Non-coated Surface Research Articles

Review on erosion phenomenon, maintenance, and financial calculation of lifetime as an asset for Pelton turbines

Prevention of greenhouse emissions is the top priority for all countries, which urges them to switch to renewable energy as much as possible. Hydropower is one of the renewables that have high flexibility and at the same time compatibility to be used with any other renewable sources. Moreover, hydropower plants operating in the Himalayas, Andes, and Alps are facing operational challenges due to the high concentration of sediment loads in rivers. Although the arrangement of traditional sediment control mechanisms like dams and sand traps, the erosion tendency of hydro-turbine components operating in this sediment-laden water increases with the increased concentration of sediments. Much past research has been directed towards understanding sediment behaviors, investigation of flow, and effect of concentration, shape, and size, especially with Francis turbines. However, there are very fewer studies regarding sediment erosion and flow behavior in the case of the Pelton turbine. Hence, delving deeper into the flow characteristics, sediment behavior, and performance of the Pelton turbine is important to better understand the flow and sediment pattern of these types of turbines. The paper consists of the evaluation of studies conducted on the flow pattern in the Pelton turbine buckets and its validation with the numerical analysis models using image processing. It is being used in the Waterpower Laboratory at the Norwegian University of Science and Technology, NTNU. This paper also evaluates the scope of investigations about erosion by sediments in Pelton buckets using image analysis and state-of-the-art technology in the hydropower sector. In addition, a review is done about the predictability of erosion based on the measurements of the quantity of sediments that passes through the turbine. This research paper can build a background for quantifying sediment erosion in Pelton turbines with a certain degree of error, which can be utilized as a reference in future studies. The life cycle estimation of a turbine is also analyzed with the consideration of its location and financial return requirements together with the type of maintenance that it may have and the repair that is foreseen, in the case of a non-coated surface.

Molecular-scale insight into improved waterproofing of cement paste by protective epoxy resins nano-coating

The durability of cement binding paste is an important challenge in building sector that can be improved by increasing the resistance to water infiltration in the cement paste. The aim of the present work is mainly devoted to analyze at nanoscale level the interfacial interaction of epoxy resins coated on (001) surface of the nanogranular Calcium-Silicate-Hydrate (CSH) paste. By means of molecular dynamics simulations, a full nano-coated CSH surfaces show that m-phenylenediamine (MPD) would highly improve the coating efficiency. Results reveal that the coated (001) CSH surface models are more stable and the calculated surface free energy is roughly 95% loss compared with the non-coated surface, reducing therefore the hydrophilicity of the CSH surface. The related values are found in the range of 33.7 mJ/m2- 45.5 mJ/m2, in agreement with experimental findings. The obtained averaged contact angle between the equilibrated water-nanodroplet and the best coated CSH is in the range of 84.29°- 91.97°, which corresponds to the observed experimental measurements. Finally, the calculated work of adhesion is estimated to102.81 mJ/m2,which is close to the experimental findings of 102.79 and 90.17 mJ/m2, corresponding to 2 and 28 days hydration of cement. Consequently, our findings reveal that 16.46 wt% of epoxy coating including 2.61% of MDP reduces by 3.14–3.57 times the hydrophilicity of CSH (001) surface, leading to a promising future of sustainable cementitious materials.

