of-principle of rapid surface modification of plasmonic nanostructured materials with oligonucleotides using low power microwave heating. Due to their interesting optical and electronic properties, silver nanoparticle films (SNFs, 2 nm thick) deposited onto glass slides were used as the model plasmonic nanostructured materials. Rapid surface modification of SNFs with oligonucleotides was carried out using two strategies (1) Strategy 1: for ss-oligonucleotides, surface hybridization and (2) Strategy 2: for ds-oligonucleotides, solution hybridization), where the samples were exposed to 10, 15, 30 and 60 seconds microwave heating. To assess the efficacy of our new rapid surface modification technique, identical experiments carried out without the microwave heating (i.e., conventional method), which requires 24 hours for the completion of the identical steps. It was found that SNFs can be modified with ss- and ds-oligonucleotides in 10 seconds, which typically requires several hours of incubation time for the chemisorption of thiol groups on to the planar metal surface using conventional techniques. PMID:23645933

  12. Surface monofunctionalized polymethyl pentene hollow fiber membranes by plasma treatment and hemocompatibility modification for membrane oxygenators

    NASA Astrophysics Data System (ADS)

    Huang, Xin; Wang, Weiping; Zheng, Zhi; Fan, Wenling; Mao, Chun; Shi, Jialiang; Li, Lei

    2016-01-01

    The hemocompatibility of polymethyl pentene (PMP) hollow fiber membranes (HFMs) was improved through surface modification for membrane oxygenator applications. The modification was performed stepwise with the following: (1) oxygen plasma treatment, (2) functionalization of monosort hydroxyl groups through NaBH4 reduction, and (3) grafting 2-methacryloyloxyethyl phosphorylcholine (MPC) or heparin. SEM, ATR-FTIR, and XPS analyses were conducted to confirm successful grafting during the modification. The hemocompatibility of PMP HFMs was analyzed and compared through protein adsorption, platelet adhesion, and coagulation tests. Pure CO2 and O2 permeation rates, as well as in vitro gas exchange rates, were determined to evaluate the mass transfer properties of PMP HFMs. SEM results showed that different nanofibril topographies were introduced on the HFM surface. ATR-FTIR and XPS spectra indicated the presence of functionalization of monosort hydroxyl group and the grafting of MPC and heparin. Hemocompatibility evaluation results showed that the modified PMP HFMs presented optimal hemocompatibility compared with pristine HFMs. Gas permeation results revealed that gas permeation flux increased in the modified HFMs because of dense surface etching during the plasma treatment. The results of in vitro gas exchange rates showed that all modified PMP HFMs presented decreased gas exchange rates because of potential surface fluid wetting. The proposed strategy exhibits a potential for fabricating membrane oxygenators for biomedical applications to prevent coagulation formation and alter plasma-induced surface topology and composition.

  13. Modification of nanostructured fused silica for use as superhydrophobic, IR-transmissive, anti-reflective surfaces

    NASA Astrophysics Data System (ADS)

    Boyd, Darryl A.; Frantz, Jesse A.; Bayya, Shyam S.; Busse, Lynda E.; Kim, Woohong; Aggarwal, Ishwar; Poutous, Menelaos; Sanghera, Jasbinder S.

    2016-04-01

    In order to mimic and enhance the properties of moth eye-like materials, nanopatterned fused silica was chemically modified to produce self-cleaning substrates that have anti-reflective and infrared transmissive properties. The characteristics of these substrates were evaluated before and after chemical modification. Furthermore, their properties were compared to fused silica that was devoid of surface features. The chemical modification imparted superhydrophobic character to the substrates, as demonstrated by the average water contact angles which exceeded 170°. Finally, optical analysis of the substrates revealed that the infrared transmission capabilities of the fused silica substrates (nanopatterned to have moth eye on one side) were superior to those of the regular fused silica substrates within the visible and near-infrared region of the light spectrum, with transmission values of 95% versus 92%, respectively. The superior transmission properties of the fused silica moth eye were virtually unchanged following chemical modification.

  14. Surface modification of polyacrylonitrile fibre by nitrile hydratase from Corynebacterium nitrilophilus.

    PubMed

    Chen, Sheng; Gao, Huihui; Chen, Jian; Wu, Jing

    2014-11-01

    Previously, nitrile hydratase (NHase) from Corynebacterium nitrilophilus was obtained and showed potential in polyacrylonitrile (PAN) fibre modification. In the present study, the modification conditions of C. nitrilophilus NHase on PAN were investigated. In the optimal conditions, the wettability and dyeability (anionic and reactive dyes) of PAN treated by C. nitrilophilus NHase reached a similar level of those treated by alkali. In addition, the chemical composition and microscopically observable were changed in the PAN surface after NHase treatment. Meanwhile, it revealed that cutinase combined with NHase facilitates the PAN hydrolysis slightly because of the ester existed in PAN as co-monomer was hydrolyzed. All these results demonstrated that C. nitrilophilus NHase can modify PAN efficiently without textile structure damage, and this study provides a foundation for the further application of C. nitrilophilus NHase in PAN modification industry. PMID:25163886

  15. Surface modification of an epoxy resin with polyamines and polydopamine: The effect on the initial electroless copper deposition

    NASA Astrophysics Data System (ADS)

    Schaubroeck, David; Mader, Lothar; De Geyter, Nathalie; Morent, Rino; Dubruel, Peter; Vanfleteren, Jan

    2014-06-01

    This paper describes the influence of polydopamine and polyamine surface modifications of an etched epoxy cresol novolak (ECN) resin on the initial electroless copper deposition. Three different strategies to introduce polyamines on a surface in aqueous environment are applied: via polyethyleneimine adsorption (PEI), via polydopamine and via polyamines grafted to polydopamine. Next, the influence of these surface modifications on the catalytic palladium activation is investigated through X-ray photoelectron spectroscopy (XPS) analysis. Finally, the initial electroless copper deposition on modified epoxy surfaces is evaluated using SEM and Energy Dispersive Spectroscopy (EDS). Grafted polyamines on polydopamine surface modifications result in a large increase of the initial deposited copper.

  16. Nanocapillary Atmospheric Pressure Plasma Jet: A Tool for Ultrafine Maskless Surface Modification at Atmospheric Pressure.

    PubMed

    Motrescu, Iuliana; Nagatsu, Masaaki

    2016-05-18

    With respect to microsized surface functionalization techniques we proposed the use of a maskless, versatile, simple tool, represented by a nano- or microcapillary atmospheric pressure plasma jet for producing microsized controlled etching, chemical vapor deposition, and chemical modification patterns on polymeric surfaces. In this work we show the possibility of size-controlled surface amination, and we discuss it as a function of different processing parameters. Moreover, we prove the successful connection of labeled sugar chains on the functionalized microscale patterns, indicating the possibility to use ultrafine capillary atmospheric pressure plasma jets as versatile tools for biosensing, tissue engineering, and related biomedical applications. PMID:27116255

  17. Modification of Photoluminescence Properties of ZnO Island Films by Localized Surface Plasmons

    NASA Astrophysics Data System (ADS)

    Zhang, Yang; Li, Xue-Hong; Peng, Cheng-Xiao

    2012-10-01

    The modification of localised surface plasmons of photoluminescence properties of ZnO is studied. It is found that the ultraviolet emission is drastically enhanced, and the visible emission related to the defects is almost completely suppressed, after an Au layer of nanoparticles is deposited on the surface of ZnO island films. This pronounced change in PL spectra is attributed to the efficient electron transfer via the coupling of localised surface plasmons at the interface between the Au nanoparticle layer and ZnO films.

  18. Visible-light sensitization of boron-doped nanocrystalline diamond through non-covalent surface modification.

    PubMed

    Krysova, Hana; Vlckova-Zivcova, Zuzana; Barton, Jan; Petrak, Vaclav; Nesladek, Milos; Cigler, Petr; Kavan, Ladislav

    2015-01-14

    A novel simple and versatile synthetic strategy is developed for the surface modification of boron-doped diamond. In a two-step procedure, polyethyleneimine is adsorbed on the hydrogenated diamond surface and subsequently modified with a model light-harvesting donor-π-bridge-acceptor molecule (coded P1). The sensitized diamond exhibits stable cathodic photocurrents under visible-light illumination in aqueous electrolyte solution with dimethylviologen serving as an electron mediator. In spite of the simplicity of the surface sensitization protocol, the photoelectrochemical performance is similar to or better than that of other sensitized diamond electrodes which were reported in previous studies (2008-2014). PMID:25418375

  19. Enhancing adhesion of yeast brewery strains to chamotte carriers through aminosilane surface modification.

    PubMed

    Berlowska, Joanna; Kregiel, Dorota; Ambroziak, Wojciech

    2013-07-01

    The adhesion of cells to solid supports is described as surface-dependent, being largely determined by the properties of the surface. In this study, ceramic surfaces modified using different organosilanes were tested for proadhesive properties using industrial brewery yeast strains in different physiological states. Eight brewing strains were tested: bottom-fermenting Saccharomyces pastorianus and top-fermenting Saccharomyces cerevisiae. To determine adhesion efficiency light microscopy, scanning electron microscopy and the fluorymetric method were used. Modification of chamotte carriers by 3-(3-anino-2-hydroxy-1-propoxy) propyldimethoxysilane and 3-(N, N-dimethyl-N-2-hydroxyethyl) ammonium propyldimethoxysilane groups increased their biomass load significantly. PMID:23420113

  20. Ion-Beam Surface Modification of Strut Dowel Used in ITER PF Support

    NASA Astrophysics Data System (ADS)

    Luo, Rongrong; Li, Pengyuan; Han, Shilei; Sun, Zhenchao; Pan, Chuanjie; Shen, Liru; Jin, Fanya

    2013-03-01

    In this paper, surface modification of the strut dowel used in ITER PF support is reported. Different ions (nitrogen/titanium) with different doses are implanted into the surface of strut dowel. The result of Auger Electron Spectroscopy (AES) indicates that nitrogen can be implanted more deeply than titanium under the implantation condition of 60 kV accelerating voltage and a dose of 8 × 1017/cm2 nitrogen. Surface Micro Hardness (SMH) and wear resistance are improved remarkably. Further SEM observation shows that there are no obvious scratches and damages after wear test.

  1. Surface modification of a POSS-nanocomposite material to enhance cellular integration of a synthetic bioscaffold

    PubMed Central

    Crowley, Claire; Klanrit, Poramate; Butler, Colin R.; Varanou, Aikaterini; Platé, Manuela; Hynds, Robert E.; Chambers, Rachel C.; Seifalian, Alexander M.; Birchall, Martin A.; Janes, Sam M.

    2016-01-01

    Polyhedral oligomeric silsesquioxane poly(carbonate-urea) urethane (POSS-PCU) is a versatile nanocomposite biomaterial with growing applications as a bioscaffold for tissue engineering. Integration of synthetic implants with host tissue can be problematic but could be improved by topographical modifications. We describe optimization of POSS-PCU by dispersion of porogens (sodium bicarbonate (NaHCO3), sodium chloride (NaCl) and sucrose) onto the material surface, with the principle aim of increasing surface porosity, thus providing additional opportunities for improved cellular and vascular ingrowth. We assess the effect of the porogens on the material's mechanical strength, surface chemistry, wettability and cytocompatibilty. Surface porosity was characterized by scanning electron microscopy (SEM). There was no alteration in surface chemistry and wettability and only modest changes in mechanical properties were detected. The size of porogens correlated well with the porosity of the construct produced and larger porogens improved interconnectivity of spaces within constructs. Using primary human bronchial epithelial cells (HBECs) we demonstrate moderate in vitro cytocompatibility for all surface modifications; however, larger pores resulted in cellular aggregation. These cells were able to differentiate on POSS-PCU scaffolds. Implantation of the scaffold in vivo demonstrated that larger pore sizes favor cellular integration and vascular ingrowth. These experiments demonstrate that surface modification with large porogens can improve POSS-PCU nanocomposite scaffold integration and suggest the need to strike a balance between the non-porous surfaces required for epithelial coverage and the porous structure required for integration and vascularization of synthetic scaffolds in future construct design. PMID:26790147

  2. Surface modification of a POSS-nanocomposite material to enhance cellular integration of a synthetic bioscaffold.

    PubMed

    Crowley, Claire; Klanrit, Poramate; Butler, Colin R; Varanou, Aikaterini; Platé, Manuela; Hynds, Robert E; Chambers, Rachel C; Seifalian, Alexander M; Birchall, Martin A; Janes, Sam M

    2016-03-01

    Polyhedral oligomeric silsesquioxane poly(carbonate-urea) urethane (POSS-PCU) is a versatile nanocomposite biomaterial with growing applications as a bioscaffold for tissue engineering. Integration of synthetic implants with host tissue can be problematic but could be improved by topographical modifications. We describe optimization of POSS-PCU by dispersion of porogens (sodium bicarbonate (NaHCO3), sodium chloride (NaCl) and sucrose) onto the material surface, with the principle aim of increasing surface porosity, thus providing additional opportunities for improved cellular and vascular ingrowth. We assess the effect of the porogens on the material's mechanical strength, surface chemistry, wettability and cytocompatibilty. Surface porosity was characterized by scanning electron microscopy (SEM). There was no alteration in surface chemistry and wettability and only modest changes in mechanical properties were detected. The size of porogens correlated well with the porosity of the construct produced and larger porogens improved interconnectivity of spaces within constructs. Using primary human bronchial epithelial cells (HBECs) we demonstrate moderate in vitro cytocompatibility for all surface modifications; however, larger pores resulted in cellular aggregation. These cells were able to differentiate on POSS-PCU scaffolds. Implantation of the scaffold in vivo demonstrated that larger pore sizes favor cellular integration and vascular ingrowth. These experiments demonstrate that surface modification with large porogens can improve POSS-PCU nanocomposite scaffold integration and suggest the need to strike a balance between the non-porous surfaces required for epithelial coverage and the porous structure required for integration and vascularization of synthetic scaffolds in future construct design. PMID:26790147

  3. Surface Modification of Biodegradable Polymers towards Better Biocompatibility and Lower Thrombogenicity

    PubMed Central

    Rudolph, Andreas; Teske, Michael; Illner, Sabine; Kiefel, Volker; Sternberg, Katrin; Grabow, Niels; Wree, Andreas; Hovakimyan, Marina

    2015-01-01

    Purpose Drug-eluting stents (DES) based on permanent polymeric coating matrices have been introduced to overcome the in stent restenosis associated with bare metal stents (BMS). A further step was the development of DES with biodegradable polymeric coatings to address the risk of thrombosis associated with first-generation DES. In this study we evaluate the biocompatibility of biodegradable polymer materials for their potential use as coating matrices for DES or as materials for fully bioabsorbable vascular stents. Materials and Methods Five different polymers, poly(L-lactide) PLLA, poly(D,L-lactide) PDLLA, poly(L-lactide-co-glycolide) P(LLA-co-GA), poly(D,L-lactide-co-glycolide) P(DLLA-co-GA) and poly(L-lactide-co-ε-caprolactone), P(LLA-co-CL) were examined in vitro without and with surface modification. The surface modification of polymers was performed by means of wet-chemical (NaOH and ethylenediamine (EDA)) and plasma-chemical (O2 and NH3) processes. The biocompatibility studies were performed on three different cell types: immortalized mouse fibroblasts (cell line L929), human coronary artery endothelial cells (HCAEC) and human umbilical vein endothelial cells (HUVEC). The biocompatibility was examined quantitatively using in vitro cytotoxicity assay. Cells were investigated immunocytochemically for expression of specific markers, and morphology was visualized using confocal laser scanning (CLSM) and scanning electron (SEM) microscopy. Additionally, polymer surfaces were examined for their thrombogenicity using an established hemocompatibility test. Results Both endothelial cell types exhibited poor viability and adhesion on all five unmodified polymer surfaces. The biocompatibility of the polymers could be influenced positively by surface modifications. In particular, a reproducible effect was observed for NH3-plasma treatment, which enhanced the cell viability, adhesion and morphology on all five polymeric surfaces. Conclusion Surface modification of

  4. Enhanced power efficiency of ZnO based organic/inorganic solar cells by surface modification

    NASA Astrophysics Data System (ADS)

    Tang, Shuangshuang; Tang, Ning; Meng, Xiuqing; Huang, Shihua; Hao, Yafei

    2016-09-01

    We present series of strategies to enhance efficiency of ZnO nanorods based organic/inorganic solar cells with spin-coated P3HT:PCBM blend as active layer. The performance of the as-fabricated devices is improved by controlling the size of ZnO nanorods, annealing temperature and time of active layer, surface modification of ZnO with PSBTBT. Optimized device of ITO/ZnO nanorod/P3HT:PCBM/Ag device with PSBTBT surface modification and air exposure reaches an efficiency of 2.02% with a short-circuit current density, open-circuit voltage and fill factor of 13.23 mA cm-2, 0.547 V and 28%, respectively, under AM 1.5 irradiation of 100 mW m-2, the increase in efficiency is 7-fold of the PSBTBT surface modified ITO/ZnO nanorods/P3HT:PCBM/Ag device compared with the unmodified one, which is own to the increased interface contact, expanded light absorption, tailored band alignment attributed to PSBTBT. We found exposure to air and surface modification is crucial to improve the device performance, and we discussed the mechanisms that affect the performance of the devices in detail.

  5. Surface modification of battery electrodes via electroless deposition with improved performance for Na-ion batteries.

    PubMed

    Lahiri, Abhishek; Olschewski, Mark; Gustus, René; Borisenko, Natalia; Endres, Frank

    2016-06-01

    Sodium-ion batteries (SIBs) are emerging as potential stationary energy storage devices due to the abundance and low cost of sodium. A simple and energy efficient strategy to develop electrodes for SIBs with a high charge/discharge rate is highly desirable. Here we demonstrate that by surface modification of Ge, using electroless deposition in SbCl3/ionic liquids, the stability and performance of the anode can be improved. This is due to the formation of GexSb1-x at the surface leading to better diffusion of Na, and the formation of a stable twin organic and inorganic SEI which protects the electrode. By judicious control of the surface modification, an improvement in the capacity to between 50% and 300% has been achieved at high current densities (0.83-8.4 A g(-1)) in an ionic liquid electrolyte NaFSI-[Py1,4]FSI. The results clearly demonstrate that an electroless deposition based surface modification strategy in ionic liquids offers exciting opportunities in developing superior energy storage devices. PMID:27189079

  6. Surface modification to produce hydrophobic nano-silica particles using sodium dodecyl sulfate as a modifier

    NASA Astrophysics Data System (ADS)

    Qiao, Bing; Liang, Yong; Wang, Ting-Jie; Jiang, Yanping

    2016-02-01

    Hydrophobic silica particles were prepared using the surfactant sodium dodecyl sulfate (SDS) as a modifier by a new route comprising three processes, namely, aqueous mixing, spray drying and thermal treatment. Since SDS dissolves in water, this route is free of an organic solvent and gave a perfect dispersion of SDS, that is, there was excellent contact between SDS and silica particles in the modification reaction. The hydrophobicity of the modified surface was verified by the contact angle of the nano-sized silica particles, which was 107°. The SDS grafting density reached 1.82 nm-2, which is near the highest value in the literature. The optimal parameters of the SDS/SiO2 ratio in the aqueous phase, process temperature and time of thermal treatment were determined to be 20%, 200 °C and 30 min, respectively. The grafting mechanism was studied by comparing the modification with that on same sized TiO2 particles, which indicated that the protons of the Brønsted acid sites on the surface of SiO2 reacted with SDS to give a carbocation which then formed a Si-O-C structure. This work showed that the hydrophilic surface of silica can be modified to be a hydrophobic surface by using a water soluble modifier SDS in a new modification route.

  7. [Research about improving flowability of powder of Chinese herbs extracts by surface modification technology].

    PubMed

    Yu, Yan-Hong; Lu, Wen-Liang; Li, Jia-Jia; Sun, Changquan Calvin; Zhou, Qun

    2014-12-01

    In this study, modification technology by surface coating was used to improve the flowability of powder of Chinese herbs extracts. Seven kinds of powder of Chinese herbs extracts were coated with 1% silica nanoparticles using an under-driven Comil. The powder characteristics tester was used to evaluate the flowability of uncoated and coated powders. Surface morphology and particle size distribution of powders were compared by scanning electron microscope (SEM) and optical microscope. The powder hygroscopicity was also investigated. The results showed that, after modification, angle of repose, angle of spatula, compressibility and adhesiveness extremely decreased, and flowability index substantially increased, the powder flowability was significantly improved, especially Gegen and Dahuang extracts powders. Scanning electron microscopy images showed the distribution of silica nanoparticles on the host drug particle surfaces. There were no remarkable changes in the particle size distribution and hygroscopicity of all powders after coating. Therefore, Comilling for surface coating modification technology was an effective method to improve the flowability of Chinese herbs extracts and suggested a possible way forward to enhance the quality of Chinese drugs pharmaceutics in their study and manufacture. PMID:25911807

  8. Formation of superpower volume discharges and their application for modification of surface of metals

    NASA Astrophysics Data System (ADS)

    Tarasenko, Victor F.; Shulepov, M. A.

    2008-05-01

    The results of experimental investigations of a volume avalanche discharge initiated by an e-beam (VADIEB) and surface layer of Cu and AlBe foils modifications at the plasma action of VADIEB are given. The volume discharge in the air of atmosphere pressure formed in the gap with the cathode having small curvature radius and with high voltage pulses of nanosecond duration and positive and negative polarity. A supershort avalanche electron beam (SAEB) with formation conditions in gases under atmospheric pressure have been investigated. It is proved that the surface layer is cleared of carbon at foil treatment, and atoms of oxygen penetrate into a foil. It is show that the cleaning depth depends on polarity of voltage pulses. At positive polarity of a copper foil electrode the cleaning is observed at the depth over 50 nm, and atoms of oxygen penetrate at the depth up to 25 nm. Plasma of the superpower volume discharge of nanosecond duration with a specific excitation power of hundreds of MW/cm3, and SAEB, and the discharge plasma radiation of various spectral ranges (including UV, VUV and X-ray) has the influence on the anode. The supershort avalanche electronic beam is generated only at negative polarity of a voltage pulse on an electrode with a small radius of curvature. SAEB influence on modifications of the copper foil surface is registered. VADIEB is easily realized in various gases and at various pressures, and, at gas pressure decrease the density of the beam current in helium can achieve 2 kA/cm2. It allows predicting an opportunity of VADIEB application for metal surface modifications in various technological processes, and for surface dielectric modifications at the certain design of the anode.

  9. Advances in identification and validation of protein targets of natural products without chemical modification.

    PubMed

    Chang, J; Kim, Y; Kwon, H J

    2016-05-01

    Covering: up to February 2016Identification of the target proteins of natural products is pivotal to understanding the mechanisms of action to develop natural products for use as molecular probes and potential therapeutic drugs. Affinity chromatography of immobilized natural products has been conventionally used to identify target proteins, and has yielded good results. However, this method has limitations, in that labeling or tagging for immobilization and affinity purification often result in reduced or altered activity of the natural product. New strategies have recently been developed and applied to identify the target proteins of natural products and synthetic small molecules without chemical modification of the natural product. These direct and indirect methods for target identification of label-free natural products include drug affinity responsive target stability (DARTS), stability of proteins from rates of oxidation (SPROX), cellular thermal shift assay (CETSA), thermal proteome profiling (TPP), and bioinformatics-based analysis of connectivity. This review focuses on and reports case studies of the latest advances in target protein identification methods for label-free natural products. The integration of newly developed technologies will provide new insights and highlight the value of natural products for use as biological probes and new drug candidates. PMID:26964663

  10. Roughness modification of surfaces treated by a pulsed dielectric barrier discharge

    NASA Astrophysics Data System (ADS)

    Dumitrascu, N.; Borcia, G.; Apetroaei, N.; Popa, G.

