Parylene C Research Articles

Enhanced Thin‐Film Encapsulation Through Micron‐Scale Anchors

AbstractImplantable medical devices require protective encapsulation to isolate them from the biological environment. Parylene‐C (PaC) is a prevalent encapsulation polymer but is susceptible to cracking, delamination, oxidation, and moisture penetration over time. This study demonstrates that 3D micro‐anchors fabricated by direct laser writing (DLW) greatly enhance PaC lifetime and encapsulation properties. The PaC film is vapor deposited onto these anchor points, followed by ultraviolet radiation (UV)‐curing‐induced shrinkage. Electrochemical impedance spectroscopy (EIS) during accelerated aging tests in reactive solutions (87 °C, 15 mM H2O2) is performed to monitor film degradation over time. Unpatterned PaC films failed before reaching the 3.25 accelerated year benchmark, while 100 µm spaced micro‐anchors extended encapsulation up to 5.5 equivalent years. Subsequent improvements are achieved with a spacing of 50 µm, demonstrating viability up to ≈6 equivalent years. This research demonstrates the benefit of engineering anchor points for preventing delamination of the PaC layer and significantly enhancing encapsulation properties. Printed 3D micro‐anchors are an extremely flexible platform, with many different shapes and sizes possible which can further enhance longevity. The success in increasing coating lifetimes offers a promising direction for improving long‐term implantable medical devices, potentially revolutionizing their longevity and reliability.

Design, Characterization, and In Vivo Application of Multi-Conductive Layer Organic Electrocorticography Probes

Biocompatible and plastic neural interface devices allow for minimally invasive recording of brain activity. Increasing electrode density in such devices is essential for high-resolution neural recordings. Superimposing conductive leads in devices can help multiply the number of recording sites while keeping probes width small and suitable for implantation. However, because of leads' vertical proximity, this can create capacitive coupling (CC) between overlapping channels, which leads to crosstalk. Here, we present a thorough investigation of CC phenomenon in multi-gold layer thin-film multi-electrode arrays with a parylene C (PaC) insulation layer between superimposed leads. We also propose a guideline on the design, fabrication, and characterization of such type of neural interface devices for high spatial resolution recording. Our results demonstrate that the capacitance created through CC between superimposed tracks decreases non-linearly and then linearly with the increase of insulation thickness. We identify an optimal PaC insulation thickness that leads to a drastic reduction of CC between superimposed gold channels while not significantly increasing the overall device thickness. Finally, we show that double gold layer electrocorticography probes with the optimal insulation thickness exhibit similar performances in vivo when compared to single-layer devices. This confirms that these probes are adequate for high-quality neural recordings.

Duty-cycle dependence of photo-induced displacement current in MISIM photocells

Organic optoelectronic conversion possesses various advantages such as low cost and tunable light sensing, but organic semiconductors suffer from significant drawbacks, such as instability in air and low carrier mobility. To overcome them, we recently proposed a [metal (M)|insulator (I)|semiconductor (S)|insulator (I)|metal (M)] structure (MISIM photocells) that can effectively induce photo-induced displacement current without any passage of carriers through the S|I and I|M interfaces. In the present work, we investigated the duty-cycle dependence of MISIM photocells, to determine the guiding principles for improving the speed and efficiency of the optoelectronic conversion toward its practical application. We formed an MISIM photocell consisting of a bilayer of zinc phthalocyanine (ZnPc) and fullerene (C 60 ) as the S layer and parylene C (PC) as the I layers, and tested the dependence of the photocurrent on the duty cycle D = t ON /( t ON + t OFF ), where t ON and t OFF are the light illumination and blocking times, respectively, in one cycle under light modulation. By independently changing t ON and t OFF in the range of 0.2–2.0 μs, the rise time of the transient photocurrent was found to be improved by approximately 30% by the duty cycle. We also revealed that the charge carriers Q generated in one cycle reached their maximum at D ≈ 0.4, and the time average increased gradually with an increase in modulation frequency. This feature of Q was well explained by a theoretical model for the MISIM photocells. • MISIM photocells: Unique optoelectrical conversion suitable for organic materials. • Pure polarization current without any passage of carriers through the S|I and I|M interfaces • Optimization of conversion efficiency and speed by tuning duty cycle. • Enhancement of conversion speed by 30%. • Successful theoretical fit to the photocurrent as a function of the light illumination and blocking times.

