Mayer Rod Research Articles

Achieving High Performance with High Oxygen Permeability Ionomer (HOPI) in Heavy Duty Fuel Cell MEAs

Heavy-duty PEM fuel cells are expected to last 25,000-30,000 hours in the field. Therefore, materials, components, and interfaces used in these systems must be highly resistant to severe mechanical and chemical stress. Novel, highly active stable Pt and ordered PtCo intermetallic nanoparticles with well-controlled particle size and composition have been synthesized on a highly efficient PGM-free single metal active site rich carbon, to maximize their synergistic effects for enhanced performance and durability. Integrating these catalysts integrated with high O2 permeability ionomer (HOPI) in membrane electrode assemblies (MEAs) improved their fuel cell performance and durability, allowing the MEAs to achieve >1.2 A/cm2 at 0.7 V after 150k square wave accelerated stress test (AST) cycles, with a performance loss < 40 mV after 150K AST cycles.In a PEM fuel cell, the catalyst ink formulation and mixing processes control catalyst layer coating quality, electrode morphology, and the resulting fuel cell performance and durability. Catalyst ink properties are a result of complex solvent-catalyst-ionomer interactions that depend on the mixing method employed. Here, we compare the performance and durability of electrodes made from ball milled inks for Mayer rod coating before and after the catalyst scale up. Ink rheology and catalyst particle size are used to correlate ink properties to electrode morphology and structure and ensure consistency from batch to batch, and from small lab scale to subsequent scale-up. We evaluate and discuss the challenges that arise when coating the more viscous inks on decals, where the HOPI creates many bubbles in the ink. We also present the challenges of hot-pressing inks that contain HOPI, and how employing a Nafion overspray made with different solvents (isopropanol vs. ethanol) can improve hot-pressing. We investigate the how ionomer to carbon ratio affects hot pressing with HOPI and crack formation in the electrode via scanning electron microscopy (SEM).This work provides a comprehensive understanding of interactions between Pt, PtCo, carbon, ionomer, membrane, and GDLs and their impact on electrode structure, fuel cell performance and durability, as well as considerations for scale up to a R2R fabrication process. The attained information will be used to improve fuel cell electrode design, fabrication and scale-up.Acknowledgement: The project is financially supported by the Department of Energy’s Fuel Cell Technology Office under the Grant DE-FOA-0002360 (Phase I) and DE-SC0021671 (Phase II). Figure 1

Engineering of Silane-Pyrrolidone Nano/Microparticles and Anti-Fogging Thin Coatings.

Polyvinylpyrrolidone (PVP) exhibits remarkable qualities; owing to the strong affinity for water of its pyrrolidone group, which enhances compatibility with aqueous systems, it is effective for stabilizing, binding, or carrying food, drugs, and cosmetics. However, coating the surface of polymeric films with PVP is not practical, as the coatings dissolve easily in water and ethanol. Poly(silane-pyrrolidone) nano/microparticles were prepared by combining addition polymerization of methacryloxypropyltriethoxysilane and N-vinylpyrrolidone, followed by step-growth Stöber polymerization of the formed silane-pyrrolidone monomer. The silane-pyrrolidone monomeric solution was spread on oxidized polyethylene films with a Mayer rod and polymerized to form siloxane (Si-O-Si) self-cross-linked durable anti-fog thin coatings with pyrrolidone groups exposed on the outer surface. The coatings exhibited similar wetting properties to PVP with significantly greater stability. The particles and coatings were characterized by microscopy, contact angle measurements, and spectroscopy, and tested using hot fog. Excellent anti-fogging activity was found.

Facile Fabrication of Transparent Conductor of Cu Nanowire-PEDOT:PSS

Facile Fabrication of Transparent Conductor of Cu Nanowire-PEDOT:PSS

Synthesis and Characterization of Durable Antifog Silane-Pyrrolidone Thin Coatings onto Polymeric Films.