    2002-05-01

    Local modifications of surface roughness are very important in many applications, as this surface property is able to generate new mechano-physical characteristics of a large category of materials. Roughness is one of the most important parameters used to characterize and control the surface morphology, and techniques that allow modifying and controlling the surface roughness present increasing interest. In this respect we propose the dielectric barrier discharge (DBD) as a simple and low cost method that can be used to induce controlled roughness on various surfaces in the nanoscale range. DBD is produced in helium, at atmospheric pressure, by a pulsed high voltage, 28 kV peak to peak, 13.5 kHz frequency and 40 W power. This type of discharge is a source of energy capable of modifying the physico-chemical properties of the surfaces without affecting their bulk properties. The discharge is characterized by means of electrical probes and, in order to analyse the heat transfer rate from the discharge to the treated surface, measurements of temperature distribution on the surface are performed. Influence of DBD on the roughness of surfaces with various properties, a semiconductor (tin oxide), a dielectric (polyvinylchloride) and a metallic (silver) surface, respectively, are investigated. Modifications of the surface morphology are detected by atomic force microscopy images, statistic roughness parameters and contact angle measurements. Results show an important increase of roughness and porosity of the thin films after DBD treatment, depending on the type of the material (semiconductor, dielectric and metallic). In the case of dielectric surfaces, this new morphology is correlated with adhesion work estimations. DBD treatments should be a convenient tool to induce a controlled roughness of various types of materials.

  11. Modification of Hydrophilic and Hydrophobic Surfaces Using an Ionic-Complementary Peptide

    PubMed Central

    Yang, Hong; Fung, Shan-Yu; Pritzker, Mark; Chen, P.

    2007-01-01

    Ionic-complementary peptides are novel nano-biomaterials with a variety of biomedical applications including potential biosurface engineering. This study presents evidence that a model ionic-complementary peptide EAK16-II is capable of assembling/coating on hydrophilic mica as well as hydrophobic highly ordered pyrolytic graphite (HOPG) surfaces with different nano-patterns. EAK16-II forms randomly oriented nanofibers or nanofiber networks on mica, while ordered nanofibers parallel or oriented 60° or 120° to each other on HOPG, reflecting the crystallographic symmetry of graphite (0001). The density of coated nanofibers on both surfaces can be controlled by adjusting the peptide concentration and the contact time of the peptide solution with the surface. The coated EAK16-II nanofibers alter the wettability of the two surfaces differently: the water contact angle of bare mica surface is measured to be <10°, while it increases to 20.3±2.9° upon 2 h modification of the surface using a 29 µM EAK16-II solution. In contrast, the water contact angle decreases significantly from 71.2±11.1° to 39.4±4.3° after the HOPG surface is coated with a 29 µM peptide solution for 2 h. The stability of the EAK16-II nanofibers on both surfaces is further evaluated by immersing the surface into acidic and basic solutions and analyzing the changes in the nanofiber surface coverage. The EAK16-II nanofibers on mica remain stable in acidic solution but not in alkaline solution, while they are stable on the HOPG surface regardless of the solution pH. This work demonstrates the possibility of using self-assembling peptides for surface modification applications. PMID:18091996

  12. Beam waist position study for surface modification of polymethyl-methacrylate with femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Caballero-Lucas, F.; Florian, C.; Fernández-Pradas, J. M.; Morenza, J. L.; Serra, P.

    2016-06-01

    Femtosecond lasers are versatile tools to process transparent materials. This optical property poses an issue for surface modification. In this case, laser radiation would not be absorbed at the surface unless the beam is just focused there. Otherwise, absorption would take place in the bulk leaving the surface unperturbed. Therefore, strategies to position the material surface at the laser beam waist with high accuracy are essential. We investigated and compared two options to achieve this aim: the use of reflectance data and transmittance measurements across the sample, both obtained during z-scans with pulses from a 1027 nm wavelength laser and 450 fs pulse duration. As the material enters the beam waist region, a reflectance peak is detected while a transmittance drop is observed. With these observations, it is possible to control the position of the sample surface with respect to the beam waist with high resolution and attain pure surface modification. In the case of polymethyl-methacrylate (PMMA), this resolution is 0.6 μm. The results prove that these methods are feasible for submicrometric processing of the surface.

  13. In vitro bioactivity investigations of Ti-15Mo alloy after electrochemical surface modification.

    PubMed

    Kazek-Kęsik, Alicja; Kuna, Karolina; Dec, Weronika; Widziołek, Magdalena; Tylko, Grzegorz; Osyczka, Anna M; Simka, Wojciech

    2016-07-01

    Titanium and its aluminum and vanadium-free alloys have especially great potential for medical applications. Electrochemical surface modification improves their surface bioactivity and stimulates osseointegration process. In this work, the effect of plasma electrolytic oxidation of the β-type alloy Ti-15Mo surface on its bioactivity is presented. Bioactivity of the modified alloy was investigated by immersion in simulated body fluid (SBF). Biocompatibility of the modified alloys were tested using human bone marrow stromal cells (hBMSC) and wild intestinal strains (DV/A, DV/B, DV/I/1) of Desulfovibrio desulfuricans bacteria. The particles of apatite were formed on the anodized samples. Human BMSC cells adhered well on all the examined surfaces and expressed ALP, collagen, and produced mineralized matrix as determined after 10 and 21 days of culture. When the samples were inoculated with D. desulfuricans bacteria, only single bacteria were visible on selected samples. There were no obvious changes in surface morphology among samples. Colonization and bacterial biofilm formation was observed on as-ground sample. In conclusion, the surface modification improved the Ti-15Mo alloy bioactivity and biocompatibility and protected surface against colonization of the bacteria. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 903-913, 2016. PMID:25952109

  14. Surface modifications of photoanodes in dye sensitized solar cells: enhanced light harvesting and reduced recombination

    NASA Astrophysics Data System (ADS)

    Saxena, Vibha; Aswal, D. K.

    2015-06-01

    In a quest to harvest solar power, dye-sensitized solar cells (DSSCs) have potential for low-cost eco-friendly photovoltaic devices. The major processes which govern the efficiency of a DSSC are photoelectron generation, injection of photo-generated electrons to the conduction band (CB) of the mesoporous nanocrystalline semiconductor (nc-SC); transport of CB electrons through nc-SC and subsequent collection of CB electrons at the counter electrode (CE) through the external circuit; and dye regeneration by redox couple or hole transport layer (HTL). Most of these processes occur at various interfaces of the photoanode. In addition, recombination losses of photo-generated electrons with either dye or redox molecules take place at the interfaces. Therefore, one of the key requirements for high efficiency is to improve light harvesting of the photoanode and to reduce the recombination losses at various interfaces. In this direction, surface modification of the photoanode is the simplest method among the various other approaches available in the literature. In this review, we present a comprehensive discussion on surface modification of the photoanode, which has been adopted in the literature for not only enhancing light harvesting but also reducing recombination. Various approaches towards surface modification of the photoanode discussed are (i) fluorine-doped tin oxide (FTO)/nc-SC interface modified via a compact layer of semiconductor material which blocks exposed sites of FTO to electrolyte (or HTL), (ii) nc-SC/dye interface modification either through acid treatment resulting in enhanced dye loading due to a positively charged surface or by depositing insulating/semiconducting blocking layer on the nc-SC surface, which acts as a tunneling barrier for recombination, (iii) nc-SC/dye interface modified by employing co-adsorbents which helps in reducing the dye aggregation and thereby recombination, and (iv) dye/electrolyte (or dye/HTL) interface modification using

  15. Thruster momentum transfer studies and magnetoplasmadynamic (MPD) thruster use in materials/surface modification

    NASA Astrophysics Data System (ADS)

    Thompson, E.; Collins, W. E.; Burger, A.; George, M. A.; Conner, J. D.

    1995-08-01

    This research project involves the systematic study of the MPD thruster for dual uses. Though it was designed as a thruster for space vehicles, the characteristics of the plasma make it an excellent candidate for industrial applications. This project will seek to characterize the system for use in materials processing and characterization. Crystals grown at Fisk University for use with solid state detectors will be studied. Surface modification on ZnCdTe, CdTe, and ZnTe will be studied using AFM, XPS and SAES. In addition to the surface modification studies, design work on a momentum transfer measurement device has been completed. The design and limitations of the device will be presented.

  16. Surface Modification of Boron-Doped Diamond with Microcrystalline Copper Phthalocyanine: Oxygen Reduction Catalysis.

    PubMed

    Gan, Patrick; Foord, John S; Compton, Richard G

    2015-10-01

    Surface modification of boron-doped diamond (BDD) with copper phthalocyanine was achieved using a simple and convenient dropcast deposition, giving rise to a microcrystalline structure. Both unmodified and modified BDD electrodes of different surface terminations (namely hydrogen and oxygen) were compared via the electrochemical reduction of oxygen in aqueous solution. A significant lowering of the cathodic overpotential by about 500 mV was observed after modification of hydrogen-terminated (hydrophobic) diamond, while no voltammetric peak was seen on modified oxidised (hydrophilic) diamond, signifying greater interaction between copper phthalocyanine and the hydrogen-terminated BDD. Oxygen reduction was found to undergo a two-electron process on the modified hydrogen-terminated diamond, which was shown to be also active for the reduction of hydrogen peroxide. The lack of a further conversion of the peroxide was attributed to its rapid diffusion away from the triple phase boundary at which the reaction is expected to exclusively occur. PMID:26491640

  17. Thruster momentum transfer studies and magnetoplasmadynamic (MPD) thruster use in materials/surface modification

    NASA Technical Reports Server (NTRS)

    Thompson, E.; Collins, W. E.; Burger, A.; George, M. A.; Conner, J. D.

    1995-01-01

    This research project involves the systematic study of the MPD thruster for dual uses. Though it was designed as a thruster for space vehicles, the characteristics of the plasma make it an excellent candidate for industrial applications. This project will seek to characterize the system for use in materials processing and characterization. Crystals grown at Fisk University for use with solid state detectors will be studied. Surface modification on ZnCdTe, CdTe, and ZnTe will be studied using AFM, XPS and SAES. In addition to the surface modification studies, design work on a momentum transfer measurement device has been completed. The design and limitations of the device will be presented.

  18. Synthesis, Phase Transfer and Surface Modification of Hydrophobic Quantum Dots for Bioapplications

    NASA Astrophysics Data System (ADS)

    Zhang, Ruili; Zhang, Xiao; Li, Xiaoyu; Yang, Ping

    2013-06-01

    We review the preparation, phase transfer, surface modification and possible bioapplications of hydrophobic CdSe based quantum dots (QDs). CdSe cores with rod and spherical morphologies were prepared through adjusting preparation conditions. The photoluminescence (PL) of the QDs depended strongly on preparation conditions. The QDs were coated with semiconductor shells to improve their PL properties. Anisotropic growth occurred during shell coating. Core/shell QDs revealed tunable PL and high PL efficiencies up to 90%. The phase transfer of QDs from oil phase to water phase was carried out via polymer or a sol-gel process. The silanization of the QDs plays an important role for the sol-gel process. Because of a SiO2 coating, the surface modification of the QDs for bioapplications became easy. After transferring into water phase, the QDs still retained high PL efficiency. Because of their high PL, these biofunctional materials could provide a platform for various applications.

  19. Surface Modification of Boron-Doped Diamond with Microcrystalline Copper Phthalocyanine: Oxygen Reduction Catalysis

    PubMed Central

    Gan, Patrick; Foord, John S; Compton, Richard G

    2015-01-01

    Surface modification of boron-doped diamond (BDD) with copper phthalocyanine was achieved using a simple and convenient dropcast deposition, giving rise to a microcrystalline structure. Both unmodified and modified BDD electrodes of different surface terminations (namely hydrogen and oxygen) were compared via the electrochemical reduction of oxygen in aqueous solution. A significant lowering of the cathodic overpotential by about 500 mV was observed after modification of hydrogen-terminated (hydrophobic) diamond, while no voltammetric peak was seen on modified oxidised (hydrophilic) diamond, signifying greater interaction between copper phthalocyanine and the hydrogen-terminated BDD. Oxygen reduction was found to undergo a two-electron process on the modified hydrogen-terminated diamond, which was shown to be also active for the reduction of hydrogen peroxide. The lack of a further conversion of the peroxide was attributed to its rapid diffusion away from the triple phase boundary at which the reaction is expected to exclusively occur. PMID:26491640

  20. Multiecho scheme advances surface NMR for aquifer characterization

    NASA Astrophysics Data System (ADS)

    Grunewald, Elliot; Walsh, David

    2013-12-01

    nuclear magnetic resonance (NMR) is increasingly used as a method to noninvasively characterize aquifers. This technology follows a successful history of NMR logging, applied over decades to estimate hydrocarbon reservoir properties. In contrast to logging, however, surface methods have utilized relatively simple acquisition sequences, from which pore-scale properties may not be reliably and efficiently estimated. We demonstrate for the first time the capability of sophisticated multiecho measurements to rapidly record a surface NMR response that more directly reflects aquifer characteristics. Specifically, we develop an adaptation of the multipulse Carr-Purcell-Meiboom-Gill (CPMG) sequence, widely used in logging, to measure the T2 relaxation response in a single scan. We validate this approach in a field surface NMR data set and by direct comparison with an NMR log. Adoption of the CPMG marked a landmark advancement in the history of logging NMR; we have now realized this same advancement in the surface NMR method.

  1. Studies on Hdpe-Coconut Flour Composites: Effect of Coupling Agents and Surface Modification

    NASA Astrophysics Data System (ADS)

    Albano, C.; González, J.; Hernández, M.; Ichazo, M. N.; Alvarado, Sinai; Ziegler, Dulce Maria

    2008-08-01

    This study investigates the mechanical, thermal and morphological behavior of coconut flour/polyethylene composites, with special interest on the influence of the surface modification of coconut flour and the presence of different coupling agents on the interfacial bonding. The different treatments of the composites with an EAA copolymer, with titanate, with 5 and 18 wt% of NaOH and acetylating, confirm the better tensile behavior of these composites.

  2. Surface modification to improve fireside corrosion resistance of Fe-Cr ferritic steels

    DOEpatents

    Park, Jong-Hee; Natesan, Krishnamurti; Rink, David L.

    2010-03-16

    An article of manufacture and a method for providing an Fe--Cr ferritic steel article of manufacture having a surface layer modification for corrosion resistance. Fe--Cr ferritic steels can be modified to enhance their corrosion resistance to liquid coal ash and other chemical environments, which have chlorides or sulfates containing active species. The steel is modified to form an aluminide/silicide passivating layer to reduce such corrosion.

  3. Advanced surface paneling method for subsonic and supersonic flow

    NASA Technical Reports Server (NTRS)

    Erickson, L. L.; Johnson, F. T.; Ehlers, F. E.

    1976-01-01

    Numerical results illustrating the capabilities of an advanced aerodynamic surface paneling method are presented. The method is applicable to both subsonic and supersonic flow, as represented by linearized potential flow theory. The method is based on linearly varying sources and quadratically varying doublets which are distributed over flat or curved panels. These panels are applied to the true surface geometry of arbitrarily shaped three dimensional aerodynamic configurations.

  4. Coal surface control for advanced fine coal flotation

    SciTech Connect

    Fuerstenau, D.W.; Sastry, K.V.; Hanson, J.S.; Harris, G.; Sotillo, F.; Diao, J.; De, A. ); Somasundaran, P.; Harris, C.C.; Vasudevan, T.; Liu, D.; Li, C. ); Hu, Weibai; Zou, Y.; Chen, W. ); Choudhry, V.; Sehgal, R.; Ghosh, A. )

    1991-03-22

    The main goal of the project is to characterize the surface and control the behavior of coal during advanced flotation processing in order to achieve an overall objective of near-total pyritic sulfur removal with a high Btu recovery. Also, investigation of the effects of weathering on the surface characteristics of coal is another important aspect of this project. The effect of butanol, dodecane, lime, calcium cyanide, hydrogen peroxide, and ph on flotation performance is discussed. 2 refs., 26 figs., 18 tabs.

  5. Surface modifications and Nano-composite coatings to improve the bonding strength of titanium-porcelain.

    PubMed

    Guo, Litong; Chen, Xiaoyuan; Liu, Xuemei; Feng, Wei; Li, Baoe; Lin, Cheng; Tao, Xueyu; Qiang, Yinghuai

    2016-04-01

    Surface modifications of Ti and nano-composite coatings were employed to simultaneously improve the surface roughness, corrosion resistance and chemical bonding between porclain-Ti. The specimens were studied by field-emission scanning electron microscopy, surface roughness, differential scanning calorimetry, Fourier transform infrared spectroscopy, corrosion resistance and bonding strength tests. The SEM results showed that hybrid structures with micro-stripes, nano-pores and nano-protuberances were prepared by surface modification of Ti, which significantly enhanced the surface roughness and corrosion resistance of Ti. Porous nano-composite coatings were synthesized on Ti anodized with pre-treatment in 40% HF acid. TiO2 nanoparticles were added into the hybrid coating to increase the solid phase content of the sols and avoid the formation of microcracks. With the TiO2 content increasing from 45 wt% to 60 wt%, the quantities of the microcracks on the coating surface gradually decreased. The optimal TiO2 content for the nanocomposite coatings is 60 wt% in this research. Compared to the uncoated group, the bonding strength of the coated groups showed a bonding strength improvement of 23.96%. The cytotoxicity of the 4# coating group was ranked as zero, which corresponds to non-cytotoxicity. PMID:26838834

  6. Surface modification of Ti dental implants by Nd:YVO 4 laser irradiation

    NASA Astrophysics Data System (ADS)

    Braga, Francisco J. C.; Marques, Rodrigo F. C.; Filho, Edson de A.; Guastaldi, Antonio C.

    2007-09-01

    Surface modifications have been applied in endosteal bone devices in order to improve the osseointegration through direct contact between neoformed bone and the implant without an intervening soft tissue layer. Surface characteristics of titanium implants have been modified by addictive methods, such as metallic titanium, titanium oxide and hydroxyapatite powder plasma spray, as well as by subtractive methods, such as acid etching, acid etching associated with sandblasting by either AlO 2 or TiO 2, and recently by laser ablation. Surface modification for dental and medical implants can be obtained by using laser irradiation technique where its parameters like repetition rate, pulse energy, scanning speed and fluency must be taken into accounting to the appropriate surface topography. Surfaces of commercially pure Ti (cpTi) were modified by laser Nd:YVO 4 in nine different parameters configurations, all under normal atmosphere. The samples were characterized by SEM and XRD refined by Rietveld method. The crystalline phases αTi, βTi, Ti 6O, Ti 3O and TiO were formed by the melting and fast cooling processes during irradiation. The resulting phases on the irradiated surface were correlated with the laser beam parameters. The aim of the present work was to control titanium oxides formations in order to improve implants osseointegration by using a laser irradiation technique which is of great importance to biomaterial devices due to being a clean and reproducible process.

  7. Enhancing the Properties of Carbon and Gold Substrates by Surface Modification

    SciTech Connect

    Jennifer Anne Harnisch

    2002-06-27

    The properties of both carbon and gold substrates are easily affected by the judicious choice of a surface modification protocol. Several such processes for altering surface composition have been published in literature. The research presented in this thesis primarily focuses on the development of on-column methods to modify carbon stationary phases used in electrochemically modulated liquid chromatography (EMLC). To this end, both porous graphitic carbon (PGC) and glassy carbon (GC) particles have been modified on-column by the electroreduction of arenediazonium salts and the oxidation of arylacetate anions (the Kolbe reaction). Once modified, the carbon stationary phases show enhanced chromatographic performance both in conventional liquid chromatographic columns and EMLC columns. Additionally, one may also exploit the creation of aryl films to by electroreduction of arenediazonium salts in the creation of nanostructured materials. The formation of mercaptobenzene film on the surface of a GC electrode provides a linking platform for the chemisorption of gold nanoparticles. After deposition of nanoparticles, the surface chemistry of the gold can be further altered by self-assembled monolayer (SAM) formation via the chemisorption of a second thiol species. Finally, the properties of gold films can be altered such that they display carbon-like behavior through the formation of benzenehexathiol (BHT) SAMs. BHT chemisorbs to the gold surface in a previously unprecedented planar fashion. Carbon and gold substrates can be chemically altered by several methodologies resulting in new surface properties. The development of modification protocols and their application in the analytical arena is considered herein.

  8. Surface modification of coconut shell based activated carbon for the improvement of hydrophobic VOC removal.

    PubMed

    Li, Lin; Liu, Suqin; Liu, Junxin

    2011-08-30

    In this study, coconut shell based carbons were chemically treated by ammonia, sodium hydroxide, nitric acid, sulphuric acid, and phosphoric acid to determine suitable modification for improving adsorption ability of hydrophobic volatile organic compounds (VOCs) on granular activated carbons (GAC). The saturated adsorption capacities of o-xylene, a hydrophobic volatile organic compound, were measured and adsorption effects of the original and modified activated carbons were compared. Results showed that GAC modified by alkalis had better o-xylene adsorption capacity. Uptake amount was enhanced by 26.5% and reduced by 21.6% after modification by NH(3)H(2)O and H(2)SO(4), respectively. Compared with the original, GAC modified by acid had less adsorption capacity. Both SEM/EDAX and BET were used to identify the structural characteristics of the tested GAC, while IR spectroscopy and Boehm's titration were applied to analysis the surface functional groups. Relationships between physicochemical characteristics of GAC and their adsorption performances demonstrated that o-xylene adsorption capacity was related to surface area, pore volume, and functional groups of the GAC surface. Removing surface oxygen groups, which constitute the source of surface acidity, and reducing hydrophilic carbon surface favors adsorption capacity of hydrophobic VOCs on carbons. The performances of modified GACs were also investigated in the purification of gases containing complex components (o-xylene and steam) in the stream. PMID:21683520

  9. Surface modification of a biomedical poly(ether)urethane by a remote air plasma

    NASA Astrophysics Data System (ADS)

    Gray, J. E.; Norton, P. R.; Griffiths, K.

    2003-07-01

    Plasma modification of polymer surfaces is widely used, but the plasma/polymer interaction is very complex and still not fully understood. In this paper, the interaction of a biomedical poly(ether)urethane with a remote air plasma treatment has been studied. Atomic force microscopy studies show the domain structure of the polymer as well as the absence of any surface roughening due to plasma treatment. Contact angle goniometry shows an improved wettability of the surface after plasma treatment. X-ray photoelectron spectroscopy indicates an increase in CO and CC at the surface, as well as the presence of new functional groups such as alcohols, ketones, aldehydes and imines. There is also evidence that the energy imparted to the polymer during plasma treatment causes surface segregation of polyol segments.

