Electropolished Stainless Steel Research Articles

The effect of Atmospheric Boundary Layer Meteorology in climate-related gases and VOCs concentrations over 3 European cities using an aerial platform

In the frame of the EU Horizon2020 ICARUS project, a N.A.S.A Awarded Light Manned Aircraft equipped with high-tech scientific instrumentation was used to perform an aerial mapping over Athens, Thessaloniki and Ljubljana greater areas. This study aimed to evaluate the effect of Atmospheric Boundary Layer (ABL) on Green House Gases (GHGs) and Volatile Organic Compounds (VOCs) concentrations over urban and rural areas of the above cities. Simultaneous ground-based measurements were performed in the respective regions. Air samples were pressurized with a stainless-steel bellows compressor into electropolished stainless steel canisters and analyzed by the use of a novel gas chromatographic system. The estimation of the mixing height (ΜΗ) of the ABL was based on the synoptic scale atmospheric circulation and the prevailing background wind. It was found that the MH variation, following the prevailing meteorological conditions, results in different concentration profiles in the lower troposphere over the examined regions. The pollutants concentrations were generally decreasing with altitude in the ABL. Under certain meteorological conditions, vertical mixing plus horizontal transport can cause a high pollution level at the top of ABL. The pollutants concentrations were low over less industrialized and upwind regions, suggesting that local emission sources play significant role on the GHGs and VOCs levels over the regions. However, due to the large scale of sampling area that the aircraft covers the above gradients in concentrations are relative low. AQ modelling activities for simulating the cases studied in the current or any relative future work could reduce operating costs and allow projections of potential impacts.

Environmentally-assisted cracking of electropolished 316L stainless steel in molten FLiNaK salt

Environmentally-assisted cracking is a well-known and extensively studied phenomenon in light water reactor environments but remains relatively unexplored in proposed molten salt reactor systems where the mechanisms at play are expected to be quite different. Here, slow strain rate testing has been performed on 316L stainless steel tensile specimens during simultaneous exposure to a molten LiF-KF-NaF eutectic salt environment at 600°C with a strain rate between 1E-5 to 1E-7 s-1. Sample ductility and ultimate tensile strength were both observed to decrease for slower strain rates/longer salt exposures. Post-mortem characterization of fractured specimens revealed Fe deposits and Cr- and O-rich precipitates decorating surface grain boundaries and crack surfaces, suggesting a cracking mechanism driven by embrittlement of the crack tip due to oxide formation. Unlike previous studies, intergranular Cr corrosion into the bulk was not observed, and distinct differences in surface morphology between electropolished and non-electropolished sample surfaces are reported. Trace metal salt chemistry measurements showed accumulation of 316L alloying elements over the course of the tests. It appears likely that the surface oxide layer induced by electropolishing, in addition to oxygen and moisture impurities in the salt, led to the formation of LiCrO2 which had a net passivating effect that prevented significant bulk corrosion, though some interplay between mechanical and environmental stressors is still observed.

Ambient non-methane hydrocarbons and their contribution to ozone formation potential in a super coal chemical industry in China’s Energy Golden Triangle

Ambient non-methane hydrocarbons (NMHCs) were investigated at Shenhua coal chemical industrial park (SH), and Baofeng coal chemical industrial park (BF) in Ningdong Energy and Chemical Industrial Base (NECIB) in China’s Energy Golden Triangle (EGT). Ambient air samples were collected using pre-evacuated 2-L electro-polished stainless steel canisters at SH and BF from 9:00 a.m. to 9:30 a.m. (UTC+8) from 22 to 31 December 2016. Fifty-seven NMHCs were analyzed using gas chromatography-mass selective detector/flame ionization detector. The average NMHCs mixing ratios were 49.05 ± 44.37 ppbv in SH, and 39.31 ± 18.77 ppbv in BF. Overall, alkanes took up the largest proportion (＞60%), followed by alkenes, acetylene, and aromatics. The propylene-equivalent (Prop-Equiv) concentration and the ozone formation potential (OFP) of NMHCs were calculated to estimate their chemical reactivities. Alkenes played a predominant role in NMHCs reactivity, among which propylene and ethylene were the largest contributors. OFP values show that alkenes and acetylene were the largest contributors (60%) to measured total NMHCs. Ethylene, propylene, m/p-xylene, n-butane, 1-butene, propane and acetylene were the major precursors in ground-level ozone formation in this region, which accounted for 66% and 62% of the total ozone formed by NMHCs at BF and SH, respectively. This study identified that industrial activities were the primary sources of NMHCs, confirmed by the high ratios of benzene to toluene (B/T = 2.23). Therefore, these organic pollutants should be monitored further based on their high toxicities.

