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Enhancing interfacial interactions in fiber-reinforced polymer composites (FRPCs) is crucial for improving their mechanical properties. This can be achieved through the incorporation of nanomaterials or chemically functional agents into FRPCs. This study reports the tailoring of the fiber–matrix interface in FRPCs using non-functionalized graphene nanoplatelets (GNPs) in combination with a waterborne, highly branched, multi-functional polyurethane dispersion (HBPUD). A unique ultrasonic spray deposition technique was utilized to deposit aqueous mixtures of GNP/HBPUDs onto the surfaces of carbon fiber fabrics, which were used to prepare epoxy-prepreg sheets and corresponding FRPC laminates. The influence of the polyurethane (PU) and GNP content and their ratio at the fiber–matrix interface on the tensile properties of resulting high-performance composites was systematically investigated using stress–strain analysis of the produced FRPC plates and SEM analysis of their fractured surfaces. A synergistic stiffening and toughening effect was observed when as low as 20 to 30 mg of GNPs was deposited per square meter of each side of the carbon fiber fabrics in the presence of the multi-functional PU layer. This resulted in a significant improvement in the tensile strength from 908 to 1022 MPa, while maintaining or slightly improving the initial Young's modulus from approximately 63 to 66 MPa. [ABSTRACT FROM AUTHOR]

This study presents the effect of spray‐coated graphene nanoplatelets on the mechanical response of various polymers to cyclic loadings. The substrates material (three polymers) and the coating (various numbers of coating layers) are assessed. The experimental results suggest that the compressive stiffness, compressive modulus, damping, and energy dissipation of the samples coated with graphene nanoplatelets improve with respect to the uncoated samples. The outcomes of this experimental research highlight the feasibility of utilizing films of graphene nanoplatelets to improve the mechanical properties of polymers for vibration isolation, foreseeing application in various environments, for instance, in buildings and infrastructures (bridges, railways) for seismic and acoustic isolation. [ABSTRACT FROM AUTHOR]

This work investigates the optimization of carbon-based electrodes employed in bio-electrochemical systems (BES) through the deposition of nanostructured layers of poly(3,4-ethylene-dioxy-thiophene) poly(styrene-sulfonate) (PEDOT:PSS) on commercial carbon paper electrodes via ultrasonic spray coating (USC). This innovative application of USC demonstrated that uniform and controlled depositions of PEDOT:PSS can be successfully performed on carbon-based electrodes. To this end, the morphology and spatial uniformity of depositions were verified via scanning electron microscopy and Raman spectroscopy. Electrochemical characterizations of fabricated electrodes demonstrated a more than two-fold increase in the electrochemical active surface area with respect to bare carbon paper. A lab-scale experiment on BES was performed, selecting microbial fuel cells (MFCs) as the reference devices. Devices featuring USC-deposited PEDOT:PSS electrodes showed a three-fold-higher energy recovery with respect to control cells, reaching a maximum value of (13 ± 2) J·m−3. Furthermore, the amount of PEDOT:PSS required to optimize MFCs' performance is in line with values reported in the literature for other deposition methods. In conclusion, this work demonstrates that USC is a promising technique for application in BES. [ABSTRACT FROM AUTHOR]

Enhancing interfacial interactions in fiber-reinforced polymer composites (FRPCs) is crucial for improving their mechanical properties. This can be achieved through the incorporation of nanomaterials or chemically functional agents into FRPCs. This study reports the tailoring of the fiber–matrix interface in FRPCs using non-functionalized graphene nanoplatelets (GNPs) in combination with a waterborne, highly branched, multi-functional polyurethane dispersion (HBPUD). A unique ultrasonic spray deposition technique was utilized to deposit aqueous mixtures of GNP/HBPUDs onto the surfaces of carbon fiber fabrics, which were used to prepare epoxy-prepreg sheets and corresponding FRPC laminates. The influence of the polyurethane (PU) and GNP content and their ratio at the fiber–matrix interface on the tensile properties of resulting high-performance composites was systematically investigated using stress–strain analysis of the produced FRPC plates and SEM analysis of their fractured surfaces. A synergistic stiffening and toughening effect was observed when as low as 20 to 30 mg of GNPs was deposited per square meter of each side of the carbon fiber fabrics in the presence of the multi-functional PU layer. This resulted in a significant improvement in the tensile strength from 908 to 1022 MPa, while maintaining or slightly improving the initial Young’s modulus from approximately 63 to 66 MPa.

