Polysaccharide Layer-by-Layer Coating for Polyimide-Based Neural Interfaces

Implantable flexible neural interfaces (IfNIs) are capable of directly modulating signals of the central and peripheral nervous system by stimulating or recording the action potential. Despite outstanding results in acute experiments on animals and humans, their long-term biocompatibility is hampered by the effects of foreign body reactions that worsen electrical performance and cause tissue damage. We report on the fabrication of a polysaccharide nanostructured thin film as a coating of polyimide (PI)-based IfNIs. The layer-by-layer technique was used to coat the PI surface due to its versatility and ease of manufacturing. Two different LbL deposition techniques were tested and compared: dip coating and spin coating. Morphological and physiochemical characterization showed the presence of a very smooth and nanostructured thin film coating on the PI surface that remarkably enhanced surface hydrophilicity with respect to the bare PI surface for both the deposition techniques. However, spin coating offered more control over the fabrication properties, with the possibility to tune the coating’s physiochemical and morphological properties. Overall, the proposed coating strategies allowed the deposition of a biocompatible nanostructured film onto the PI surface and could represent a valid tool to enhance long-term IfNI biocompatibility by improving tissue/electrode integration

Structure and properties of nanostructured ZrN coatings obtained by vacuum-arc evaporation using RF discharge

Nanostructured films of zirconium nitride have been synthesized using an ion plasma vacuum-arc deposition technique in combination with a high-frequency (RF) discharge on AISI 430 stainless steel at 150 °C. Structural examination using X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM) with microanalysis (EDX), transmission electron microscopy (TEM), and nanoidentation was undertaken to reveal phase and chemical composition, surface morphology, microstructure and nanohardness of the coatings. The developed technology provided low-temperature film synthesis, minimized discharge breakdown decreasing formation of macroparticles (MPs) and allowed to deposit ZrN coatings with hardness variation 26.6–31.5 GPa and enhanced corrosion resistance characteristics. It was revealed that ZrN single-phase coatings of cubic modification with fine-crystalline grains of 20 nm in size were formed. The corrosion resistance of coatings has been tested in 0.9% quasiphysiological NaCl solution

Structure and properties of nanostructured ZrN coatings obtained by vacuum-arc evaporation using RF discharge

Nanostructured films of zirconium nitride have been synthesized using an ion plasma vacuum-arc deposition technique in combination with a high-frequency (RF) discharge on AISI 430 stainless steel at 150 °C. Structural examination using X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM) with microanalysis (EDX), transmission electron microscopy (TEM), and nanoidentation was undertaken to reveal phase and chemical composition, surface morphology, microstructure and nanohardness of the coatings. The developed technology provided low-temperature film synthesis, minimized discharge breakdown decreasing formation of macroparticles (MPs) and allowed to deposit ZrN coatings with hardness variation 26.6–31.5 GPa and enhanced corrosion resistance characteristics. It was revealed that ZrN single-phase coatings of cubic modification with fine-crystalline grains of 20 nm in size were formed. The corrosion resistance of coatings has been tested in 0.9% quasiphysiological NaCl solution

Antibacterial Nanostructured Ti Coatings by Magnetron Sputtering: From Laboratory Scales to Industrial Reactors

Based on an already tested laboratory procedure, a new magnetron sputtering methodology to simultaneously coat two-sides of large area implants (up to ~15 cm2) with Ti nanocolumns in industrial reactors has been developed. By analyzing the required growth conditions in a laboratory setup, a new geometry and methodology have been proposed and tested in a semi-industrial scale reactor. A bone plate (DePuy Synthes) and a pseudo-rectangular bone plate extracted from a patient were coated following the new methodology, obtaining that their osteoblast proliferation efficiency and antibacterial functionality were equivalent to the coatings grown in the laboratory reactor on small areas. In particular, two kinds of experiments were performed: Analysis of bacterial adhesion and biofilm formation, and osteoblasts–bacteria competitive in vitro growth scenarios. In all these cases, the coatings show an opposite behavior toward osteoblast and bacterial proliferation, demonstrating that the proposed methodology represents a valid approach for industrial production and practical application of nanostructured titanium coatings.EU-FEDER and the MINECO-AEI 201560E055EU-FEDER and the MINECO-AEI MAT2014-59772-C2-1-PEU-FEDER and the MINECO-AEI MAT2016-75611-REU-FEDER and the MINECO-AEI MAT2016-79866-REU-FEDER and the MINECO-AEI MAT2015-69035-REDCUniversity of Seville (Spain) V and VI PPIT-USMINECO CSIC13-4E-179