Resistance to fracture due to cyclic fatigue of stainless steel manual files and its association to surface roughness.

The aim of this study was to evaluate the possible association between the roughness of 5 brands of stainless steel endodontic files and their resistance to fracture due to cyclic fatigue. The study included five different brands of stainless steel endodontic files: SybroEndo Triple-Flex Files (Kerr, Glendora, USA), Ready Steel K-Flexofile (Dentsply Sirona, Ballaigues, Switzerland), Mani Flexile Files (Mani, Tochigi- Ken, Japan), FKG K-Files (FKG, La Chaux-de-Fonds, Switzerland) and Zipperer Flexicut Files (VDW, Munich, Germany). Twelve files per brand (total 60 files) were evaluated. File surface roughness over an area (Sa) was quantified using a focus variation microscope. Then the files were subject to a cyclical fatigue test to determine the number cycles to fracture due to fatigue and length of fractured fragment. Finally, fractographic analysis was performed using a scanning electron microscope. The electropolished Ready Steel K-Flexofile® files had the highest roughness according to Sa parameters, though they also had the highest resistance to fracture due to cyclic fatigue and the longest fractured fragment. Moderate positive correlation was found between fractured fragment length and roughness. The fractured surface showed characteristics of ductile fracture with cracks and plastic deformation. The electropolished stainless steel Ready Steel K-Flexofile® files were the most resistant to fracture due to cyclic fatigue even though they had highest surface roughness.

Hydrocarbon emissions in flex fuel vehicles using ethanol: Preliminary results using a method implemented in Brazil

Vehicle emissions are the main source of hydrocarbons (HC) in many urban areas. However, the determination of HC in exhaust emissions of vehicles fueled with ethanol is a great challenge, from the analytical point of view, due to the interference of several contaminants. In this study, sampling and analytical methods were implemented and optimized. Contamination during sampling and interference of non-burned ethanol and carbonyl compounds were minimized through a rigorous sampling and analytical procedure. Two flex fuel vehicles, using 100% v/v hydrous ethanol (E100), were tested. Vehicle exhaust samples were collected during emission testing with EPA-75 drive cycle (according to ABNT/NBR 6601) for each of the three phases: cold start, stabilized and hot start. The exhaust was collected in Tedlar® bags and transferred to electropolished stainless steel canisters. HC (C2-C12) in samples were analyzed using thermal desorption and gas chromatography with a mass spectrometry detector. Ethene, ethyne and ethane represented approximately 95% of measured non-methane hydrocarbons (C2-C12). Aromatic compounds were considered negligible (<2%). Since speciated HC emission results are required to calculate MIR (maximum incremental reactivity) and OFP (ozone forming potential) factors, these results can be useful for technical discussions about the ozone formation in a Brazilian fuel scenario. To our knowledge, this was the first HC speciated analysis developed in Brazil using ethanol and Brazilian flex fuel vehicles.

Electropolishing of 316L Stainless Steel Using Sulfuric Acid-Free Electrolyte

Abstract The study is to investigate the electropolishing characteristics of 316L stainless steel in a sulfuric acid-free electrolyte of phosphoric acid and glycerol and to explore the possibility of using this eco-friendly electrolyte instead of the widely used sulfuric acid-based electrolyte. The influences of process parameters on polishing effects and the corrosion resistance of electropolished samples are investigated. The experimental results show that the electropolishing temperature and acid concentration are directly related to the mass transport mechanism in the limiting current plateau region. The grain boundaries of workpiece were electrochemically dissolved faster than the grain themselves at the beginning of the electropolishing process because they are more reactive than grains. Moreover, the conventional sulfuric—phosphoric acid electrolyte was also used to electropolish the 316L stainless steel, and the electropolished surfaces were compared with the sulfuric acid-free electrolyte proposed in this study. When the sulfuric acid-free electrolyte was used to electropolish the 316L stainless steel, the X-ray photoelectron spectroscopy (XPS) analysis shows that atomic Cr/Fe ratio of 316L stainless steel was increased from 0.802 to 1.909 after electropolishing process in the sulfuric acid-free electrolyte of phosphoric acid and glycerol. The corrosion resistance of the electropolished 316L stainless steel is studied using electrochemical analysis, and the results are verified experimentally.