Kesterite Cu2ZnSnS4 (CZTS) has emerged as a potential alternative absorber for thin-film solar cells (TFSCs) and tandem applications owing to their earth-abundant, non-toxic materials and suitable direct bandgap (1.5 eV). This work reports the synthesis of CZTS molecular inks and subsequent deposition by ultrasonic spray coating. Clear and stable molecular inks of CZTS are synthesized with methanol as a solvent in a controlled environment. Characterization of the deposited material revealed smooth, homogeneous and compact films of pure single phase p-type kesterite, with an energy bandgap of 1.52 eV and activation energy of 44 meV. Fabrication of photovoltaic (PV) functional layers via ink-based deposition have the potential to bring down costs and allow sustainable growth of the technology. [ABSTRACT FROM AUTHOR]

Finding the optimum structure in porous transport electrodes (PTEs) for proton exchange membrane water electrolyzer anodes is one of the central current technological challenges. Both the structure of the porous transport layer (PTL) and its interaction with the catalyst layer are crucial in finding this optimum structure. In this regard, manufacturing the catalyst layer on top of a PTL as a structure‐building process must be understood to find improved transport electrode structures. This work presents a PTE tomography where the catalyst ink is directly processed on a PTL. The catalyst distribution of anodic PTEs is analyzed and compared via X‐ray microtomography and cross‐sectional imaging of embedded PTE samples. The majority of the catalyst lies within the first 100 µm of the PTE. Considering the penetration depth of the membrane, a maximum of 60% of the catalyst is effectively used. For the first time, a voxel‐based catalyst layer deposition model is created and analyzed that is based on simple assumptions in the deposition process. This deposition model fits very well with the previous tomographic analysis. In the future, this model will allow more profound insight into the manufacturing process and is an important prerequisite for a future optimum design of PTEs. [ABSTRACT FROM AUTHOR]

Abstract Modern lighting is expected to be light weight, flexible, efficient, non‐expensive and environmentally friendly fabricated. Organic light emitting diodes (OLEDs) meet all these requirements and can be manufactured using inexpensive and roll‐to‐roll compatible printing techniques. They, however, often use low work function, highly reactive metals, such as barium and calcium to facilitate electron injection, deposited using expensive and non‐continuous vacuum techniques. Efficient and stable alternatives can be found in the aliphatic amines, polyethylenimine (PEI) and polyethylenimine(ethoxylated) (PEIE), that shift the work function of aluminum favorably for electron injection. This work demonstrates ultrasonic spray coating of PEI(E) as electron injection and transport layer for OLEDs, reducing the work function of the aluminum cathode by 0.355 eV allowing a luminous efficacy comparable to that of the OLEDs using calcium/aluminum electrodes. Slightly higher luminous results are noted for the OLEDs with spin coated PEI(E), indicating that the surface morphology and thickness of the PEI(E) layer are crucial factors: ultrasonic spray coated PEI(E) layers have an increased overall thickness and surface roughness. This study shows the potential of ultrasonic spray coating and the suitability of PEI(E) as excellent electron injection and transport layer for OLEDs and paves the way towards fully spray coated OLEDs.

This work investigates the optimization of carbon-based electrodes employed in bio-electrochemical systems (BES) through the deposition of nanostructured layers of poly(3,4-ethylene-dioxy-thiophene) poly(styrene-sulfonate) (PEDOT:PSS) on commercial carbon paper electrodes via ultrasonic spray coating (USC). This innovative application of USC demonstrated that uniform and controlled depositions of PEDOT:PSS can be successfully performed on carbon-based electrodes. To this end, the morphology and spatial uniformity of depositions were verified via scanning electron microscopy and Raman spectroscopy. Electrochemical characterizations of fabricated electrodes demonstrated a more than two-fold increase in the electrochemical active surface area with respect to bare carbon paper. A lab-scale experiment on BES was performed, selecting microbial fuel cells (MFCs) as the reference devices. Devices featuring USC-deposited PEDOT:PSS electrodes showed a three-fold-higher energy recovery with respect to control cells, reaching a maximum value of (13 ± 2) J·m−3. Furthermore, the amount of PEDOT:PSS required to optimize MFCs’ performance is in line with values reported in the literature for other deposition methods. In conclusion, this work demonstrates that USC is a promising technique for application in BES.