Surface Material Effects on Wax Deposition in Noncoated Pipelines

Nonsteel pipes are being more widely used in gathering and transporting oil and gas due to their low-cost and anticorrosion properties. Most of the existing literature studies wax deposition on pristine steel surfaces, with very limited attention to nonsteel pipes. To fill this gap, in the current work, we aim to elucidate the surface material effects on wax deposition in noncoated and nonsteel pipelines. Copper and PTFE were chosen as the surface materials for their high (1362 mN/m) and low (18 mN/m) surface free energy, respectively, so that a wide range of surface free energies was created to maximize the strength of the effect observed. For the first time, a customized cold finger apparatus with specially designed cold fingers was constructed to generate consistent surface temperatures when different surface materials were employed, so that the thermal effects and surface effects on wax deposition could be isolated. Continuous thickness data was collected via a custom computer vision software, and deposits were weighed and analyzed for composition after the tests were finished. It was found that the deposits formed on PTFE and copper have similar thickness but the deposits formed on PTFE have a higher fraction of heavy components, with a slightly larger mass. The differences in deposit mass, thickness, and composition between PTFE and copper are relatively small, contrary to the much larger effects reported in the prior literature in which no attempts were made to control the surface temperatures. These observations indicate that depositional differences between different noncoated surface materials could also be caused by alterations to the heat transfer process, rather than through the surface energy and chemistry alone, an important insight that would benefit the design of remediation practices (i.e., pigging) for wax deposition in non-steel pipelines.

Mast cell chymase is in contact with melanoma cells in vivo and it detaches melanoma cells from the substratum in vitro.

Mast cell chymase, a chymotryptic serine proteinase, is a powerful enzyme that may liberate adherent tumor cells thereby promoting tumor spread. This study investigated interactions between cells containing immunoreactive chymase and melanoma cells in 101 melanoma and 50 nevus specimens as well as used recombinant human (rh)-chymase and WM115 and G361 primary melanoma cell lines in culture. Rh-chymase at low concentration (0.1 µg/mL) detached both melanoma cell lines from noncoated or collagen-coated plastic surface, but this effect was regulated by heparin and heparinase. After prolonged treatment at high rh-chymase (1-5 µg/mL) the growth pattern of detached and re-seeded cells was abnormal. Decreased migration and proliferation at up to 0.005-0.01 µg/mL rh-chymase was noticed in WM115 cells, while rh-chymase at 1-5 µg/mL partially reduced the viability of G361 cells. Of importance is the finding that melanoma cell lines are not uniform as there was variation between cell lines with regard to the concentration of rh-chymase needed for these effects. Sonicates prepared from the cell lysates did not inhibit the enzymatic activity of rh-chymase. The interactions were confirmed morphologically by detecting apparent contacts between chymase+ cells and melanoma cells in melanoma specimens. These results suggest that chymase can detach melanoma cells from the tumor, but this effect is regulated by heparin, and their proliferation, migration or viability can be reduced by chymase. Thus, the effect of chymase may be antitumorigenic, rather than protumorigenic.

Submerged surfaces exposed to marine biofouling – Experimental investigation of cleaning parameters effectiveness

Physical cleaning, an important factor in maintaining ships' hulls free from biofouling, can help to prolong the lifetime of fouling-control coating systems. This study investigated how mechanical cleaning parameters (cleaning force, duration and frequency) affected antifouling coatings' performance including fouling resistance property and cleaning efficiency using a specially designed manual cleaning system. Meanwhile, coating surface conditions, including visual appearance condition, roughness, contact angle were evaluated in detail. Biocide release rates of copper-based soluble antifouling paint (Cu-AF) under different cleaning conditions were also assessed by Scanning Electron Microscopy - Energy Dispersive X-ray (SEM-EDX) analysis. Results from the field testing in Danish sea area showed that cleaning frequency affected more than cleaning force and duration on antifouling coating performance. Algae glue attachment increased the difficulty in the cleaning of non-coated acrylic surface (A-BS) and fluorine-based copper free insoluble antifouling paint (F-AF). For Cu-AF coated panels, no significant mechanical damages were observed after cleaning. For F-AF, scratches formed on the coating surface after cleaning were more related to cleaning force and cleaning frequency. The biocide release rates of Cu-AF under various cleaning condition were between 15.7 and 24.6 μg Cu cm−2 day−1. Gentle cleaning of Cu-AF with proper frequency has little influence on the copper release rate. This study provides guidance on cleaning strategies for antifouling coatings.

