Metal-polymer Interface Research Articles

Investigating Gold Deposition with High-Power Impulse Magnetron Sputtering and Direct-Current Magnetron Sputtering on Polystyrene, Poly-4-vinylpyridine, and Polystyrene Sulfonic Acid.

Fabricating thin metal layers and particularly observing their formation process in situ is of fundamental interest to tailor the quality of such a layer on polymers for organic electronics. In particular, the process of high power impulse magnetron sputtering (HiPIMS) for establishing thin metal layers has sparsely been explored in situ. Hence, in this study, we investigate the growth of thin gold (Au) layers with HiPIMS and compare their growth with thin Au layers prepared by conventional direct current magnetron sputtering (dcMS). Au was chosen because it is an inert noble metal and has a high scattering length density. This allows us to track the growing nanostructures via grazing incidence scattering. In particular, Au deposition on the polymer polystyrene (PS) with the respective structural analogues poly-4-vinlypyridine (P4VP) and polystyrene sulfonic acid (PSS) is studied. Additionally, the nanostructured layers on these different polymer films are further probed by field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), X-ray reflectometry (XRR), and four-point probe measurements. We report that HiPIMS leads to smaller island-to-island distances throughout the whole sputter process. Moreover, an increased cluster density and an earlier percolation threshold are achieved compared to dcMS. Additionally, in the early stage, we observe a significant increase in coverage by HiPIMS, which is favorable for the improvement of the polymer-metal interface.

Study of Ion-to-Electron Transducing Layers for the Detection of Nitrate Ions Using FPSX(TDDAN)-Based Ion-Sensitive Electrodes.

The development of ISE-based sensors for the analysis of nitrates in liquid phase is described in this work. Focusing on the tetradodecylammonium nitrate (TDDAN) ion exchanger as well as on fluoropolysiloxane (FPSX) polymer-based layers, electrodeposited matrixes containing double-walled carbon nanotubes (DWCNTs), embedded in either polyethylenedioxythiophene (PEDOT) or polypyrrole (PPy) polymers, ensured improved ion-to-electron transducing layers for NO3- detection. Thus, FPSX-based pNO3-ElecCell microsensors exhibited good detection properties (sensitivity up to 55 mV/pX for NO3 values ranging from 1 to 5) and acceptable selectivity in the presence of the main interferent anions (Cl-, HCO3-, and SO42-). Focusing on the temporal drift bottleneck, mixed results were obtained. On the one hand, relatively stable measurements and low temporal drifts (~1.5 mV/day) were evidenced on several days. On the other hand, the pNO3 sensor properties were degraded in the long term, being finally characterized by high response times, low detection sensitivities, and important measurement instabilities. These phenomena were related to the formation of some thin water-based layers at the polymer-metal interface, as well as the physicochemical properties of the TDDAN ion exchanger in the FPSX matrix. However, the improvements obtained thanks to DWCNT-based ion-to-electron transducing layers pave the way for the long-term analysis of NO3- ions in real water-based solutions.

Highly conductive rubber-based electrode with a robust wrinkled mesh-like copper coating for stretchable triboelectric nanogenerator

Stretchable triboelectric nanogenerators (TENGs) have gained increasing attention for their potential applications in wearable electronics. However, the fabrication of metal-coated flexible electrodes with a robust metal-polymer interface, high conductivity, and stretchability remains challenging for stretchable TENGs. Herein, a stretchable triboelectric nanogenerator (TENG) was designed using a highly conductive natural rubber (NR) electrode with a wrinkled mesh-like copper coating, which was chemically plated onto its surface by polymer-assisted metal deposition (PAMD) technology. To enable the PAMD process, a layer of polyacrylic acid (PAA) polymer brushes was first grafted onto the NR surface. This could not only assist the chemical plating but also improve the interfacial adhesion between the copper coating and the NR substrates. More importantly, the PAA layer facilitated the interconversion between the wrinkled structure and mesh-like structure of the copper coating during stretching cycles to ensure its conductivity and mechano-electrical stability. With this intrinsically stretchable rubber-based electrode, TENG devices were designed in a contact-separation configuration, which could effectively harvest mechanical energy in both pressing and stretching modes and show excellent electrical output performance. Notably, the rubber-based TENG could work stably at 100 % strain and produce a maximum power density of 0.14 mW/m2 at the resistance load of 3×107 Ω. Therefore, the stretchable rubber-based TENG in this work demonstrated a potential solution to flexible micromechanical energy harvesters for wearable devices.