  10. Silicon Surface Modification Using C4F8+O2 Plasma for Nano-Imprint Lithography.

    PubMed

    Lee, Junmyung; Efremov, Alexander; Lee, Jaemin; Yeom, Geun Young; Kwon, Kwang-Ho

    2015-11-01

    The investigation of C4F8+O2 feed gas composition on both plasma parameters and plasma treated silicon surface characteristics was carried out. The combination of plasma diagnostics by Langmuir probes and plasma modeling indicated that an increase in O2 mixing ratio results in monotonically decreasing densities of CF(x) (x = 1-3) radicals as well as in non-monotonic behavior of F atom density. The surface characterization by X-ray photoelectron spectroscopy and contact angle measurements showed that the C4F8+O2 mixtures with less than 60% 02 result in modification of Si surfaces due to the deposition of the FC polymer films while the change of O2 mixing ratio in the range of 30%-60% provides an effective adjustment of the surface characteristics such as surface energy, contact angle, etc. PMID:26726589

  11. Long Range Modification of a Metal Surface Electronic Structure by an Organic Semiconductor

    NASA Astrophysics Data System (ADS)

    Wang, Jingying; Dougherty, Daniel

    2015-03-01

    In an organic spintronic device the interaction between electrode surface and organic semiconductor layer plays an important role in spin injection at this interface. The antiferromagnetic material Cr(001) is known to have a spin-polarized state near Fermi level that could potentially hybridize with organic molecules. Here we report our STM/STS study of electronic structure at interface between an organic semiconductor, PTCDA, and Cr(001) surface. The study shows that the surface state at Fermi level of Cr(001) can be broadened by PTCDA molecules deposited on the surface due to hybridization of PTCDA molecular orbital and conduction sp band of Cr(001). This indirect modification is not only localized at molecular adsorption sites, but also extends several nm to bare surrounding Cr(001) surface and decays with distance away from PTCDA molecules.

  12. Improved polymeric surface for adhesion through electron stimulated chemical modification of polymeric surface

    DOEpatents

    Kelber, J.A.

    1987-04-08

    Treating polymer surfaces, e.g., Teflon, particularly very thin surfaces, e.g., 50-10,000 A, with low energy electron radiation, e.g., 100-1000 eV, in a high vacuum environment, e.g., less than 10 /sup /minus/6/ Torr, to enhance the ability of the surface to be adhered to a variety of substrates.

  13. Surface modification for patterned cell growth on substrates with pronounced topographies using sacrificial photoresist and parylene-C peel-off

    NASA Astrophysics Data System (ADS)

    Larramendy, Florian; Yoshida, Shotaro; Jalabert, Laurent; Takeuchi, Shoji; Paul, Oliver

    2016-09-01

    A range of methods including soft lithography are available for patterning protein layers for cell adhesion on quasi-planar substrates. Suitably structured, these layers favor the geometrically constrained, controlled growth of cells and the development of cellular extensions on them. For this purpose, the ability to control the shape and dimension of cell-adhesive areas with high precision is crucial. For more advanced studies of cell interactions, the surface modification or functionalization of substrates with complex topographies is desirable. This paper describes a simple technique allowing to produce surface modification patterns using delicate molecules such as laminin on substrates exhibiting pronounced topographies with recessed and protruding microstructures. The technique is based on the combination of sacrificial photoresist structures with a connected parylene-C layer. This layer locally adheres to the substrate wherever the substrate needs to be protected against the surface modification. After surface modification, the parylene-C layer is peeled off. Patterns comprising arbitrary networks of modified and unmodified substrate areas can thus be realized. We demonstrate the technique with the guided growth of neuron-like PC12 cells on networks of laminin lines on substrates structured with micropillars and microwells.

  14. Enhanced removal of nitrate from water using surface modification of adsorbents--a review.

    PubMed

    Loganathan, Paripurnanda; Vigneswaran, Saravanamuthu; Kandasamy, Jaya

    2013-12-15

    Elevated concentration of nitrate results in eutrophication of natural water bodies affecting the aquatic environment and reduces the quality of drinking water. This in turn causes harm to people's health, especially that of infants and livestock. Adsorbents with the high capacity to selectively adsorb nitrate are required to effectively remove nitrate from water. Surface modifications of adsorbents have been reported to enhance their adsorption of nitrate. The major techniques of surface modification are: protonation, impregnation of metals and metal oxides, grafting of amine groups, organic compounds including surfactant coating of aluminosilicate minerals, and heat treatment. This paper reviews current information on these techniques, compares the enhanced nitrate adsorption capacities achieved by the modifications, and the mechanisms of adsorption, and presents advantages and drawbacks of the techniques. Most studies on this subject have been conducted in batch experiments. These studies need to include continuous mode column trials which have more relevance to real operating systems and pilot-plant trials. Reusability of adsorbents is important for economic reasons and practical treatment applications. However, only limited information is available on the regeneration of surface modified adsorbents. PMID:24211565

  15. Surface modification of magnesium alloys developed for bioabsorbable orthopedic implants: a general review.

    PubMed

    Wang, Jiali; Tang, Jian; Zhang, Peng; Li, Yangde; Wang, Jue; Lai, Yuxiao; Qin, Ling

    2012-08-01

    As a bioabsorbable metal with mechanical properties close to bone, pure magnesium or its alloys have great potential to be developed as medical implants for clinical applications. However, great efforts should be made to avoid its fast degradation in vivo for orthopedic applications when used for fracture fixation. Therefore, how to decease degradation rate of pure magnesium or its alloys is one of the focuses in Research and Development (R&D) of medical implants. It has been recognized that surface modification is an effective method to prevent its initial degradation in vivo to maintain its desired mechanical strength. This article reviews the recent progress in surface modifications for prevention of fast degradation of magnesium or its alloys using in vitro testing model, a fast yet relevant model before moving towards time-consuming and expensive in vivo testing. Pros and cons of various surface modifications are also discussed for the goal to design available products to be applied in clinical trials. PMID:22566412

  16. Surface modification of TiO{sub 2} nanoparticles for photochemical reduction of nitrobenzene.

    SciTech Connect

    Makarova, O. V.; Rajh, T.; Thurnauer, M. C.; Martin, A.; Kemme, P. A.; Cropek, D.; Chemistry; USA CERL

    2000-11-15

    The effects of surface modification of nanocrystalline titanium dioxide (TiO{sub 2}) with specific chelating agents on photocatalytic degradation of nitrobenzene (NB) was investigated in order to design a selective and effective catalyst for removal of nitroaromatic compounds from contaminated waste streams. Mechanisms of NB adsorption and photodecomposition were investigated using infrared absorption and electron paramagnetic resonance spectroscopy. Liquid chromatography and gas chromatography/mass spectrometry were used for byproduct analyses. Arginine, lauryl sulfate, and salicylic acid were found to bind to TiO{sub 2} via their oxygen-containing functional groups. Modification of the TiO{sub 2} surface with arginine resulted in enhanced NB adsorption and photodecomposition, and compared to unmodified TiO{sub 2}. The initial quantum yield for photodegradation of NB in this system was found to be {Phi}{sub init} = 0.31 as compared to the one obtained for Degussa P25 of {Phi}{sub init} = 0.18. NB degradation followed a reductive pathway over arginine-modified TiO{sub 2} and was enhanced upon addition of methanol. No degradation of arginine was detected under the experimental conditions. Arginine improved the coupling between NB and TiO{sub 2} and facilitated the transfer of photogenerated electrons from the TiO{sub 2} conduction band to the adsorbed NB. These results indicate that surface modification of nanocrystalline TiO{sub 2} with electron-donating chelating agents is an effective route to enhance photodecomposition of nitroaromatic compounds.

  17. Critical overview of Nitinol surfaces and their modifications for medical applications

    SciTech Connect

    Shabalovskaya, S.; Anderegg, J.; Van Humbeeck, J.

    2008-02-06

    Nitinol, a group of nearly equiatomic shape memory and superelastic NiTi alloys, is being extensively explored for medical applications. Release of Ni in the human body, a potential problem with Nitinol implant devices, has stimulated a great deal of research on its surface modifications and coatings. In order to use any of the developed surfaces in implant designs, it is important to understand whether they really have advantages over bare Nitinol. This paper overviews the current situation, discusses the advantages and disadvantages of new surfaces as well as the limitations of the studies performed. It presents a comprehensive analysis of surface topography, chemistry, corrosion behavior, nickel release and biological responses to Nitinol surfaces modified mechanically or using such methods as etching in acids and alkaline solutions, electropolishing, heat and ion beam treatments, boiling in water and autoclaving, conventional and ion plasma implantations, laser melting and bioactive coating deposition. The analysis demonstrates that the presently developed surfaces vary in thickness from a few nanometers to micrometers, and that they can effectively prevent Ni release if the surface integrity is maintained under strain and if no Ni-enriched sub-layers are present. Whether it is appropriate to use various low temperature pre-treatment protocols ({le} 160 C) developed originally for pure titanium for Nitinol surface modifications and coatings is also discussed. The importance of selection of original Nitinol surfaces with regard to the performance of coatings and comparative performance of controls in the studies is emphasized. Considering the obvious advantages of bare Nitinol surfaces for superelastic implants, details of their preparation are also outlined.

  18. Influence of surface self-modification in Ringer's solution on the passive behavior of titanium.

    PubMed

    Alkhateeb, E; Virtanen, S

    2005-12-15

    The influence of the spontaneous surface modification of titanium by exposure to Ringer's solution at open-circuit conditions on the passive behavior was studied. The electrochemical behavior of Ti was compared in a simple NaCl and in Ringer's physiological solution. Potentiodynamic polarization curves show significantly higher passive current densities in Ringer's solution as compared with the simple saline solution. Furthermore, impedance spectra measured at the open-circuit potential as a function of time indicate that in saline solution a long-term exposure over some days leads to a strong increase of the protectiveness of the passive film. This improvement of the passive behavior cannot be observed in Ringer's solution, but a strong modification of the passive film/electrolyte interface can be seen in the impedance spectra. The changes in the impedance spectra can be correlated with the results observed by surface characterization regarding the morphology (scanning electron microscopy) and chemical composition of the surface (X-ray photoelectron spectroscopy). In agreement with previous work by others, a spontaneous modification of the surface of Ti by Ca and P species was observed. The composition of the Ca/P precipitates changes as a function of time, indicating a slow formation of a hydroxyapatite-like deposit layer on the surface. The results of the present work indicate that the formation of the outer Ca-P deposit layer on the passive Ti surface (which is beneficial for the biological performance) hinders the normal aging of the passive TiO(2). Even though the protectiveness of the passive film can be considered as high also in Ringer's solution, significantly higher passive dissolution rates (i.e., higher metal-ion release) for Ti exposed to Ringer's solution can be expected as compared with a simple saline solution. PMID:16123977

  19. Surface modifications on InAs decrease indium and arsenic leaching under physiological conditions

    NASA Astrophysics Data System (ADS)

    Jewett, Scott A.; Yoder, Jeffrey A.; Ivanisevic, Albena

    2012-11-01

    Devices containing III-V semiconductors such as InAs are increasingly being used in the electronic industry for a variety of optoelectronic applications. Furthermore, the attractive chemical, material, electronic properties make such materials appealing for use in devices designed for biological applications, such as biosensors. However, in biological applications the leaching of toxic materials from these devices could cause harm to cells or tissue. Additionally, after disposal, toxic inorganic materials can leach from devices and buildup in the environment, causing long-term ecological harm. Therefore, the toxicity of these materials along with their stability in physiological conditions are important factors to consider. Surface modifications are one common method of stabilizing semiconductor materials in order to chemically and electronically passivate them. Such surface modifications could also prevent the leaching of toxic materials by preventing the regrowth of the unstable surface oxide layer and by creating an effective barrier between the semiconductor surface and the surrounding environment. In this study, various surface modifications on InAs are developed with the goal of decreasing the leaching of indium and arsenic. The leaching of indium and arsenic from modified substrates was assessed in physiological conditions using inductively coupled plasma mass spectrometry (ICP-MS). Substrates modified with 11-mercapto-1-undecanol (MU) and graft polymerized with poly(ethylene) glycol (PEG) were most effective at preventing indium and arsenic leaching. These surfaces were characterized using contact angle analysis, ellipsometry, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). Substrates modified with collagen and synthetic polyelectrolytes were least effective, due to the destructive nature of acidic environments on InAs. The toxicity of modified and unmodified InAs, along with raw indium, arsenic, and PEG components was assessed

  20. Characterizing the modification of surface proteins with poly(ethylene glycol) to interrupt platelet adhesion

    PubMed Central

    Xu, Haiyan; Kaar, Joel L.; Russell, Alan J.; Wagner, William R.

    2010-01-01

    Surface protein modification with poly(ethylene glycol) (PEG) can inhibit acute thrombosis on damaged vascular and biomaterial surfaces by blocking surface protein–platelet interactions. However, the feasibility of employing protein reactive PEGs to limit intravascular and biomaterial thrombosis in vivo is contingent upon rapid and extensive surface protein modification. To characterize the factors controlling this potential therapeutic approach, the model protein bovine serum albumin was adsorbed onto polyurethane surfaces and modified with PEG-carboxymethyl succinimidyl ester (PEG-NHS), PEG-isocyanate (PEG-ISO), or PEG-diisocyanate (PEG-DISO) in aqueous buffer at varying concentrations and contact times. It was found that up to 5 PEGs could be attached per albumin molecule within one min and that adsorbed albumin PEGylation approached maximal levels by 6 min. The lability of reactive PEGs in aqueous buffer reduced total protein modification by 50% when the PEG solution was incubated for 7 min prior to application. For fibrinogen PEGylation (performed in the solution phase), PEG-NHS was more reactive than PEG-ISO or PEG-DISO. The γ peptide of fibrinogen, which contains several key platelet-binding motifs, was highly modified. A marked reduction in platelet adhesion was observed on fibrinogen-adsorbed polyurethane treated with PEG-NHS or PEG-DISO. Relative differences in platelet adhesion on PEG-NHS and PEG-DISO modified surfaces could be attributed to differences in reactivity towards fibrinogen and the size of the polymer backbone. Taken together, these findings provide insight and guidance for applying protein reactive PEGs for the interruption of acute thrombotic deposition. PMID:16457880

  1. Temporal trends of time to antiretroviral treatment initiation, interruption and modification: examination of patients diagnosed with advanced HIV in Australia

    PubMed Central

    Wright, Stephen T; Law, Matthew G; Cooper, David A; Keen, Phillip; McDonald, Ann; Middleton, Melanie; Woolley, Ian; Kelly, Mark; Petoumenos, Kathy

    2015-01-01

    Introduction HIV prevention strategies are moving towards reducing plasma HIV RNA viral load in all HIV-positive persons, including those undiagnosed, treatment naïve, on or off antiretroviral therapy. A proxy population for those undiagnosed are patients that present late to care with advanced HIV. The objectives of this analysis are to examine factors associated with patients presenting with advanced HIV, and establish rates of treatment interruption and modification after initiating ART. Methods We deterministically linked records from the Australian HIV Observational Database to the Australian National HIV Registry to obtain information related to HIV diagnosis. Logistic regression was used to identify factors associated with advanced HIV diagnosis. We used survival methods to evaluate rates of ART initiation by diagnosis CD4 count strata and by calendar year of HIV diagnosis. Cox models were used to determine hazard of first ART treatment interruption (duration >30 days) and time to first major ART modification. Results Factors associated (p<0.05) with increased odds of advanced HIV diagnosis were sex, older age, heterosexual mode of HIV exposure, born overseas and rural–regional care setting. Earlier initiation of ART occurred at higher rates in later periods (2007–2012) in all diagnosis CD4 count groups. We found an 83% (69, 91%) reduction in the hazard of first treatment interruption comparing 2007–2012 versus 1996–2001 (p<0.001), and no difference in ART modification for patients diagnosed with advanced HIV. Conclusions Recent HIV diagnoses are initiating therapy earlier in all diagnosis CD4 cell count groups, potentially lowering community viral load compared to earlier time periods. We found a marked reduction in the hazard of first treatment interruption, and found no difference in rates of major modification to ART by HIV presentation status in recent periods. PMID:25865372

  2. Surface modification of an epoxy resin with polyamines and polydopamine: Adhesion toward electroless deposited copper

    NASA Astrophysics Data System (ADS)

    Schaubroeck, David; Mader, Lothar; Dubruel, Peter; Vanfleteren, Jan

    2015-10-01

    In this paper the influence of the epoxy roughness, surface modifications and ELD (electroless copper deposition) temperatures on the adhesive strength of the copper is studied. Good adhesion at low roughness values is targeted due to their applicability in high density electronic circuits. Roughened epoxy surfaces are modified with adsorbed polyamines, polydopamine and polyamines grafted to polydopamine. Next the, adhesive strength of ELD copper is determined with peel strength measurements and the interphases are examined with SEM (scanning electron microscopy). Polydopamine and polyamines grafted to polydopamine can lead to increased adhesive strength at lower roughness values compared to the non-modified samples at specific plating temperatures.

  3. [Surface modification and microstructure of single-walled carbon nanotubes for dental composite resin].

    PubMed

    Xia, Yang; Zhang, Feimin; Xu, Li'na; Gu, Ning

    2006-12-01

    In order to improve its dispersion condition in dental composite resin and enhance its interaction with the matrix, single-walled carbon nanotubes(SWNTs) were refluxed and oxidized, then treated by APTE. Their outer surface were coated by nano-SiO2 particles using sol-gel process, then further treated by organosilanes ATES. IR and TEM were used to analyze modification results. TEM pictures showed nano-particles were on the surface of SWNTs; IR showed characteristic adsorbing bands of SiO2. Composite resin specimen with modified SWNTs was prepared and examined by TEM. SWNTs were detected in composite resin matrix among other inorganic fillers. PMID:17228726

  4. Controllable local modification of fractured Nb-doped SrTiO{sub 3} surfaces.

    SciTech Connect

    Chien, T. Y.; Santos, T. S.; Bode, M.; Guisinger, N. P.; Freeland, J. W.

    2009-01-01

    Nanoscale surface modification of a fractured Nb-doped SrTiO{sub 3} surface is demonstrated in a controlled way by scanning tunneling microscopy. By applying positive voltage pulses, holes can be created and the width and depth of the hole can be controlled by selecting the appropriate bias and pulse duration. The process shows a threshold condition for creation of the holes and change in the local electronic density of state consistent with exposure of the underlying TiO{sub 2} layer by removal of SrO. By applying negative bias, the hole can be partially refilled from the transfer of adsorbates on the tip.

  5. TOPICAL REVIEW: Surface modification and characterization for dispersion stability of inorganic nanometer-scaled particles in liquid media

    NASA Astrophysics Data System (ADS)

    Kamiya, Hidehiro; Iijima, Motoyuki

    2010-08-01

    Inorganic nanoparticles are indispensable for science and technology as materials, pigments and cosmetics products. Improving the dispersion stability of nanoparticles in various liquids is essential for those applications. In this review, we discuss why it is difficult to control the stability of nanoparticles in liquids. We also overview the role of surface interaction between nanoparticles in their dispersion and characterization, e.g. by colloid probe atomic force microscopy (CP-AFM). Two types of surface modification concepts, post-synthesis and in situ modification, were investigated in many previous studies. Here, we focus on post-synthesis modification using adsorption of various kinds of polymer dispersants and surfactants on the particle surface, as well as surface chemical reactions of silane coupling agents. We discuss CP-AFM as a technique to analyze the surface interaction between nanoparticles and the effect of surface modification on the nanoparticle dispersion in liquids.

  6. Influence of surface modification on corrosion and biocompatibility of titanium alloys

    NASA Astrophysics Data System (ADS)

    Rahman, Zia Ur

    Titanium alloys are playing a vital role in the field of biomaterials due to their excellent corrosion resistance and biocompatibility. These alloys enhance the quality and longevity of human life by replacing or treating various parts of the body. However, as these materials are in constant contact with the aggressive body fluids, corrosion leads to metal ions dissolution. These ions leach to the adjacent tissues and causes adverse reactions. Surface modifications are used to improve corrosion resistance and biological activity without changing their bulk properties. In this investigation, electropolishing, magnetoelectropolishing, titanium coating and hydroxiapatitecoating were carried out on commercially pure titanium (CPTi), Ti6Al4V and Ti6Al4V-ELI (Extra Low Interstitials). These surface modifications are known to effect surface charge, chemistry, morphology; wettability, corrosion resistance and biocompatibility of these materials. In vitro cyclic potentiodynamic polarization tests were conducted in phosphate buffer saline in compliance with ASTM standard. The surface morphology, roughness and wettability of these alloys were studied using scanning electron microscope, atomic force microscope and contact angle meter, respectively. Moreover, biocompatibility of titanium alloys was assessed by growing MC3T3 pre-osteoblast cells on their surfaces

  7. Rapid Covalent Modification of Silicon Oxide Surfaces through Microwave-Assisted Reactions with Alcohols.

    PubMed

    Lee, Austin W H; Gates, Byron D

    2016-07-26

    We demonstrate the method of a rapid covalent modification of silicon oxide surfaces with alcohol-containing compounds with assistance by microwave reactions. Alcohol-containing compounds are prevalent reagents in the laboratory, which are also relatively easy to handle because of their stability against exposure to atmospheric moisture. The condensation of these alcohols with the surfaces of silicon oxides is often hindered by slow reaction kinetics. Microwave radiation effectively accelerates this condensation reaction by heating the substrates and/or solvents. A variety of substrates were modified in this demonstration, such as silicon oxide films of various thicknesses, glass substrates such as microscope slides (soda lime), and quartz. The monolayers prepared through this strategy demonstrated the successful formation of covalent surface modifications of silicon oxides with water contact angles of up to 110° and typical hysteresis values of 2° or less. An evaluation of the hydrolytic stability of these monolayers demonstrated their excellent stability under acidic conditions. The techniques introduced in this article were successfully applied to tune the surface chemistry of silicon oxides to achieve hydrophobic, oleophobic, and/or charged surfaces. PMID:27396288

  8. Low energy oxygen ion beam modification of the surface morphology and chemical structure of polyurethane fibers

    NASA Astrophysics Data System (ADS)

    Wong, K. H.; Zinke-Allmang, M.; Wan, W. K.; Zhang, J. Z.; Hu, P.

    2006-01-01

    Energetic O+ ions were implanted into polyurethane (PU) fiber filaments, at 60 and 100 keV with doses of 5 × 1014 and 1 × 1015 ions/cm2, to modify the near-surface fiber morphology. The implantations were performed at room temperature and at -197 °C, a temperature well below the glass transition temperature for this system. At room temperature, the lower energy implantation heats the fibers primarily near their surface, causing the fiber surface to smoothen and to develop a flattened shape. At the higher energy, the ion beam deposits its energy closer to the fiber core, heating the fiber more uniformly and causing them to re-solidify slowly. This favors a cylindrical equilibrium shape with a smooth fiber surface and no crack lines. The average fiber diameter reduced during 100 keV implantation from 3.1 to 2.3 μm. At -197 °C, the ion implantation does not provide enough heat to cause notable physical modifications, but the fibers crack and break during subsequent warming to room temperature. The dose dependence of the crack formation along the fiber intersections is presented. The ion beams further cause near-surface chemical modifications in the fibers, particularly introducing two new chemical functional groups (C-(Cdbnd O)-C and C-N-C).