In this work, we focused on Electrospray (ES) and Ultrasonic Spray Coating (USC) as two promising and innovative fabrication techniques for the optimisation of carbon electrode surfaces to be employed in Bio-Electrochemical Systems. We performed, on commercial carbon paper electrodes, controlled depositions of a nanostructured layer containing PEO and PEDOT:PSS. We then employed electron microscopy and Raman spectroscopy to characterise the morphology and superficial uniformity of the so-obtained electrodes. Together with electrochemical characterisations and experiments in bio-electrochemical devices, we demonstrated how ES and USC represent promising techniques for the optimisation of carbon electrodes’ surfaces, obtained with the deposition of a conductive nanostructured layer.

This study deals with the manufacturing of catalyst-coated membranes (CCMs) for newcomers in the field of coating. Although there are many studies on electrode ink composition for improving the performance of proton-exchange membrane fuel cells (PEMFCs), there are few papers dealing with electrode coating itself. Usually, it is a know-how that often remains secret and constitutes the added value of scientific teams or the business of industrialists. In this paper, we identify and clarify the role of key parameters to improve coating quality and also to correlate coating quality with fuel cell performance via polarization curves and electrochemical active surface area measurements. We found that the coating configurations can affect the performance of lab-made CCMs in PEMFCs. After the repeatability of the performance obtained by our coating method has been proved, we show that: (i) edge effects, due to mask shadowing - cannot be neglected when the active surface area is low, (ii) a heterogeneous thickness electrode produces performance lower than a homogeneous thickness electrode, and (iii) the origin and storage of platinum on carbon powders are a very important source of variability in the obtained results. [Display omitted] • The coating thickness and its profile depend on the type of Pt/C powder. • The coating configuration pattern affects the performance in PEMFC. • The thickness of the mask affects the homogeneity of the coating. • The type and storage of Pt/C are a source of variability in the obtained results. [ABSTRACT FROM AUTHOR]

Modern lighting is expected to be light weight, flexible, efficient, non‐expensive and environmentally friendly fabricated. Organic light emitting diodes (OLEDs) meet all these requirements and can be manufactured using inexpensive and roll‐to‐roll compatible printing techniques. They, however, often use low work function, highly reactive metals, such as barium and calcium to facilitate electron injection, deposited using expensive and non‐continuous vacuum techniques. Efficient and stable alternatives can be found in the aliphatic amines, polyethylenimine (PEI) and polyethylenimine(ethoxylated) (PEIE), that shift the work function of aluminum favorably for electron injection. This work demonstrates ultrasonic spray coating of PEI(E) as electron injection and transport layer for OLEDs, reducing the work function of the aluminum cathode by 0.355 eV allowing a luminous efficacy comparable to that of the OLEDs using calcium/aluminum electrodes. Slightly higher luminous results are noted for the OLEDs with spin coated PEI(E), indicating that the surface morphology and thickness of the PEI(E) layer are crucial factors: ultrasonic spray coated PEI(E) layers have an increased overall thickness and surface roughness. This study shows the potential of ultrasonic spray coating and the suitability of PEI(E) as excellent electron injection and transport layer for OLEDs and paves the way towards fully spray coated OLEDs. [ABSTRACT FROM AUTHOR]