The Role of Surface Treatment and Coupling Agents for Adhesion between Stainless Steel (SUS) and Polyamide (PA) of Heterojunction Bilayer Composites.

The growing demand for lightweight and durable materials in industries, such as the automotive, aerospace, and electronics industries, has spurred the development of heterojunction bilayer composites, combining the structural integrity of metals with the versatility of polymers. This study addresses the critical interface between stainless steel (SUS) and polyamide 66 (PA66), focusing on the pivotal role of surface treatments and various silane coupling agents in enhancing the adhesion strength of heterojunction SUS/PA66 bilayer composites. Through systematic surface modifications-highlighted by scanning electron microscopy, atomic force microscopy, and contact angle analyses-the study assessed the impact of increasing the surface area, roughness, and energy of SUS. X-ray photoelectron spectroscopy evaluations confirmed the strategic selection of specific silane coupling agents. Although some coupling agents barely influenced the mechanics, notably, aminopropyl triethoxysilane (A1S) and 3-glycidyl oxypropyl trimethoxysilane (ES) significantly enhanced the mechanical properties of the heterojunction bilayer composites, evidenced by the improved lap shear strength, elongation at break, and toughness. These advancements were attributed to the interfacial interactions at the metal-polymer interface. This research underscored the significance of targeted surface treatment and the judicious selection of coupling agents in optimizing the interfacial adhesion and overall performance of metal-polymer composites, offering valuable insights for the fabrication of materials where reduced weight and enhanced durability are paramount.

Eliminating surface cracks in metal film-polymer substrate for reliable flexible piezoelectric devices

In a flexible piezoelectric-metal-polymer device, the occurrence of surface cracks in metal-polymer interface may cause unstable metal connections, unreliable piezoelectric yield, poor passivation behaviour and metal electrode delamination. In this study, the properties of polydimethylsiloxane (PDMS) polymer substrate are optimised, and the sputter-deposition of aluminium (Al) and molybdenum (Mo) metal film layer is controlled to eradicate cracks and promote only surface wrinkles on large area metal-polymer interface. The PDMS substrate thickness of ∼123.8 µm, 20:1 prepolymer base to curing agent weight ratio, 50 °C PDMS curing temperature and 30 min of Al sputtering time have been discovered to produce crack-free wrinkle-only Al thin film layer on PDMS substrate. The Al thin film is 100 % conductive over large area and adhere well on PDMS with 0 % of Al removal. The grown zinc oxide (ZnO) and aluminium nitride (AlN) piezoelectric layer on the improved Al-PDMS are of good crystal quality, generating low leakage current and decent piezoelectric voltage. The attained crack-free wrinkled-only metal film-polymer substrate interface is vital for flexible piezoelectric-metal-polymer device to perform well as an acoustic sensor, energy harvester, or even as an insulation/buffer layer in stretchable electronics.