The fogging of transparent surfaces-condensation of water vapor in the air to a small liquid surface at specific environmental conditions-scatters incident light, creating a blurry vision. Fogging presents a significant challenge in various industries, adversely affecting numerous applications including plastic packaging, agricultural films, and various optical devices. Superhydrophobic or superhydrophilic coatings are the main strategies used to induce antifogging to minimize light scattering. Here, an innovative approach is introduced to mitigate fogging by modifying the surface properties of polymeric films, focusing on corona-treated polyethylene as a model. Coatings were prepared in two successive steps: the addition of radical co-polymerization of methacryloxypropyltriethoxysilane and N-vinylpyrrolidone followed by the step-growth Stöber polymerization of the formed silane monomer. The polymeric dispersion was spread on oxidized films via a Mayer rod and dried. Scanning and force microscopy, FIB, XPS, and UV-vis spectroscopy revealed a thin coating composed of cross-linked siloxane (Si-O-Si) covalently bonded to surface hydroxyls exposing pyrrolidone groups. Contact angle measurements, hot-fog examination, and durability tests indicated a durable antifogging activity.

Infiltration-assisted colloidal assembly of amorphous photonic crystal patterns with high color saturation and mechanical stability

Fabrication of a steady APC pattern with high color saturation and mechanical stability via the IFAST Mayer rod coating method.

Deposition of Transparent Ag Nanowires‐Based Top Electrode for the Development of Double‐Side Green Light Hybrid Photodetector

Herein, various silver nanowires (AgNWs) deposition techniques, i.e., spin coating, Mayer rod coating, and spray coating are used to fabricate ZnO/P3HT‐based double‐side hybrid photodetectors and their photoresponse for 520 nm green light has been compared. The electrodes are coated over the polyethylene terephthalate sheet separately and laminated over the indium tin oxide (ITO)/ZnO/P3HT. Mayer rod‐coated electrodes are found to have a sheet resistance (Rsh) of 24 Ω Sq.−1 and a light transmission of 91%. Additionally, spin‐ and spray‐coated AgNW electrodes exhibit Rsh of 20 and 23 Ω Sq.−1, respectively, along with 80% and 85% transparencies. As the device consists of transparent electrodes on both sides, it can detect light from both the top and bottom sides. Mayer rod‐coated AgNW electrode‐based device has produced better photosensitivity of 1500 (for ITO side illumination) and 630 (for AgNWs side illumination) at λ = 525 nm. Further, the device has demonstrated the responsivity of 124 mAW−1 and specific detectivity of 3 × 1011 Jones.

Fabrication and Scale-up of Highly Durable Heavy Duty Fuel Cell MEAs

Medium and heavy-duty PEM fuel cells operate under much harsher conditions than light duty fuel cells and are expected to last 25,000-30,000 hours in the field. These systems must operate successfully in the presence of impurities, starting and stopping, freezing and thawing, humidity and load cycling. Therefore, materials, components, and interfaces used in such systems must be highly resistant to severe mechanical and chemical stress.Novel, highly active stable Pt and ordered PtCo intermetallic nanoparticles with well-controlled particle size and composition have been synthesized on a highly efficient PGM-free single metal active site rich carbon, to maximize their synergistic effects for enhanced performance and durability. Integrating these catalysts integrated with high O2 permeability ionomer (HOPI) in membrane electrode assemblies (MEAs) improved their fuel cell performance and durability, allowing the MEAs to achieve >600 mA/mgPt at 0.9 VIR-free with a mass activity loss < 30% after 150k square wave accelerated stress test (AST) cycles; and > 600 mA/cm2 (~65% efficiency) at 0.8 V, with a performance loss < 40 mV after 150K AST cycles.In a PEM fuel cell, the catalyst ink formulation and mixing processes control catalyst layer coating quality, electrode morphology, and the resulting fuel cell performance and durability. Catalyst ink properties are a result of complex solvent-catalyst-ionomer interactions that depend on the mixing method employed. Here, we compare the performance and durability of electrodes made from bath sonicated inks for ultrasonic spray coating before and after the catalyst scale up. Ink rheology and catalyst particle size are used to correlate ink properties to electrode morphology and structure and ensure consistency from batch to batch, and from small lab scale to subsequent scale-up. We evaluate and discuss the challenges that arise when transitioning from spray coating catalyst ink on a small scale, directly on a membrane, to coating more viscous inks on gas diffusion layers (GDLs), made via Mayer rod coating of ball milled inks, in anticipation of developing a roll-to-roll (R2R) fabrication process. The MEA performance and durability of the novel catalyst was also evaluated under heavy duty operating conditions using M2FCT’s AST, i.e., in H2/Air, 90 ⁰C, and 50% RH.This work provides a comprehensive understanding of interactions between Pt, PtCo, carbon, ionomer, membrane, and GDLs and their impact on electrode structure, fuel cell performance and durability, as well as considerations for scale up to a R2R fabrication process. The attained information will be used to improve fuel cell electrode design, fabrication and scale-up.Acknowledgement: The project is financially supported by the Department of Energy’s Fuel Cell Technology Office under the Grant DE-SC0021671. Figure 1. (a) Comparison of H2-air fuel cell performance of HOPI-based CCMs prepared with different volume ratios of H2O to n-propanol (nPA). (b) Dependence of fuel cell performance at 0.8 and 0.7 V of the CCMs prepared with different volume ratios of H2O to nPA. (c) MEA performance of the best performing Pt (40 wt. %)/Mn-N-C MEA under various relative humidity. (d) The high-frequency resistance (HFR) of HOPI-based CCMs prepared with a volume ratio of 2:1. All of the tests were performed with a 5 cm2 differential cell with 14 parallel channels. The cell temperature was 80 ⁰C, the flow rates for H2 and air are 500 and 2000 sccm, and the backpressure is 250 kPaabs. The Pt loading in the anode and cathode are 0.1 and 0.2 mgPt/cm2, respectively. Figure 1