Effect of metal foil size on the actuation properties of micro-chip exploding foil initiator

Exploding foil initiator (EFI)is a special kind of actuator that is used to drive the flyer. To realize high-velocity flyer output and low-energy firing, the size of bridge foil and corresponding structures of EFI were studied. Four kinds of micro-chip exploding foil initiators (McEFI) with different bridge foil sizes were prepared in batches using Micro-Electro-Mechanical System technology. Furthermore, the primary characteristics of the four kinds of bridge foils were comparatively performed and discussed, including the electro-thermal simulation, electrical-explosion properties, and flyer velocities capabilities. Most importantly, the velocities of the ParyleneC (PC) flyer were measured by photonic doppler velocimetry, indicating the PC flyer had better velocity capabilities with the reduction of the size of the bridge foil. The firing property of McEFI was validated by initiating HNS-IV pellets, and the critical threshold energy was determined as 0.22 μF/1095 V based on the sensitivity test. This structural change truly implements the popularization of the high-velocity flyer actuator or initiator.

Cell viability and cytotoxicity of inkjet-printed flexible organic electrodes on parylene C.

This study reports on the fabrication of biocompatible organic devices by means of inkjet printing with a novel combination of materials. The devices were fabricated on Parylene C (PaC), a biocompatible and flexible polymer substrate. The contact tracks were inkjet-printed using a silver nanoparticle ink, while the active sites were inkjet-printed using a poly (3,4ethylenedioxythiophene)/polystyrene sulfonate (PEDOT:PSS) solution. To insulate the final device, a polyimide ink was used to print a thick film, leaving small open windows upon the active sites. Electrical characterization of the final device revealed conductivities in the order of 103 and 102S.cm-1 for Ag and PEDOT based inks, respectively. Cell adhesion assays performed with PC-12 cells after 96h of culture, and B16F10 cells after 24h of culture, demonstrated that the cells adhered on top of the inks and cell differentiation occurred, which indicates Polyimide and PEDOT:PSS inks are non-toxic to these cells. The results indicate that PaC, along with its surface-treated variants, is a potentially useful material for fabricating cell-based microdevices.

Effect of the Al2O3 Deposition Method on Parylene C: Highlights on a Nanopillar-Shaped Surface.

Parylene C (PC) has attracted tremendous attention throughout the past few years due to its extraordinary properties such as high mechanical strength and biocompatibility. When used as a flexible substrate and combined with high-κ dielectrics such as aluminum oxide (Al2O3), the Al2O3/PC stack becomes very compelling for various applications in fields such as biomedical microsystems and microelectronics. For the latter, the atomic layer deposition of oxides is particularly needed as it allows the deposition of high-quality and nanometer-scale oxide thicknesses. In this work, atomic layer deposition (ALD) and electron beam physical vapor deposition (EBPVD) of Al2O3 on a 15 μm-thick PC layer are realized and their effects on the Al2O3/PC resulting stack are investigated via X-ray photoelectron spectroscopy combined with atomic force microscopy. An ALD-based Al2O3/PC stack is found to result in a nanopillar-shaped surface, while an EBPVD-based Al2O3/PC stack yields an expected smooth surface. In both cases, the Al2O3/PC stack can be easily peeled off from the reusable SiO2 substrate, resulting in a flexible Al2O3/PC film. These fabrication processes are economic, high yielding, and suitable for mass production. Although ALD is particularly appreciated in the semiconducting industry, EBPVD is here found to be better for the realization of the Al2O3/PC flexible substrate for micro- and nanoelectronics.

Sound Absorption and Transmission in Nanoengineered Polymers

In this study we use vapor deposition to incorporate carbon nanotubes (CNTs) and silicon dioxide nanopowder (nanosilica) in Polyurethane (PU) as well as to engineer Parylene C (PC) in a microfibrous thin film (µFTF) and bulk forms in an attempt to examine acoustic absorption and transmission properties in the low frequency (50 to 200 Hz) range. Incorporating CNTs or/and nanosilica into PU significantly increases its acoustic transmission, presumably due to increased rigidity caused by nanoparticle (CNTs and nanosilica) addition. This is explained as due to adding nanosilica or/and CNTs to PU increases its rigidity and, hence, its sound transmission. On the other hand, engineering the PC in the µFTF form enhances acoustic absorption in the film, especially at the resonant frequencies associated with oscillations of the microfibers making up the PC µFTF.