Corrosion Protection of Galvanised Steel Using Organic Coatings Containing Inhibitive Additives Based on Benzothiazoyl Succinic Acid

It is increasingly apparent that the replacement of highly effective, but environmentally unacceptable chromium (VI)- based inhibitive pigment technologies within protective coatings requires the use of combinations of anti-corrosion additives. There is currently significant interest in using organic inhibitors containing hetero-atoms of nitrogen and/or sulphur in conjunction with conventional Cr(vi)-free inorganic pigments as a means of providing equivalent corrosion protection. One such organic inhibitor is benzothiazoyl succinic acid (BTSA), which is presently commercially available as an in-coating anti-corrosion additive, which can improve the protection capability in existing chromate free formulations. In this work we investigate the ability of BTSA to mitigate corrosion-driven organic coating failure within model coatings applied to hot-dip galvanised steel. In addition, the ability of BTSA to inhibit localised corrosion on bare zinc surfaces when released from a protective coating into corrosive electrolyte within a penetrative defect is also evaluated. A combination of time-lapse imaging and in-situ scanning Kelvin probe (SKP) potentiometry is employed to quantify cathodic delamination rates of model poly-vinyl butyral (PVB) coatings containing varying levels of BTSA additions. It is demonstrated that in-coating BTSA, both added directly to PVB or stored as an exchangeable anion in a layered double hydroxide “smart-release” pigment reduce rates of cathodic disbondment by up to a factor of 20. For both methods of incorporating in-coating BTSA, an increasing loading produces a progressive decrease in delamination rates and a transition from linear to parabolic coating failure kinetics. In addition, it is also demonstrated that BTSA dissolved in the aqueous NaCl (aq) electrolyte applied to a defect can also significantly reduce the rate of cathodic disbondment observed for an unpigmented PVB coating. Highly effective inhibition of localised corrosion of bare HDG surfaces by BTSA additions made to NaCl (aq) electrolyte is demonstrated by a combination on SVET and potentiodynamic studies. Linear polarisation resistance experiments demonstrate an inhibition efficiency of 95% for a 10 mM BTSA addition made to 1% w/v NaCl (aq) at pH 7, while SVET-derived, area averaged current density value are shown to decrease by over an order of magnitude compared with an un-inhibited case over a 6 h immersion period. Using polarisation curves obtained for HDG surfaces in the presence and absence of varying concentrations of dissolved BTSA, a mixed inhibition mechanism is proposed. At intermediate concentrations (1 – 10 mM), BTSA strongly adsorbs on the oxide covered Zn surface via its two carboxylate functional groups, thus hindering electron transfer reactions and providing net cathodic inhibition. At higher concentrations (> 10 mM) an additional reinforcement of any weak points in the adsorbed layer is achieved by virtue of the formation of an insoluble salt formed by reaction with Zn(ii) cations, producing a positive shift in free corrosion potential. In-coating BTSA appears to stifle cathodic disbondment by adsorbing strongly on the intact organic-coated metal, which in turn hinders underfilm oxygen reduction and the dissolution of the amphoteric zinc(hydr)oxide layer at the metal-polymer interface.

Mechanism Study of Molecular Trap in All-Organic Polystyrene-Based Dielectric Composite.

It is a huge challenge to explore how charge traps affect the electric breakdown of polymer-based dielectric composites. In this paper, alkane and aromatic molecules with different substituents are investigated according to DFT theoretical method. The combination of strong electron-withdrawing groups and aromatic rings can establish high electron affinity molecules. 4'-Nitro-4-dimethylaminoazobenzene (NAABZ) with a vertical electron affinity of 1.39eV and a dipole moment of 10.15 D is introduced into polystyrene (PSt) to analyze the influence of charge traps on electric properties. Marcus charge transfer theory is applied to calculate the charge transfer rate between PSt and NAABZ. The nature of charge traps is elaborated from a dynamic perspective. The enhanced breakdown mechanism of polymers-based composites stems from the constraint of carrier mobility caused by the change in transfer rate. But the electrophile nature of high electron affinity filler can decrease the potential barriers at the metal-polymer interface. Simultaneously, the relationship between the electron affinity of fillers and the breakdown strength of polymer-based composites is nonlinear because of the presence of the inversion region. Based on the deep understanding of the molecular trap, this work provides the theoretical calculation for the design and development of high-performance polymer dielectrics.

The Role of Self-Assembled Monolayers in the Surface Modification and Interfacial Contact of Copper Fillers in Electrically Conductive Adhesives.