  9. Nano-scale surface modification of a segmented polyurethane with a phospholipid polymer.

    PubMed

    Morimoto, Nobuyuki; Watanabe, Akihiko; Iwasaki, Yasuhiko; Akiyoshi, Kazunari; Ishihara, Kazuhiko

    2004-10-01

    Nano-scale modification of a segmented polyurethane (SPU) with cross-linked 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer was performed to obtain a biocompatible elastomer. To control the domain size and the depth of the modified layer, various compositions of monomers, including MPC, 2-ethylhexyl methacrylate (EHMA), and glycerol 1,3-diglycerolate diacrylate, were examined. SPU film was immersed in the monomer solution and visible light irradiation was applied to initiate polymerization to the SPU film that was held by mica to condense MPC units at the surface. The surfaces of the obtained film were analyzed by X-ray photoelectron spectroscopy and water contact angle measurement. The surface density of MPC units changed with the monomer concentration, and the density was the highest when the ratio between MPC and EHMA was 7:3. In modified SPU films, 6- to 25-nm MPC unit-enriched domains were observed and the density of these domains gradually decreased with depth. The sizes of the domains depended on the MPC composition in the monomer solution. The mechanical properties of the modified films as evaluated by tensile strength measurement under wet conditions were not significantly different from those of SPU. With increase in the existence of MPC unit-enriched domains on the MEG film surface, platelet adhesion and activation were remarkably reduced compared to the SPU film. This nano-scale surface modification may be a useful technique for applying elastic polymer biomaterials. PMID:15130720

  10. Polydopamine-Based Simple and Versatile Surface Modification of Polymeric Nano Drug Carriers

    PubMed Central

    Park, Joonyoung; Brust, Tarsis F.; Lee, Hong Jae; Lee, Sang Cheon; Watts, Val J.; Yeo, Yoon

    2014-01-01

    The surface of a polymeric nanoparticle (NP) is often functionalized with cell-interactive ligands and/or additional polymeric layers to control NP interaction with cells and proteins. However, such modification is not always straightforward when the surface is not chemically reactive. For this reason, most NP functionalization processes employ reactive linkers or coupling agents or involve pre-functionalization of the polymer, which are complicated and inefficient. Moreover, pre-functionalized polymers can lose the ability to encapsulate and retain a drug if the added ligands change chemical properties of the polymer. To overcome this challenge, we use dopamine polymerization as a way of functionalizing NP surfaces. This method includes brief incubation of the pre-formed NPs in a weak alkaline solution of dopamine, followed by secondary incubation with desired ligands. Using this method, we have functionalized poly(lactic-co-glycolic acid) (PLGA) NPs with three representative surface modifiers: a small molecule (folate), a peptide (Arg-Gly-Asp), and a polymer [poly(carboxybetaine methacrylate)]. We confirmed that the modified NPs showed the expected cellular interactions with no cytotoxicity or residual bioactivity of dopamine. The dopamine polymerization method is a simple and versatile surface modification method, applicable to a variety of NP drug carriers irrespective of their chemical reactivity and the types of ligands. PMID:24628245

  11. Surface modification of tooth root canal after application of an X-ray opaque waveguide

    NASA Astrophysics Data System (ADS)

    Dostálová, T.; Jelínková, H.; Šulc, J.; Němec, M.; Koranda, P.; Bartoňová, M.; Radina, P.; Miyagi, M.; Shi, Y.-W.; Matsuura, Y.

    The interest in endodontic use of dental laser systems has been increasing. With the development of thin and flexible delivery systems for various wavelengths, laser applications in endodontics may become even more desirable. The aim of this study is to check the X-ray opacity of a hollow waveguide and to observe the results after laser root canal treatment. The root canal systems of 10 molars were treated endodontically by laser. For the laser radiation source, an Er:YAG laser system generating a wavelength of 2940 nm and an Alexandrite laser system generating a wavelength of 375 nm were used. The hollow waveguide used was checked under X-ray . A root canal surface treated by laser radiation was analyzed by a scanning electron microscope (SEM). The special hollow glass waveguide used was visible in the root canal system under X-ray imaging. Surface modification of the root canal after laser treatment was not found. After conventional treatment the root canal was enlarged. The surface was covered with a smear layer. After application of both laser systems, the smear layer was removed. The resulting canal surface was found to be clean and smooth. Under SEM observation open dentinal tubules were visible. No cracks were present, nor were surface modifications observed.

  12. Ion Beam and Plasma Technology Development for Surface Modification at Los Alamos National Laboratory

    SciTech Connect

    Davis, H.A.; Munson, C.P.; Wood, B.P.; Bitteker, L.J.; Nastasi, M.A.; Rej, D.J.; Waganaar, W.J.; Walter, K.C.; Coates, D.M.; Schleinitz, H.M.

    1997-12-31

    We are developing two high-throughput technologies for materials modification. The first is a repetitive intense ion beam source for materials modification through rapid surface melt and resolidification (up to 10{sup 10} deg/sec cooling rates) and for ablative deposition of coatings. The short range of the ions (typically 0.1 to 5 micrometers) allows vaporization or melting at moderate beam energy density (typically 1-50 J/cm{sup 2}). A new repetitive intense ion beam accelerator called CHAMP is under development at Los Alamos. The design beam parameters are: E=200 keV, I=15 kA, {tau}=1 {micro}s, and 1 Hz. This accelerator will enable applications such as film deposition, alloying and mixing, cleaning and polishing, corrosion and wear resistance, polymer surface treatments, and nanophase powder synthesis. The second technology is plasma source ion implantation (PSII) using plasmas generated from both gas phase (using radio frequency excitation) and solid phase (using a cathodic arc) sources. We have used PSII to directly implant ions for surface modification or as method for generating graded interfaces to enhance the adhesion of surface coatings. Surfaces with areas of up to 16 m{sup 2} and weighing more than a thousand kilograms have been treated in the Los Alamos PSII chamber. In addition, PSII in combination with cathodic source deposition has been used to form highly adherent, thick Er{sub 2}O{sub 3} coatings on steel for reactive metal containment in casting. These coatings resist delamination under extreme mechanical and thermal stress.

  13. Surface modification of PLGA nanoparticles via human serum albumin conjugation for controlled delivery of docetaxel

    PubMed Central

    2013-01-01

    Background Poly lactic-co-glycolic acid (PLGA) based nanoparticles are considered to be a promising drug carrier in tumor targeting but suffer from the high level of opsonization by reticuloendothelial system due to their hydrophobic structure. As a result surface modification of these nanoparticles has been widely studied as an essential step in their development. Among various surface modifications, human serum albumin (HSA) possesses advantages including small size, hydrophilic surface and accumulation in leaky vasculature of tumors through passive targeting and a probable active transport into tumor tissues. Methods PLGA nanoparticles of docetaxel were prepared by emulsification evaporation method and were surface conjugated with human serum albumin. Fourier transform infrared spectrum was used to confirm the conjugation reaction where nuclear magnetic resonance was utilized for conjugation ratio determination. In addition, transmission electron microscopy showed two different contrast media in conjugated nanoparticles. Furthermore, cytotoxicity of free docetaxel, unconjugated and conjugated PLGA nanoparticles was studied in HepG2 cells. Results Size, zeta potential and drug loading of PLGA nanoparticles were about 199 nm, −11.07 mV, and 4%, respectively where size, zeta potential and drug loading of conjugated nanoparticles were found to be 204 nm, −5.6 mV and 3.6% respectively. Conjugated nanoparticles represented a three-phasic release pattern with a 20% burst effect for docetaxel on the first day. Cytotoxicity experiment showed that the IC50 of HSA conjugated PLGA nanoparticles (5.4 μg) was significantly lower than both free docetaxel (20.2 μg) and unconjugated PLGA nanoparticles (6.2 μg). Conclusion In conclusion surface modification of PLGA nanoparticles through HSA conjugation results in more cytotoxicity against tumor cell lines compared with free docetaxel and unconjugated PLGA nanoparticles. Albumin conjugated PLGA nanoparticles may

  14. Surface modification of bioactive glasses and preparation of PDLLA/bioactive glass composite films.

    PubMed

    Gao, Yuan; Chang, Jiang

    2009-08-01

    In order to improve the homogeneous dispersion of particles in the polymeric matrix, 45S5, mesoporous 58S, and 58S bioactive glasses were surface modified by esterification reactions with dodecyl alcohol at reflux temperature of 260 degrees C (named as m-45S5, m-mesoporous 58S, and m-58S, respectively). The modified particles showed better hydrophobicity and longer time of suspension in organic matrix. The PDLLA/bioactive glass composite films were fabricated using surface modified bioactive glass particles through solvent casting-evaporation method. Surface morphology, mechanical property, and bioactivity were investigated. The results revealed that the inorganic particle distribution and tensile strength of the composite films with modified bioactive glass particles were significantly improved while great bioactive properties were maintained. Scanning electron microscopy (SEM) observation illustrated that the modified bioactive glass particles were homogeneously dispersed in the PDLLA matrix. The maximum tensile strengths of composite films with modified bioactive glass particles were higher than that of composite films with unmodified bioactive glass particles. The bioactivity of the composite films were evaluated by being soaked in the simulated body fluid (SBF) and the SEM observation of the films suggested that the modified composite films were still bioactive in that they could induce the formation of HAp on its surface and the distribution of HAp was even more homogeneous on the film. The results mentioned above indicated that the surface modification of bioactive glasses with dodecyl alcohol was an effective method to prepare PDLLA/bioactive glass composites with enhanced properties. By studying the comparisons of modification effects among the three types of bioactive glasses, we could get the conclusion that the size and morphology of the inorganic particles would greatly affect the modification effects and the properties of composites. PMID:18801895

  15. Plasma modification of polypropylene surfaces and its alloying with styrene in situ

    NASA Astrophysics Data System (ADS)

    Ma, Gui-qiu; Liu, Ben; Li, Chen; Huang, Dinghai; Sheng, Jing

    2012-01-01

    The treatment of polypropylene surfaces has been studied by dielectric barrier discharges plasma of Ar. The structure and morphology of polypropylene surfaces of Ar plasma modification are characterized by X-ray photoelectron spectroscopy, Fourier transform infrared spectrometers and scanning electron microscope. The modified by plasma treatment of iPP (isotactic polypropylene) surface properties have been examined in a determination of free radicals. The modified active surfaces of polypropylene can induce grafting copolymerization of styrene onto polypropylene. The structure of grafting copolymer is characterized and the grafting percent of styrene onto polypropylene is calculated. The homopolymer of styrene can be formed under grafting copolymerization of styrene onto polypropylene, which follows that the alloying of polypropylene with styrene is achieved in situ.

  16. Tuning the resistance of polycarbonate membranes by plasma-induced graft surface modification

    NASA Astrophysics Data System (ADS)

    Baumann, Lukas; Hegemann, Dirk; de Courten, Damien; Wolf, Martin; Rossi, René M.; Meier, Wolfgang P.; Scherer, Lukas J.

    2013-03-01

    To tune the permeability resistance of porous polycarbonate (PC) membranes for caffeine, their surfaces were plasma modified with different monomers in a grafting from process. These coatings provided characteristic surface hydrophilicities. It was found that membranes with more hydrophilic surfaces have lower resistances to let caffeine pass through than membranes with hydrophobic surfaces. Additionally, it was possible to post-modify a poly(2-aminoethyl methacrylate) (AEMA) coated PC membrane with octanoic acid (Oct) under mild conditions. This post modification allowed transforming a slightly hydrophilic PC-AEMA membrane with a moderate permeability resistance into a hydrophobic PC-AEMA-Oct membrane with a high permeability resistance. Overall, it was possible to tune the PC membrane resistance for caffeine in a range from 5100 up to 15,100 s/cm.

  17. Enhancement of resistance of polyethylene to seawater-promoted degradation by surface modification

    NASA Astrophysics Data System (ADS)

    Baird, Richard W.

    Low-density polyethylene was subjected to several surface-modification techniques, and the effectiveness of each method in retarding seawater-promoted degradation was evaluated. Surface treatments studied included radio-frequency glow-discharge exposure in air followed by diacid or triisocyanate co-polymerization and surface irradiation with 500 keV electrons of very low penetration. Plasma and co-polymerization treatments were monitored by ESCA and ATR IR spectroscopy, from which tentative conclusions were possible concerning reaction rates and probable chemical nature of the modified surface regions. Electron irradiation was monitored by gel content and cellophane dosimetry. Samples of treated polyethylene were subjected to accelerated testing by cyclic flexure in seawater and wide-angle X-ray diffraction results showed that each treatment method studied caused retardation of degradation; however, the relative effectiveness of the various techniques varied greatly.

  18. Surface modification and electrochemical properties of activated carbons for supercapacitor electrodes

    NASA Astrophysics Data System (ADS)

    Yang, Dan; Qiu, Wenmei; Xu, Jingcai; Han, Yanbing; Jin, Hongxiao; Jin, Dingfeng; Peng, Xiaoling; Hong, Bo; Li, Ji; Ge, Hongliang; Wang, Xinqing

    2015-12-01

    Modifications with different acids (HNO3, H2SO4, HCl and HF, respectively) were introduced to treat the activated carbons (ACs) surface. The microstructures and surface chemical properties were discussed by X-ray diffraction (XRD), thermogravimetric analysis (TGA), ASAP, Raman spectra and Fourier transform infrared (FTIR) spectra. The ACs electrode-based supercapacitors were assembled with 6 mol ṡ L-1 KOH electrolyte. The electrochemical properties were studied by galvanostatic charge-discharge and cyclic voltammetry. The results indicated that although the BET surface area of modified ACs decreased, the functional groups were introduced and the ash contents were reduced on the surface of ACs, receiving larger specific capacitance to initial AC. The specific capacitance of ACs modified with HCl, H2SO4, HF and HNO3 increased by 31.4%, 23%, 21% and 11.6%, respectively.

  19. Surface Modification of Material by Irradiation of Low Power Atmospheric Pressure Plasma Jet

    SciTech Connect

    Akamatsu, Hiroshi; Ichikawa, Kazunori; Azuma, Kingo; Onoi, Masahiro

    2010-10-13

    Application of a low power atmospheric pressure plasma jet for surface modifications of acrylic, aluminum, and highly crystalline graphite has been carried out experimentally. The plasma jet was generated with batteries-driven high voltage modulator. The power consumed for the plasma generation was estimated to be 0.12 W. The plasma had hydroxyl radicals, which is known as a strong oxider from an observation of optical emission spectrum. After the irradiation of the plasma, the surfaces of acrylic and aluminum became to be hydrophilic from the compartment of contact angle of water on these surfaces. The surface of highly crystalline graphite irradiated by the plasma jet had oxygen-rich functional groups such as C-O, C = O, and O = C-O.

  20. Chemical modification of TiO2 surfaces with methylsilanes and characterization by infrared absorption spectroscopy

    NASA Technical Reports Server (NTRS)

    Finklea, H. O.; Vithanage, R.

    1982-01-01

    Infrared absorption spectra of methylsilanes bonded to a TiO2 powder were obtained. The reacting silanes include Me sub (4-n)SiX sub n (n=1-4; X=Cl, OMe) and hexamethyldisilazane (HMDS). Reactions were performed on hydroxylated-but-anhydrous TiO2 surfaces in the gas phase. IR spectra confirm the presence of a bonded silane layer. Terminal surface OH groups are found to react more readily than bridging OH groups. By-products of the modification adsorp tenaciously to the surface. The various silanes show only small differences in their ability to sequester surface OH groups. Following hydrolysis in moist air, Si-OH groups are observed only for the tetrafunctional silanes.

  1. Study on Surface Modification of Polymer Films by Using Atmospheric Plasma Jet Source

    NASA Astrophysics Data System (ADS)

    Takemura, Yuichiro; Yamaguchi, Naohiro; Hara, Tamio

    2008-07-01

    Reactive gas plasma treatments of poly(ethylene terephthalate) (PET) and polyimide (Kapton) have been performed using an atmospheric plasmas jet source. Characteristics of surface modification have been examined by changing the distance between the plasma jet source and the treated sample, and by changing the working gas spaces. Simultaneously, each plasma jet source has been investigated by space-resolving spectroscopy in the UV/visible region. Polymer surfaces have been analyzed by X-ray photoelectron spectroscopy (XPS). A marked improvement in the hydrophilicity of the polymer surfaces has been made by using N2 or O2 plasma jet source with a very short exposure time of about 0.01 s, whereas the less improvement has been obtained using on air plasma jet source because of NOx compound production. Changes in the chemical states of C of the polymer surfaces have been observed in XPS spectra after N2 plasma jet spraying.

  2. Extreme ultraviolet (EUV) surface modification of polytetrafluoroethylene (PTFE) for control of biocompatibility

    NASA Astrophysics Data System (ADS)

    Ahad, Inam Ul; Butruk, Beata; Ayele, Mesfin; Budner, Bogusław; Bartnik, Andrzej; Fiedorowicz, Henryk; Ciach, Tomasz; Brabazon, Dermot

    2015-12-01

    Extreme ultraviolet (EUV) surface modification of polytetrafluoroethylene (PTFE) was performed in order to enhance the degree of biocompatibility. Polymer samples were irradiated by different number of EUV shots using a laser-plasma based EUV source in the presence of nitrogen gas. The physical and chemical properties of EUV modified PTFE samples were studied using Atomic Force Microscopy, X-ray photoelectron spectroscopy and water contact angle (WCA) methods. Pronounced wall type micro and nano-structures appeared on the EUV treated polymer surfaces resulting in increased surface roughness and hydrophobicity. Stronger cell adhesion and good cell morphology were observed on EUV modified surfaces by in-vitro cell culture studies performed using L929 fibroblasts.

  3. Negative-tone block copolymer lithography by in situ surface chemical modification.

    PubMed

    Kim, Bong Hoon; Byeon, Kyeong-Jae; Kim, Ju Young; Kim, Jinseung; Jin, Hyeong Min; Cho, Joong-Yeon; Jeong, Seong-Jun; Shin, Jonghwa; Lee, Heon; Kim, Sang Ouk

    2014-10-29

    Negative-tone block copolymer (BCP) lithography based on in situ surface chemical modification is introduced as a highly efficient, versatile self-assembled nanopatterning. BCP blends films consisting of end-functionalized low molecular weight poly(styrene-ran-methyl methacrylate) and polystyrene-block-Poly(methyl methacylate) can produce surface vertical BCP nanodomains on various substrates without prior surface chemical treatment. Simple oxygen plasma treatment is employed to activate surface functional group formation at various substrates, where the end-functionalized polymers can be covalently bonded during the thermal annealing of BCP thin films. The covalently bonded brush layer mediates neutral interfacial condition for vertical BCP nanodomain alignment. This straightforward approach for high aspect ratio, vertical self-assembled nanodomain formation facilitates single step, site-specific BCP nanopatterning widely useful for various substrates. Moreover, this approach is compatible with directed self-assembly approaches to produce device oriented laterally ordered nanopatterns. PMID:24912807

  4. Surface modification of alloys for improved oxidation resistance in SOFC applications

    SciTech Connect

    Alman, D.E.; Jablonski, P.D.; Kung, S.C.

    2006-11-01

    This research is aimed at improving the oxidation behavior of metallic alloys for SOFC application, by the incorporation of rare earths through surface treatments. This paper details the effect of such surface modification on the behavior of Crofer 22 APU, a ferritic steel designed specifically for SOFC application, and Type 430 stainless steel. Two pack cementation like treatments were used to incorporate Ce into the surface of the alloys. After 4000 hours of exposure at 800oC to air+3%H2O, the weight gain of Crofer 22APU samples that were Ce surface modified were less than half that of an unmodified sample, revealing the effectiveness of the treatments on enhancing oxidation resistance. For Type-430, the treatment prevented scale spalling that occurred during oxidation of the unmodified alloy.

  5. Water dispersible upconverting nanoparticles: effects of surface modification on their luminescence and colloidal stability

    NASA Astrophysics Data System (ADS)

    Wilhelm, Stefan; Kaiser, Martin; Würth, Christian; Heiland, Josef; Carrillo-Carrion, Carolina; Muhr, Verena; Wolfbeis, Otto S.; Parak, Wolfgang J.; Resch-Genger, Ute; Hirsch, Thomas

    2015-01-01

    We present a systematic study on the effect of surface ligands on the luminescence properties and colloidal stability of β-NaYF4:Yb3+,Er3+ upconversion nanoparticles (UCNPs), comparing nine different surface coatings to render these UCNPs water-dispersible and bioconjugatable. A prerequisite for this study was a large-scale synthetic method that yields ~2 g per batch of monodisperse oleate-capped UCNPs providing identical core particles. These ~23 nm sized UCNPs display an upconversion quantum yield of ~0.35% when dispersed in cyclohexane and excited with a power density of 150 W cm-2, underlining their high quality. A comparison of the colloidal stability and luminescence properties of these UCNPs, subsequently surface modified with ligand exchange or encapsulation protocols, revealed that the ratio of the green (545 nm) and red (658 nm) emission bands determined at a constant excitation power density clearly depends on the surface chemistry. Modifications relying on the deposition of additional (amphiphilic) layer coatings, where the initial oleate coating is retained, show reduced non-radiative quenching by water as compared to UCNPs that are rendered water-dispersible via ligand exchange. Moreover, we could demonstrate that the brightness of the upconversion luminescence of the UCNPs is strongly affected by the type of surface modification, i.e., ligand exchange or encapsulation, yet hardly by the chemical nature of the ligand.We present a systematic study on the effect of surface ligands on the luminescence properties and colloidal stability of β-NaYF4:Yb3+,Er3+ upconversion nanoparticles (UCNPs), comparing nine different surface coatings to render these UCNPs water-dispersible and bioconjugatable. A prerequisite for this study was a large-scale synthetic method that yields ~2 g per batch of monodisperse oleate-capped UCNPs providing identical core particles. These ~23 nm sized UCNPs display an upconversion quantum yield of ~0.35% when dispersed in

  6. Laser Surface Modification of H13 Die Steel using Different Laser Spot Sizes

    NASA Astrophysics Data System (ADS)

    Aqida, S. N.; Naher, S.; Brabazon, D.

    2011-05-01

    This paper presents a laser surface modification process of AISI H13 tool steel using three sizes of laser spot with an aim to achieve reduced grain size and surface roughness. A Rofin DC-015 diffusion-cooled CO2 slab laser was used to process AISI H13 tool steel samples. Samples of 10 mm diameter were sectioned to 100 mm length in order to process a predefined circumferential area. The parameters selected for examination were laser peak power, overlap percentage and pulse repetition frequency (PRF). Metallographic study and image analysis were done to measure the grain size and the modified surface roughness was measured using two-dimensional surface profilometer. From metallographic study, the smallest grain sizes measured by laser modified surface were between 0.51 μm and 2.54 μm. The minimum surface roughness, Ra, recorded was 3.0 μm. This surface roughness of the modified die steel is similar to the surface quality of cast products. The grain size correlation with hardness followed the findings correlate with Hall-Petch relationship. The potential found for increase in surface hardness represents an important method to sustain tooling life.

  7. Adsorbate modification of the structural, electronic, and magnetic properties of ferromagnetic fcc {110} surfaces

    NASA Astrophysics Data System (ADS)

    Gunn, D. S. D.; Jenkins, Stephen J.

    2011-03-01

    We identify trends in structural, electronic, and magnetic modifications that occur on ferromagnetic {110} surfaces upon varying either the substrate material or the adsorbate species. First, we have modeled the adsorption of several first-row p-block elements on the surface of fcc Co{110} at two coverages [0.5 and 1.0 monolayer (ML)]. All adsorbates were found to expand the distance between the first and second substrate layers and to contract the distance between the second and third layers. The energetic location of a characteristic trough in the density-of-d-states difference plot correlates with the direction of the adsorbate magnetic coupling to the surface, and a trend of antiferromagnetic to ferromagnetic coupling to the surface was observed across the elements from boron to fluorine. A high fluorine adatom coverage (1.0 ML) was found to enhance the surface spin magnetic moment by 11%. Second, we also calculate and contrast adsorption of 0.5 and 1.0 ML of carbon, nitrogen, and oxygen adatoms on fcc iron, cobalt, and nickel {110} surfaces and compare the structural, electronic, and magnetic properties of these systems. Carbon and nitrogen are found to couple antiferromagnetically, and oxygen ferromagnetically, to all surfaces. It was found that antiferromagnetically coupled adsorbates retained their largest spin moment values on iron, whereas ferromagnetically coupled adsorbates possessed their lowest moments on this surface. The strongly localized influence of these adsorbates is clearly illustrated in partial density-of-states plots for the surface atoms.