Laminar flow cleaning of gelatinised, partially hydrolysed starch

SummaryThe cleanability of food contact materials is, among others, determined by the physico‐chemical properties of the soiling material. In the current study, starch of different origin was gelatinised and partially hydrolysed with diastase. The degree of hydrolysis was determined as the reducing capacity in terms of dextrose equivalents, and by the changes in apparent viscosity and surface tension. After spreading the starch paste on electropolished stainless steel coupons and subsequent drying, the removal was studied with a laboratory flow cell. These cleaning tests revealed a higher cleaning effectivity for smaller dextrins, which can be attributed to corresponding changes in solubility. Furthermore, the addition of commercially available diastase to demineralised water increased the cleaning effectivity of starch and dextrin soils at 25 °C. The results indicate that smaller starch breakdown products require reduced energy for removal so that cleaning processes can be adequately adjusted.

Adhesiveness of TiO2 PVD coating on electropolished stainless steel 17–4 PH orthodontic bracket

Performance of stainless steel 17-4 PH as the orthodontic bracket can be improved by titanium dioxide (TiO2) coating. In order to produce a good quality of the coating layer, the substrate had to be smooth and free from any contaminants. The electropolishing method was used to clean bracket’s surface from oxides substances which formed during sintering by reducing its surface roughness. Bath temperature and electropolishing time were varied to 30 °C and 70 °C, for 15 and 25 min, respectively. Those differences in electropolishing condition would affect the final surface’s roughness of the substrate. The atmosphere during PVD was controlled using oxygen and argon gases with the flowing rate ratio of 10:90 sccm and 50:50 sccm, and these gases would affect TiO2 coating mechanical properties. The lowest roughness of 0.99 μm and the highest roughness of 2.85 μm were obtained after electropolishing. The coating quality on the substrates with different roughness was assessed through coating adhesivity on the substrate by micro Vickers qualitatively. The results showed that the TiO2 coating layer on the substrate with a lower roughness had better adhesivity rather than on the substrate with higher roughness.

Cryopumping of hydrogen on stainless steel in the temperature range between 7 and 18 K

In cryogenic vacuum accelerator systems operated at temperatures below 20 K, hydrogen is typically the predominant residual gas component. The understanding of the cryopump mechanism of hydrogen on cryogenically refrigerated surfaces is thus a crucial prerequisite for a reliable design of such vacuum systems. Adsorption isotherms represent an experimental approach to understand the cryopump effect as a physisorption process of gases on cryogenic surfaces. Using a specially designed pumping system, the adsorption of hydrogen on an electropolished stainless steel surface was experimentally investigated in the temperature range between 7 and 18 K. The analysis of the measured H2 adsorption isotherms showed that the Dubinin-Radushkevich-Kaganer (DRK) isotherm, which is commonly used to theoretically describe the cryosorption process in the submonolayer coverage range, can be applied in the entire temperature range studied. The adsorption isotherms agree sufficiently well with the prediction of the DRK theory. Additionally, results on measurements of the sticking probability of H2 on stainless steel are presented for the above mentioned temperature range. Using the measured isotherms and sticking probabilities, the harmonic mean sojourn times of H2 molecules cryosorbed on a stainless steel surface were calculated as a function of temperature and surface coverage.In cryogenic vacuum accelerator systems operated at temperatures below 20 K, hydrogen is typically the predominant residual gas component. The understanding of the cryopump mechanism of hydrogen on cryogenically refrigerated surfaces is thus a crucial prerequisite for a reliable design of such vacuum systems. Adsorption isotherms represent an experimental approach to understand the cryopump effect as a physisorption process of gases on cryogenic surfaces. Using a specially designed pumping system, the adsorption of hydrogen on an electropolished stainless steel surface was experimentally investigated in the temperature range between 7 and 18 K. The analysis of the measured H2 adsorption isotherms showed that the Dubinin-Radushkevich-Kaganer (DRK) isotherm, which is commonly used to theoretically describe the cryosorption process in the submonolayer coverage range, can be applied in the entire temperature range studied. The adsorption isotherms agree sufficiently well with the prediction of the DRK theory....