The expanding field of flexible organic electronics has led to a high demand for flexible, stable, and transparent electrodes that retain their conductivity at high‐strain deformation. Among many transparent conductive electrodes (TCEs) of which indium tin oxide (ITO) is the most renowned, silver nanowires (AgNWs) prove to be an excellent highly conductive and transparent alternative. These 1D silver nanostructures form a flexible mesh of nanometer‐thin wires that can be applied using solution‐processing and printing techniques. Ultrasonic spray coating is a high‐end low‐cost, environmentally friendly, and roll‐to‐roll compatible printing technique. AgNWs with three different diameters (50, 70, and 115 nm) are ultrasonically spray coated on glass and demonstrate sheet resistances lower than 10 Ω sq−1 combined with transparencies up to 88%. Consequently, the conductive polymer poly(3,4‐ethylenedioxythio‐phene):poly(styrene sulfonate) (PEDOT:PSS) is ultrasonically spray coated to fill up the cavities between the AgNW mesh and to planarize the surface. The ultrasonically spray coated AgNWs/PEDOT:PSS electrodes are employed as TCEs for organic light‐emitting diodes (OLEDs) showing very promising results with a luminous flux of 1.75 lm and a luminous efficacy of about 11 lm W−1 at 3 V driving voltage. Herein, ultrasonic spray coating is demonstrated as an excellent printing technique to apply AgNWs and PEDOT:PSS. [ABSTRACT FROM AUTHOR]

Piezoelectric Poly (vinylidene fluoride) (PVDF) films with high flexibility are a suitable and promising replacement for rigid ceramic piezoelectric materials. However, for this purpose, enhancing piezoelectric properties and adopting an industrial fabrication method are of great importance. In this study, 5–9 µm thick PVDF films were fabricated by a nozzle-less ultrasonic spray coating (USC) system, followed by an annealing process at 100 °C. By applying proper spraying parameters, we could obtain highly uniform films with large d33 values (48 pm/V) and 56% crystallinity. Results show that the uniformity of the films plays an important role in the final piezoelectric properties. Thus, ultrasonic spray coating method can be used for fabrication of large-scale piezoelectric films with no need for poling or stretching processes.

The performance of spray-coated polymer solar cells could be largely improved via morphologies and phase optimization by solvent engineering. However, there is still a lack of fundamental knowledge and know-how in controlling blend morphology by using various solvents. Here, the effect of adding low polar benzene and non-halogen benzene derivatives with triple symmetric molecular has been systematically investigated and discussed. It is found that the triple symmetric non-halogen benzene could promote the formation of preferential face-on molecule orientation for PBDB-T-2Cl:IT4F films by grazing incidence wide-angle X-ray scattering. The X-ray photoelectron spectroscopy shows that PBDB-T-2Cl could be transported to the surface of the blend film during drying process. A 3D opt-digital microscope shows that triple symmetric non-halogen benzene could also improve the morphologies of active layers by reducing the coffee ring or other micro-defects. Due to the appropriate vapor pressures, devices with mixing 20% benzene or the triple symmetric non-halogen in spray solution could significantly improve the device performance. Device prepared using 20% 1,3,5-trimethylbenzene (TMB) and 80% chlorobenzene (CB) mixture solvent has the best morphology and phase structure, and the power conversion efficiency (PCE) of the device was increased nearly 60 to 10.21% compared with the device using CB as the only solvent.

Global environmental regulations have accelerated the research on smart windows that can make efficient use of energy. Vanadium dioxide (VO2) is a material whose crystal structure changes depending on the external environment and can reflect part of the sunlight. We manufactured smart window thin film through solution process using VO2 nanoink instead of traditional dry process such as CVD and sputtering. VO2 thin film was manufactured by ultrasonic spray coating onto PEN (polyethylene naphthalate) and the coating behavior of the thin film was studied by controlling the deflector flow rate, which is considered to have the greatest influence on thin-film formation among various process variables. The solvent contained in the droplet is affected by the air from the deflector, and as the deflector flow increases, the droplet size decreases due to the acceleration of solvent evaporation. The behavior of the thin-film formation depends on the fluidity of the droplets remaining on the substrate. If the fluidity of the droplets is high, the leveling effect will form a uniform thin film; otherwise the adjacent droplets may only combine to form a non-uniform thin film. When the deflector flow rate was 6 L/min, it was impossible to form a uniform thin film due to lack of fluidity. [ABSTRACT FROM AUTHOR]