  8. Surface Modification of Droplet Polymeric Microfluidic Devices for the Stable and Continuous Generation of Aqueous Droplets

    PubMed Central

    Subramanian, Balamurugan; Kim, Namwon; Lee, Wonbae; Spivak, David A.; Nikitopoulos, Dimitris E.; McCarley, Robin L.; Soper, Steven A.

    2012-01-01

    Droplet microfluidics performed in poly(methylmethacrylate), PMMA, microfluidic devices resulted in significant wall wetting by water droplets formed in a liquid-liquid segmented flow when using a hydrophobic carrier fluid, such as perfluorotripropylamine (FC-3283). This wall wetting led to water droplets with non-uniform sizes that were often trapped on the wall surfaces leading to unstable and poorly controlled liquid-liquid segmented flow. To circumvent this problem, we developed a two-step procedure to hydrophobically modify the surfaces of PMMA and other thermoplastic materials commonly used for making microfluidic devices. The surface modification route involved the introduction of hydroxyl groups by oxygen plasma treatment of the polymer surface followed by a solution phase reaction with heptadecafluoro-1,1,2,2–tetrahydrodecyl trichlorosilane dissolved in the fluorocarbon solvent FC-3283. This procedure was found to be useful for the modification of PMMA and other thermoplastic surfaces, including polycyclic olefin copolymer (COC) and polycarbonate (PC). Angle-resolved X-ray photoelectron spectroscopy indicated that the fluorination of these polymers took place with high surface selectivity. This procedure was used to modify the surface of a PMMA droplet microfluidic device (DMFD) and was shown to be useful to reduce the wetting problem during the generation of aqueous droplets in a perfluorotripropylamine (FC-3283) carrier fluid and could generate stable segmented flows for hours of operation. In the case of the PMMA DMFD, oxygen plasma treatment was carried out after the PMMA cover plate was thermally fusion bonded to the PMMA microfluidic chip. Because the appended chemistry to the channel wall created a hydrophobic surface, it will accommodate the use of other carrier fluids that are hydrophobic as well, such as hexadecane or mineral oils. PMID:21608975

  9. Effects of Surface Modification Conditions on Hydrophobicity of Silica-based Coating Additives

    SciTech Connect

    Armstrong, Beth L; Pawel, Steven J; Hunter, Scott Robert; Haynes, James A; Hillesheim, Daniel A

    2013-01-01

    Superhydrophobic silica (SHS) powders are being evaluated as a potential additive to the polyurethane topcoats used in Chemical Agent Resistant Coating (CARC) systems, with the goal of improving water repellency and corrosion protection characteristics. The current generation of CARC topcoats is already highly loaded with solids, and thus there is a premium on minimization of the total SHS powder required to achieve the desired properties. Therefore, efficient surface modification of the silica and proper dispersion in the coating will be required. The effect of a dispersant on the surface modification of silica particles by chlorosilanes was addressed in this study. The properties of various SHS powders were characterized by thermogravimetric analysis and mass spectroscopy. Correlations between powder modification conditions and the ultimate effects of the modified particles on hydrophobicity of CARC topcoats were assessed. The use of contact and rolling angle measurements along with scanning electron microscopy are discussed as they pertain to the ability to quantify the effects of modified silicas on corrosion prevention coatings. Furthermore, a systematic approach to modifying and testing both powders and top coats of corrosion prevention systems is presented.

  10. Surface modification of polydimethylsiloxane with photo-grafted poly(ethylene glycol) for micropatterned protein adsorption and cell adhesion.

    PubMed

    Sugiura, Shinji; Edahiro, Jun-ichi; Sumaru, Kimio; Kanamori, Toshiyuki

    2008-06-01

    In this study, we applied photo-induced graft polymerization to micropatterned surface modification of polydimethylsiloxane (PDMS) with poly(ethylene glycol). Two types of monomers, polyethylene glycol monoacrylate (PEGMA) and polyethylene glycol diacrylate (PEGDA), were tested for surface modification of PDMS. Changes in the surface hydrophilicity and surface element composition were characterized by contact angle measurement and electron spectroscopy for chemical analysis. The PEGMA-grafted PDMS surfaces gradually lost their hydrophilicity within two weeks. In contrast, the PEGDA-grafted PDMS surface maintained stable hydrophilic characteristics for more than two months. Micropatterned protein adsorption and micropatterned cell adhesion were successfully demonstrated using PEGDA-micropatterned PDMS surfaces, which were prepared by photo-induced graft polymerization using photomasks. The PEGDA-grafted PDMS exhibited useful characteristics for microfluidic devices (e.g. hydrophilicity, low protein adsorption, and low cell attachment). The technique presented in this study will be useful for surface modification of various research tools and devices. PMID:18242961

  11. A novel surface modification of carbon fiber for high-performance thermoplastic polyurethane composites

    NASA Astrophysics Data System (ADS)

    Zhang, Yuanyuan; Zhang, Yizhen; Liu, Yuan; Wang, Xinling; Yang, Bin

    2016-09-01

    Properties of carbon fiber (CF) reinforced composites depend largely on the interfacial bonding strength between fiber and the matrix. In the present work, CF was grafted by 4,4‧-diphenylmethane diisocyanate (MDI) molecules after electrochemical oxidation treatment. The existence of functional groups introduced to the fiber surface and the changes of surface roughness were confirmed by FTIR, AFM, XPS, SEM and Raman spectroscopy. To evaluate the possible applications of this surface modification of carbon fiber, we examined the mechanical properties as well as the friction and wear performance of pristine CF and MDI-CF reinforced thermoplastic polyurethane (TPU) composites with 5-30 wt.% fiber contents, and found that the mechanical properties of TPU composites were all significantly improved. It is remarkable that when fiber content was 30 wt.%, the tensile strength of TPU/MDI-CF was increased by 99.3%, which was greater than TPU/CF (53.2%), and the friction loss of TPU/MDI-CF was decreased by 49.09%. The results of DMA and SEM analysis indicated the positive effects of MDI modification on the interfacial bonding between fibers and matrix. We believed that this simple and effective method could be used to the development of surface modified carbon fiber for high-performance TPU.

  12. Plasma immersion ion implantation for the efficient surface modification of medical materials

    SciTech Connect

    Slabodchikov, Vladimir A. Borisov, Dmitry P. Kuznetsov, Vladimir M.

    2015-10-27

    The paper reports on a new method of plasma immersion ion implantation for the surface modification of medical materials using the example of nickel-titanium (NiTi) alloys much used for manufacturing medical implants. The chemical composition and surface properties of NiTi alloys doped with silicon by conventional ion implantation and by the proposed plasma immersion method are compared. It is shown that the new plasma immersion method is more efficient than conventional ion beam treatment and provides Si implantation into NiTi surface layers through a depth of a hundred nanometers at low bias voltages (400 V) and temperatures (≤150°C) of the substrate. The research results suggest that the chemical composition and surface properties of materials required for medicine, e.g., NiTi alloys, can be successfully attained through modification by the proposed method of plasma immersion ion implantation and by other methods based on the proposed vacuum equipment without using any conventional ion beam treatment.

  13. Surface modification and characterization of electrosprayed Sn-doped In2O3 thin films.

    PubMed

    Koo, Bon-Ryul; Ahn, Hyo-Jin

    2014-12-01

    We synthesized Sn-doped In2O3 (Indium tin oxide, ITO) thin films using electrospray and spin-coating. Scanning electron microscopy, atomic force spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Hall-effect measurement, and UV-vis spectrophotometry measurements were performed to investigate the morphological, structural, chemical, electrical, and optical properties of the electrosprayed ITO films with a sol-layer coating for surface modification. To obtain the optimum performance of the resultant ITO thin films after surface modification, we heat-treated them at four different temperatures of 450 degrees C (sample A), 550 degrees C (sample B), 650 degrees C (sample C), and 750 degrees C (sample D) using microwave heating. Surface modified ITO thin films calcined at 550 degrees C (sample B) using electrospray and spin-coating are observed to have superior resistivity (9.9 x 10(-3) 2 Ω x cm) and optical transmittance (-92.08%) owing to the improved densification of the ITO surface by spin-coating and the formation of uniform ITO thin films by electrospraying. PMID:25971111

  14. Selective deposition of conductive copper films on glass surfaces using femtosecond laser surface modification and electroless plating

    NASA Astrophysics Data System (ADS)

    Xu, Jian; Liao, Yang; Zeng, Huidan; Zhou, Zenghui; Sun, Haiyi; Song, Juan; Wang, Xinshun; Cheng, Ya; Xu, Zhizhan; Sugioka, Koji; Midorikawa, Katsumi

    2008-03-01

    In this paper, selective deposition of conductive copper films on glass surfaces is demonstrated with the assistance of femtosecond laser surface modification followed by electroless plating. Irradiation of femtosecond laser makes it possible to selectively deposit copper films in the irradiated area on glass surfaces coated with silver nitrate films. The influence of the laser direct writing parameters and the electroless plating process on the formation of copper films is discussed. Meanwhile, the electric properties of copper films are investigated, which confirms that copper films are conductive. A tentative mechanism of the selective deposition process is also proposed. In addition, the potential application of this technique for integrating electrical and thermal functions into microdevices is discussed.

  15. The effects of size and surface modification of amorphous silica particles on biodistribution and liver metabolism in mice

    NASA Astrophysics Data System (ADS)

    Lu, Xiaoyan; Ji, Cai; Jin, Tingting; Fan, Xiaohui

    2015-05-01

    Engineered nanoparticles, with unconventional properties, are promising platforms for biomedical applications. Since they may interact with a wide variety of biomolecules, it is critical to understand the impact of the physicochemical properties of engineered nanoparticles on biological systems. In this study, the effects of particle size and surface modification alone or in combination of amorphous silica particles (SPs) on biological responses were determined using a suite of general toxicological assessments and metabonomics analysis in mice model. Our results suggested that amino or carboxyl surface modification mitigated the liver toxicity of plain-surface SPs. 30 nm SPs with amino surface modification were found to be the most toxic SPs among all the surface-modified SP treatments at the same dosage. When treatment dose was increased, submicro-sized SPs with amino or carboxyl surface modification also induced liver toxicity. Biodistribution studies suggested that 70 nm SPs were mainly accumulated in liver and spleen regardless of surface modifications. Interestingly, these two organs exhibited different uptake trends. Furthermore, metabonomics studies indicated that surface modification plays a more dominant role to affect the liver metabolism than particle size.

  16. Surface modifications induced by bismuth on (0 0 1) GaAs surfaces

    NASA Astrophysics Data System (ADS)

    Jiang, W. Y.; Liu, J. Q.; So, M. G.; Myrtle, K.; Kavanagh, K. L.; Watkins, S. P.

    2005-04-01

    We report the identification of reflectance difference (RD) spectra for GaAs (0 0 1) surfaces in the presence of small quantities of trimethylbismuth (TMBi) vapor under organometallic vapor phase epitaxy (OMVPE) conditions. An RD spectrum similar to that observed from the previously reported ( 3×8) Sb-terminated surface of GaAs is reported, suggesting strong similarities between the Bi and Sb terminated surfaces. Because of the low vapor pressure of Bi, it is stable under extended hydrogen purges at growth temperatures of 450C. Whereas As or Sb coverage typically saturates at 1-2 monolayers on the GaAs (0 0 1) surface under OMVPE conditions, no saturation of the Bi coverage is observed in this work. Extended exposure to TMBi results in the formation of Bi islands whose size increase with exposure time and TMBi concentration.

  17. Toward potent antibiofilm degradable medical devices: a generic method for the antibacterial surface modification of polylactide.

    PubMed

    El Habnouni, Sarah; Lavigne, Jean-Philippe; Darcos, Vincent; Porsio, Barbara; Garric, Xavier; Coudane, Jean; Nottelet, Benjamin

    2013-08-01

    The effects of biomaterials on their environment must be carefully modulated in most biomedical applications. Among other approaches, this modulation can be obtained through the modification of the biomaterial surface. This paper proposes a simple and versatile strategy to produce non-leaching antibacterial polylactide (PLA) surfaces without any degradation of the polyester chains. The method is based on a one-pot procedure that provides a "clickable" PLA surface via anionic activation which is then functionalized with an antibacterial quaternized poly(2-(dimethylamino)ethyl methacrylate) (QPDMAEMA) by covalent immobilization on the surface. The anti-adherence and antibiofilm activities of modified PLA surfaces are assessed for different QPDMAEMA molecular weights and different quaternization agents. Antibacterial PLA surfaces are shown to be very active against Gram-negative and Gram-positive strains, with adherence reduction factors superior to 99.999% and a marked reduction in biofilm on the most potent surfaces. In addition to this substantial antibacterial activity, the proposed PLA surfaces are also cytocompatible, as demonstrated through the proliferation of L929 fibroblasts. PMID:23603533

  18. Active screen plasma surface modification of polycaprolactone to improve cell attachment.

    PubMed

    Fu, Xin; Sammons, Rachel L; Bertóti, Imre; Jenkins, Mike J; Dong, Hanshan

    2012-02-01

    To tailor polycaprolactone (PCL) surface properties for biomedical applications, film samples of PCL were surface modified by the active screen plasma nitriding (ASPN) technique. The chemical composition and structure were characterized by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The wettability of the surface modified polymers was investigated by contact angle and surface energy methods. Biocompatibility of the prepared PCL samples was evaluated in vitro using MC3T3-E1 osteoblast-like cells. The degradability was assessed by determining the self-degradation rate (catalyzed by lipase). The results show that ASPN surface modification can effectively improve osteoblast cell adhesion and spreading on the surface of PCL. The main change in chemical composition is the exchange of some carboxyl groups on the surface for hydroxyl groups. The active-screen plasma nitriding technique has been found to be an effective and practical method to effectively improve osteoblast cell adhesion and spreading on the PCL surface. Such changes have been attributed to the increase in wettablity and generation of new hydroxyl groups by plasma treatment. After active-screen plasma treatment, the PCL film is still degradable, but the enzymatic degradation rate is slower compared with untreated PCL film. PMID:22179939

  19. Non-textured laser modification of silica glass surface: Wettability control and flow channel formation

    NASA Astrophysics Data System (ADS)

    Aono, Yuko; Hirata, Atsushi; Tokura, Hitoshi

    2016-05-01

    Local wettability of silica glass surface is modified by infrared laser irradiation. The silica glass surface exhibits hydrophobic property in the presence of sbnd CF3 or sbnd (CH3)2 terminal functional groups, which are decomposed by thermal treatment, and degree of the decomposition depends on the applied heat. Laser irradiation can control the number of remaining functional groups according to the irradiation conditions; the contact angle of deionized water on the laser modified surfaces range from 100° to 40°. XPS analysis confirms that the variation in wettability corresponds to the number of remaining sbnd CF3 groups. The laser irradiation achieves surface modification without causing any cracks or damages to the surface, as observed by SEM and AFM; moreover, surface transparency to visible light and surface roughness remains unaffected. The proposed method is applied to plane flow channel systems. Dropped water spreads only on the hydrophilic and invisible line modified by the laser irradiation without formation of any grooves. This indicates that the modified line can act as a surface channel. Furthermore, self-transportation of liquid is also demonstrated on a channel with gradually-varied wettability along its length. A water droplet on a hydrophobic side is self-transported to a hydrophilic side due to contact-angle hysteresis force without any actuators or external forces.

  20. Surface modification of montmorillonite on surface Acid-base characteristics of clay and thermal stability of epoxy/clay nanocomposites.

    PubMed

    Park, Soo-Jin; Seo, Dong-Il; Lee, Jae-Rock

    2002-07-01

    In this work, the effect of surface treatments on smectitic clay was investigated in surface energetics and thermal behaviors of epoxy/clay nanocomposites. The pH values, X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR) were used to analyze the effect of cation exchange on clay surface and the exfoliation phenomenon of clay interlayer. The surface energetics of clay and thermal properties of epoxy/clay nanocomposites were investigated in contact angles and thermogravimetric analysis (TGA), respectively. From the experimental results, the surface modification of clay by dodecylammonium chloride led to the increases in both distance between silicate layers of about 8 A and surface acid values, as well as in the electron acceptor component (gamma(+)(s)) of surface free energy, resulting in improved interfacial adhesion between basic (or electron donor) epoxy resins and acidic (electron acceptor) clay interlayers. Also, the thermal stability of nanocomposites was highly superior to pure epoxy resin due to the presence of the well-dispersed clay nanolayer, which has a barrier property in a composite system. PMID:16290714

  1. Evaluation of Surface Modification as a Lunar Dust Mitigation Strategy for Thermal Control Surfaces

    NASA Technical Reports Server (NTRS)

    Gaier, James R.; Waters, Deborah L.; Misconin, Robert M.; Banks, Bruce A.; Crowder, Mark

    2011-01-01

    Three surface treatments were evaluated for their ability to lower the adhesion between lunar simulant dust and AZ93, AlFEP, and AgFEP thermal control surfaces under simulated lunar conditions. Samples were dusted in situ and exposed to a standardized puff of nitrogen gas. Thermal performance before dusting, after dusting, and after part of the dust was removed by the puff of gas, were compared to perform the assessment. None of the surface treatments was found to significantly affect the adhesion of lunar simulants to AZ93 thermal control paint. Oxygen ion beam texturing also did not lower the adhesion of lunar simulant dust to AlFEP or AgFEP. But a workfunction matching coating and a proprietary Ball Aerospace surface treatment were both found to significantly lower the adhesion of lunar simulants to AlFEP and AgFEP. Based on these results, it is recommended that all these two techniques be further explored as dust mitigation coatings for AlFEP and AgFEP thermal control surfaces.

  2. Surface modification of activated carbon for enhanced adsorption of perfluoroalkyl acids from aqueous solutions.

    PubMed

    Zhi, Yue; Liu, Jinxia

    2016-02-01

    The objective of the research was to examine the effect of increasing carbon surface basicity on uptake of perfluorooctane sulfonic (PFOS) and carboxylic acids (PFOA) by activated carbon. Granular activated carbons made from coal, coconut shell, wood, and phenolic-polymer-based activated carbon fibers were modified through high-temperature and ammonia gas treatments to facilitate systematical evaluation of the impact of basicity of different origins. Comparison of adsorption isotherms and adsorption distribution coefficients showed that the ammonia gas treatment was more effective than the high-temperature treatment in enhancing surface basicity. The resultant higher point of zero charges and total basicity (measured by total HCl uptake) correlated with improved adsorption affinity for PFOS and PFOA. The effectiveness of surface modification to enhance adsorption varied with carbon raw material. Wood-based carbons and activated carbon fibers showed enhancement by one to three orders of magnitudes while other materials could experience reduction in adsorption towards either PFOS or PFOA. PMID:26469934

  3. Inner Surface Modification of a Tube by Magnetic Glow-Arc Plasma Source Ion Implantation

    NASA Astrophysics Data System (ADS)

    Zhang, Gu-Ling; Wang, Jiu-Li; Wu, Xing-Fang; Feng, Wen-Ran; Chen, Guang-Liang; Gu, Wei-Chao; Niu, Er-Wu; Fan, Song-Hua; Liu, Chi-Zi; Yang, Si-Ze

    2006-05-01

    A new method named the magnetic glow-arc plasma source ion implantation (MGA-PSII) is proposed for inner surface modification of tubes. In MGA-PSII, under the control of an axial magnetic field, which is generated by an electric coil around the tube sample, glow arc plasma moves spirally into the tube from its two ends. A negative voltage applied on the tube realized its inner surface implantation. Titanium nitride (TiN) films are prepared on the inner surface of a stainless steel tube in diameter 90 mm and length 600 mm. Hardness tests show that the hardness at the tube centre is up to 20 GPa. XRD, XPS and AES analyses demonstrate that good quality of TiN films can be achieved.

  4. One-step surface modification of polyurethane using affinity binding peptides for enhanced fouling resistance.

    PubMed

    Wang, Yibing; Yu, Yong; Zhang, Liting; Qin, Peng; Wang, Ping

    2015-01-01

    Affinity binding peptides were examined for surface fabrication of synthetic polymeric materials. Peptides possessing strong binding affinities toward polyurethane (PU) were discovered via biopanning of M13 phage peptide library. The apparent binding constant (K(app)) was as high as 2.68 × 10(9) M(-1) with surface peptide density exceeded 1.8 μg/cm(2). Structural analysis showed that the ideal peptide had a high content (75%) of H-donor amino acid residues, and that intensified hydrogen bond interaction was the key driving force for the highly stable binding of peptides on PU. PU treated with such affinity peptides promises applications as low-fouling materials, as peptides increased its wettability and substantially reduced protein adsorption and cell adhesion. These results demonstrated a facile but highly efficient one-step strategy for surface property modification of polymeric materials for biotechnological applications. PMID:25732121

  5. Comparison of surface modifications of poly(ether urethanes) by chemical infusion and graft polymerization

    SciTech Connect

    Wrobleski, D.A.; Cash, D.L.; Hermes, R.E.

    1988-01-01

    Our approach to surface modification uses the chemical infusion process to introduce materials into the outermost layer of the polymeric material, thereby altering the surface without changing the bulk properties of the polymer. The infused materials may slowly diffuse out of the infusion layer if they are volatile or highly mobile. However, if polymeric infusant materials are employed, they may become chain entangled with the host polymer and result in a permanently modified surface. A second approach utilizes photo-initiated graft polymerization of poly(ether urethanes) with an appropriate monomer. We have explored both of these methods by examining the infusion of polyvinylpyrrolidone (PVP) and poly(ethylene glycol) (PEG) into commercially available poly(ether urethanes) and the graft polymerization of N-vinyl pyrrolidone onto poly(ether urethanes). Results are presented here. 7 refs., 1 tab.

  6. Surface Modification of Silver Nanowires for Morphology and Processing Control in Composite Transparent Electrodes.

    PubMed

    Liang, Zhiming; Graham, Kenneth R

    2015-10-01

    Silver nanowires are attractive components for a number of materials and applications, including silver nanowire (AgNW)-polymer composites, electrically conductive coatings, and transparent electrodes. In this manuscript, the ability of thiols with hydrophobic to ionic end groups to bind to AgNW surfaces is investigated, followed by how the polarity of the surface modifying thiol influences the morphological and electrical properties of both AgNW/PEDOT:PSS blend films and pure AgNW networks. Utilizing surface modification of AgNWs with sodium 3-mercapto-1-propanesulfonate (MPS), morphologically homogeneous AgNW/PEDOT:PSS thin films with an order of magnitude lower sheet resistance at similar transmittance values than unmodified AgNWs are obtained with a one-step processing method. Brief optimization of MPS-AgNW/PEDOT:PSS blends yields a sheet resistance of 22.6 Ω/□ at 81.4% transmittance. PMID:26389535

  7. Very high cycle fatigue behavior of SAE52100 bearing steel by ultrasonic nanocrystalline surface modification.

    PubMed

    Cho, In Shik; He, Yinsheng; Li, Kejian; Oh, Joo Yeon; Shin, Keesam; Lee, Chang Soon; Park, In Gyu

    2014-11-01

    In this paper, the SAE52100 bearing steel contained large quantities of cementite dispersed in ferrite matrix was subjected to the ultrasonic nanocrystalline surface modification (UNSM) treatment that aims for the extension of fatigue life. The microstructure and fatigue life of the untreated and treated specimens were studied by using electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM), and a developed ultra-high cycle fatigue test (UFT). After UNSM treatment, the coarse ferrite grains (- 10 μm) were refined to nanosize (- 200 nm), therefore, nanostructured surface layers were fabricated. Meanwhile, in the deformed layer, the number density and area fraction of cementite were increased up to - 400% and - 550%, respectively, which increased with the decrease in depth from the topmost treated surface. The improvement of hardness (from 200 Hv to 280 Hv) and high cycles fatigue strength by - 10% were considered the contribution of the developed nanostructure in the UNSM treated specimen. PMID:25958512

  8. Comparative temporal analysis of multiwalled carbon nanotube oxidation reactions: Evaluating chemical modifications on true nanotube surface

    NASA Astrophysics Data System (ADS)

    Pacheco, Flávia G.; Cotta, Alexandre A. C.; Gorgulho, Honória F.; Santos, Adelina P.; Macedo, Waldemar A. A.; Furtado, Clascídia A.