A Spectroscopy and Microscopy Study of Parylene-C OFETs for Explosive Sensing

In this paper, we have explored Parylene-C (PC) as a sensing material for its unique signature and selectivity for explosive sensing. We have used a bi-layer deposition process to fabricate bottom-gate-top-contact organic field effect transistor (OFET) structures. Opening of dangling bonds on subjecting PC to plasma oxidation (POPC) renders these molecules to be employed as a receptor material in sensing vapors of both explosives and non-explosives, such as Trinitrotoulene (TNT), 1,3,5 trinitro-1,3,5-triazacyclohexane(RDX), PETN, Dinitrobenzene (DNB), Nitrobenzene (NB), Benzoquinone (BQ), and Benzophenone (BP). The change in: 1) the vibrational modes of the molecule by infrared spectroscopy; 2) surface potential of POPC by Kelvin probe force microscopy (KPFM); and 3) electrical characterization by I-V measurements of PC-based OFET on exposing to vapors have been systematically studied. Different signatures for all the analytes have been observed while exact and perfect selectivity for TNT, RDX were found from I-V studies and for PETN by KPFM studies. Thus, the OFET device-based chemical sensors demonstrated here with improved sensitivity and excellent selectivity, stand as promising candidates for explosives detection.

Improving adhesion strength between layers of an implantable parylene-C electrode

Parylene-C (PC) is one of the most frequently used materials for flexible implantable electrode. Its interface with metal or other PC layer is critical in PC–metal-PC “sandwich” implantable neural electrodes in relation to their long-term reliability. In this study, we aim to develop a method to improve metal-PC and PC–PC adhesion in PC-based neural electrodes. “Nano-forest” structure, composed of nanopillar array is fabricated on the surface of bottom PC by oxygen reactive ion etching (RIE). The contribution of this layer of nano-structure to mechanical adhesion and sealing property are evaluated respectively. The results verify that for PC based “sandwich” electrode, not only the mechanical adhesion among three layers, but also the sealing ability between PC layers are significantly improved.

Histopathological Effects of Parylene C (poly-chloro-p-xylylene) in the Inner Ear.

To assess the histopathological effects of parylene C (PC) (poly-chloro-p-xylylene) in the inner ear. Nine adult Dunkin Hartley guinea pigs (500-600 g) were included in the study. PC pieces were inserted into the cochlea in the right ear of the animals (study group). The round windows were punctured in the left ears comprised the control group. After three months, the animals were sacrificed, and the dissected temporal bones were examined under a light microscope. No significant difference was revealed between the study and control groups regarding histopathological findings such as perineural congestion, perineural inflammation, neural fibrosis, number of ganglion cells, edema, and degeneration of ganglion cells (p>0.05). PC did not cause any additional histopathologic damage in the cochlea. This finding may be promising regarding the use of PC in cochlear implant electrodes as an alternative to silicon materials in the future.

Isolation of circulating tumor cells by a magnesium-embedded filter

Circulating tumor cells (CTCs) are rare cancer cells that are shed by tumors into the bloodstream and that can be valuable biomarkers for various types of cancers. However, CTCs captured on the filter could not be released easily using the existing CTC analysis platforms based on size. To address this limitation, we have developed a novel magnesium (Mg)-embedded cell filter for capture, release and isolation of CTCs. The CTC-filter consists of a thin Ebeam-deposited Mg layer embedded between two parylene-C (PA-C) layers with designed slots for filtration and CTC capture. Thin Mg film has proved highly biocompatible and can be etched in saline, PBS and Dulbecco’s modified eagle medium (DMEM) etc, properties that are of great benefit to help dissociate the filter and thus release the cells. The finite element method (FEM) analysis was performed on the Mg etching process in DMEM for the structure design. After the filtration process, the filter was submerged in DMEM to facilitate Mg etching. The top PA-C filter pieces break apart from the bottom after Mg completely dissolves, enabling captured CTCs to detach. The released CTC can be easily aspirated into a micropipette for further analysis. Thus, the Mg-embedded cell filter provides a new and effective approach for CTCs isolation from the filter, making this a promising new strategy for cancer detection.

Superiority of Graphene over Polymer Coatings for Prevention of Microbially Induced Corrosion.