Summary: Symmetric supercapacitors (SSCs) with remarkable energy storing capability, high specific power as well as long‐term cyclic stability were fabricated from nickel tungstate (NiWO4) @ nickel oxide (NiOx) decorated commercial cotton fabrics (CCFs). A commercial cotton‐based textile was first made conductive by the state of the art ultrasonic spray coating method. This was followed by chemical and electrochemical processes to decorate activated CCFs with NiOx and NiWO4, respectively. The assembled SSCs had the merit of high specific energy of 12 μWh cm−2 at a specific power of 69 μW cm−2 while showing reasonable cyclic stability. Fabricated devices retained over 80% of their initial capacitance after 5500 continuous charge/discharge cycles. The flexibility of the devices was investigated under bending, twisting, and folding providing reliable evidence on the wearability of the fabricated SSCs. Cyclic voltammograms of the fabricated NiWO4@NiOx@CCF SSCs showed only a slight change and retained over 95% of the capacitance under bending and folding. The fabricated NiWO4@NiOx@CCF SSCs, in this regard, are promising energy storage systems to power up high‐performance wearable electronics. [ABSTRACT FROM AUTHOR]

Piecewise spray has the advantage of controlling the component distribution, i.e., constructing vertical phase‐separated active layers, to improve the charge generation efficiency of large‐scale polymer solar cells. However, it brings a connection problem because of the drastic difference in the donor/acceptor ratio of continuous coatings using the conventional solvent. Assisted by 1,3,5‐trimethylbenzene‐based solvent engineering, a solvent driving force is formed, resulting in a continuous interface for piecewise spray‐coated active layers. The blend film forms a bicontinuous interpenetrating network in the active layer and provides efficient percolation pathways for charge carrier transport, resulting in a considerable improvement in the photovoltaic performance. When the donor/acceptor ratio is 1:2 in the first coating and 2:1 in the second coating, and the thickness of each coating is 90 nm, the performance of the PBDB‐T‐2Cl:IT4F photovoltaic device shows a notable conversion efficiency of 12.29% with a high short‐circuit current density of 21.55 mA cm−2. Importantly, this piecewise spray technique can be used for large‐scale module fabrication. [ABSTRACT FROM AUTHOR]

Surface treatment is critical for homogeneous coating over a large area and high-resolution patterning of nanodiamond (ND) particles. To optimize the interaction between the surface of a substrate and the colloid of ND particles, it is essential to remove hydrocarbon contamination by surface treatment and to increase the surface energy of the substrate, hence improving the diamond film homogeneity upon its deposition. However, the impact of substrate surface treatment on the properties of coatings and patterns is not fully understood. This study explores the impact of UV-ozone, O 2 plasma, and CF 4 plasma treatments on the wetting properties of the fused silica glass substrate surface. We identify the optimal time interval between the treatment and subsequent ND coating/patterning processes, which were conducted using inkjet printing and ultrasonic spray coating techniques. Our results showed that UV-ozone and O 2 plasma resulted in hydrophilic surfaces, while CF 4 plasma treatment resulted in hydrophobic surfaces. We demonstrate the use of CF 4 plasma treatment before inkjet printing to generate high-resolution patterns with dots as small as 30 μm in diameter. Ultrasonic spray coating showed homogeneous coatings after using UV-ozone and O 2 plasma treatment. The findings of this study provide valuable insights into the hydrocarbon airborne contamination on cleaned surfaces over time even in clean-room environments and have a notable impact on the performance of liquid coatings and patterns. We highlight the importance of timing between the surface treatment and printing in achieving high resolution or homogeneity.

Triboelectric nanogenerators (TENGs) are widely studied as a source to power wearable electronics. Herein we developed a truly wearable, fabric-based TENG device, with ultrasonic spray-coated graphene nanoplatelets as the electrode on a polyester fabric substrate and PDMS polymer as the dielectric layer on one-half of the TENG. This part is tested against a variety of materials with a copper electrode and a triboseries is generated based on these tested materials. The PDMS side against nylon fabric is able to produce around 397 V and 6.8 μ A at 1 Hz frequency without using any output amplifying components. They are further studied in detail to understand the effect of different parameters such as contact-separation frequency, contact force, separation distance, contact area and chemical modification of tribolayer on the TENG operation. The durability and stability of the TENG devices are studied and their potential to be integrated to self-powered smart textiles as power sources are demonstrated. [Display omitted] • Novel fabric-based TENG device with ultrasonic spray-coated graphene electrode. • Simple device structure with no added metal nanoparticles and amplification. • PDMS-nylon TENG, able to produce a power density of up to 0.3 W/m2. • Quantitative study on effects of fluorination, frequency, distance, force & area. • Device performs as a power source and wearable pressure sensor. [ABSTRACT FROM AUTHOR]