Effect of a Coated Wall on Wax–Asphaltene Molecule Diffusion, Aggregation, and Adhesion Mechanism: A Molecular Dynamics Simulation Study

Coating is increasingly used as a cost-effective strategy for controlling heavy component deposition in waxy crude oil transportation flowlines. This paper systematically investigated the micro influence mechanism of the coated wall on the diffusion, aggregation, and adhesion behavior of wax–asphaltene molecules by the molecular dynamics (MD) method. A set of experiments was performed to determine the properties of the waxy crude oil. For overcoming the limitations of the model simplification of previous MD studies, the MD models based on experimental data were developed to characterize the motion behavior of wax–asphaltene molecules on non-coated and coated wall surfaces, and the simulated densities of crude oil components had an error of less than 5% with the National Institute of Standards and Technology (NIST) data, which showed that the established model was accurate and reliable. The simulation results showed that two condensate oil layers were formed on the non-coated wall surface, the diffusion and aggregation behavior of wax–asphaltene molecules were enhanced under the low-temperature condition, and there was considerably heavy component molecules adhesion to the non-coated wall surface. The analysis of mean square displacement, radial distribution function, and relative concentration distribution revealed that 288.15 K was the peak wax precipitation, which was consistent with the experimental conclusion. It was also found that the presence of low surface energy coating weakened the diffusion of heavy component molecules. The epoxy silicone-coated had the weakest interaction with wax–asphaltene molecules. Moreover, the fact that the coated wall had a certain inhibitory effect on the aggregation and adhesion of wax–asphaltene molecules in the pipeline was proven, where the epoxy silicone-coated had the strongest inhibitory effect. These investigations present new insights and guidance for controlling heavy component deposition by coating in the pipeline transportation process of waxy crude oil.

Evaluating a transparent coating on a face shield for repelling airborne respiratory droplets.

A face shield is an important personal protective equipment to avoid the airborne transmission of COVID-19. We assess a transparent coating on a face shield that repels airborne respiratory droplets to mitigate the spread of COVID-19. The surface of the available face shield is hydrophilic and exhibits high contact angle hysteresis. The impacting droplets stick on it, resulting in an enhanced risk of fomite transmission of the disease. Further, it may get wetted in the rain, and moisture may condense on it in the presence of large humidity, which may blur the user's vision. Therefore, the present study aims to improve the effectiveness of a face shield. Our measurements demonstrate that the face shield, coated by silica nanoparticles solution, becomes superhydrophobic and results in a nominal hysteresis to the underlying surface. We employ high-speed visualization to record the impact dynamics of microliter droplets with a varying impact velocity and angle of attack on coated and non-coated surfaces. While the droplet on non-coated surface sticks to it, in the coated surface the droplets bounce off and roll down the surface, for a wide range of Weber number. We develop an analytical model and present a regime map of the bouncing and non-bouncing events, parametrized with respect to the wettability, hysteresis of the surface, and the Weber number. The present measurements provide the fundamental insights of the bouncing droplet impact dynamics and show that the coated face shield is potentially more effective in suppressing the airborne and fomite transmission.

Enhancing surface characteristics of additively manufactured fiber reinforced thermoplastic mold using thermoset coating with ceramic particles

A commercially available thermoset polymer liquid coating reinforced with ceramic particles was applied on the surface of an additively manufactured carbon fiber reinforced thermoplastic composites to improve its surface characteristics for composite mold application. The mold demonstrated herein was fabricated via material extrusion additive manufacturing (MEAM) and served for the fabrication of autoclave-cured laminated composite structures. Test specimens used in this investigation were additively manufactured with Polyphenylene Sulfide (PPS) reinforced with 50% by weight of carbon fiber. Following the printing process, the surface of the specimens was finished in a numerical controlled milling machine. The effect of machining parameters such as the surface speed and the chip load on the surface roughness was investigated. The machining parameters that yielded the lowest surface roughness were used to machine the specimens used in this work. Following machining, an approximately 10 μm thick coating based on a thermoset resin reinforced with ceramic particles was applied on the surface of flat specimens via the liquid spray coating technique and cured at elevated temperature. Surface characteristics relevant to molds used in composite manufacturing such as surface roughness, abrasion resistance , hardness, friction, and vacuum integrity were assessed for the coated and noncoated specimens. The results showed that the coating decreased the abrasion wear index by about 89%, decreased the vacuum loss by about 95%, and lowered the static and kinetic friction by about 40% and 38%, respectively, compared to the non-coated printed material. However, the coated surface did not improve hardness nor roughness of the surface. • Thermoset liquid polymer coating with ceramic particle was applied to additively manufactured fiber reinforced composite. • The abrasion resistance of the additively manufactured carbon fiber reinforced composite was significantly increased with the coating. • The polymer coating did not improve surface hardness and roughness of the additively manufactured carbon fiber reinforced composite. • The coating provided lower static and kinetic surface friction coefficient compared to the non-coated surface of the composite. • Vacuum integrity of the additively manufactured fiber reinforced composite surface was significantly improved with the coating.