Prevention of microbially induced corrosion (MIC) is of great significance in many environmental applications. Here, we report the use of an ultra-thin, graphene skin (Gr) as a superior anti-MIC coating over two commercial polymeric coatings, Parylene-C (PA) and Polyurethane (PU). We find that Nickel (Ni) dissolution in a corrosion cell with Gr-coated Ni is an order of magnitude lower than that of PA and PU coated electrodes. Electrochemical analysis reveals that the Gr coating offers ~10 and ~100 fold improvement in MIC resistance over PU and PA coatings respectively. This finding is remarkable considering that the Gr coating (1–2 nm) is ~25 and ~4000 times thinner than the PA (40–50 nm), and PU coatings (20–80 μm), respectively. Conventional polymer coatings are either non-conformal when deposited or degrade under the action of microbial processes, while the electro-chemically inert graphene coating is both resistant to microbial attack and is extremely conformal and defect-free. Finally, we provide a brief discussion regarding the effectiveness of as-grown vs. transferred graphene films for anti-MIC applications. While the as-grown graphene films are devoid of major defects, wet transfer of graphene is shown to introduce large scale defects that make it less suitable for the current application.

Assessment of Parylene C Thin Films for Heart Valve Tissue Engineering.

Scaffolds are a key component of tissue-engineered heart valves (TEHVs). Several approaches had been adopted in the design of scaffolds using both natural and synthetic resources. We have investigated the suitability of parylene C (PC), a vapor deposited polymeric material, for the use as a scaffold in TEHV. To evaluate the adsorption of extracellular matrix components onto plasma-activated PC and study the biocompatibility of PC by measuring cellular adhesion, viability, apoptosis, and phenotypic expression of valve endothelial and interstitial cells. Finally, the mechanical properties of PC were compared with those of native aortic valve cusp tissue. PC slides were plasma activated and then coated with gelatin, type I collagen, or fibronectin. Porcine pulmonary valve endothelial and interstitial cells were then grown on plasma oxidized PC with different types of coatings and their adhesion was observed after 20 h of incubation. Cell viability was tested using the MTS assay, and apoptosis was estimated using TUNEL staining. The mechanical properties of PC and valve tissue were measured using a Bose Mechanical Tester. Finally, cell-seeded PC films were exposed to pulsatile pressure and aortic shear stress, respectively, to test their durability in a dynamic environment. Our findings show that collagen and fibronectin could bind to plasma oxidized PC. Both valve endothelial and interstitial cells adhered to protein-coated ECM. PC had a profile of mechanical stiffness and ultimate tensile strength that were comparable with or in excess of those seen in porcine aortic valve cusps. Cells were still attached to PC films after 3 days of exposure to up to 50 mmHg pulsatile pressure or aortic levels of shear stress. PC is a promising candidate for use as a scaffold in tissue engineering heart valves. Additional studies are required to determine both the durability and long-term performance of cell-seeded PC when in a similar hemodynamic environment to that of the aortic valve.

Improving the Surface Wettability of Parylene C Film by Hyperthermal Hydrogen Induced Cross-Linking Technology

In this paper, we present a new approachcalled hyperthermal hydrogen induced cross-linking (HHIC) technology,which can successfully enhance the surface wettability of Parylene C (PC) film via cross-linking hydrophilic polyacrylic acid（PAA）on its surface. Water Contact Angle Meter and Fourier Transform Infrared Spectroscopy (FTIR) were used to characterize wetting property, surface chemical structureof PC film before or after HHIC treatment,respectively. The results show that PAA with polar functional groups can be successfully grafted onto the PC film. As a result, the water contact angle of the modified PC membrane surface decreased from 84° to 23°,PC membrane surface wettability is improved effectively.

Laser-induced forward transfer of multi-layered structures for OTFT applications

We report on the one-step laser printing of multi-layered organic-based field effect transistors, using thin films of bis(2-phenylethynyl) end-substituted terthiophene (diPhAc-3T) as semiconductor, parylene-C (Py-C) as dielectric and silver (Ag) as gate electrode, respectively. The laser-induced forward transfer (LIFT) process was used to transfer pixels from donor to receiver substrates. The latter included pre-designed source and drain gold electrodes to form complete organic thin films transistors (OTFTs). Such laser-induced forward transfer used a single 50ps duration pulse delivered by a Nd:YAG laser operating at 355nm to print transistor pixel arrays under ambient temperature. The pixels (350μm sized-squares, and 700±40nm in thickness), fabricated in the top gate configuration, were investigated for their current–voltage characteristics immediately after printing. Electrical characterization demonstrated that the laser printed transistor is fully functional with hole mobilities of 4×10−4cm2/Vs, a threshold voltage Vt near −10V, Ion/Ioff ratio near to 104–105 and the sub-threshold slope (S) of 14–18V/decade. The efficient cohesion between the three different layers composing the pixels offers an exceptionally high strength to laser printing, while maintaining the electrical properties.