Engineered Cross-Linked Silane with Urea Polymer Thin Durable Coatings onto Polymeric Films for Controlled Antiviral Release of Activated Chlorine and Essential Oils.

In March 2020, the World Health Organization announced a pandemic attributed to SARS-CoV-2, a novel beta-coronavirus, which spread widely from China. As a result, the need for antiviral surfaces has increased significantly. Here, the preparation and characterization of new antiviral coatings on polycarbonate (PC) for controlled release of activated chlorine (Cl+) and thymol separately and combined are described. Thin coatings were prepared by polymerization of 1-[3-(trimethoxysilyl)propyl] urea (TMSPU) in ethanol/water basic solution by modified Stöber polymerization, followed by spreading the formed dispersion onto surface-oxidized PC film using a Mayer rod with appropriate thickness. Activated Cl-releasing coating was prepared by chlorination of the PC/SiO2-urea film with NaOCl through the urea amide groups to form a Cl-amine derivatized coating. Thymol releasing coating was prepared by linking thymol to TMSPU or its polymer via hydrogen bonds between thymol hydroxyl and urea amide groups. The activity towards T4 bacteriophage and canine coronavirus (CCV) was measured. PC/SiO2-urea-thymol enhanced bacteriophage persistence, while PC/SiO2-urea-Cl reduced its amount by 84%. Temperature-dependent release is presented. Surprisingly, the combination of thymol and chlorine had an improved antiviral activity, reducing the amount of both viruses by four orders of magnitude, indicating synergistic activity. For CCV, coating with only thymol was inactive, while SiO2-urea-Cl reduced it below a detectable level.