Biobased and biodegradable polymers represent a valid and sustainable alternative to oil-based plastics, as they are renewable and address the issue related to the end-of-life of non-compostable materials. However, the poor gas barrier of biopolymers limits their use in several applications, including food packaging. In this work, chitosan/graphene oxide (CS/GO) nanocomposite coatings were successfully deposited by ultrasonic spray on a compostable polybutylene succinate (PBS) film. The moisture resistance of the chitosan coatings was improved by crosslinking with polyethyleneglycol diglycidyl ether (PEGDE). The resulting coatings were transparent, with thickness in the 1–2.5 μm range, and exhibited good adhesion to the PBS film and mechanical and scratch resistance due to the presence of GO nanofiller. In detail, the PEGDE-crosslinked CS/GO (CS/PEGDE/GO) nanocomposite coating containing 1 wt% GO allowed to reduce O 2 and CO 2 transmission rates by 85 % and 93 %, respectively, compared to uncoated PBS film. The permeability reduction is ascribed to the formation of compact coatings with GO nanoplates oriented parallel to the PBS substrate. Furthermore, the improvement in CO 2 barrier properties was up two-time more than that related to oxygen, suggesting the use of CS/PEGDE/GO coatings in applications where gas permselectivity is required. This research demonstrates the potential of the ultrasonic spray technique for producing bionanocomposite barrier coatings with improved gas barrier performance. [Display omitted] • Chitosan/GO nanocomposite coatings were successfully fabricated using Ultrasonic Spray Coating. • The deposition technique enabled the formation of an oriented layered morphology of GO. • The developed coatings significantly improved the O 2 and CO 2 barrier performance of PBS substrates. [ABSTRACT FROM AUTHOR]

To reduce the high surface roughness of additive manufactured (AM) products, typically a post-treatment is required. Subtractive post-treatments are often performed by hand and are therefore expensive and time consuming, whereas conventional additive post-treatments, such as pneumatic spray coating, require large quantities of coating material. Ultrasonic spray coating, in contrast, is an additive post-treatment technology capable of applying coatings in an efficient way, resulting in less material usage. In this paper, we investigate the application of the ultrasonic spray coating process and the final properties of the coated AM part by applying a thin coating to reduce surface roughness of the AM substrate and to impart hydrophobic functionality. The hydrophobic coating is applied onto flat selective laser sintered (SLS) surfaces prepared from polyamide 12 (PA12) having a surface roughness of Ra = 20 μm. The hydrophobic coating consists of 5 wt % polyvinylidene fluoride (PVDF) in acetone. The coated substrates are analyzed for roughness using a profilometer, a contact angle using a goniometer, and a coating uniformity and thickness using light and scanning electron microscopes. The layer formation applying the ultrasonic spray coating is studied and compared with layer formation using pneumatic spray coating. It is found that a roughness reduction down to 5 μm was achieved via an ultrasonic spray coating with 30 layers of PVDF solution. It is shown in cross-section electron microscopy pictures that, due to the nature of the ultrasonically generated droplets, the rough and porous surface of the SLS surface is filled with the PVDF material after which the roughness is reduced by adding a thin layer on top. In comparison to a standard industry-applied pneumatic spray coating process, the results obtained from ultrasonic spray coating show less material usage, a reduced roughness, and a better filling of the pores, obviously resulting in optimized adhesion. [ABSTRACT FROM AUTHOR]