Stretchable electrochemical impedance sensors for intravascular detection of lipid-rich lesions in New Zealand White rabbits

Flexible electronics have enabled catheter-based intravascular sensing. However, real-time interrogation of unstable plaque remains an unmet clinical challenge. Here, we demonstrate the feasibility of stretchable electrochemical impedance spectroscopy (EIS) sensors for endoluminal investigations in New Zealand White (NZW) rabbits on diet-induced hyperlipidemia. A parylene C (PAC)-based EIS sensor mounted on the surface of an inflatable silicone balloon affixed to the tip of an interrogating catheter was deployed (1) on the explants of NZW rabbit aorta for detection of lipid-rich atherosclerotic lesions, and (2) on live animals for demonstration of balloon inflation and EIS measurements. An input peak-to-peak AC voltage of 10mV and sweeping-frequency from 300kHz to 100Hz were delivered to the endoluminal sites. Balloon inflation allowed EIS sensors to be in contact with endoluminal surface. In the oxidized low-density-lipoprotein (oxLDL)-rich lesions from explants of fat-fed rabbits, impedance magnitude increased significantly by 1.5-fold across the entire frequency band, and phase shifted ~5° at frequencies below 10kHz. In the lesion-free sites of the normal diet-fed rabbits, impedance magnitude increased by 1.2-fold and phase shifted ~5° at frequencies above 30kHz. Thus, we demonstrate the feasibility of stretchable intravascular EIS sensors for identification of lipid rich lesions, with a translational implication for detecting unstable lesions.

Poly-N-(4-benzoylphenyl)methacrylamide nanoparticles: preparation, characterization, and photoreactivity features

The design and preparation of novel photo- reactive poly-N-(4-benzoylphenyl)methacrylamide-based nanoparticles (NPs) are reported herein. The starting photoreactive monomer, N-4-benzoylphenyl methacryla- mide, was prepared by amidation of the photoreactive species 4-aminobenzophenone with methacryloyl chlo- ride in the presence of triethylamine. Corresponding 97 nm-sized NPs were obtained using a dispersion poly- merization technique. Deep surface and bulk characteriza- tion of resulting polyBPMA NPs were performed using a combination of transmission and scanning electron micros- copies (NP morphology), dynamic light scattering (NP size and size distribution), ζ potential (surface NP charge), thermo-gravimetric measurements (weight loss profiling), differential scanning calorimetry (heat transmission fea- tures), infrared and ultra-violet spectroscopies (functionality checking), nuclear magnetic resonance ( 1 H-NMR, func- tionality confirmation), gel permeation chromatography (average polymer molecular weight), and mass spectrome- try (average polymer molecular weight). Different reaction conditions were investigated for optimal fabrication of corresponding polyBPMA NPs. In addition and most importantly, their UV-mediated photo-reactivity with non- functional parylene C (PC) polymer coatings has been investigated towards NP covalent attachment. The success- ful bonding of such photo-reactive polymeric NPs onto PC films was confirmed by FTIR-ATR spectroscopy and by both atomic force- and scanning electron-microscopies.

Surface chemical immobilization of parylene C with thermosensitive block copolymer brushes based onN‐isopropylacrylamide andN‐tert‐butylacrylamide: Synthesis, characterization, and cell adhesion/detachment