    2015-12-01

    The influence of extensive purification on oxidized multiwalled carbon nanotube surface composition was studied through the characterization and differentiation of the actual surface submitted to three oxidation methods: microwave-assisted acid oxidation, hydrogen peroxide reflux, and Fenton reaction. The oxidized samples were purified by a multi-step procedure including the sequential use of basic reflux and dispersion in dimethylformamide (DMF). The results showed a significant increase in the amount of oxidation debris with hydrogen peroxide and Fenton reaction times longer than 8 h and strong surface characteristic modification. With regard to sample purification, basic reflux led to a reduction in oxygenated group concentration of only 10% in the samples treated by acid oxidation. On the other hand, the subsequent use of DMF led to a further decrease in concentration of 39%, proving to be a more efficient method for the removal of oxidation debris.

  9. Laser and chemical surface modifications of titanium grade 2 for medical application

    NASA Astrophysics Data System (ADS)

    Kwaśniak, P.; Pura, J.; Zwolińska, M.; Wieciński, P.; Skarżyński, H.; Olszewski, L.; Marczak, J.; Garbacz, H.; Kurzydłowski, K. J.

    2015-05-01

    The article presents combined, chemical and physical approach to titanium surface functionalization designed for biomedical applications. The topography modification has been obtained by employing the double laser beam interference technique and chemical etching. In the outcome, clean and smooth Ti surface as well as periodic striated topography with the roughness range from nano- to micrometers were created. The obtained structures were characterized in terms of shape, roughness, chemical composition, mechanical properties and microstructures. In order to achieve all information, numerous of research methods have been used: scanning electron microscopy, atomic force microscopy, optical profilometry and microhardness measurements. Demonstrated methodology can be used as an effective tool for manufacturing controlled surface structures improving the bone-implants interactions.

  10. Modification of anodised aluminium surfaces using a picosecond fibre laser for printing applications.

    PubMed

    Ansari, I A; Watkins, K G; Sharp, M C; Hutchinson, R A; Potts, R M; Clowes, J

    2012-06-01

    The use of an ultrafast fibre laser at a wavelength of 1064 nm has allowed the surface modification of anodised aluminium plates coated with a 2 micron thick anodised layer for potential industrial applications. The micro- and nano-scale structuring of the anodised aluminium using picosecond pulses of approximately 25 ps duration at 200 kHz repetition rate was investigated. The interaction of the laser with the substrate created a hydrophilic surface, giving a contact angle of less than 10 degrees. On examination under a Scanning Electron Microscope (SEM), a morphology created due to laser induced spallation was observed. It has been found that these laser processed hydrophilic surfaces revert to a hydrophobic state with time. This has potential for application in the printing industry and offers reusability and sustainability of the process materials. This has been confirmed in initial trials. PMID:22905556

  11. Modification of the surface morphology of silicon(111) with growth temperature

    NASA Astrophysics Data System (ADS)

    Charles, M.; Hartmann, J. M.

    2013-02-01

    Silicon epitaxy has been performed on nominally on-axis silicon(111) substrates by reduced pressure chemical vapour deposition at a variety of temperatures, keeping a constant deposited thickness. Atomic force microscopy of the resulting growth surfaces shows well defined step edges, and a clear modification of the surface morphology from smooth terraces to triangular island structures as the growth temperature is reduced. The radius of curvature of these growth forms links the diffusion distance to an Arrhenius plot, with a value of EA > 400 kJ/mol, which is nearly double the energy of a silicon-silicon bond (226 kJ/mol). This implies that the silicon atoms are held on the two dimensional surface by more than just a single Sisbnd Si bond. In addition, small residual islands on the smooth terraces have a similar density to that seen in similar growth studies on silicon(100).

  12. Preliminary study of surface modification of 3D Poly (ɛ - caprolactone) scaffolds by ultrashort laser irradiation

    NASA Astrophysics Data System (ADS)

    Daskalova, A.; Bliznakova, I.; Iordanova, E.; Yankov, G.; Grozeva, M.; Ostrowska, B.

    2016-02-01

    Three - dimensional poly (e- caprolactone) (PCL) scaffolds as suitable biocompatible material for manufacturing tissue replacements are utilized for tissue engineering purposes. The porous structures are fabricated by rapid prototyping method (Bioscaffolder) based on hypodermic dispensing process. The consecution of experiments demonstrated the possibility on creation of surface micro formations, applying different laser fluences, at 1 kHz repetition rate for fixed time of exposure 1 sec at 800 nm central wavelength. The combination of both methods offers possibilities for successful production of 3D matrices with modified surfaces. The obtained results of laser - induced surface modifications of PCL demonstrate the potential of the method to microprocess this kind of material for possible applications in regenerative medicine.

  13. The use of surface modification techniques for the corrosion protection of aluminum and aluminum alloys

    SciTech Connect

    Natishan, P.M.; McCafferty, E.; Donovon, E.P.; Hubler, G.K.

    1995-12-31

    Surface modification techniques such as ion beam assisted deposition (IBAD) and radio frequency plasma enhanced chemical vapor deposition (PECVD) offer a means to produce surfaces with unique and improved properties. This paper reviews the advantages of the IBAD and PECVD processes and discusses the preparation and pitting corrosion behavior of IBAD modified aluminum surfaces and PECVD coatings on a 7075 aluminum alloy. Pitting potential values for the base materials and for the base materials with silicon nitride IBAD, tantalum oxide IBAD, or PECVD diamond-like carbon coatings were determined in deaerated 0.1M NaCl solutions. The thickness of the modified region ranged from 0.01 to 5.0 {micro}m. All three coatings improved the resistance to pit initiation.

  14. Surface modification during Nd:YAG (1064 nm) pulsed laser cleaning of organic fibrous materials

    NASA Astrophysics Data System (ADS)

    Strlič, Matija; Kolar, Jana; Šelih, Vid-Simon; Marinček, Marko

    2003-02-01

    Formation of yellow chromophores on artificially soiled surfaces of cellulose sheets, rag paper, linen, cotton, wool and silk during Nd:YAG (1064 nm) pulsed laser cleaning was followed using Vis and FTIR diffuse reflectance spectrometry. Content of reducing carbonyl groups and changes in FTIR reflectance spectra of cellulose are indicative of surface chemical modifications typical of thermal degradation at elevated temperatures. Two types of soiling were used: well-characterised natural dust and carbon powder and no difference in laser-induced formation of chromophores on material surface was observed at low deposit densities. The influence of laser fluence and number of repetitions was studied and a single pulse of a higher fluence (1 J cm -1) is in general more advisable. No bleaching of the chromophores formed was noticed after repeated treatments.

  15. Surface modification of ferritic and Ni based alloys for improved oxidation resistance of SOFC interconnect applications

    SciTech Connect

    Jablonski, Paul D.; Alman, David E.; Kung, Steven C.

    2005-08-01

    This research is aimed at evaluating a surface modification of ferritic stainless steels (Type-430 and Crofer 22APU) and nickel-base alloys (Haynes 230) for use in the SOFC temperature range of 700 to 800°C. A surface treatment was devised to enhance the stability of the base metal oxide that forms and to reduce the oxidation rate of the materials at high temperature. Oxidation tests (in wet air; treated and untreated) were conducted at 800°C to evaulate the corrosion resistance of the alloys. It was found that the surface treatment improved the oxidation resistance of all the alloys tested. However, the treatment improved the performance of 430SS more than that of the other alloys.

  16. Water transport mechanism through open capillaries analyzed by direct surface modifications on biological surfaces.

    PubMed

    Ishii, Daisuke; Horiguchi, Hiroko; Hirai, Yuji; Yabu, Hiroshi; Matsuo, Yasutaka; Ijiro, Kuniharu; Tsujii, Kaoru; Shimozawa, Tateo; Hariyama, Takahiko; Shimomura, Masatsugu

    2013-01-01

    Some small animals only use water transport mechanisms passively driven by surface energies. However, little is known about passive water transport mechanisms because it is difficult to measure the wettability of microstructures in small areas and determine the chemistry of biological surfaces. Herein, we developed to directly analyse the structural effects of wettability of chemically modified biological surfaces by using a nanoliter volume water droplet and a hi-speed video system. The wharf roach Ligia exotica transports water only by using open capillaries in its legs containing hair- and paddle-like microstructures. The structural effects of legs chemically modified with a self-assembled monolayer were analysed, so that the wharf roach has a smart water transport system passively driven by differences of wettability between the microstructures. We anticipate that this passive water transport mechanism may inspire novel biomimetic fluid manipulations with or without a gravitational field. PMID:24149467

  17. Effect of surface modification and UVA photoactivation on antibacterial bioactivity of zinc oxide powder

    NASA Astrophysics Data System (ADS)

    Ann, Ling Chuo; Mahmud, Shahrom; Bakhori, Siti Khadijah Mohd; Sirelkhatim, Amna; Mohamad, Dasmawati; Hasan, Habsah; Seeni, Azman; Rahman, Rosliza Abdul

    2014-02-01

    The effects of surface modification of zinc oxide (ZnO) powder and UVA illumination on the powder towards Escherichia coli and Staphylococcus aureus were investigated. FESEM-EDS results showed that oxygen annealing increased the O:Zn ratio on the surface of ZnO-rod and ZnO-plate samples. Surface conductances of ZnO-rod and ZnO-plate pellets were reduced from 1.05 nS to 0.15 nS and 1.34 nS to 0.23 nS, respectively. Meanwhile, UVA illumination on the surface of the ZnO-rod and ZnO-plate samples was found to improve surface conductance to 7.08 nS and 6.51 nS, respectively, due to the release of charge carrier. Photoluminescence results revealed that oxygen annealing halved the UV emission intensity and green emission intensity, presumably caused by oxygen absorption in the ZnO lattice. The antibacterial results showed that oxygen-treated ZnO exhibited slightly higher growth inhibition on E. coli and S. aureus compared with unannealed ZnO. UVA illumination on ZnO causes the greatest inhibition toward E. coli and S. aureus. Under the UVA excitation, the inhibition of E. coli increased by 18% (ZnO-rod) and 13% (ZnO-plate) while the inhibition of S. aureus increased by 22% (ZnO-rod) and 21% (ZnO-plate). Release of reactive oxygen species were proposed in antibacterial mechanisms, which were aided by surface modification and UVA photoactivation. The reactive oxygen species disrupted the DNA and protein synthesis of the bacterial cell, causing bacteriostatic effects toward E. coli and S. aureus.

  18. Facile hydrophobicity/hydrophilicity modification of SMP surface based on metal constrained cracking

    NASA Astrophysics Data System (ADS)

    Han, Yu; Li, Peng; Zhao, Liangyu; Wang, Wenxin; Leng, Jinsong; Jin, Peng

    2015-04-01

    This study demonstrates an easy way to change surface characteristics, the water contact angle on styrene based shape memory polymer (SMP) surface alters before and after cracking formation and recovery. The contact angle of water on the original SMP surface is about 85 degree, after coating with Al and then kneading from side face at glass transition temperature Tg, cracking appeared both on Al film and SMP; cooling down and removing the Al film, cracks remain on SMP surface while the contact angle reduced to about 25 degree. When reheated above Tg, the cracks disappeared, and the contact angle go back to about 85 degree. The thin Al film bonded on SMP surface was coated by spurting, that constrains the deformation of SMP. Heating above Tg, there are complex interactions between soft SMP and hard metal film under kneading. The thin metal film cracked first with the considerable deformation of soft polymer, whereafter, the polymer was ripped by the metal cracks thus polymer cracked as well. Cracks on SMP can be fixed cooling down Tg, while reheated, cracks shrinking and the SMP recovers to its original smooth surface. Surface topography changed dramatically while chemical composition showed no change during the deformation and recovery cycle, as presented by SEM and EDS. Furthermore, the wetting cycle is repeatable. This facile method can be easily extended to the hydropobicity/hydrophilicity modification of other stimuli-responsive polymers and put forward many potential applications, such as microfluidic switching and molecule capture and release.

  19. Facile surface modification of silicone rubber with zwitterionic polymers for improving blood compatibility.

    PubMed

    Liu, Pingsheng; Chen, Qiang; Yuan, Bo; Chen, Mengzhou; Wu, Shishan; Lin, Sicong; Shen, Jian

    2013-10-01

    A facile approach to modify silicone rubber (SR) membrane for improving the blood compatibility was investigated. The hydrophobic SR surface was firstly activated by air plasma, after which an initiator was immobilized on the activated surface for atom transfer radical polymerization (ATRP). Three zwitterionic polymers were then grafted from SR membrane via surface-initiated atom transfer radical polymerization (SI-ATRP). The surface composition, wettability, and morphology of the membranes before and after modification were characterized by X-ray photoelectron spectroscopy (XPS), static water contact angle (WCA) measurement, and atomic force microscopy (AFM). Results showed that zwitterionic polymers were successfully grafted from SR surfaces, which remarkably improved the wettability of the SR surface. The blood compatibility of the membranes was evaluated by protein adsorption and platelet adhesion tests in vitro. As observed, all the zwitterionic polymer modified surfaces have improved resistance to nonspecific protein adsorption and have excellent resistance to platelet adhesion, showing significantly improved blood compatibility. This work should inspire many creative uses of SR based materials for biomedical applications such as vessel, catheter, and microfluidics. PMID:23910289

  20. Surface modification and characterization of functional oxide ceramics using CO 2 laser

    NASA Astrophysics Data System (ADS)

    Okutomi, Mamoru; Nomura, Haruhiko; Tsukamoto, Takeyo; Dahotre, N. B.; Shen, Honglie

    2000-06-01

    Surface of powder-sintered oxides such as superconductor and ferroelectric barium titanate ceramics were recrystallized using scanned CO 2 laser irradiation. Conventionally, the ceramic is sintered at high temperature, to increase adhesive forces between powdered ceramic grain. During such process, however, many micro-pores and -cracks are produced owing to large shrinkage of fine aggregate grains into the surface layer. Superconductor surface does not allow the flow of superconductor current uniformly and the flow is concentrated on the surface. Thus properties of superconductor are so sensitive to their surface condition that some substantial modifications of the material are necessary. To clarify this issues, both sample of the powder-sintered superconductor YBa xSr 2- xCu 3O 7- y and the BaTiO 3 ceramic film were modified by laser irradiation to recrystallize only the surface layer. Their microstructural features in the surface, the characteristic of superconducting and ferroelectric have been investigated. Thus laser-scanning process appears to be suited to generating large grains with preferred orientation by changing of irradiation condition.

  1. Hydrophobic modification of wood via surface-initiated ARGET ATRP of MMA

    NASA Astrophysics Data System (ADS)

    Fu, Yanchun; Li, Gang; Yu, Haipeng; Liu, Yixing

    2012-01-01

    To convert the hydrophilic surface of wood into a hydrophobic surface, the present study investigated activators regenerated by electron transfer for atom transfer radical polymerization (ARGET ATRP) as a method of grafting methyl methacrylate (MMA) onto the wood surface. The wood treated with 2-bromoisobutyryl bromide and with the subsequently attached MMA via ARGET ATRP under different polymerization times (2 h, 4 h, 6 h, 8 h) were examined using scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. All the analyses confirmed that PMMA had been grafted onto the wood surface. Water contact angle measurement proved that the covering layer of PMMA on wood made the surface hydrophobic. Polymerization time had a positive influence on the contact angle value and higher contact angle can be produced with the prolongation of the polymerization time. When the reaction time was extended to 8 h, the contact angle of treated wood surface reached 130° in the beginning, and remained at 116° after 60 s. The ARGET ATRP method may raise an alteration on the wood surface modification.

  2. Surface modification of titanium using steel slag ball and shot blasting treatment for biomedical implant applications

    NASA Astrophysics Data System (ADS)

    Arifvianto, Budi; Suyitno; Mahardika, Muslim

    2013-08-01

    Surface modification is often performed using grit or shot blasting treatment for improving the performances of biomedical implants. The effects of blasting treatments using steel slag balls and spherical shots on the surface and subsurface of titanium were studied in this paper. The treatments were conducted for 60-300 s using 2-5 mm steel slag balls and 3.18 mm spherical shots. The surface morphology, roughness, and elemental composition of titanium specimens were examined prior to and after the treatments. Irregular and rough titanium surfaces were formed after the treatment with the steel slag balls instead of the spherical shots. The former treatment also introduced some bioactive elements on the titanium surface, but the latter one yielded a harder surface layer. In conclusion, both steel slag ball and shot blasting treatment have their own specialization in modifying the surface of metallic biomaterials. Steel slag ball blasting is potential for improving the osseointegration quality of implants; but the shot blasting is more appropriate for improving the mechanical properties of temporary and load bearing implants, such as osteosynthesis plates.

  3. Novel approaches to the surface modification of glass by thermo-electric poling

    NASA Astrophysics Data System (ADS)

    Smith, Nicholas J.

    Many new and emerging applications of glass rely critically on surface properties, and have led to an ever-increasing demand for methods to controllably modify glass surfaces as a pathway to enhanced properties. The genesis of this thesis arose from such pursuits, wherein the thermo-electric poling of glass---encompassing treatment with high voltage and blocking electrodes at moderate temperatures---was found to provide a fertile research area. Versatile in its application to a variety of glasses, as well as the diversity of phenomena it produces, several novel approaches to the thermo-electric treatments of multicomponent glass are carried out in this work. This included (1) poling to produce normally-forbidden, second-order nonlinearity in high breakdown strength glasses as a potential avenue to greater nonlinear coefficients; (2) capitalizing on poling-induced modifications toward the novel end of manipulating the observed breakdown strength of glass; and (3) venturing outside the "typical" parameter space of poling treatments in order to realize even greater modifications to surface composition and structure by electrolyzing the glass network. The primary outcome for the first study indicates that, contrary to the usual assumption, the stored internal field from poling is limited to a substantial fraction of the intrinsic breakdown strength, and seemingly in a broad range of glass systems. This is most likely due to nonlinear conduction effects at the high poling temperatures. Meanwhile, the results of the second study indicate that the observed breakdown strength of glass is minimally influenced by the presence of a stored space charge field, and is likely attributable to the presence of the modified surface layer concentrating the applied voltage. The results of the last study provide the most intriguing possibilities for extensive and stable surface modification. Applied to a model alkali-free glass, a nanoscale layer is formed adjacent to the anodic surface

  4. Enhancement of biocompatibility of nickel-titanium by laser surface modification technology

    NASA Astrophysics Data System (ADS)

    Ng, Ka Wai

    Nickel Titanium is a relatively new biomaterial that has attracted research interest for biomedical application. The good biocompatibility with specific functional properties of shape memory effect and superelasticity creates a smart material for medical applications. However, there are still concerns on nickel ion release of this alloy if it is going to be implanted for a long time. Nickel ion is carcinogenic and also causes allergic response and degeneration of muscle tissue. The subsequent release of Ni+ ions into the body system is fatal for the long term application of this alloy in the human body. To improve the long term biocompatibility and corrosion properties of NiTi, different surface treatment techniques have been investigated but no optimum technique has been established yet. This project will investigate the feasibility of applying laser surface alloying technique to improve the corrosion resistance and biocompatibility of NiTi in simulated body fluid condition. This thesis summarizes the result of laser surface modification of NiTi with Mo, Nb and Co using CO2 laser. The modified layer, which is free of microcracks and pores, acts as physical barrier to reduce nickel release and enhance the surface properties. The hardness values of the Mo-alloyed NiTi, Nb-alloyed NiTi and Co-alloyed NiTi surface were found to be three to four times harder than the NiTi substrate. Corrosion polarization tests also showed that the alloyed NiTi are significantly more resistant than the NiTi alloy. The release of Ni ions can be greatly reduced after laser surface alloying NiTi with Mo, Nb and Co. The improvement in wettability characteristics, the growth of the apatite on the specimen's surface and the adhesion of cell confirm the good biocompatibility after laser surface alloying. It is concluded that laser surface alloying is one of the potential technique not only to improve the corrosion resistance with low nickel release rate, but also retain the good

  5. Improved Thermoelectric Performances of SrTiO3 Ceramic Doped with Nb by Surface Modification of Nanosized Titania.

    PubMed

    Li, Enzhu; Wang, Ning; He, Hongcai; Chen, Haijun

    2016-12-01

    Nb-doped SrTiO3 ceramics doped with the surface modification of nanosized titania was prepared via liquid phase deposition approach and subsequent sintered in an Ar atmosphere. The surface modification of nanosized titania significantly improved the ratio of the electrical conductivity to thermal conductivity of SrTiO3 ceramic doped with Nb, and has little impact on the Seebeck coefficient, thus obviously improving the dimensionless thermoelectric figure of merit (ZT value). The surface modification of nanosized titania is a much better method to lower the thermal conductivity and to enhance the electrical conductivity than the mechanical mixing process of nanosized titania. The highest ZT value of 0.33 at 900 K was obtained. The reason for the improved thermoelectric performances by the surface modification of nano-sized titania was preliminary investigated. PMID:27067736

  6. Improved Thermoelectric Performances of SrTiO3 Ceramic Doped with Nb by Surface Modification of Nanosized Titania

    NASA Astrophysics Data System (ADS)

    Li, Enzhu; Wang, Ning; He, Hongcai; Chen, Haijun

    2016-04-01

    Nb-doped SrTiO3 ceramics doped with the surface modification of nanosized titania was prepared via liquid phase deposition approach and subsequent sintered in an Ar atmosphere. The surface modification of nanosized titania significantly improved the ratio of the electrical conductivity to thermal conductivity of SrTiO3 ceramic doped with Nb, and has little impact on the Seebeck coefficient, thus obviously improving the dimensionless thermoelectric figure of merit ( ZT value). The surface modification of nanosized titania is a much better method to lower the thermal conductivity and to enhance the electrical conductivity than the mechanical mixing process of nanosized titania. The highest ZT value of 0.33 at 900 K was obtained. The reason for the improved thermoelectric performances by the surface modification of nano-sized titania was preliminary investigated.

  7. Identification and mitigation of T-S waves using localized dynamic surface modification

    NASA Astrophysics Data System (ADS)

    Amitay, Michael; Tuna, Burak A.; Dell'Orso, Haley

    2016-06-01

    The control of transition from a laminar to a turbulent flow over a flat plate using localized dynamic surface modifications was explored experimentally in Rensselaer Polytechnic Institute's subsonic wind tunnel. Dynamic surface modification, via a pair of Piezoelectrically Driven Oscillating Surface (PDOS) actuators, was used to excite and control the T-S wave over a flat plate. Creating an upstream, localized small disturbance at the most amplified frequency of fact = 250 Hz led to phase-locking the T-S wave. This enabled observation of the excited T-S wave using phase-locked stereoscopic particle image velocimetry. The growth of the T-S wave as it moved downstream was also measured using this technique (25% growth over four wavelengths of the excited wave). Activation of a downstream PDOS actuator (in addition to the upstream PDOS) at the appropriate amplitude and phase shift resulted in attenuation of the peak amplitude of the coherent velocity fluctuations (by up to 68%) and a substantial reduction of the degree of coherence of the T-S wave. Since the PDOS actuators used in this work were localized, the effect of the control strategy was confined to the region directly downstream of the PDOS actuator.