Comparison of electropolished 316L steel samples manufactured by SLM and traditional technology

PurposeThis paper aims to present the way of modifying surfaces of 316L stainless steel elements that were manufactured in the selected laser melting (SLM) technology and then subjected to mechanical and electrolytic processing (electropolishing [EP]). The surface of the as-generated and commercial produced parts was modified by grinding and EP, and the results were compared. The authors also present an example of the application of EP for the final processing of a sample technological model – an initial prototype of a 316L steel implant manufactured in the SLM technology.Design/methodology/approachThe analyzed properties included surface topography, roughness, resistance to corrosion, microhardness and the chemical composition of the surface before and after EP. The roughness described with the Ra, Rt and Rz was determined before and after EP of samples manufactured from 316L steel with use of traditional methods and additive technologies.FindingsEP provides us with the opportunity to process elements with a complex structure, which would not be possible with use of other methods (such as milling or grinding). Depending on the expected final surface of elements after the SLM process, it is possible to reduce the surface roughness with the use of EP (for t = 20 min, Ra = 3.53 ± 0.37 µm and for t = 40 min, Ra = 3.23 ± 0.22 µm) or mechanical processing and EP (for t = 4 min, Ra = 0.13 ± 0.02 µm). The application of the EP method to elements made from 316L steel, in a bath consisting of sulfuric acid (VI), H2SO4 (35 Vol.%), phosphoric acid (V), H3PO4 (60.5 Vol.%) and triethanolamine 99 per cent (4.5 Vol.%), allows us to improve the surface smoothness and to obtain a value of the Ra parameter ranging from 0.11 to 0.15 µm. The application of a current density of 20 A/dm2 and a bath temperature of 55ºC results in an adequate smoothing of the surface (Ra < 0.16 µm) for both cold rolled and SLM elements after grinding. The application of EP, to both cold rolled elements and those after SLM, considerably improves the resistance to corrosion. The results of potentiodynamic corrosion resistance tests (jkor, EKA and Vp) of the 316L stainless steel samples demonstrate that the values of Vp for elements subjected to EP (commercial material: 1.3·10-4 mm/year, SLM material: 3.5·10-4 mm/year) are lower than for samples that were only ground (commercial material: 4.0·10-4 mm/year, SLM material: 9.6·10-4 mm/year). The microhardness was found to be significantly higher in elements manufactured using SLM technology than in those cold rolled and ground. The ground 316L steel samples were characterized by a microhardness of 318 HV (cold rolled) and 411 HV (SLM material), whereas the microhardness of samples subjected to EP was 230 HV (commercial material) and 375 HV (SLM material).Originality/valueThe 316L samples were built by SLM method. The surface of the SLM samples was modified by EP. Surface morphological changes after EP were studied using optical methods. Potentiodynamic tests enabled to notice changes in the corrosion resistance of 316L. Microhardness results after electropolished 316L stainless steel were shown. The chemical composition of 316L surface samples was presented. The smoothening of the surface amounted to Ra = 0.16 µm.

Characterization of textured Cr2O3 layer formed on AISI440A stainless steel via anisotropic electropolishing for electrosurgical instruments

This paper presents the development of a textured Cr2O3 layer on electropolished surgical AISI440A stainless steel with a layer thickness less than 50 μm for the miniaturization of electrosurgical instruments. The electropolished surgical AISI440A steel specimens were investigated using x-ray diffraction, scanning electron microscopy, atomic force microscopy, corrosion resistance testing, and contact angle measurements. The results showed that the textured Cr2O3 layer with a (202) preferred orientation possessed a texture coefficient greater than that for the (300) orientation, and in terms of lower surface roughness, a thicker Cr2O3 layer, which extends the passivation range, reduced the corrosion current density (Icorr) of 9.4 nA cm−2, and enhanced the corrosion resistance. The contact angle measurements revealed a large contact angle, indicating reduced surface energy and hydrophobic anti-adhesion property. This elucidated the relationship between the crystalline orientation and the properties of the textured Cr2O3 layer, which were attributed to anisotropic electropolishing.