Poly(N-isopropylacrylamide) (pNIPAM), poly(N-tert-butylacrylamide) (pNTBAM), and their copolymer brushes were covalently immobilized onto parylene C (PC) surfaces via surface initiated atom transfer radical polymerization (ATRP). Contact angle measurement between 13 and 40°C showed that the hydrophobicity of the modified PC surfaces was thermally sensitive. Among these samples, PC grafted with pNIPAM (PC-NI), PC grafted with pNTBAM (PC-NT) and PC grafted with copolymer brushes containing pNTBAM and pNIPAM (PC-NT-NI) exhibited the lower critical solution temperature (LCST) at 29, 22, and 24°C, respectively. Cytocompatibility study for the modified surfaces was performed by 5 days human skin fibroblast culture at 37°C. Data showed that only a very small amount of cells adhered on the PC and PC-NI surfaces, while a significantly higher amount of cell adhesion and growth was observed on PC-NT and PC-NT-NI surfaces. Furthermore, cell detachment at the temperatures of 24 and 6°C were studied after the substrates were cultured with cells at 37°C for 24 h. The results showed that the cells on PC-NI formed the aggregations and loosely attached on the substrate after 30-min culture at 24°C, while no significant cell detachment was observed for PC-NT and PC-NT-NI samples at this temperature. By continuing the cell culture for additional 100 min at 6°C for PC-NT and PC-NT-NI, about 10 and 35% of the cells were found detached respectively, and the unattached cells aggregated on the substrate. In comparison, cells cultured on the tissue culture petri dish (TCP) exhibited no quantity and morphology changes at the culture temperatures of 37, 24, and 6°C. This study showed that: (1) immobilization of PC with nonthermal sensitive pNTBAM could provide PC surface thermal sensitive hydrophilicity; (2) the chlorines on the polymer brushes of PC-NT could be used to further initiate the ATRP pNIPAM and form block copolymer brushes; (3) the incorporation of pNTBAM into pNIPAM on PC-NT-NI could change the surface thermal hydrophilicity property, and be further applied to decrease the LCST of the modified PC surface; (4) grafted pNIPAM brushes on PC-NI by ATRP showed very low cell adhesion and proliferation in 5 days fibroblast culture at 37°C, and cell detached at 24°C; (5) the incorporation of pNTBAM into pNIPAM on PC-NT-NI decreased the thermal sensitivity of cell adhesion/detachment, cell detached at 6°C, but the cell adhesion and proliferation were significantly improved at a wide temperature range.

Chemical surface modification of parylene C for enhanced protein immobilization and cell proliferation

To introduce the adhesion site of proteins and/or cells on parylene C (PC)-coated medical devices that can be used as implantable biosensors or drug delivery capsules, the PC surfaces were initially modified by the Friedel–Crafts acylation reaction to generate active chlorines. These chlorines were then employed to initiate the atom transfer radical polymerization of tert-butyl acrylate (TBA) and form a polymer brush layer of polyTBA on PC; the acrylate groups in the polymer brushes were hydrolyzed to carboxylic acid groups and further activated into succinimidyl ester groups via the 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide coupling reaction. The PC surface grafted with polymer brushes and activated by succinimide showed efficient attachment of proteins, including gelatin, contortrostatin (CN) and bovine serum albumin (BSA), all at high density on the PC surface. The CN density on the surface was evaluated for both monolayer and polymer brush-based coatings. Based on fluorescence measurements, the polymer brush gives a 60-fold higher surface protein density than the monolayer-based system. Gelatin was used as a model protein and covalently coated onto the modified PC surface for cell culture study. Substrates with gelatin coating showed a significantly higher cell attachment and proliferation in 7 days cultures as compared to the uncoated substrates. In addition, a conventional photolithography technique was coupled with the surface chemistry to successfully pattern the BSA labeled with fluorescein isothiocyanate on the modified PC surfaces.

Model Study Investigating the Role of Interfacial Factors in Electrochemical Impedance Spectroscopy Measurements

Abstract To observe the effect of interfacial factors on electrochemical impedance spectroscopy (EIS), model systems consisting of Parylene C (PC) film coated on Alclad 7075-T6 (UNS A97075) sheets and freestanding PC films were investigated. To modify the top surface of PC coating, the coating on Al alloy panels were treated with two plasmas: trimethylsilane (TMS) and a mixture of TMS + O2. Plasma polymerization of TMS followed by hexafluoroethane (HFE) also was applied to the substrate surface prior to the deposition of PC film to improve the adhesion of the film to the surface. Coating performance was evaluated using EIS, and interfacial factors produced by plasma treatments were studied by applying suitable equivalent circuit models, which take into account all the interfacial parameters and bulk coating. Simulations performed with circuit models proposed in this work indicated that top surface modification with plasma treatment influenced the salt intrusion property of the top layer as well as of the ...