Printing of electrical circuits and interconnects using isotropic conductive adhesives (ICAs) is of great interest due to their low-temperature processing and compatibility with substrates for applications in sensors, healthcare, and flexible devices. As a lower cost alternative to silver (Ag), copper (Cu)-filled ICAs are desirable but limited by the formation of high-resistivity Cu surface oxides. To overcome this limitation, self-assembled monolayers (SAMs) of octadecanethiol (ODT) have been demonstrated to reduce the oxidation of micrometer-scale Cu powder particles for use in ICAs. However, the deposition and function of the SAM require further investigation, as described in this paper. As part of this work, the stages of the SAM deposition process, which included etching with hydrochloric acid to remove pre-existing oxides, were studied using X-ray photoelectron spectroscopy (XPS), which showed low levels of subsequent Cu oxidation when ODT coated. The treated Cu powders were combined with one- or two-part epoxy resins to make Cu-ICAs, and the effect of the Cu surface condition and weight loading on electrical conductivity was examined. When thermally cured in an inert argon atmosphere, ICAs filled with Cu protected by ODT achieved electrical conductivity up to 20 × 105 S·m-1, comparable to Ag-ICAs, and were used to make a functional circuit. To understand the function of the SAM in these Cu-ICAs, scanning and transmission electron microscopy were used to examine the internal micro- and nano-structures along with the elemental distribution at the interfaces within sections taken from cured samples. Sulfur (S), indicative of the ODT, was still detected at the internal polymer-metal interface after curing, and particle-to-particle contacts were also examined. XPS also identified S on the surface of cured Cu-ICAs even after thermal treatment. Based on the observations, electrical contact and conduction mechanisms for these Cu-filled ICAs are proposed and discussed.

Ionic Polymer-Metal Composites: From Material Engineering to Flexible Applications.

ConspectusIonic polymer-metal composites (IPMCs) are one kind of artificial muscles that can realize energy conversions in response to external stimulus with merits of lightweight, scalability, quick response, and flexibility and have been treated as an important platform in artificial intelligence, such as bionic robotics, smart sensors, and micro-electromechanical systems. It is well-known that IPMC devices are mainly composed of one electrolyte layer laminated with symmetric electrode layers and realize energy conversion based on ion migration and redistribution inside the devices. However, several critical issues have greatly impeded the practical applications of IPMC devices, including metal electrode cracks, metal-polymer interface detachment, and water loss in the electrolyte. In the past decade, our group and collaborators have made attempts to address the mentioned critical issues with the purpose of accelerating practical applications of IPMC devices. First, in order to address the metal electrode cracks, we have developed various electrode materials to replace the metal electrode material, such as black phosphorus and graphdiyne. These materials display superior electrical and mechanical properties with enhanced material stability without cracking. Second, to address metal-polymer interface detachment, we have designed robust interfaces for IMPC devices with vertical array structures. The as-prepared interfaces present high ionic conductivity with excellent mechanical stability under bending states. As a result, the IPMC devices deliver high working stability exceeding a million cycles under air conditions. Third, in order to avoid water loss in the electrolyte, especially at ambient conditions, we have developed ionogel electrolytes containing highly stable ionic liquids as active ion sources. The ionogel electrolytes effectively prevent water loss in conventional water-containing electrolytes, just like Nafion electrolytes and greatly improve the working stability of IPMC devices. After addressing the key issues of IPMC devices, we finally obtained many high-performing IPMC devices and explored various intelligent applications of them. For instance, we have demonstrated the smart functions of IPMC devices as sensitive strain sensors, such as sign language recognition, handwriting detection, and human muscle monitoring. In addition, we have developed bionic flying robots with a vibration frequency as high as 30 Hz with the aid of high-performance IPMC actuators. A medical catheter based on IPMC actuators has been put forward by our group and can realize multiple degrees of freedom deformation under a low driving voltage of 2.5 V, which presents great potential for application in medical instruments. Lastly, a perspective on critical challenges and future research directions on IPMC materials and devices is highlighted for accelerating practical application.