Reciprocating Wear Behavior of Noncoated and Polymer/Composite Coated AISI 316L Steel: Role of Surface Mechanical Attrition Treatment

The current work investigates the reciprocating wear behavior of surface mechanical attrition–treated (SMAT) AISI 316L stainless steel with and without polymer and composite coatings. The high-performance aromatic thermoset polymer (ATSP) and its composite with MoS2 are deposited on non-SMATed and SMATed steel using the spin coating technique. Further, a reciprocating wear test is performed on non-SMATed, SMATed, and coated surfaces against an alumina ball using different loads and reciprocation cycles. Enhanced surface hardness (∼89%), presence of an α′ (body-centered cubic [bcc] Fe) phase, and lower oxidation during reciprocation cause a decrease in wear loss and coefficient of friction (COF) of the SMATed surface by ∼37, and ∼20%, respectively, under 15 N load and most extended reciprocation cycle. The wear loss and COF of the steel are further reduced by depositing ATSP polymer and ATSP-MoS2 composite coatings. The adhesion and durability of coatings are enhanced by the SMAT process. This enhanced durability lowers the wear loss and COF of ATSP and ATSP-MoS2 composite coatings when deposited on the SMATed substrate. Polymer coating reduces the COF of non-SMATed and SMATed steel by ∼68 and ∼85%, respectively. Depending on the concentration of MoS2 in the composite coating, the COF ranges from 0.04 to 0.32 and from 0.02 to 0.07 for non-SMATed and SMATed specimens, respectively. The best performance of a composite coating was observed at ∼10 wt% MoS2. The COF of composite coated steel is ∼96% lower than that of the noncoated and nontreated steel surface. The SMAT processing of substrate and ATSP-MoS2 composite coating considerably enhances the tribological performance of AISI 316L steel.

A Thermo-Sensitive and Injectable Hydrogel Derived From Decellularized Amniotic Membrane to Prevent Intrauterine Adhesion by Accelerating Endometrium Regeneration

Objective: To investigate the effect of the injectable hydrogel generated from decellularized amniotic membrane (dAM)-gel on preventing development of intrauterine adhesion (IUA) in a rat model. Methods: The dAM-gel was developed from amniotic membrane (AM) by a process of decellularization, lyophilization, and enzyme digestion. Histological analysis, residual component determination, electronic microscopy and turbidimetric gelation kinetics analysis were performed to characterize dAM-gel. The proliferation and migration of endometrial cells on dAM-gel coated surface was examined. IUA was surgically created in rats and received dAM-gel injection immediately after wound creation. Gene profiles of epithelial cell cultured on dAM-gel coated surface was evaluated by RNA-sequencing. Results: Collagen content was retained in dAM-gel while GAG content decreased significantly compared with fresh AM (fAM). Gelation of the gel is temperature sensitive and showed a matrix concentration dependent manner. Transplantation of dAM-gel significantly reduced fibrosis of IUA with recovered uterine cavity, regenerated endometrium and increased microvascular density, along with elevated pregnancy rate compared with IUA control groups. Migration of epithelial cells was greatly promoted by dAM-gel in a surgically created wound model in uterine. By comparing the RNA-sequence data of epithelial cells that cultured on dAM-gel coated and non-coated surface, respectively, distinct gene profiles relative to cellular migration, adhesion and angiogenesis and involved signaling pathway were identified. Conclusions: The injectable dAM-gel developed from AM offers a promising option for preventing endometrial fibrosis by promotion of re-epithelialization of damaged endometrium.