Interfacial Colloidal Self-Assembly for Functional Materials

ConspectusSelf-assembly bridges nanoscale and microscale colloidal particles into macroscale functional materials. In particular, self-assembly processes occurring at the liquid/liquid or solid/liquid/air interfaces hold great promise in constructing large-scale two- or three-dimensional (2D or 3D) architectures. Interaction of colloidal particles in the assemblies leads to emergent collective properties not found in individual building blocks, offering a much larger parameter space to tune the material properties. Interfacial self-assembly methods are rapid, cost-effective, scalable, and compatible with existing fabrication technologies, thus promoting widespread interest in a broad range of research fields.Surface chemistry of nanoparticles plays a predominant role in driving the self-assembly of nanoparticles at water/oil interfaces. Amphiphilic nanoparticles coated with mixed polymer brushes or mussel-inspired polydopamine were demonstrated to self-assemble into closely packed thin films, enabling diverse applications from electrochemical sensors and catalysis to surface-enhanced optical properties. Interfacial assemblies of amphiphilic gold nanoparticles were integrated with graphene paper to obtain flexible electrodes in a modular approach. The robust, biocompatible electrodes with exceptional electrocatalytic activities showed excellent sensitivity and reproducibility in biosensing. Recyclable catalysts were prepared by transferring monolayer assemblies of polydopamine-coated nanocatalysts to both hydrophilic and hydrophobic substrates. The immobilized catalysts were easily recovered and recycled without loss of catalytic activity. Plasmonic nanoparticles were self-assembled into a plasmonic substrate for surface-enhanced Raman scattering, metal-enhanced fluorescence, and modulated fluorescence resonance energy transfer (FRET). Strong Raman enhancement was accomplished by rationally directing the Raman probes to the electromagnetic hotspots. Optimal enhancement of fluorescence and FRET was realized by precisely controlling the spacing between the metal surface and the fluorophores and tuning the surface plasmon resonance wavelength of the self-assembled substrate to match the optical properties of the fluorescent dye.At liquid/solid interfaces, infiltration-assisted (IFAST) colloidal self-assembly introduces liquid infiltration in the substrate as a new factor to control the degree of order of the colloidal assemblies. The strong infiltration flow leads to the formation of amorphous colloidal arrays that display noniridescent structural colors. This method is compatible with a broad range of colloidal particle inks, and any solid substrate that is permeable to dispersing liquids but particle-excluding is suitable for IFAST colloidal assembly. Therefore, the IFAST technology offers rapid, scalable fabrication of structural color patterns of diverse colloidal particles with full-spectrum coverage and unprecedented flexibility. Metal-organic framework particles with either spherical or polyhedral morphology were used as ink particles in the Mayer rod coating on wettability patterned photopapers, leading to amorphous photonic structures with vapor-responsive colors. Anticounterfeiting labels have also been developed based on the complex optical features encoded in the photonic structures.Interfacial colloidal self-assembly at the water/oil interface and IFAST assembly at the solid/liquid/air interface have proven to be versatile fabrication platforms to produce functional materials with well-defined properties for diverse applications. These platform technologies are promising in the manufacturing of value-added functional materials.

Large-area ultra-thin GO nanofiltration membranes prepared by a pre-crosslinking rod coating technique

In existing separation membranes, it is difficult to quickly produce large-area graphene oxide (GO) nanofiltration membranes with high permeability and high rejection, which is the bottleneck of industrialization. In this study, a pre-crosslinking rod-coating technique is reported. A GO-P-Phenylenediamine (PPD) suspension was obtained by chemically crosslinking GO and PPD for 180 min. After scraping and coating with a Mayer rod, the ultra-thin GO-PPD nanofiltration membrane with an area of 400 cm2 and a thickness of 40 nm was prepared in 30 s. The PPD formed an amide bond with GO to improve its stability. It also increased the layer spacing of GO membrane, which could improve the permeability. The prepared GO nanofiltration membrane had a 99 % rejection rate for dyes such as methylene blue, crystal violet, and Congo red. Meanwhile, the permeation flux reached to 42 LMH/bar, which was 10 times that of the GO membrane without PPD crosslinking, and it still maintained excellent stability under strongly acidic and basic conditions. This work successfully solved the problems of GO nanofiltration membranes, including the large-area fabrication, high permeability and high rejection.

Comparative Study on Preparation Methods for Transparent Conductive Films Based on Silver Nanowires.

Silver nanowires, which have high optoelectronic properties, have the potential to supersede indium tin oxide in the field of electrocatalysis, stretchable electronic, and solar cells. Herein, four mainstream experimental methods, including Mayer-rod coating, spin coating, spray coating, and vacuum filtration methods, are employed to fabricate transparent conductive films based on the same silver nanowires to clarify the significance of preparation methods on the performance of the films. The surface morphology, conductive property, uniformity, and flexible stability of these four Ag NW-based films, are analyzed and compared to explore the advantages of these methods. The transparent conductive films produced by the vacuum filtration method have the most outstanding performance in terms of surface roughness and uniformity, benefitting from the stronger welding of NW-NW junctions after the press procedure. However, limited by the size of the membrane and the vacuum degree of the equipment, the small-size Ag films used in precious devices are appropriate to obtain through this method. Similarly, the spin coating method is suited to prepare Ag NWs films with small sizes, which shows excellent stability after the bending test. In comparison, much larger-size films could be obtained through Mayer-rod coating and spray coating methods. The pull-down speed and force among the Mayer-rod coating process, as well as the spray distance and traveling speed among the spray coating process, are essential to the uniformity of Ag NW films. After being treated with NaBH4 and polymethyl methacrylate (PMMA), the obtained Ag NW/PMMA films show great potential in the field of film defogging due to the Joule heating effect. Taken together, based on the advantages of each preparation method, the Ag NW-based films with desired size and performances are easier to prepare, meeting the requirements of different application fields.