Exploring fatigue characteristics of metallic boss-polymer liner adhesion in hydrogen storage tanks: Experimental insights post surface treatment

Progress in hydrogen fuel powered systems has been propelled by the implementation of secure, reliable, and cost-effective hydrogen storage and transportation technologies. The fourth category, distinguished by a polymer liner serving as a hydrogen diffusion barrier, fully encapsulated within a fiber-reinforced composite to bestow structural integrity, has garnered substantial attention from the automotive industry due to its lightweight nature and rational manufacturing process. The method of rotomolding has sparked interest among manufacturers due to its capability to directly bond the metallic component to the polymer substrate, specifically the liner, thus negating the need for welding and its attendant imperfections. In fact, a pivotal facet of fourth-generation hydrogen storage systems revolves around the interface connection between the polymer liner and the metallic boss, posing as a structural Achilles' heel. For the study's purposes, a scaled-down demonstrator was fabricated using rotomolding in which a nozzle-liner interface mimics the boss-liner interface of the actual system. This demonstrator was designed to facilitate the mechanical characterization of the interface under quasi-static and fatigue loading. The thermal cycling phases of rotational molding and the surface treatments undertaken have been optimized in order to enhance direct adhesion within the metal-polymer interface. This study commences by assessing the efficacy of two treatments (sandblasting and flaming) applied to the aluminum nozzle surface. Subsequently, we explore the adhesion microstructural and mechanical characteristics of the treated nozzle onto a medium-density polyethylene polymer (liner). Lastly, we delve into an exploration of the damage and fatigue behaviors endemic to the metal-polymer interface region. The obtained Wöhler curves disclose a linear trend for the metal-polymer interface. Moreover, the metal-polymer interface evinces heightened resilience against damage and fracture for sandblasted interfaces. This inquiry underscores the potency of innovative polymer-metal interfaces treatment in amplifying the reliability and robustness of hydrogen storage technology.

Moisture-induced defects produced by direct laser joining of AA7075 aluminum and PEEK

The present investigation aims to determine how polymer moisture and volatile compounds influence the mechanical behavior of hybrid metal-polymer joints made by Laser-Assisted Joining. Experimental laser joining tests were performed on AA7075 aluminum alloy and Polyetheretherketone (PEEK). Some polymer samples were pre-treated through drying to remove the moisture stored in the PEEK before joining. Laser spot joints were produced with dried and as-received samples at different heating times. Different characterization techniques were adopted to determine the influence of moisture on the performance of the joints. Single lap shear tests were performed to assess the mechanical behavior of the joints. Fracture surface analysis was carried out through Optical Microscopy to determine the influence of the moisture content on the mechanical behavior. The results indicated a significant influence of moisture on the mechanical behavior of the joints. This led to the formation and coalescence of voids at the metal-polymer interface that affected the mechanical behavior of the joints. Dried samples were characterized by higher shear force (up to 33 %) and higher toughness (up to 130 %) compared to as-received samples.

Computational modelling of collagen-based flexible electronics: assessing the effect of hydration

Collagen substrates in flexible electronics emerged as an alternative to the commonly used stretchable synthetic polymers such as polyethylene terephthalate, polyether sulfone, polydimethylsiloxane etc., thanks to their biocompatibility, flexibility and piezoelectric behaviour. Although researchers were successful in manufacturing these flexible-electronics component, still, the mismatch in the levels of stiffness between a softer polymeric substrate and a stiffer metallic layer (electrodes) might cause interfacial delamination. In use, collagen-based flexible electronics might be exposed to both dry and wet conditions. Experimental analysis showed a drastic change in the mechanical behaviour for these two conditions (the modulus changed by three orders of magnitude); hence, it is essential to investigate the behaviour of polymer-metal interface in both situations. In addition, the effect of geometry and orientation of metallic layers should also be considered; this could help to optimize the design of these electronic devices. In this study, 3D computational models were developed in Abaqus Simulia CAE with dimensions similar to those of elements in collagen-based flexible electronics—collagen (substrate) being the base layer while gold (conductive) and chromium (adhesive) were the top and middle layers, respectively. It was found that delamination in wet collagen was much less pronounced and slower as compared to dry collagen. The effects of geometry and orientation also showed significant differences in the pattern and an area of delamination.