Polydopamine-based biofunctional substrate coating promotes mesenchymal stem cell migration

Rapid migration of mesenchymal stem cells (MSCs) on device surfaces could support in vivo tissue integration and might facilitate in vitro organoid formation. Here, polydopamine (PDA) is explored as a biofunctional coating to effectively promote MSC motility. It is hypothesized that PDA stimulates fibronectin deposition and in this way enhances integrin-mediated migration capability. The random and directional cell migration was investigated by time-lapse microscopy and gap closure assay respectively, and analysed with softwares as computational tools. A higher amount of deposited fibronectin was observed on PDA substrate, compared to the non-coated substrate. The integrin β1 activation and focal adhesion kinase (FAK) phosphorylation at Y397 were enhanced on PDA substrate, but the F-actin cytoskeleton was not altered, suggesting MSC migration on PDA was regulated by integrin initiated FAK signalling. This study strengthens the biofunctionality of PDA coating for regulating stem cells and offering a way of facilitating tissue integration of devices.Graphic abstractPolydopamine-coated substrate induces increased fibronectin deposition of mesenchymal stem cells, and promotes cell migration via integrin-initiated FAK signaling, compared to non-coated polystyrene-based standard tissue culture surface. In this way, multifunctional PDA coating could support in vivo tissue integration on implant surface and promote in vitro organoid formation.

Frosting and defrosting on the hydrophilic nylon-6 nanofiber membrane–coated surfaces

Ice formation on various surfaces causes catastrophic consequences or enormous economic losses. Superhydrophobic surfaces with extreme water repellency were applied for removing ice efficiently; however, their practical applications are hindered by the fabrication of the complicated micro/nanostructures of the surfaces. In this work, we proposed using hydrophilic nylon-6 nanofiber membrane coating for enhancing deicing. The nylon-6 nanofiber membrane can be easily made by electrospinning. Given the abundant kink sites provided by a large number of ice nucleation sites on the membrane, the formed ice layer could be removed quickly in the deicing process on the membrane-coated surfaces. The total time required for the ice to completely dissipated has decreased by 80% compared with a noncoated surface. The substantially enhanced deicing ability of the nylon-6 nanofiber membrane indicates its potential for practical applications.

Deposition of TaN Film on Commercial Pure Titanium Disk by Modified Reactive Plasma Sputtering Technique

Background: The new trend of implants is to find materials which accelerate bone formation at bone implant interface and improve Osseo integration to provide immediate or early loading after placement and eliminate waiting period which is uncomfortable and disturbs patients. Titanium as an implant material still need some improvement of surface properties physically and chemically. Tantalum which is gaining more attention as a new metallic biomaterial. Coating layer over implant is an important way for improvement of surface properties of titanium. Plasma used for surface modification, has several advantages such as changing surface topography, increasing surface roughness and in increasing the wettability of the surface. Aim of study: To evaluate the effect of TaN coating by modified plasma sputtering technique of commercially pure titanium disk on wettability, surface roughness, surface chemical composition in comparison to noncoated surface. Materials and methods: Two groups were tested in this study which include non -coated commercial pure titanium disks and coated commercial pure titanium with TaN. Modified reactive plasma sputtering apparatus was used to coat CpTi with TaN at 4, 6 &8, h. Surface characterization by x-ray diffraction (XRD) analysis, scanning electron microscope (SEM), energy dispersive spectroscopy(EDS), contact angle measurement, were carried out for coated and uncoated disks. Results: The result of coating specimen with TaN at times (4,6&8) h showed that 8 h coating time was the best time. And this was according to the results of X-ray diffraction analysis which show a new peak formation of Ta N coated CpTi disk which was not present in non- coated CpTi disk. The results of wettability test for CpTi disk coated with TaN disk was more than wettability of non- coated CpTi disk. Surface Roughness was more and better distributed in CpTi coated with TaN disk than non- coated one which appear clearly in electron microscope.