Cleaning verification: A five parameter study of a Total Organic Carbon method development and validation for the cleaning assessment of residual detergents in manufacturing equipment

A Total Organic Carbon (TOC) based analytical method to quantitate trace residues of clean-in-place (CIP) detergents CIP100® and CIP200® on the surfaces of pharmaceutical manufacturing equipment was developed and validated. Five factors affecting the development and validation of the method were identified: diluent composition, diluent volume, extraction method, location for TOC sample preparation, and oxidant flow rate. Key experimental parameters were optimized to minimize contamination and to improve the sensitivity, recovery, and reliability of the method. The optimized concentration of the phosphoric acid in the swabbing solution was 0.05M, and the optimal volume of the sample solution was 30mL. The swab extraction method was 1min sonication. The use of a clean room, as compared to an isolated lab environment, was not required for method validation. The method was demonstrated to be linear with a correlation coefficient (R) of 0.9999. The average recoveries from stainless steel surfaces at multiple spike levels were >90%. The repeatability and intermediate precision results were ≤5% across the 2.2–6.6ppm range (50–150% of the target maximum carry over, MACO, limit). The method was also shown to be sensitive with a detection limit (DL) of 38ppb and a quantitation limit (QL) of 114ppb. The method validation demonstrated that the developed method is suitable for its intended use. The methodology developed in this study is generally applicable to the cleaning verification of any organic detergents used for the cleaning of pharmaceutical manufacturing equipment made of electropolished stainless steel material.

Electropolishing Behavior of Additive Layer Manufacturing 316L Stainless Steel in Deep Eutectic Solvents

The development and improvement of new manufacturing processes during the four last decades, lead up to consider new post-treatment techniques in order to have surface finishing similar to the one obtained by mechanical technics such as milling. Actually, conventional mechanical machining is no longer suitable in terms of cost and time for the geometric complexity of the additively manufactured structures, which may present inner channels. The aim of this study is then to develop an electropolishing process as a method to improve the surface finish dedicated to Additive Layer Manufacturing (ALM) parts. Electropolishing is usually carried out in concentrated acid media according to metal type, such as phosphoric acid, sulfuric acid and their mixtures [1]. These electrolytes are difficult to handle because of their relative toxicity and hazardousness. In order to improve working conditions and safe disposal of waste solutions, the use of alternative electrolytes is welcome. In this respect, ionic liquids and especially Deep Eutectic Solvents [2] based on Choline Chloride are herein tested. Electropolishing of ALM and “cast” 316L stainless steel was studied in a mixture of Choline Chloride and Ethylene Glycol. The mechanism was investigated by Linear Sweep Voltammetry and Electrochemical Impedance Spectroscopy. The limiting current density on the electropolishing plateau follows the Levich law showing that this reaction is under diffusional control in DES. The electropolishing window is wider for cast materials in DES than for ALM. The best conditions were obtained for potential at the end of the electropolishing range for both materials. Roughness, morphology and structure of samples were evaluated by respectively Stylus Profiler, Secondary Electron Microscopy, Atomic Force Microscopy and X-Ray Diffraction. Electropolished surface was bright and smooth for cast and ALM materials despite differences in their microstructures, with a composition being equal. In order to complete the study, corrosion measurements were performed before and after electropolishing (for the best conditions) for each manufacturing process. Benefits of the process were confirmed on corrosion resistance. The main operating parameters determined from laboratory experiments, allowed to design and build a pilot for electropolishing of larger and complex geometry parts. This new reactor provide optimisation of hydrodynamic conditions to improve surface finishing in particular in hollow area. Forced convection generated by ultrasound and jet flow can remove bubbles produced by reactions which are trapped into the viscous layer. Thus, electropolishing process is heightened on these materials. [1] P.J. Núñez, E. García-Plaza, M. Hernando, R. Trujillo, Characterization of Surface Finish of Electropolished Stainless Steel AISI 316L with Varying Electrolyte Concentrations, Procedia Eng. 63 (2013) 771–778. [2] E.L. Smith, A.P. Abbott, K.S. Ryder, Deep Eutectic Solvents (DESs) and Their Applications, Chem. Rev. 114 (2014) 11060–11082. Figure 1

Influence of steel implant surface microtopography on soft and hard tissue integration.