Mapping the coating failure modes of electroless plated metal on ABS polymer with micro-nano structured interface

Electroless plating is the default industrial process for depositing glossy metallic coatings on polymeric parts, most often made of acrylonitrile–butadiene–styrene (ABS) plastic. Unfortunately, the adhesion of plated metals on ABS requires harsh acid etching of the polymer, leaving hazardous chemical waste. We recently offered “Greener electrochemical plating of ABS polymer with unprecedented adhesion via hierarchical micro-nano texturing”. Understanding of the coating failure mechanism at the micro–nano structured interface would allow programming the adhesion strength via the topographical design of the interface. This study develops a theoretical map of coating failure modes versus geometrical parameters of the metal–polymer interface and validate via precise nanofabrication experiments. The ABS polymer was hot embossed with 2–6 μm wide, 2–6 μm deep micro-textures, then it was acid-etched for 1 min to superpose nano-texture over the micro-textures prior to the electroless Cu plating, coating peeling test, and microscopic characterization of the fractured interface. We observed four coating failure modes: (1) adhesive failure at interface, (2) mixed adhesive/cohesive failure, (3) cohesive failure of metal, and (4) cohesive failure of polymer; the last one demonstrated the highest peeling forces. Surprisingly, the proportionality of the adhesion force to the texture aspect ratio was valid only up to a certain threshold, beyond which the adhesion forces falls down due to the fail of metal. The results presented here allows one to control/program the adhesion strength at the metal-polymer interface and optimize the micro-texture of ABS parts for greener electroless plating and durable coating adhesion.

Rational design, synthesis, and characterization of facilitated transport membranes exhibiting enhanced permeability, selectivity and stability

Despite outperforming conventional polymer membranes in the short time frame, facilitated transport membranes (FTMs) are prone to photo/chemical aging, which causes a rapid decay of their performance. Moreover, when embedded in polymer materials to fabricate mixed matrix membranes, structural defects may form at the metal-polymer interface, causing a selectivity loss. To overcome these issues, a series of poly(amic acid)s (PAAs) have been synthesized using 4,4’-oxydiphathalic anhydride (ODPA) and Jeffamine monomers of varying molecular weight, and used to fabricate silver nanoparticles via the chelating reaction with silver ions, in attempts to simultaneously i) achieve defect-free mixed matrix membranes (MMMs), ii) target CO2 selective transport, and iii) enhance long-term stability. The occurrence of the chelating reaction between silver and the PAA was confirmed, and as a result, individual and un-aggregated PAA-coated silver nanoparticles were obtained and incorporated into a commercial polymer, Pebax 1657, to fabricate defect-free mixed matrix membranes. The effect of the PAA length and ether functional group concentration on the structure and performance of the resulting mixed matrix membranes was systematically investigated. Remarkably, inclusion of only 2 wt% nanoparticles in Pebax enhances the CO2 permeability by 50% and CO2 selectivity by 100% relative to neat polymer. A detailed analysis of the sorption and diffusion coefficients was performed to elucidate the molecular origin of the observed membrane performance. Finally, preliminary data show that the newly synthesized materials exhibit high chemical stability upon exposure to pure H2.

Improved Performance of Organic Thermoelectric Generators Through Interfacial Energetics.