Hyaluronan Induces a Mitochondrial Functional Switch in Fast-Proliferating Human Mesenchymal Stem.

Background and ObjectivesHyaluronan preserves the proliferation and differentiation potential of mesenchymal stem cells. Supplementation of low-concentration hyaluronan (SHA) in stem cells culture medium increases its proliferative rate, whereas coated-surface hyaluronan (CHA) maintains cells in a slow-proliferating mode. We have previously demonstrated that in CHA, the metabolic proliferative state of stem cells was influenced by upregulating mitochondrial biogenesis and function. However, the effect of SHA on stem cells’ energetic status remains unknown. In this study, we demonstrate the effect that low-concentration SHA at 0.001 mg/ml (SHA0.001) and high-concentration SHA at 5 mg/ml (SHA5) exert on stem cells’ mitochondrial function compared with CHA and noncoated tissue culture surface (control).Methods and ResultsFast-proliferating human placenta-derived mesenchymal stem cells (PDMSCs) cultured on SHA0.001 exhibited reduced mitochondrial mass, lower mitochondrial DNA copy number, and lower oxygen consumption rate compared with slow-proliferating PDMSCs cultured on CHA at 5.0 (CHA5) or 30 µg/cm2 (CHA30). The reduced mitochondrial biogenesis observed in SHA0.001 was accompanied by a 2-fold increased ATP content and lactate production, suggesting that hyaluronan-induced fast-proliferating PDMSCs may rely less on mitochondrial function as an energy source and induce a mitochondrial functional switch to glycolysis.ConclusionsPDMSCs cultured on both CHA and SHA exhibited a reduction in reactive oxygen species levels. The results from this study clarify our understandings on the effect of hyaluronan on stem cells and provide important insights into the effect of distinct supplementation methods used during cell therapies.

Enhancement of convective quenching heat transfer by coated tubes and intermittent cryogenic pulse flows

This paper reports heat transfer enhancement techniques for the cryogenic quenching process. An experiment was performed to evaluate the enhancement of quenching heat transfer by two techniques: 1. Using intermittent pulse flows and 2. Coating the inner surface of a test tube with layers of low thermal conductivity films. Pulsed liquid nitrogen flows with various duty cycles and periods were applied in the quenching of a room-temperature metal tube coated with four layers of Teflon thin films on the inner surface. In general, the results obtained indicate that the quenching thermal efficiency that measures the effectiveness of heat transfer enhancement increases with decreasing duty cycle, however it is relatively independent of the period. Comparing with non-coated bare surface test tube, the low-conductivity coating substantially improved the thermal efficiency and reduced the total quenching time. Additionally, the thermal efficiency was found to increase with decreasing source inlet pressure or coolant mass flow rate. The savings on the amount of cryogen consumed follow the same trends as those for the thermal efficiency with pulse flows and tube coating.

Secretion of fibronectin by human pancreatic stellate cells promotes chemoresistance to gemcitabine in pancreatic cancer cells