Surface Characterization of Catalyst-Ionomer Interactions for Pt Fuel Cell Electrodes Using Varied Carbon Supports

Proton exchange membrane fuel cells (PEMFCs) are a progressive technology capable of providing on-demand energy without contributing to greenhouse gases. To meet the needs of transitioning from lab-scale fabrication to large-scale manufacturing, further analysis of catalyst layers is necessary. A common issue within the cathode catalyst layer (CL) is non-uniform distribution of the ionomer within the catalyst layer. Additionally, the interface between catalyst and ionomer is not well understood.X-ray photoelectron spectroscopy (XPS) is a highly surface-sensitive technique primed to provide new insights into the challenging interfacial interactions and chemistries among the catalyst, support, and ionomer. Although Nafion is inherently susceptible to X-ray degradation, XPS can be used effectively through a modified acquisition strategy developed previously in our group. In this work, XPS has been used to probe CLs with focus on the catalyst-ionomer interface and interactions using a series of electrodes prepared by a Mayer rod coating method. The catalyst-ionomer interface was investigated as a function of support material, Pt loading on the support, and ionomer loading. Surface information was acquired using ex situ and in situ XPS to emphasize the evolution of this technique’s capabilities at probing ionomer interactions. Complementary characterization with scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM) in combination with energy-dispersive X-ray spectroscopy (EDS) mapping of catalysts and electrode cross-sections were utilized to visualize distribution of catalyst, carbon, and ionomer in the CL to assist with interpretation of XPS data. Results from this dataset emphasize the potential of this technique to study complex interfaces in PEM catalysts layers motivating further work expanding to other catalysts and ionomers.

Mayer Rod‐Coated Organic Light‐Emitting Devices: Binary Solvent Inks, Film Topography Optimization, and Large‐Area Fabrication

Homogeneous pinhole‐free functional films are essential in the manufacturing of large‐area high‐performance flexible electronics. Mayer rod coating is used to create high‐quality organic electroluminescent (EL) films herein. Various factors that affect the film quality of Mayer rod coating, including Mayer rod coating processing, solvent engineering, emitting material concentrations, and the ionic conductor proportions, are systematically investigated and optimized. Accordingly, uniform large‐area EL polymer films are achieved using Mayer rod coating. Meanwhile, large‐area polymer‐based light‐emitting electrochemical cells (PLECs) manufactured by printing methodology are successfully constructed. The resulting printed large‐area PLECs manifest enhanced performance by a factor of 2.37 compared with the corresponding spin‐cast counterparts.

Facile Fabrication of Amorphous Colloidal Array Patterns with Good Mechanical Stability via an Infiltration-Driven Mayer Rod Coating Method

In this study, cationic monodisperse polystyrene (PS) microspheres and polybutyl acrylate (PBA) nanoparticles were synthesized and used in combination to fabricate various steady amorphous colloidal array (ACA) patterns via an infiltration-driven Mayer rod coating method. During the rapid assembly process, PBA nanoparticles were embedded in PS microsphere voids to lock the colloidal array, thereby promoting its mechanical stability. Meanwhile, the fabricated ACA patterns could still exhibit bright angle-independent structural color when moderate PBA nanoparticles introduced. In summary, this study provides a convenient and fast method to fabricate steady ACA patterns, which is a promising potential substitute for traditional ink printing.