  8. Effect of carbon surface modification with dimethylamine on reactive adsorption of NO(x).

    PubMed

    Deliyanni, Eleni; Bandosz, Teresa J

    2011-03-01

    The wood-based activated carbon, either as received or oxidized with nitric acid, was exposed to dimethylamine vapors. This modification was expected to introduce nitrogen groups. Then, the modified samples were used as adsorbents of NO(2) under dynamic conditions. Both NO(2) breakthrough curves and the NO concentration curves were recorded. The samples before and after exposure to NO(2) were characterized using adsorption of nitrogen, elemental analysis, potentiometric titration, FTIR, and thermal analysis. Modifications with amines resulted in an increase in NO(2) adsorption and in a decrease in NO emission. The effects were more visible when oxidation was used as a pretreatment of the carbon surface. This process increased the incorporation of nitrogen to the carbon matrix via acid-based reactions resulting in the formation of amides and amine carboxylic salts. Besides this, dimethylamine was strongly adsorbed on the carbon surface via hydrogen bonding with oxygen-containing groups. When the samples were exposed to nitrogen dioxide, there was an indication that nitramine and nitrosoamine were formed in the reactions of NO(2) with either amides or amines. In the reactions of amines with NO, nitrosoamines are the likely products. As a next step, the surface of the carbon matrix is reoxidized by NO(2), which is accompanied by the release of NO. PMID:21188988

  9. Preparation of coatings and surface modification by plasma and thermal processes

    NASA Astrophysics Data System (ADS)

    Yamashina, Toshiro; Hino, Tomoaki

    1987-05-01

    The application of various plasma and ion beam processes for the production of coatings and surface modification of materials, are reviewed. We describe, in particular, cold plasma techniques for the preparation of nitrides, carbides, oxides, bondes and so on and ion implantation techniques for modification of surfaces and interfaces by ion beam mixing to form alloys and chemical compounds on materials. Further, we present our recent collaborative studies on in situ coatings by a dc glow discharge of H 2 + CH 4 gas in torus devices. The carbon coatings deposited on surface probes at liner positions of TEXTOR and JIPPT-IIU are characterized in terms of depth composition profiles, chemical binding states and hydrogen concentration. Properties of these coatings produced by the dc glow discharge are compared with those by an ECR plasma and by a thermal decomposition of hydrocarbons at high temperature. Finally, our recent results on the formation of ceramics by the exposure of Tokamak plasmas and thermal heating will be discussed. TiC layers on a Ti-coated graphite probe and TiB x layers on a B-coated Ti probe were formed after the exposure to the scrape-off layer plasma in JIPPT-IIU, and TiC-TiN double layers on Ti-coated stainless steels were formed by vacuum heating at 600-1000°C.

  10. In situ analysis of ion-induced polymer surface modification using secondary ion mass spectroscopy

    NASA Astrophysics Data System (ADS)

    Okuji, Shigeto; Kitazawa, Hideaki; Takeda, Yoshihiko

    2016-06-01

    We have investigated the surface modification process consisting of ion irradiation immediately followed by exposure to ambient gas for three types of polymers having the same main chain, sbnd Csbnd Csbnd , but different atoms bound to the main chain, using in situ secondary ion mass spectroscopy. The polymers' surface was irradiated with 30 keV Au ions at a total fluence for up to 1 × 1017 cm-2 and exposed to ambient gas in a ultra-high-vacuum chamber (1 × 10-6 Pa) for 30 min after the ion irradiation. Low density polyethylene mainly exhibited a hydrogen dissociation during the ion irradiation and a recombination with hydrogen atoms by the exposure, polytetrafluoroethylene mainly showed a main chain scission and no recombination during the exposure, and polyvinylidene difluoride lost hydrogen and fluorine atoms by the ion irradiation and partially recombined with hydrogen and fluorine atoms upon the exposure. The deposited energy density on the polymer surfaces reflects the dependence of the modification on the incident ion species, Au or Ga ions.

  11. Surface modification of polymeric substrates by plasma-based ion implantation

    NASA Astrophysics Data System (ADS)

    Okuji, S.; Sekiya, M.; Nakabayashi, M.; Endo, H.; Sakudo, N.; Nagai, K.

    2006-01-01

    Plasma-based ion implantation (PBII) as a tool for polymer modification is studied. Polymeric films have good performances for flexible use, such as food packaging or electronic devices. Compared with inorganic rigid materials, polymers generally have large permeability for gases and moisture, which causes packaged contents and devices to degrade. In order to add a barrier function, surface of polymeric films are modified by PBII. One of the advantageous features of this method over deposition is that the modified surface does not have peeling problem. Besides, micro-cracks due to mechanical stress in the modified layer can be decreased. From the standpoint of mass production, conventional ion implantation that needs low-pressure environment of less than 10-3 Pa is not suitable for continuous large-area processing, while PBII works at rather higher pressure of several Pa. In terms of issues mentioned above, PBII is one of the most expected techniques for modification on flexible substrates. However, the mechanism how the barrier function appears by ion implantation is not well explained so far. In this study, various kinds of polymeric films, including polyethyleneterephthalate (PET), are modified by PBII and their barrier characteristics that depend on the ion dose are evaluated. In order to investigate correlations of the barrier function with implanted ions, modified surface is analyzed with X-ray photoelectron spectroscopy (XPS). It is assumed that the diffusion and sorption coefficients are changed by ion implantation, resulting in higher barrier function.

  12. Surface modification of poly(ethylene terephthalate) fabric via photo-chemical reaction of dimethylaminopropyl methacrylamide

    NASA Astrophysics Data System (ADS)

    Mohamed, Nasser H.; Bahners, Thomas; Wego, Andreas; Gutmann, Jochen S.; Ulbricht, Mathias

    2012-10-01

    Photo-chemical reactions and surface modifications of poly(ethylene terephthalate) (PET) fabrics with the monomer dimethylaminopropyl methacrylamide (DMAPMA) and benzophenone (BP) as photo-initiator using a broad-band UV lamp source were investigated. The tertiary amino groups of the grafted poly(DMAPMA) chains were subsequently quaternized with alkyl bromides of different chain lengths to establish antibacterial activity. The surface composition, structure and morphology of modified PET fabrics were characterized by Fourier transform infrared spectroscopy (FTIR/ATR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). To evaluate the amount of quaternary and tertiary ammonium groups on the modified surface, PET was dyed with an acid dye which binds to the ammonium groups. Therefore, the color depth is a direct indicator of the amount of ammonium groups. The resulting antibacterial activity of the modified PET fabrics was tested with Escherichia coli. The results of all experiments show that a photochemical modification of PET is possible using DMAPMA, benzophenone and UV light. Also, the quaternization of tertiary amino groups as well as the increase in antibacterial activity of the modified PET by the established quaternary ammonium groups were successful.

  13. Fatigue Characteristics of SKD-61 by Ultrasonic Nanocrystal Surface Modification Technology Under Static Load Variation

    NASA Astrophysics Data System (ADS)

    Suh, Chang-Min; Lee, Moon-Hwan; Pyoun, Young-Sik

    At first, the specimens of SKD-61 are prepared and tested to verify the effects of ultrasonic nano-crystal surface modification (UNSM) technology on the variation of mechanical properties under static load variation. 20 kHz frequency was applied to the ball tip, and the applied static forces were changed three kinds of load level 40, 60, and 80 N, respectively. The grain size of SKD-61 surface treated by UNSM becomes very fine to nano-scale crystal and structure is observed till certain depth. The compressive residual stress becomes -810, -1200 and -1400 MPa to a 150 µm depth after the UNSM process according to three kinds of load level 40, 60, and 80 N, respectively. Fatigue limits of 107 cycles are increased by 8.3, 11.2, and 17.9% after UNSM at the smooth specimen according to three kinds of load level, respectively. Interior-originating fracture, fish-eye crack, occurs after UNSM because of a nano structured modification by a surface plastic deformation and compressive residual stress in the case of the smooth specimen. UNSM improves the mechanical properties effectively and is becoming a practical method to improve the service life of the trimming knives. Productivity and reliability of a cold rolling process have improved more than 2 times by the application of the UNSM trimming knives.

  14. Modification of Surface Layers by Surfacing Intermetallic Coatings with Variable Properties

    NASA Astrophysics Data System (ADS)

    Makeev, D. N.; Zakharov, O. V.; Vinogradov, A. N.; Kochetkov, A. V.

    2016-02-01

    The paper considers the possibility of forming coating layers for parts within wide limits of microhardness. The technology uses surfacing of intermetallic coatings provided by a unique experimental setup. Theoretical and experimental dependence of the coating layer microhardness on the filler concentration using the changes in the speed of the filler wire feed and current intensity were determined.

  15. Enhanced surface functionality via plasma modification and plasma deposition techniques to create more biologically relevant materials

    NASA Astrophysics Data System (ADS)

    Shearer, Jeffrey C.

    Functionalizing nanoparticles and other unusually shaped substrates to create more biologically relevant materials has become central to a wide range of research programs. One of the primary challenges in this field is creating highly functionalized surfaces without modifying the underlying bulk material. Traditional wet chemistry techniques utilize thin film depositions to functionalize nanomaterials with oxygen and nitrogen containing functional groups, such as --OH and --NHx. These functional groups can serve to create surfaces that are amenable to cell adhesion or can act as reactive groups for further attachment of larger structures, such as macromolecules or antiviral agents. Additional layers, such as SiO2, are often added between the nanomaterial and the functionalized coating to act as a barrier films, adhesion layers, and to increase overall hydrophilicity. However, some wet chemistry techniques can damage the bulk material during processing. This dissertation examines the use of plasma processing as an alternative method for producing these highly functionalized surfaces on nanoparticles and polymeric scaffolds through the use of plasma modification and plasma enhanced chemical vapor deposition techniques. Specifically, this dissertation will focus on (1) plasma deposition of SiO2 barrier films on nanoparticle substrates; (2) surface functionalization of amine and alcohol groups through (a) plasma co-polymerization and (b) plasma modification; and (3) the design and construction of plasma hardware to facilitate plasma processing of nanoparticles and polymeric scaffolds. The body of work presented herein first examines the fabrication of composite nanoparticles by plasma processing. SiOxC y and hexylamine films were coated onto TiO2 nanoparticles to demonstrate enhanced water dispersion properties. Continuous wave and pulsed allyl alcohol plasmas were used to produce highly functionalized Fe2 O3 supported nanoparticles. Specifically, film composition was

  16. One-step surface modification of poly(dimethylsiloxane) by undecylenic acid

    NASA Astrophysics Data System (ADS)

    Zhou, Jinwen; McInnes, Steven J. P.; Md Jani, Abdul Mutalib; Ellis, Amanda V.; Voelcker, Nicolas H.

    2008-12-01

    Poly(dimethylsiloxane) (PDMS) is a popular material for microfluidic devices due to its relatively low cost, ease of fabrication, oxygen permeability and optical transmission characteristics. However, its highly hydrophobic surface is still the main factor limiting its wide application, in particular as a material for biointerfaces. A simple and rapid method to form a relatively stable hydrophilised PDMS surface is reported in this paper. The PDMS surface was treated with pure undecylenic acid (UDA) for 10 min, 1 h and 1 day at 80 °C in a sealed container. The effects of the surface modification were investigated using water contact angle (WCA) measurements, Fourier transform infrared spectroscopy in attenuated total reflection mode (FTIR-ATR), and streaming zeta-potential analysis. The water contact angle of 1 day UDAmodified PDMS was found to decrease from that of native PDMS (110 °) to 75 °, demonstrating an increase in wettability of the surface. A distinctive peak at 1715 cm-1 in the FTIR-ATR spectra after UDA treatment was representative of carboxylation of the PDMS surface. The measured zeta-potential (ζ) at pH 4 changed from -27 mV for pure PDMS to -19 mV after UDA treatment. In order to confirm carboxylation of the surface visually, Lucifer Yellow CH fluorescence dye was reacted via a condensation reaction to the 1 day UDA modified PDMS surface. Fluorescent microscopy showed Lucifer Yellow CH fluorescence on the carboxylated surface, but not on the pure PDMS surface. Stability experiments were also performed showing that 1 day modified UDA samples were stable in both MilliQ water at 50 °C for 17 h, and in a desiccator at room temperature for 19.5 h.

  17. Surface Modification of Gel-Free Microchannel Surface Electrophoresis Device for DNA Identification

    NASA Astrophysics Data System (ADS)

    Lee, Hyun Ho; Kuo, Yue

    2008-04-01

    A gel-free microchannel electrophoresis device for DNA separation and identification was studied. DNA fragments ranging from 3.5 to 21.2 kbp were effectively separated and identified. The channel's bottom surface was composed of silicon wafer or glass, and the channel wall was composed of SU-8 photoresist. The channel surface was modified with various solutions or plasmas. The separated DNA on the detection electrode was confirmed by electron spectroscopy for chemical analysis. DNA mobility on the glass substrate was higher than that on the Si substrate. In addition, the increase of the ionic strength of the solution on the device decreased the mobility of DNA. In summary, this new device is applicable to large DNA samples.

  18. Surface modification of TiO₂ nanocrystals by WO(x) coating or wrapping: solvothermal synthesis and enhanced surface chemistry.

    PubMed

    Epifani, Mauro; Díaz, Raül; Force, Carmen; Comini, Elisabetta; Manzanares, Marta; Andreu, Teresa; Genç, Aziz; Arbiol, Jordi; Siciliano, Pietro; Faglia, Guido; Morante, Joan R

    2015-04-01

    TiO2 anatase nanocrystals were prepared by solvothermal processing of Ti chloroalkoxide in oleic acid, in the presence of W chloroalkoxide, with W/Ti nominal atomic concentration (R(w)) ranging from 0.16 to 0.64. The as-prepared materials were heat-treated up to 500 °C for thermal stabilization and sensing device processing. For R(0.16), the as-prepared materials were constituted by an anatase core surface-modified by WO(x) monolayers. This structure persisted up to 500 °C, without any WO3 phase segregation. For R(w) up to R(0.64), the anatase core was initially wrapped by an amorphous WO(x) gel. Upon heat treatment, the WO(x) phase underwent structural reorganization, remaining amorphous up to 400 °C and forming tiny WO3 nanocrystals dispersed into the TiO2 host after heating at 500 °C, when part of tungsten also migrated into the TiO2 structure, resulting in structural and electrical modification of the anatase host. The ethanol sensing properties of the various materials were tested and compared with pure TiO2 and WO3 analogously prepared. They showed that even the simple surface modification of the TiO2 host resulted in a 3 orders of magnitude response improvement with respect to pure TiO2. PMID:25775118

  19. Morphology modification of gold nanoparticles from nanoshell to C-shape: Improved surface enhanced Raman scattering

    NASA Astrophysics Data System (ADS)

    Xing, Ting-Yang; Zhu, Jian; Li, Jian-Jun; Zhao, Jun-Wu

    2016-06-01

    Morphology modification of nanostructures is of great interest, because it can be used to fabricate nanostructures which are hard to be done using other methods. Different from traditional lithographic technique which is slow and expensive, morphology modification is easy, cheap, and reproducible. In this paper, modification of the optical and morphological properties of a hollow gold nanoshell (HGNS) is achieved by using H2O2 as an oxidizer. The reshaping of these nanostructures has been demonstrated as a consequence of an oxidation process in which HGNSs are dissolved by H2O2 under the acidic conditions provided by HCl. We investigate the oxidation process by a transmission electron microscope and propose a reshaping model involving four different shapes (HGNS, HGNS with hole, gold nanoring, and C-shaped gold nanoparticle) which are corresponding to the oxidation products of HGNSs at different pH values. Besides, the surface enhanced Raman scattering (SERS) activity of each oxidation product has been evaluated by using rhodamine 6G as the Raman active probe. It has been observed that the C-shaped gold nanoparticles which are corresponding to the oxidation products at the minimum pH value have the highest SERS activity and this result can also be interpreted by discrete-dipole approximation simulations. We demonstrate that the morphology modification of HGNSs becomes possible in a controlled manner using wet chemistry and can be used in preparation of gold nanoparticles such as HGNS with hole, gold nanoring, and C-shaped gold nanoparticle with large SERS activity. These nanostructures must have potential use in many plasmonic areas, including sensing, catalysis, and biomedicine.

  20. Surface modification and laser pulse length effects on internal energy transfer in DIOS.

    PubMed

    Luo, Guanghong; Chen, Yong; Siuzdak, Gary; Vertes, Akos

    2005-12-29

    Benzyl-substituted benzylpyridinium (BP) chloride salts were used as a source of thermometer ions to probe the internal energy (IE) transfer in desorption/ionization on porous silicon (DIOS). To modify their wetting properties and the interaction energies with the thermometer ions, the DIOS surfaces were silylated to produce trimethylsilyl- (TMS), amine- (NH2), perfluoroalkyl- (PFA), and perfluorophenyl-derivatized (PFP) surfaces. Two laser sources--a nitrogen laser with pulse length of 4 ns and a mode locked 3 x omega Nd:YAG laser with a pulse length of 22 ps--were utilized to induce desorption/ionization and fragmentation at various laser fluence levels. The corresponding survival yields were determined as indicators of the IE transfer and the IE distributions were extracted. In most cases, with increasing the laser fluence in a broad range (approximately 20 mJ/cm2), no change in IE transfer was observed. For ns excitation, this was in remarkable contrast with MALDI, where increasing the laser fluence resulted in sharply (within approximately 5 mJ/cm2) declining survival yields. Derivatization of the porous silicon surface did not affect the survival yields significantly but had a discernible effect on the threshold fluence for ion production. The IE distributions determined for DIOS and MALDI from alpha-cyano-4-hydroxycinnamic acid reveal that the mean IE value is always lower for the latter. Using the ps laser, the IE distribution is always narrower for DIOS, whereas for ns laser excitation the width depends on surface modification. Most of the differences between MALDI and DIOS described here are compatible with the different dimensionality of the plume expansion and the differences in the activation energy of desorption due to surface modifications. PMID:16375447

  1. Laser-Assisted Surface Modification of Alumina and Its Tribological Behavior

    NASA Astrophysics Data System (ADS)

    Wallstabe, R.

    2013-01-01

    High performance friction systems, e.g., dry clutches and brakes, require a good wear resistance and a friction coefficient that is nearly independent from sliding velocity and environmental conditions. Organic-based friction materials have reached their limitations regarding higher power densities. Engineering ceramics such as alumina (Al2O3) or silicon carbide (SiC) offer a great potential since remarkably higher thermal and mechanical loading is possible. However, the tribological performance of these monolithic ceramics is still insufficient. The aim of the present study was to assess the potential of a laser-assisted surface modification process in order to improve the tribological performance with regard to the application in dry friction systems. Therefore, commercially available alumina was modified using a newly developed laser-assisted preheating process and subsequent melting of the ceramic's surface using a CO2-laser and modification by additives such as TiC, TiN, B4C, WC, ZrB2, Cr, Ni, Cu, and Ti. A systematic variation of additives and process parameters led to different multiphase microstructures. Subsequently, these were characterized using scanning electron microscopy and surface analysis methods (wavelength dispersive X-ray spectroscopy, energy dispersive X-ray spectroscopy). Finally, the tribological properties were investigated using a laboratory tribometer. The surface-modified ceramics were tested in unidirectional sliding motion against steel disks. The tribological results of the surface-modified ceramics were compared to those of monolithic Al2O3 and SiC ceramics and showed a reduced dependence of friction coefficient on sliding velocity. Moreover, the multi-phase ceramics possessed a higher wear resistance than the monolithic ones.

  2. A new setup for the investigation of swift heavy ion induced particle emission and surface modifications.

    PubMed

    Meinerzhagen, F; Breuer, L; Bukowska, H; Bender, M; Severin, D; Herder, M; Lebius, H; Schleberger, M; Wucher, A

    2016-01-01

    The irradiation with fast ions with kinetic energies of >10 MeV leads to the deposition of a high amount of energy along their trajectory (up to several ten keV/nm). The energy is mainly transferred to the electronic subsystem and induces different secondary processes of excitations, which result in significant material modifications. A new setup to study these ion induced effects on surfaces will be described in this paper. The setup combines a variable irradiation chamber with different techniques of surface characterizations like scanning probe microscopy, time-of-flight secondary ion, and neutral mass spectrometry, as well as low energy electron diffraction under ultra high vacuum conditions, and is mounted at a beamline of the universal linear accelerator (UNILAC) of the GSI facility in Darmstadt, Germany. Here, samples can be irradiated with high-energy ions with a total kinetic energy up to several GeVs under different angles of incidence. Our setup enables the preparation and in situ analysis of different types of sample systems ranging from metals to insulators. Time-of-flight secondary ion mass spectrometry enables us to study the chemical composition of the surface, while scanning probe microscopy allows a detailed view into the local electrical and morphological conditions of the sample surface down to atomic scales. With the new setup, particle emission during irradiation as well as persistent modifications of the surface after irradiation can thus be studied. We present first data obtained with the new setup, including a novel measuring protocol for time-of-flight mass spectrometry with the GSI UNILAC accelerator. PMID:26827329

  3. A new setup for the investigation of swift heavy ion induced particle emission and surface modifications

    NASA Astrophysics Data System (ADS)

    Meinerzhagen, F.; Breuer, L.; Bukowska, H.; Bender, M.; Severin, D.; Herder, M.; Lebius, H.; Schleberger, M.; Wucher, A.

    2016-01-01

    The irradiation with fast ions with kinetic energies of >10 MeV leads to the deposition of a high amount of energy along their trajectory (up to several ten keV/nm). The energy is mainly transferred to the electronic subsystem and induces different secondary processes of excitations, which result in significant material modifications. A new setup to study these ion induced effects on surfaces will be described in this paper. The setup combines a variable irradiation chamber with different techniques of surface characterizations like scanning probe microscopy, time-of-flight secondary ion, and neutral mass spectrometry, as well as low energy electron diffraction under ultra high vacuum conditions, and is mounted at a beamline of the universal linear accelerator (UNILAC) of the GSI facility in Darmstadt, Germany. Here, samples can be irradiated with high-energy ions with a total kinetic energy up to several GeVs under different angles of incidence. Our setup enables the preparation and in situ analysis of different types of sample systems ranging from metals to insulators. Time-of-flight secondary ion mass spectrometry enables us to study the chemical composition of the surface, while scanning probe microscopy allows a detailed view into the local electrical and morphological conditions of the sample surface down to atomic scales. With the new setup, particle emission during irradiation as well as persistent modifications of the surface after irradiation can thus be studied. We present first data obtained with the new setup, including a novel measuring protocol for time-of-flight mass spectrometry with the GSI UNILAC accelerator.

  4. Preparation and ozone-surface modification of activated carbon. Thermal stability of oxygen surface groups

    NASA Astrophysics Data System (ADS)

    Jaramillo, J.; Álvarez, P. M.; Gómez-Serrano, V.

    2010-06-01

    The control of the surface chemistry of activated carbon by ozone and heat treatment is investigated. Using cherry stones, activated carbons were prepared by carbonization at 900 °C and activation in CO 2 or steam at 850 °C. The obtained products were ozone-treated at room temperature. After their thermogravimetric analysis, the samples were heat-treated to 300, 500, 700 or 900 °C. The textural characterization was carried out by N 2 adsorption at 77 K, mercury porosimetry, and density measurements. The surface analysis was performed by the Bohem method and pH of the point of zero charge (pH pzc). It has been found that the treatment of activated carbon with ozone combined with heat treatment enables one to control the acidic-basic character and strength of the carbon surface. Whereas the treatment with ozone yields acidic carbons, carbon dioxide and steam activations of the carbonized product and the heat treatment of the ozone-treated products result in basic carbons; the strength of a base which increases with the increasing heat treatment temperature. pH pzc ranges between 3.6 and 10.3.