BackgroundGemcitabine remains a cornerstone in chemotherapy of pancreatic ductal adenocarcinoma (PDAC) despite suboptimal clinical effects that are partly due to the development of chemoresistance. Pancreatic stellate cells (PSCs) of the tumor stroma are known to interact with pancreatic cancer cells (PCCs) and influence the progression of PDAC through a complex network of signaling molecules that involve extracellular matrix (ECM) proteins. To understand tumor-stroma interactions regulating chemosensitivity, the role of PSC-secreted fibronectin (FN) in the development of gemcitabine resistance in PDAC was examined.MethodsPSC cultures obtained from ten different human PDAC tumors were co-cultured with PCC lines (AsPC-1, BxPC-3, Capan-2, HPAF-II, MIA PaCa-2, PANC-1 and SW-1990) either directly, or indirectly via incubation with PSC-conditioned medium (PSC-CM). Gemcitabine dose response cytotoxicity was determined using MTT based cell viability assays. Protein expression was assessed by western blotting and immunofluorescence. PSC-CM secretome analysis was performed by proteomics-based LC-MS/MS, and FN content in PSC-CM was determined with ELISA. Radiolabeled gemcitabine was used to determine the capacity of PCCs to uptake the drug.ResultsIn both direct and indirect co-culture, PSCs induced varying degrees of resistance to the cytotoxic effects of gemcitabine among all cancer cell lines examined. A variable degree of increased phosphorylation of ERK1/2 was observed across all PCC lines upon incubation with PSC-CM, while activation of AKT was not detected. Secretome analysis of PSC-CM identified 796 different proteins, including several ECM-related proteins such as FN and collagens. Soluble FN content in PSC-CM was detected in the range 175–350 ng/ml. Neither FN nor PSC-CM showed any effect on PCC uptake capacity of gemcitabine. PCCs grown on FN-coated surface displayed higher resistance to gemcitabine compared to cells grown on non-coated surface. Furthermore, a FN inhibitor, synthetic Arg-Gly-Asp-Ser (RGDS) peptide significantly inhibited PSC-CM-induced chemoresistance in PCCs via downregulation of ERK1/2 phosphorylation.ConclusionsThe findings of this study suggest that FN secreted by PSCs in the ECM plays a key role in the development of resistance to gemcitabine via activation of ERK1/2. FN-blocking agents added to gemcitabine-based chemotherapy might counteract chemoresistance in PDAC and provide better clinical outcomes.

Inhibition of bacterial attachment and biofilm formation by a novel intravenous catheter material using an in vitro percutaneous catheter insertion model.

IntroductionDespite sterile barrier precautions and vigorous skin antisepsis, percutaneous insertion of intravenous catheters has been shown to result in attachment to the catheter surface of bacteria residing in the deep structures of the skin. Such attachment poses the risk of biofilm formation and eventual catheter-related bloodstream infection (CRBSI). This study was undertaken to assess whether the non-coated surface treatment of a unique catheter material (ChronoFlex C® with BioGUARD™) could inhibit bacterial attachment and biofilm formation.MethodsA novel in vitro model and fluorescence microscopy were used to compare two intravascular catheter materials with respect to bacterial attachment and biofilm formation. The control material was a commonly used polyurethane. The study material was a unique copolymer, treated so as to remove surface additives, alter hydrophobicity and create surface micro-patterning. Outcomes were assessed using both a membrane potential indicator and a cell death reporter with appropriate fluorescent channels. Thus, bacterial cells attached to the catheter surface (living and dead) were imaged without mechanical disruption.ResultsBoth bacterial attachment and biofilm formation are significantly inhibited by the study catheter material. In fact, over 5 times more bacteria were able to attach and grow on the control polyurethane material than on the study material (P=0.0020). Moreover, those few bacteria that were able to attach to the study material had a 1.5 times greater likelihood of dying.ConclusionUsing a novel in vitro percutaneous catheter insertion model, ChronoFlex C with BioGUARD is proven to significantly inhibit bacterial attachment and biofilm formation as compared with a commonly used polyurethane catheter material.

In vitro evaluation of a multispecies oral biofilm over antibacterial coated titanium surfaces.