Knock phenomenon analysis on a diesel-CNG dual fuel engine using experimental fuel ratio

Knock avoidance is crucial to establish a proper Diesel-CNG Dual Fuel (DDF) engine. The causes of this phenomenon are still vague due to the lack of knock detection and characterization methods available. This study presents a knock characterization technique using a statistical analysis based on engine block vibration signal. Several experiments were conducted on a 2.5-litre converted DDF engine running at a constant engine speed between 1400 rpm and 3000 rpm with several diesel to CNG fuel ratio. This study found that when the diesel to CNG fuel ratio reached 70:30 at 1800 rpm to 3000 rpm, and 60:40 at 1400 rpm and 1600 rpm, engine knock was detected. A knock index was calculated from the vibration signal using Band-pass, Rectify, Integrate, and Compare (BRIC) method to determine knock intensity for each engine cycle. A three-sigma rule was applied to determine the threshold level of knock occurrence at the tested engine speeds. The knock thresholds at 1400 rpm, 1600 rpm, 1800 rpm, 2000 rpm, 2200 rpm, 2400 rpm, 2600 rpm, 2800 rpm, and 3000 rpm were found to have a knock index of 3.72, 3.49, 3.21, 2.71, 2.27, 1.80, 2.02, 1.80, and 1.73 respectively. Using a 5% knock cycle occurrence within the third and sixth standard deviation as a deciding criteria, a knock quality level was categorised as a vague, light, medium, and heavy knock. The analysed result shows that a severe knock occurred due to a sudden transition between a low and high knock intensity in a consecutive engine cycle, which yields a non-periodic mechanical shock. The calculated coefficient of variation of the knock index (COVKI) shows that the severe knock occurred when the COVKI is 0.30 and above. It suggests that the knock phenomenon on a DDF engine occurs due to an abrupt heat release rate during the mixing-controlled combustion phase and micro-explosion during the late combustion phase

Nanostructured ZrO₂ ceramic PVD coatings on Nd-Fe-B permanent magnets

The results of vacuum-arc deposition (PVD) of thin ZrO2 coatings to protect the surface of Nd-Fe-B permanent magnets used as repelling devices in orthodontics are presented. Magnetic devices are offered as an optimum and biologically safe forcegenerating system for orthodontic tooth movement. The structure, phase composition and mechanical properties of zirconium oxide films have been investigated by means of SEM, XRD, EDX, XRF and nanoindentation methods. The coatings are formed of polycrystalline ZrO2 films of monoclinic modification with average grain size 25 nm. The influence of the ZrO2 coating in terms of its barrier properties for corrosion in quasiphysiological 0.9% NaCl solution has been studied. Electrochemical measurements indicated good barrier properties of the coating on specimens in the physiological solution environment

Nanostructured nickel film deposition on carbon fibers for improving reinforcement-matrix interface in metal matrix composites

The issues in dispersing any form of carbon in metal matrix is the major problem in the field of metal matrix composites with carbon reinforcement (MMCcr). The low wettability of carbon in molten metals and the difference in density are some of the difficulties to obtain a good dispersion of carbon fibers in the matrix and, as a consequence, an improvement of some critical properties for metals in a wide range of application (mechanical properties, electrical properties, optical properties). For this reason, the aim of this work is to obtain a metallic coated carbon fiber to enhance the interaction between the reinforcement and the matrix. Moreover, also the density of carbon fibers could be adjusted depending on the thickness of the coating. Electroless Nickel-Phosphorus Plating (ENP) is one of the candidate to be a coating technique to improve the interaction between the carbon fibers and the metal matrix. Despite of its versatility in terms of complex geometry of the substrate and homogeneity and adhesion of the coating, the presence of the phosphorus in the alloy could create some problems with the metal matrix such as the formation of metal-phosphorus products that can drastically decrease the mechanical properties of the composite. For this reason, in this work, is presented a new way of Electroless Pure Nickel Plating (EPP) without any introduction of phosphorus in the nickel coating. The dependence of the coating thickness and the density of the coated fibers were studied under different plating parameters (temperature of the plating solution, deposition rate and plating solution composition). All the samples were characterized with SEM and XRD and the thickness, density and homogeneity were compared for all the samples obtained

Method for phase boundary structure control of laminated materials; destruction process investigations of nanostructured coatings with predetermined phase boundary texture

New surface texturing method by means of microplasma coating deposition with the following etching of the coating was shown and described. The method of step by step microplasma texturing was proposed to control the phase boundary of laminated materials. Micrographs of nanostructured inorganic non-metallic coating surface were obtained and analyzed before and after mechanical deformation. The nature of cracks formation and growth was investigated