After implantation of an internal fracture fixation device, blood contacts the surface, followed by protein adsorption, resulting in either soft-tissue adhesion or matrix adhesion and mineralization. Without protein adsorption and cell adhesion under the presence of micro-motion, fibrous capsule formation can occur, often surrounding a liquid filled void at the implant-tissue interface. Clinically, fibrous capsule formation is more prevalent with electropolished stainless steel (EPSS) plates than with current commercially pure titanium (cpTi) plates. We hypothesize that this is due to lack of micro-discontinuities on the standard EPSS plates. To test our hypothesis, four EPSS experimental surfaces with varying microtopographies were produced and characterized for morphology using the scanning electron microscope, quantitative roughness analysis using laser profilometry and chemical analysis using X-ray photoelectron spectroscopy. Clinically used EPSS (smooth) and cpTi (microrough) were included as controls. Six plates of each type were randomly implanted, one on both the left and right intact tibia of 18 white New Zealand rabbits for 12 weeks, to allow for a surface interface study. The results demonstrate that the micro-discontinuities on the upper surface of internal steel fixation plates reduced the presence of liquid filled voids within soft-tissue capsules. The micro-discontinuities on the plate under-surface increased bony integration without the presence of fibrous tissue interface. These results support the hypothesis that the fibrous capsule and the liquid filled void formation occurs mainly due to lack of micro-discontinuities on the polished smooth steel plates and that bony integration is increased to surfaces with higher amounts of micro-discontinuities. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 705-715, 2018.

An improved, automated whole air sampler and gas chromatography mass spectrometry analysis system for volatile organic compounds in the atmosphere

Abstract. Volatile organic compounds were quantified during two aircraft-based field campaigns using highly automated, whole air samplers with expedited post-flight analysis via a new custom-built, field-deployable gas chromatography–mass spectrometry instrument. During flight, air samples were pressurized with a stainless steel bellows compressor into electropolished stainless steel canisters. The air samples were analyzed using a novel gas chromatograph system designed specifically for field use which eliminates the need for liquid nitrogen. Instead, a Stirling cooler is used for cryogenic sample pre-concentration at temperatures as low as −165 °C. The analysis system was fully automated on a 20 min cycle to allow for unattended processing of an entire flight of 72 sample canisters within 30 h, thereby reducing typical sample residence times in the canisters to less than 3 days. The new analytical system is capable of quantifying a wide suite of C2 to C10 organic compounds at part-per-trillion sensitivity. This paper describes the sampling and analysis systems, along with the data analysis procedures which include a new peak-fitting software package for rapid chromatographic data reduction. Instrument sensitivities, uncertainties and system artifacts are presented for 35 trace gas species in canister samples. Comparisons of reported mixing ratios from each field campaign with measurements from other instruments are also presented.

Impact of electrolyte concentration on surface gloss in electropolished stainless steel

Electropolishing is a surface finishing process of metals and alloys that enhances brilliant surface finishes with low surface roughness values. The most widely used electrolytes for the electropolishing of stainless steel are varying concentrations of phosphoric and sulphuric acid, and occasionally additives such as chromic acid. The objective of this study was to assess the performance of three commonly used industrial electrolytes in terms of the surface gloss of electro polished stainless steel AISI 316L. Each electrolyte had varying sulphuric-phosphoric acid combinations with or without chromic acid. The following electropolishing conditions were assessed: current density, bath temperature, electropolishing time, electrode position, and initial surface texture. The results revealed that adding chromic acid to the electrolyte did not significantly enhance gloss ranges. Current density and electropolishing time were the most significant parameters of surface gloss.

Drug-eluting coating of ginsenoside Rg1 and Re incorporated poly(lactic-co-glycolic acid) on stainless steel 316L: Physicochemical and drug release analyses

Active ingredients of ginsenoside, Rg1 and Re, are able to inhibit the proliferation of vascular smooth muscle cells and promote the growth of vascular endothelial cells. These capabilities are of interest for developing a novel drug-eluting stent to potentially solve the current problem of late-stent thrombosis and poor endotheliazation. Therefore, this study was aimed to incorporate ginsenoside into degradable coating of poly(lactic-co-glycolic acid) (PLGA). Drug mixture composed of ginseng extract and 10% to 50% of PLGA (xPLGA/g) was coated on electropolished stainless steel 316L substrate by using a dip coating technique. The coating was characterized principally by using attenuated total reflectance-Fourier transform infrared spectroscopy, scanning electron microscopy and contact angle analysis, while the drug release profile of ginsenosides Rg1 and Re was determined by using mass spectrometry at a one month immersion period. Full and homogenous coating coverage with acceptable wettability was found on the 30PLGA/g specimen. All specimens underwent initial burst release dependent on their composition. The 30PLGA/g and 50PLGA/g specimens demonstrated a controlled drug release profile having a combination of diffusion- and swelling-controlled mechanisms of PLGA. The study suggests that the 30PLGA/g coated specimen expresses an optimum composition which is seen as practicable for developing a controlled release drug-eluting stent.