The interfacial energetics are known to play a crucial role in organic diodes, transistors, and sensors. Designing the metal-organic interface has been a tool to optimize the performance of organic (opto)electronic devices, but this is not reported for organic thermoelectrics. In this work, it is demonstrated that the electrical power of organic thermoelectric generators (OTEGs) is also strongly dependent on the metal-organic interfacial energetics. Without changing the thermoelectric figure of merit (ZT) of polythiophene-based conducting polymers, the generated power of an OTEG can vary by three orders of magnitude simply by tuning the work function of the metal contact to reach above 1000µWcm-2 . The effective Seebeck coefficient (Seff ) of a metal/polymer/metal single leg OTEG includes an interfacial contribution (Vinter /ΔT) in addition to the intrinsic bulk Seebeck coefficient of the polythiophenes, such that Seff =S + Vinter /ΔT varies from 22.7µVK-1 [9.4µVK-1 ] with Al to 50.5µVK-1 [26.3µVK-1 ] with Pt for poly(3,4-ethylenedioxythiophene):p-toluenesulfonate [poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate)]. Spectroscopic techniques are used to reveal a redox interfacial reaction affecting locally the doping level of the polymer at the vicinity of the metal-organic interface and conclude that the energetics at the metal-polymer interface provides a new strategy to enhance the performance of OTEGs.

The effect of surface nucleation modulation on the mechanical and biocompatibility of metal-polymer biomaterials.

The deployment of hernia repair patches in laparoscopic procedures is gradually increasing. In this technology, however, understanding the new phases of titanium from the parent phase on polymer substrates is essential to control the microstructural transition and material properties. It remains a challenging area of condensed matter physics to predict the kinetic and thermodynamic properties of metals on polymer substrates from the molecular scale due to the lack of understanding of the properties of the metal-polymer interface. However, this paper revealed the mechanism of nucleation on polymer substrates and proposed for the first record a time-dependent regulatory mechanism for the polymer-titanium interface. The interconnection between polymer surface chain entanglement, nucleation and growth patterns, crystal structure and surface roughness were effectively unified. The secondary regulation of mechanical properties was accomplished simultaneously to satisfy the requirement of biocompatibility. Titaniumized polypropylene patches prepared by time-dependent magnetron sputtering technology demonstrated excellent interfacial mechanical properties and biocompatibility. In addition, modulation by low-temperature plasma metal deposition opened a new pathway for biomaterials. This paper provides a solid theoretical basis for the research of titanium nanofilms on medical polypropylene substrates and the medical industry of implantable biomaterials, which will be of great value in the future.

Interface Wetting Driven by Laplace Pressure on Multiscale Topographies and Its Application to Performance Enhancement of Metal-Composite Hybrid Structure

Surface topography reconstruction is extensively used to address the issue of weak bonding at the polymer-metal interface of metal-composite hybrid structure, while enhancement from this approach is seriously impaired by insufficient interface wetting. In this study, the wetting behavior of polymer on aluminum surfaces with multiscale topographies was theoretically and experimentally investigated to realize stable and complete wetting. Geometric dimensions of multiscale surface topographies have a notable impact on interfacial forces at the three-phase contact line of polymer/air/aluminum, and a competition exists between Laplace pressure and bubble pressure in dominating the wetting behavior. Laplace pressure facilitates the degassing of trapped air bubbles in grooves, bringing more robust interfacial wettability to grooves than dimples and grids. Conversely, dimples with excessive dimensions generate interfacial pores, and this intrinsic mechanism is theoretically unraveled. Moreover, different degrees of interface wetting cause variations in bonding strength of polymer-aluminum interface, which changes from ∼18% improvement to ∼17% reduction compared to original strength. Finally, groove topography perfectly achieved complete wetting between polymer and aluminum and consequently improved flexure performance by over 11% for the aluminum-carbon fiber hybrid side impact bar, which verifies the importance of complete wetting at a part scale. This study deepens the understanding of wetting behavior and clarifies the intrinsic correlation between interfacial bonding performance and surface topography.