Comparison of Anode-Catalyst-Layer Coating Methods for Low-Temperature Electrolysis

Iridium oxide (IrO2) anode catalyst layers are prepared by liquid film coating a dispersion of the IrO2 catalyst and ionomer onto a substrate. In many research studies these catalyst layers are prepared by ultrasonic spray coating or hand-painting. However, for gigawatt-scale deployment of electrolyzers which is required to enable a hydrogen economy, the catalyst layers will likely need to be produced using higher-throughput continuous roll-to-roll (R2R) coating methods that are capable of coating speeds of square meters per minute (if not per second). Many of the cost estimates for electrolyzer production at scale assume the use of R2R coating methods,1 however it is yet to be proven that these methodologies are capable of producing low-loading catalyst layers with similar performance and durability to those produced with lab-scale coating methods. In this study we have compared various lab-scale and R2R-coating methods to determine their impact on catalyst layer morphology and performance. Ultrasonic spray coating is used as the baseline coating method. Mayer rod and blade coating, which represent scalable coating methods with ink formulations and coating and drying physics similar to R2R coating, are used to prepare small-scale coatings. In addition, direct gravure coating is used as another R2R coating method. Device testing of membrane electrode assemblies (MEAs) fabricated using catalyst layers prepared from the different coating methodologies show that using blade coating and R2R-gravure coating produce catalyst layers with the same performance as ultrasonic spray coating while increasing production rate by orders of magnitude. Interestingly, the catalyst layers produced using scalable coating methods show better kinetic performance than spray coated layers. These results show that R2R-coating methods are likely viable for large-scale manufacturing of electrolyzers.This work was authored by the National Renewable Energy Laboratory, operated by Alliance for Sustainable Energy, LLC, for the U.S. Department of Energy (DOE) under Contract No. DE-AC36-08GO28308. Funding provided by U.S. Department of Energy Office of Energy Efficiency and Renewable Energy Hydrogen and Fuel Cell Technologies Office. The views expressed in the article do not necessarily represent the views of the DOE or the U.S. Government. The U.S. Government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this work, or allow others to do so, for U.S. Government purposes.References(1) Mayyas, A. T.; Ruth, M. F.; Pivovar, B. S.; Bender, G.; Wipke, K. B. Manufacturing Cost Analysis for Proton Exchange Membrane Water Electrolyzers; NREL/TP-6A20-72740; National Renewable Energy Lab. (NREL), Golden, CO (United States), 2019. https://doi.org/10.2172/1557965. Figure 1

Highly thermally conductive, superior flexible and surface metallisable boron nitride paper fabricated by a facile and scalable approach

High thermal conductivity and high flexibility, required by advanced microelectronic devices, are hard to be combined in composites, because their dependences on components concentration often contradict each other. Here, the conflicting goals are achieved by preparing meter-level BN paper containing 82.6 wt% commercial micron BN sheets with dihydromyricetin (DMY) from herbal medicine as a novel surface modifier and high molecular weight acrylate copolymer as adhesive. Thanks to the polycyclic aromatic hydrocarbons of DMY coupled with abundant functional groups, which form conjugation with the inert BN and increase its hydrophilicity, tough interphases are established in the oriented nacre-like BN composite architecture when Mayer rod method is used. The resultant BN paper can be folded into complicated shapes, possessing decent tensile properties (strength = 8.49 MPa; failure strain = 3.8%), as well as excellent in-plane and through-plane thermal conductivities (8.97 and 2.14 W m−1 K−1). Besides, the DMY attached to BN sheets can further coordinate with Pd2+, catalyzing copper deposition and producing flexible copper-clad BN paper. Considering the cost-effective and easy-accessible raw materials and the simple assembly technique, which avoid the limitation of lab-scale BN nano-sheets, the present approach may be feasible for producing flexible electronic components with highly efficient thermal dissipation ability.