A Modular Flow Cell System for Studying Biomimetic and BioinspiredAnti-Adhesive and Antimicrobial Surfaces

ABSTRACTBiofouling causes serious problems in many kinds of technical equipment. Consequently, there is great interest in developing surfaces with anti-adhesive and antimicrobial properties. Many such surfaces exist in nature, and artificial systems that mimic or are inspired by these natural systems could potentially be valuable technical surfaces. Recent studies on the interactions of bacteria with cicada wings revealed that rather than the wings being effective at repelling bacteria, after attachment the wing surface disrupts bacterial cell walls. Inspired by these structures, SmartMembranes GmbH used electrochemical precision etching to produce porous anodized aluminum oxide (AAO) membranes with structurally well-defined surface nanopatterns having pore diameters of 200–300 nm. We investigated the surfaces of these AAO membranes to assess their potential to prevent biofouling, using Escherichia coli as a model microbe. Bacterial adhesion tests were conducted using a modular flow cell system that is designed to enable on-line observation of biofilm formation in continuous flow on opaque surfaces using a fluorescence microscope. The system was adapted to permit testing of multiple samples with various dimensions and material properties simultaneously. Bacterial adhesion tests showed that AAO surfaces with pore diameters of 300 nm exhibit 99% less biofilm growth than widely used electropolished stainless steel.

An apparatus for studying electrical breakdown in liquid helium at 0.4 K and testing electrode materials for the neutron electric dipole moment experiment at the Spallation Neutron Source

We have constructed an apparatus to study DC electrical breakdown in liquid helium at temperatures as low as 0.4 K and at pressures between the saturated vapor pressure and ∼600 Torr. The apparatus can house a set of electrodes that are 12 cm in diameter with a gap of 1-2 cm between them, and a potential up to ±50 kV can be applied to each electrode. Initial results demonstrated that it is possible to apply fields exceeding 100 kV/cm in a 1 cm gap between two electropolished stainless steel electrodes 12 cm in diameter for a wide range of pressures at 0.4 K. We also measured the current between two electrodes. Our initial results, I < 1 pA at 45 kV, correspond to a lower bound on the effective volume resistivity of liquid helium of ρV > 5 × 10(18) Ω cm. This lower bound is 5 times larger than the bound previously measured. We report the design, construction, and operational experience of the apparatus, as well as initial results.

Titanium and steel fracture fixation plates with different surface topographies: Influence on infection rate in a rabbit fracture model

IntroductionImplant-related infection is a challenging complication in musculoskeletal trauma surgery. In the present study, we examined the role of implant material and surface topography as influencing factors on the development of infection in an experimental model of plating osteosynthesis in the rabbit. MethodsThe implants included in this experimental study were composed of: standard Electropolished Stainless Steel (EPSS), standard titanium (Ti-S), roughened stainless steel (RSS) and surface polished titanium (Ti-P). Construct stability and load-to-failure of Ti-P implants was compared to that of Ti-S implants in a rabbit cadaveric model. In an in vivo study, a rabbit humeral fracture model was used. Each rabbit received one of three Staphylococcus aureus inocula, aimed at determining the infection rate at a low, medium and high dose of bacteria. Outcome measures were quantification of bacteria on the implant and in the surrounding tissues, and determination of the infectious dose 50 (ID50). ResultsNo significant differences were observed between Ti-S and Ti-P regarding stiffness or failure load in the cadaver study. Of the 72 rabbits eventually included in the in vivo study, 50 developed an infection. The ID50 was found to be: EPSS 3.89×103 colony forming units (CFU); RSS 8.23×103 CFU; Ti-S 5.66×103 CFU; Ti-P 3.41×103 CFU. Significantly lower bacterial counts were found on the Ti-S implants samples compared with RSS implants (p<0.001) at the high inoculum. Similarly, lower bacterial counts were found in the bone samples of animals in the Ti-S group in comparison with both RSS and EPSS groups, again at the high inoculation dose (p<0.005). ConclusionNo significant differences were seen in susceptibility to infection when comparing titanium and steel implants with conventional or modified topographies. Ti-P implants, which have previously been shown in preclinical studies to reduce complications associated with tissue adherence, do not affect infection rate in this preclinical fracture model. Therefore, Ti-P implants are not expected to affect the infection rate, or influence implant stability in the clinical situation.