Peri-implantitis is an infectious disease that affects the supporting soft and hard tissues around dental implants and its prevalence is increasing considerably. The development of antibacterial strategies, such as titanium antibacterial-coated surfaces, may be a promising strategy to prevent the onset and progression of peri-implantitis. The aim of this study was to quantify the biofilm adhesion and bacterial cell viability over titanium disc with or without antibacterial surface treatment. Five bacterial strains were used to develop a multispecies oral biofilm. The selected species represent initial (Streptococcus oralis and Actinomyces viscosus), early (Veillonella parvula), secondary (Fusobacterium nucleatum) and late (Porphyromonas gingivalis) colonizers. Bacteria were sequentially inoculated over seven different types of titanium surfaces, combining different roughness level and antibacterial coatings: silver nanoparticles and TESPSA silanization. Biofilm formation, cellular viability and bacterial quantification over each surface were analyzed using scanning electron microscopy, confocal microscopy and real time PCR. Biofilm formation over titanium surfaces with different bacterial morphologies could be observed. TESPSA was able to significantly reduce the cellular viability when compared to all the surfaces (p < 0.05). Silver deposition on titanium surface did not show improved results in terms of biofilm adhesion and cellular viability when compared to its corresponding non-coated surface. The total amount of bacterial biofilm did not significantly differ between groups (p > 0.05). TESPSA was able to reduce biofilm adhesion and cellular viability. However, silver deposition on titanium surface seemed not to confer these antibacterial properties.

Identifying degradation mechanisms in lithium-ion batteries with coating defects at the cathode

Understanding the effect of electrode manufacturing defects on lithium-ion battery (LIB) performance is key to reducing the scrap rate and cost during cell manufacturing. In this regard, it is necessary to quantify the impact of various defects that are generated during the electrode coating process. To this end, we have tested large-format 0.5 Ah LiNi0.5Mn0.3Co0.2O2/graphite pouch cells with defects intentionally introduced into the cathode coating. Different types of coating defects were tested including agglomerates, pinholes, and non-uniform coating. Electrodes with larger non-coated surface had greater capacity fade than baseline electrodes, while pinholes and agglomerates did not affect performance adversely. Post cycle analysis of electrodes showed that the anode facing the defective region in the cathode was clearly impacted by the defect. Further characterization using Raman spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction provided evidence for a proposed mechanism for material degradation related to the most detrimental type of coating defect.

Turbulent channel flow over riblets with superhydrophobic coating

The performance of riblet surfaces after applying a superhydrophobic coating (SHC) is evaluated by planar particle image velocimetry (PIV) measurement at riblet tip spacing of s+ = 8.6, 17.3, and 34.6 (normalized using wall unit). The three riblet sizes correspond to an undersized (small drag reduction), an optimum (maximum drag reduction), and an oversized (drag increase) riblet, respectively. All the experiments are carried out in a turbulent water channel flow at constant ReH = 4360 (based on channel height H and average velocity). The superhydrophobic layer is formed by spray coating of micro/nano particles with a thickness of ∼1λ (wall unit). The results show smaller mean velocity over the s+ = 8.6 and s+ = 17.3 riblets when coated with the superhydrophobic layer at near-wall region of y+ < 15 while the mean velocity over the s+ = 34.6 riblet with SHC is larger relative to the non-coated counterpart. The SHC increased 〈u2〉 over the s+ = 8.6 and 17.3 surfaces while 〈u2〉 reduced over the s+ = 34.6 surface in the near wall region of y+ < 40. A smaller 〈v2〉 value is observed in the near-wall region (y+ < 50) of all three riblets upon applying the SHC while the reduction is smaller for smaller riblets. The 〈v2〉 peak also shifts away from the wall upon coating the s+ = 34.6 riblet. The Reynolds shear stress over s+ = 8.6 and s+ = 17.3 riblets is not considerably different relative to the superhydrophobic coated counterparts while a large reduction of 〈uv〉 is observed at y+ < 30 after coating the s+ = 34.6 riblet. The estimation of drag reduction (DR) based on weighted integral of 〈uv〉 shows 6.0% and 10.1% reduction of drag over the s+ = 8.6 and s+ = 17.3 riblets after the SHC process, respectively. SHC on the oversized s+ = 34.6 riblet improves the performance from 9.0% drag increase (DI) over the non-coated surface to 1.2% DR, equivalent to 10.2% reduction of drag upon coating the riblet. The larger improvement of oversized riblets (s+ > 30) is associated with the effectiveness of the SHC in the larger riblet valley and consequently attenuation of ejection and sweep motions. The SHC broadens the operation range of larger riblets, which are easier to manufacture.