On the Limits of the EIS Low-Frequency Impedance Modulus as a Tool to Describe the Protection Properties of Organic Coatings Exposed to Accelerated Aging Tests

This study analyzes the limitations of the low-frequency EIS impedance modulus as a tool to describe the protective properties of organic coatings subjected to accelerated aging tests. Acrylic clear-coated steel and hot-dip galvanized steel were exposed to accelerated test methods such as the neutral salt spray chamber and the Prohesion test for up to 2000 and 3000 h, respectively. During exposure, the protective properties of the coatings were monitored by EIS and visual inspection. We observed a significant discrepancy between the measured impedance modulus in the low frequency range (|Z0.01Hz|), and the actual deterioration of the metal–paint interface. The degradation of the two painted substrates is independent of the accelerated test considered. The |Z0.01Hz| values do not represent the actual degradation state of the metal–polymer interface. The manuscript discusses the reasons for the lack of agreement between EIS and visual inspection. The limitations of using the low-frequency EIS impedance modulus to describe the protective properties of organic coatings are highlighted, and several cautions for interpreting the raw EIS data are suggested. The reliability of possible thresholds of |Z0.01Hz| (e.g., failure below 106 ohm∙cm2) to define the protective performance of the coating turned out to be misleading.

Hybrid Ti6Al4V/Silk Fibroin Composite for Load-Bearing Implants: A Hierarchical Multifunctional Cellular Scaffold.

Despite the tremendous technological advances that metal additive manufacturing (AM) has made in the last decades, there are still some major concerns guaranteeing its massive industrial application in the biomedical field. Indeed, some main limitations arise in dealing with their biological properties, specifically in terms of osseointegration. Morphological accuracy of sub-unital elements along with the printing resolution are major constraints in the design workspace of a lattice, hindering the possibility of manufacturing structures optimized for proper osteointegration. To overcome these issues, the authors developed a new hybrid multifunctional composite scaffold consisting of an AM Ti6Al4V lattice structure and a silk fibroin/gelatin foam. The composite was realized by combining laser powder bed fusion (L-PBF) of simple cubic lattice structures with foaming techniques. A combined process of foaming and electrodeposition has been also evaluated. The multifunctional scaffolds were characterized to evaluate their pore size, morphology, and distribution as well as their adhesion and behavior at the metal–polymer interface. Pull-out tests in dry and hydrated conditions were employed for the mechanical characterization. Additionally, a cytotoxicity assessment was performed to preliminarily evaluate their potential application in the biomedical field as load-bearing next-generation medical devices.

Interfacial polarization suppression of P(VDF-HFP) film through 2D montmorillonite nanosheets coating

Polymer based dielectrics with excellent high electric field withstanding capability are of great significance for enhancing the power density and payload efficiency for both electrical and electronic systems. However, polymer-metal interface is prone to defect formation, leading to the dielectric aging and the initialization of electrical breakdown failure. A facile Montmorillonite (MMT) coating is self-co-assembled on the surface of P(VDF-HFP) high-k film to form hundreds of 2D nanosheets layers to impede the charge injection over the metal-polymer interface. The MMT coating increases the breakdown strength of the P(VDF-HFP) co-polymer film from 405 to 452 MV/m. The high field conduction study reveals a highly enhanced Schottky injection barrier that blocks the charge injection from electrodes to polymer bulk, leading to significantly suppressed charge injection and conduction loss in polymer. In addition, the introduction of MMT layered coating leads to prominent suppression of interfacial polarization loss, a phenomenon known as the blocking capacitance, which would otherwise stem from the accumulated charges of polymer-metal interface, by one order of magnitude, as demonstrated by the dielectric response analysis by using the Dissado-Hill model over a broad range of temperature and frequency. The superior charge injection and interfacial polarization suppression via the application of MMT coating impart the P(VDF-HFP) co-polymer film with higher breakdown strength, and provides an effective approach to develop high performance polymer dielectrics by interfacial engineering. This work provides insights into the understanding of the enhancement mechanism of 2D coating.