Engineering of new durable cross-linked poly(styryl bisphosphonate) thin coatings onto polypropylene films for biomedical applications

Bone tissue engineering uses biocompatible biomaterials to stimulate bone regeneration. Bone has two major components, organic collagen fibers and inorganic hydroxyapatite (HAP) which makes up about 60 percent of bone. Bisphosphonates (BPs) are compounds which are used clinically for bone disorders because of their high affinity for calcium ions. Previously, we reported on the synthesis of cross-linked poly(styryl bisphosphonate) nanoparticles (poly(StBP) NPs) which demonstrated a strong affinity for calcium ions. Here, we describe the use of these NPs for the synthesis of new durable cross-linked poly(StBP) thin coatings on corona-treated polypropylene films by means of a simple method of UV-curing. To produce the coatings, poly(StBP) NPs were mixed with the cross-linking monomer poly(ethylene glycol) dimethacrylate and a photo-initiator, spread on the PP films using a Mayer rod, and then UV-cured. The coatings were characterized using XPS, AFM, FIB, and water contact angle goniometry. Wettability, durability, and optical properties of the coatings were also studied. It was found that HAP flower-like crystals grew on the surface of the coated films but not on the control films, indicating that the poly(StBP) coating may be a good candidate for use in bone tissue engineering.

A method to fabricate uniform silver nanowires transparent electrode using Meyer rod coating and dynamic heating

It is commonly believed that silver nanowires transparent electrode is one of the promising substitutions of indium tin oxide. Silver nanowires transparent electrode has two important properties including high transparency and high conductivity. There are several articles reporting they have successfully fabricated high performance of nanowires electrode with high transmittance and high conductivity, however, those transparent electrodes usually have a poor uniformity, which limits the application of silver nanowires. This paper brings out a simple method to fabricate electrode, which has a high uniformity using Mayer rod coating, and dynamic heating, leading to 24 Ω/sq sheet resistance, 91% light transmittance. The research of this subject can expand the application range of silver nanowires electrode and further promote the development of flexible electronic devices.

Engineering of Durable Antifog Thin Coatings on Plastic Films by UV-Curing of Proteinoid Prepolymers with PEG-Diacrylate Monomers.

Fog formation on transparent surfaces constitutes a major challenge in several optical applications, such as plastic packaging, lenses, mirrors, and windshields. To overcome this problem, we prepared and characterized durable antifog thin coatings on plastic films such as polyethylene terephthalate (PET). Proteinoids are biocompatible random polymers made of α-amino acids by thermal step-growth polymerization. Proteinoid prepolymers were prepared by adding activated double bonds to proteinoids via the Michael addition reaction. A series of thin antifog cross-linked coatings were prepared by spreading on PET films with a Mayer rod various mixtures of the proteinoid prepolymers, polyethylene glycol diacrylate, and a photoinitiator, followed by UV-curing of the dried coatings. The antifog properties of the coatings were determined by the contact angle, roughness, haze, and gloss measurements, as well as hot and cold fog tests, to examine the optical properties of the films under fog formation conditions. Mechanical properties such as adhesion, robustness, and abrasion resistance of the antifog coatings were examined by tape, knife-scratch, and sandpaper abrasion tests. The effect of coating composition, wettability, and roughness on the antifog properties of the coated PET films was elucidated. The formula was optimized, and the corresponding UV-cured antifog cross-linked thin coating exhibited transparency with good adhesion and excellent durable antifog performance.

Facile fabrication of large-scale silver nanowire-PEDOT:PSS composite flexible transparent electrodes for flexible touch panels

Large-scale silver nanowire (AgNW)-poly(3,4-ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT:PSS) composite transparent flexible electrodes (FTEs) were fabricated via a Mayer rod coating method, and the optoelectrical properties, surface topography, mechanical stability and touch sensing performance were investigated in detail. The AgNW-PEDOT:PSS composite FTEs show high optoelectrical properties with a sheet resistance of 12 Ω/sq and a transmittance of 96% at 550 nm, and can maintain after 100 times of wiping or 5000 times of bending. The PEDOT:PSS aggregating at the junctions of AgNWs provides highly conductive pathways and enhances the adhesion between AgNWs and substrates. As a proof of concept demonstration, 7 × 7 cm2 transparent touch panel is fabricated using AgNW-PEDOT:PSS composite FTEs as top and bottom electrodes, and can operate on a non-flat surface and perform properly after 2000 times of writing or operating 24 h. The newly designed AgNW-PEDOT:PSS composite FTE is a promising candidate of brittle and expensive ITO for flexible optoelectrical devices.