  5. Dropwise Evaporative Cooling of Heated Surfaces with Various Wettability Characteristics Obtained by Nanostructure Modifications

    NASA Astrophysics Data System (ADS)

    Chen, Jian-nan; Zhang, Zhen; Ouyang, Xiao-long; Jiang, Pei-xue

    2016-03-01

    A numerical and experimental investigation was conducted to analyze dropwise evaporative cooling of heated surfaces with various wettability characteristics. The surface wettability was tuned by nanostructure modifications. Spray-cooling experiments on these surfaces show that surfaces with better wettability have better heat transfer rate and higher critical heat flux (CHF). Single droplet impingement evaporative cooling of a heated surface was then investigated numerically with various wettability conditions to characterize the effect of contact angle on spray-cooling heat transfer. The volume of fluid (VOF) model with variable-time stepping was used to capture the time-dependent liquid-gas interface motion throughout the computational domain with the kinetic theory model used to predict the evaporation rate at the liquid-gas interface. The numerical results agree with the spray-cooling experiments that dropwise evaporative cooling is much better on surfaces with better wettability because of the better liquid spreading and convection, better liquid-solid contact, and stronger liquid evaporation.

  6. Surface modification induced by UV nanosecond Nd:YVO4 laser structuring on biometals

    NASA Astrophysics Data System (ADS)

    Fiorucci, M. Paula; López, Ana J.; Ramil, Alberto

    2014-08-01

    Laser surface texturing is a promising tool for improving metallic biomaterials performance in dental and orthopedic bone-replacing applications. Laser ablation modifies the topography of bulk material and might alter surface properties that govern the interactions with the surrounding tissue. This paper presents a preliminary evaluation of surface modifications in two biometals, stainless steel 316L and titanium alloy Ti6Al4V by UV nanosecond Nd:YVO4. Scanning electron microscopy of the surface textured by parallel micro-grooves reveals a thin layer of remelted material along the grooves topography. Furthermore, X-ray diffraction allowed us to appreciate a grain refinement of original crystal structure and consequently induced residual strain. Changes in the surface chemistry were determined by means of X-ray photoelectron spectroscopy; in this sense, generalized surface oxidation was observed and characterization of the oxides and other compounds such hydroxyl groups was reported. In case of titanium alloy, oxide layer mainly composed by TiO2 which is a highly biocompatible compound was identified. Furthermore, laser treatment produces an increase in oxide thickness that could improve the corrosion behavior of the metal. Otherwise, laser treatment led to the formation of secondary phases which might be detrimental to physical and biocompatibility properties of the material.

  7. Dropwise Evaporative Cooling of Heated Surfaces with Various Wettability Characteristics Obtained by Nanostructure Modifications.

    PubMed

    Chen, Jian-Nan; Zhang, Zhen; Ouyang, Xiao-Long; Jiang, Pei-Xue

    2016-12-01

    A numerical and experimental investigation was conducted to analyze dropwise evaporative cooling of heated surfaces with various wettability characteristics. The surface wettability was tuned by nanostructure modifications. Spray-cooling experiments on these surfaces show that surfaces with better wettability have better heat transfer rate and higher critical heat flux (CHF). Single droplet impingement evaporative cooling of a heated surface was then investigated numerically with various wettability conditions to characterize the effect of contact angle on spray-cooling heat transfer. The volume of fluid (VOF) model with variable-time stepping was used to capture the time-dependent liquid-gas interface motion throughout the computational domain with the kinetic theory model used to predict the evaporation rate at the liquid-gas interface. The numerical results agree with the spray-cooling experiments that dropwise evaporative cooling is much better on surfaces with better wettability because of the better liquid spreading and convection, better liquid-solid contact, and stronger liquid evaporation. PMID:27003427

  8. Infrared spectroscopic studies of galvanic effect influence on surface modification of sulfide minerals by surfactant adsorption.

    PubMed

    Mielczarski, Ela; Mielczarski, Jerzy A

    2005-08-15

    The influence of interaction between mineral components in natural mixtures on the adsorption of organic and inorganic species on the mineral surfaces is recognized. However, the surface phenomena have been meagerly investigated. In this study the formation of different surface species of surfactant (amyl xanthate, C5H11OC(S)S-) adsorbed on FeS2, PbS, and CuFeS2 has been spectroscopically investigated in single-mineral and complex systems. The type and amount of adsorbed species were determined directly on each mineral surface by infrared external reflection spectroscopy. Galvanic interaction between grains of different minerals could have tremendous consequence on the adsorption of surfactants on each mineral component and their future reactivity. The detected changes are dramatic, from no adsorption to the formation of several layers of hydrophobic or hydrophilic surface products depending on which minerals are in contact. It has been documented that even very short contact time between different mineral grains by collision is sufficient to produce dramatic modification of the surface composition and structure. The results obtained indicate clearly that the observations and conclusions aboutthe surfactant adsorption made in a single mineral system cannot be simply extrapolated to describe the real situation in natural multicomponent mineral systems. The obtained information on sulfide mineral interaction in complex systems is indispensable to understand processes taking place in nature at mineral-water interfaces (dissolution of heavy metals). An additional benefit is the improved ability to design efficient separation processes of these minerals. PMID:16173571

  9. Surface Modification of a Perfluorinated Ionomer Using a Glow Discharge Deposition Method to Control Protein Adsorption

    PubMed Central

    Valdes, T.I.; Ciridon, W.; Ratner, B.D.; Bryers, J.D.

    2008-01-01

    Nafion™ is the membrane material preferred for in situ glucose sensors. Unfortunately, surface properties of Nafion promote random protein adsorption and eventual foreign body encapsulation thus leading to loss if glucose signal over time. Here we detail surface modifications made by RF plasma deposition to Nafion with the intent to prevent random protein adsorption while providing enough functional sites (hydroxyl groups) to bind a biologically active peptide known to induce cellular adhesion (YRGDS). Nafion surfaces were modified by RF plasma polymerizing five different combinations of (1) tetraethylene glycol dimethyl ether (tetraglyme) and (2) 2-hydroxyethyl methacrylate (HEMA): pure tetraglyme, 2.5% HEMA/97.5% tetraglyme; 5% HEMA/95% tetraglyme, 10% HEMA/90% tetraglyme; and pure HEMA. Resultant surfaces were characterized by XPS (low and high resolution), dynamic contact angle, and atomic force microscopy. Protein adsorption and retention was determined and correlated to surface layer composition. The ability to bind a cell adhesion peptide was also determined and correlated well with surface layer composition. PMID:18155292

  10. Platinum electrode modification: Unique surface carbonization approach to improve performance and sensitivity.

    PubMed

    Lee, Hwi Yong; Barber, Cedrick; Minerick, Adrienne R

    2015-08-01

    Many microfluidic devices, also known as lab-on-a-chip devices, employ electrochemical detection methods using microelectrodes. Miniaturizing electrodes inevitably reduces electrode sensitivity and decreases the S/N, which limits applications within microfluidic devices. However, microelectrode surface modification can increase the surface area and sensitivity. In the present work, we report substantial improvement in platinum electrode performance and sensitivity by coating with carbon from red blood cells. The larger goal of this work was to measure DC electrical resistances of red blood cell suspensions in a microchannel for hematocrit determination. It was observed that as current responses of red blood cell suspensions were measured, the platinum electrode performance (reproducibility and S/N) improved with time. The platinum electrode electrocatalytic activity for red blood cell current measurements improved by 140%. Systematic experimentation revealed that red blood cells adsorb and carbonize the platinum electrode surfaces. The electrode surfaces before and after performance improvements were analyzed by field emission scanning electron microscopy, energy dispersive spectrometry, and Raman spectrometry. The formed carbon layers on the electrode surfaces were found to be proteomic and increased surface area with a porous three-dimensional structure, thus improving performance and stabilizing currents. PMID:26032065

  11. Surface modification of nanocrystalline zinc oxide for bio-sensing applications

    NASA Astrophysics Data System (ADS)

    Soares, Jason W.; Steeves, Diane M.; Ziegler, David; DeCristofano, Barry S.

    2006-10-01

    Zinc Oxide (ZnO) is a wide bandgap semiconductor that has been the subject of considerable research due to its potential applications in the areas of photonics, electronics and sensors. Nano-ZnO offers several advantages over existing biosensing platforms, most notably a large surface area for greater bio-functionalization and an inherent photoluminescence (PL) signal consisting of two emission peaks. One peak is in the UV, due to near band edge emission and the other is in the visible (green) region, due to oxygen vacancies caused by crystalline defects. Real-time detection of surface binding events may be possible if changes to the PL spectrum of a ZnO-based bio-sensor can be induced. Here we describe the surface modification of nanocrystalline zinc oxide (nano-ZnO) to introduce chemically reactive functionality for subsequent bio-functionalization. We have demonstrated through TEM-EDS that nano-ZnO powders have been surface modified with a heterobifunctional organosilane crosslinking agent that contains an amine-reactive aldehyde group. Furthermore, we have attached a fluorophore to the reactive aldehyde verifying the modified nano-ZnO surface is available for subsequent biomolecular covalent attachment. The introduction of a chemically reactive modifier to the surface of the nano-ZnO presents a template for the design of new, optically responsive bio-sensing platforms.

  12. Surface modifications and surface-protective coatings analyzed by means of thermal waves (invited) (abstract)

    NASA Astrophysics Data System (ADS)

    Bein, B. K.; Fotsing, J. L. N.; Gibkes, J.; Delgadillo-Holtfort, I.; Dietzel, D.; Pelzl, J.

    2003-01-01

    The depth profiles of the thermophysical properties of alloy systems, for example, shape memory alloys (NiTi), steel, and tool steel, can vary considerably due to rolling, surface machining, heat treatment, mechanical wear, and erosion. The same is true for coated tool steel samples, which show variations of the effective thermal depth profiles due to the effects of substrate preparation and deposition of the coatings, for example, plasma-etching, arc erosion, nitriding, chemical vapor deposition (CVD), physical vapor deposition (PVD), sputter deposition, and plasma spraying. In this work we present a large variety of measured effective thermal depth profiles. In a first step, we identify the effects of coating deposition and substrate preparation on the measured depth profiles. In a second step, we identify and try to quantify the effects of mechanical wear and erosion of both coated and uncoated surface. To this finality, the signals, which have been measured with the help of IR radiometry as a function of the modulation frequency, have been calibrated with reference signals measured for homogeneous samples of glassy carbon. The normalized amplitudes and phases have been approximated using layer models, mainly the two- and three-layer model with an opaque first layer, with respect to both the visible and the IR spectrum. Additionally, the signals measured for different coatings have been normalized against each other. By this latter calibration procedure, even smaller details and differences of coating deposition and substrate preparation can be identified, as well as the effects of wear and surface erosion. The virgin coated samples normally can well be described by the two-layer model, and the thermal transport parameters of the coatings as a whole can be determined quantitatively with rather good reliability (Ref. 1). The deviations from the two-layer model, which can be related to details of the deposition process, for example, to gradient layers or bond

  13. Effects of low-temperature surface-wave plasma treatment with various gases on surface modification of chitosan

    NASA Astrophysics Data System (ADS)

    Ogino, Akihisa; Kral, Martin; Yamashita, Mitsuji; Nagatsu, Masaaki

    2008-12-01

    The effect of low-temperature surface-wave plasma treatment with various gases on surface modification of chitosan was investigated using the surface-wave plasma. Chitosan is a nontoxic, biocompatible and biodegradable polymer. It is thought that an increase in amino groups, a key constituent of chitosan molecules, will be useful for biomedical applications, such as improvement of blood clotting properties, drug delivery system, prodrug using derivatization and so on. In this study, therefore, we have focused on the amino group introduction on chitosan surface by using Ar, O 2, NH 3 and NH 3-He mixed gas plasmas. The experimental results of X-ray photoelectron spectroscopy measurements showed that N/C atomic ratio increased from 6.8% to 14.7% after NH 3 plasma treatment. With O 2 plasma treatment, the surface roughness of chitosan film was significantly modified from 1.96 nm to 14.6 nm. The blood clotting time of the sample treated by NH 3 and He plasma with O 2 pretreatment was reduced to 55.2% of that of untreated one.

  14. Indium arsenide as a material for biological applications: Assessment of surface modifications, toxicity, and biocompatibility

    NASA Astrophysics Data System (ADS)

    Jewett, Scott A.

    III-V semiconductors such as InAs have recently been employed in a variety of applications where the electronic and optical characteristics of traditional, silicon-based materials are inadequate. InAs has a narrow band gap and very high electron mobility in the near-surface region, which makes it very attractive for high performance transistors, optical applications, and chemical sensing. However, InAs forms an unstable surface oxide layer in ambient conditions, which can corrode over time and leach toxic indium and arsenic components. Current research has gone into making InAs more attractive for biological applications through passivation of the surface by adlayer adsorption. In particular, wet-chemical methods are current routes of exploration due to their simplicity, low cost, and flexibility in the type of passivating molecule. This dissertation focuses on surface modifications of InAs using wet-chemical methods in order to further its use in biological applications. First, the adsorption of collagen binding peptides and mixed peptide/thiol adlayers onto InAs was assessed. X-ray photoelectron spectroscopy (XPS) along with atomic force microscopy (AFM) data suggested that the peptides successfully adsorbed onto InAs, but were only able to block oxide regrowth to a relatively low extent. This low passivation ability is due to the lack of covalent bonds of the peptide to InAs, which are necessary to effectively block oxide regrowth. The addition of a thiol, in the form of mixed peptide/thiol adlayers greatly enhanced passivation of InAs while maintaining peptide presence on the surface. Thiols form tight, covalent bonds with InAs, which prevents oxide regrowth. The presence of the collagen-binding peptide on the surface opens the door to subsequent modification with collagen or polyelectrolyte-based adlayers. Next, the stability and toxicity of modified InAs substrates were determined using inductively coupled plasma mass spectrometry (ICP-MS) and zebrafish

  15. Impact of surface modification in BSA nanoparticles for uptake in cancer cells.

    PubMed

    Choi, Jin-Seok; Meghani, Nilesh

    2016-09-01

    Recent studies have shown that cellular uptake of nanoparticles are strongly affected by the presence and physicochemical characteristics of protein on the surface of these nanoparticles. Hence, We developed surface-modified bovine serum albumin (BSA) nanoparticles (NPs) and evaluated the effect of surface modification on cellular uptake in two types of cancer cells, MCF-7 and A549. BSA NPs were prepared by desolvation method and their surface was modified with apo-transferrin, hyaluronic acid, and Poly(allylamine hydrochloride) (PAH). Morphology of surface-modified BSA NPs was characterized by field emission scanning electron microscopy and differential scanning calorimetry. In vitro-fluorescence release study was performed in phosphate buffered saline with trypsin (100μL/mL (v/v)) for 24h. Confocal microscopy was performed to evaluate cellular uptake followed by fluorescence analysis to evaluate the quantitative uptake of nanoparticles at 0.5, 1, and 2h. Different types of BSA NPs with a mean size of ∼100nm were successfully prepared. In vitro-fluorescent release showed sustained release pattern in surface-modified BSA NPs compared to unmodified BSA NPs. Surface-modified BSA NPs showed more cellular internalization than unmodified BSA NPs. The uptake of PAH-BSA NPs was about 2 times higher than that of unmodified BSA NPs in both cell types. In conclusion, surface-modified BSA NPs showed enhanced cellular uptake, and PAH-BSA NPs are more effective compared to ligand-specific surface-modified BSA NPs (HA-BSA NPs and Tf-BSA NPs). PMID:27289306

  16. Photoreactive Polymers Bearing a Zwitterionic Phosphorylcholine Group for Surface Modification of Biomaterials.

    PubMed

    Lin, Xiaojie; Fukazawa, Kyoko; Ishihara, Kazuhiko

    2015-08-12

    Photoreactive polymers bearing zwitterionic phosphorylcholine and benzophenone groups on the side chain were synthesized and used as surface modification reagents for biomaterials. A photoreactive methacrylate containing the benzophenone group, 3-methacryloyloxy-2-hydroxypropyl-4-oxybenzophenone (MHPBP), was synthesized via a ring-opening and addition reaction between glycidyl methacrylate and 4-hydroxybenzophenone. Then, water-soluble, amphiphilic polymers poly(2-methacryloyloxyethyl phosphorylcholine (MPC)-co-MHPBP) (PMH) and poly(MPC-co-n-butyl methacrylate-co-MHPBP), with different monomer unit compositions, were synthesized through radical polymerization. Ultraviolet-visible (UV/vis) absorption spectra of these polymer solutions showed that these polymers have maximum absorption peaks at 254 and 289 nm that can be attributed to the benzophenone unit. The intensity of UV adsorption at 289 nm was decreased with increased UV irradiation time, and it was saturated within a few minutes, indicating that the polymers are highly sensitive to UV irradiation. A commercial material (i.e., cyclic polyolefin) was simply modified by a UV irradiation for 1.0 min. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analysis results indicated that the stability of the polymer on the surface was dramatically enhanced because of the photochemical reaction of the benzophenone moiety. The air contact angles of PMH surfaces measured in water were up to 160°. Thus, highly hydrophilic surfaces were obtained. The critical surface tension of the PMH-modified surface was 45.7 mN/m. By evaluating the biological reactivity of the treated surface, protein adsorption and cell adhesion were completely inhibited on the surface, which was prepared using a photopatterning procedure using PMH. In conclusion, photoreactive MPC polymers with a benzophenone moiety could be used as a novel and effective surface modifier. PMID:26202385

  17. Tuning Solid Surfaces from Hydrophobic to Superhydrophilic by Submonolayer Surface Modification

    SciTech Connect

    Meng, Sheng; Zhang, Zhenyu; Kaxiras, Efthimios

    2006-01-01

    Molecular-scale understanding and manipulation of the wetting behavior of water on solids remains a fundamental challenge. Using diamond as a model system, we show that the naturally hydrophobic behavior of a hydrogen-terminated C(111) surface can be manipulated by replacing the H termination with a monolayer of adsorbate. In particular, a mixed monolayer of 1 3 Na and 2 3 F atoms leads to superhydrophilic behavior, as shown by first-principles calculations. The physical origin of the superhydrophilic behavior is attributed to the ionic nature of the Na adatoms, which mediate the right degree of binding strength between water molecules and the substrate.

  18. Human epithelial cells exposed to functionalized multiwalled carbon nanotubes: interactions and cell surface modifications.

    PubMed

    Fanizza, C; Casciardi, S; Incoronato, F; Cavallo, D; Ursini, C L; Ciervo, A; Maiello, R; Fresegna, A M; Marcelloni, A M; Lega, D; Alvino, A; Baiguera, S

    2015-09-01

    With the expansion of the production and applications of multiwalled carbon nanotubes (MWCNTs) in several industrial and science branches, the potential adverse effects on human health have attracted attention. Numerous studies have been conducted to evaluate how chemical functionalization may affect MWCNT effects; however, controversial data have been reported, showing either increased or reduced toxicity. In particular, the impact of carboxylation on MWCNT cytotoxicity is far from being completely understood. The aim of this work was the evaluation of the modifications induced by carboxylated-MWCNTs (MWCNTs-COOH) on cell surface and the study of cell-MWCNT-COOH interactions by means of field emission scanning electron microscope (FESEM). Human pulmonary epithelial cells (A549) were incubated with MWCNTs-COOH for different exposure times and concentrations (10 μg/mL for 1, 2, 4 h; 5, 10, 20 μg/mL for 24 h). At short incubation time, MWCNTs-COOH were easily observed associated with plasma membrane and in contact with microvilli. After 24 h exposure, FESEM analysis revealed that MWCNTs-COOH induced evident changes in the cellular surface in comparison to control cells: treated cells showed blebs, holes and a depletion of the microvilli density in association with structure modifications, such as widening and/or lengthening. In particular, an increase of cells showing holes and microvilli structure alterations was observed at 20 μg/mL concentration. FESEM analysis showed nanotube agglomerates, of different sizes, entering into the cell with two different mechanisms: inward bending of the membrane followed by nanotube sinking, and nanotube internalization directly through holes. The observed morphological microvilli modifications, induced by MWCNTs-COOH, could affect epithelial functions, such as the control of surfactant production and secretion, leading to pathological conditions, such as alveolar proteinosis. More detailed studies will be, however, necessary to

  19. Polyamide desalination membrane characterization and surface modification to enhance fouling resistance.

    SciTech Connect

    Sharma, Mukul M.; Freeman, Benny D.; Van Wagner, Elizabeth M.; Hickner, Michael A.; Altman, Susan Jeanne

    2010-08-01

    The market for polyamide desalination membranes is expected to continue to grow during the coming decades. Purification of alternative water sources will also be necessary to meet growing water demands. Purification of produced water, a byproduct of oil and gas production, is of interest due to its dual potential to provide water for beneficial use as well as to reduce wastewater disposal costs. However, current polyamide membranes are prone to fouling, which decreases water flux and shortens membrane lifetime. This research explored surface modification using poly(ethylene glycol) diglycidyl ether (PEGDE) to improve the fouling resistance of commercial polyamide membranes. Characterization of commercial polyamide membrane performance was a necessary first step before undertaking surface modification studies. Membrane performance was found to be sensitive to crossflow testing conditions. Concentration polarization and feed pH strongly influenced NaCl rejection, and the use of continuous feed filtration led to higher water flux and lower NaCl rejection than was observed for similar tests performed using unfiltered feed. Two commercial polyamide membranes, including one reverse osmosis and one nanofiltration membrane, were modified by grafting PEGDE to their surfaces. Two different PEG molecular weights (200 and 1000) and treatment concentrations (1% (w/w) and 15% (w/w)) were studied. Water flux decreased and NaCl rejection increased with PEGDE graft density ({micro}g/cm{sup 2}), although the largest changes were observed for low PEGDE graft densities. Surface properties including hydrophilicity, roughness and charge were minimally affected by surface modification. The fouling resistance of modified and unmodified membranes was compared in crossflow filtration studies using model foulant solutions consisting of either a charged surfactant or an oil in water emulsion containing n-decane and a charged surfactant. Several PEGDE-modified membranes demonstrated improved

  20. Deuterium retention and surface modifications of nanocrystalline tungsten films exposed to high-flux plasma

    NASA Astrophysics Data System (ADS)

    `t Hoen, M. H. J.; Dellasega, D.; Pezzoli, A.; Passoni, M.; Kleyn, A. W.; Zeijlmans van Emmichoven, P. A.

    2015-08-01

    Deuterium retention studies are presented for nanostructured tungsten films exposed to high-flux deuterium plasmas. Thin tungsten films of ∼1 μm thickness were deposited with pulsed laser deposition (PLD) on bulk tungsten. Surface modifications were studied with scanning electron microscopy and deuterium retention with thermal desorption spectroscopy. Three types of PLD films with different densities and crystallinity were studied after exposure to deuterium plasmas. The surface temperature ranged from about 460 K at the periphery to about 520 K in the centre of the targets. The films withstand the intense plasma exposure well and maintain their overall integrity. An increase of deuterium retention is observed with decreasing tungsten density and crystallite size. We found that the filling of these thin films with deuterium is significantly faster than for pre-damaged polycrystalline tungsten. We observed formation of micrometer-sized blisters as well as structures on the nanometer scale, both depending on the layer type.