PEDOT:PSS is a high-conductivity hole-transporting polymer that is widely used in polymer and perovskite photovoltaic devices, as well as in a host of other antistatic applications. Here we show that modification of PEDOT:PSS inks using ternary solvents and by the addition of small amounts of a high molecular weight polymer make it possible to deposit highly uniform thin films via ultrasonic spray coating. Such films can be deposited using a single pass in the wet phase without the use of surfactants; a process that greatly simplifies their deposition. Using this technique we create films having thickness and roughness comparable to that of spin coated films, whilst properties such as the conductivity and stability can be improved. [ABSTRACT FROM AUTHOR]

This work investigates four different methods for the seeding of nanodiamond (ND) particles towards applying nanocrystalline diamond coatings on glass. The standard spin coating and dip coating are investigated together with two droplet-based techniques, ink-jet printing and ultrasonic spray coating (USSC). The application of these last two techniques for diamond coatings on glass is novel and is specifically designed for patterning and large area deposition, respectively. Comparing the seeding processes, their impact on the chemical vapor deposited nanocrystalline diamond (NCD) layers is unclear. Here, particularly the impact on the morphological, optical, and mechanical properties, are studied. In this work, borosilicate glass substrates were seeded, after which diamond layers were grown in a linear antenna microwave plasma-enhanced chemical vapor deposition reactor to thicknesses of 45, 100, and 500 nm. The coatings showed a roughness that is 2 to 3 times higher for the droplet-based seeding techniques compared to spin coating. It was found that the optical absorption coefficient for 100 nm thick samples prepared using USSC was 2400 cm−1 at the wavelength of 550 nm, compared to 1500 cm- 1 using spin and dip seeding techniques. The stress in the film was compressive as determined by curvature measurements. Sand-trickling tests on samples coated with 100 nm thick diamond films showed similar resistance against damaging for all seeding techniques without delamination. Therefore, the different techniques achieve mechanically competitive performance. On top USSC and ink-jet printing have the opportunity to fully cover substrates on large-scale flat and even 3D surfaces, or pattern fine structures, which is not possible for standard spin and dip coating. It can be concluded that diamond coatings on large glass plates for scratch resistance, and sensing due their somewhat higher roughness, are within reach using these innovative droplet-based seeding technologies. • Roll to roll compatible techniques for nanodiamond seeding are investigated. • Layer formation of ultrasonic spray and inkjet seeding has been studied. • Optical, mechanical and morphological characterization shows promising results. • Ultrasonic spray and inkjet seeding are compared with standard spin and dip coating. • Large area or patterned diamond coatings for anti-scratch or sensing are in reach. [ABSTRACT FROM AUTHOR]

Thin solid oxide films are crucial for developing high-performance solid oxide-based electrochemical devices aimed at decarbonizing the global energy system. Among various methods, ultrasonic spray coating (USC) can provide the throughput, scalability, quality consistency, roll-to-roll compatibility, and low material waste necessary for scalable production of large-sized solid oxide electrochemical cells. However, due to the large number of USC parameters, systematic parameter optimization is required to ensure optimal settings. However, the optimizations in previous literature are either not discussed or not systematic, facile, and practical for scalable production of thin oxide films. In this regard, we propose an USC optimization process assisted with mathematical models. Using this method, we obtained optimal settings for producing high-quality, uniform 4 × 4 cm 2 oxygen electrode films with a consistent thickness of ∼27 μm in 1 min in a facile and systematic way. The quality of the films is evaluated at both micrometer and centimeter scales and meets desirable thickness and uniformity criteria. To validate the performance of USC-fabricated electrolytes and oxygen electrodes, we employ protonic ceramic electrochemical cells, which achieve a peak power density of 0.88 W cm -2 in the fuel cell mode and a current density of 1.36 A cm -2 at 1.3 V in the electrolysis mode, with minimal degradation over a period of 200 h. These results demonstrate the potential of USC as a promising technology for scalable production of large-sized solid oxide electrochemical cells.

Nanoparticles have been increasingly studied due to their unique properties. The deposition of uniform layers with these nanoparticles however is a crucial step in many of their applications. In this work, ultrasonic spray coating is the technique of choice as it is by design well-suited for the deposition of nano-suspension dispersions. The influence of different deposition parameters, ink composition and post-treatment are subject of study in this paper. It is shown in this work that (mass-) production of uniform nanoparticle layers is possible due to the narrow distribution of the droplet size and the deagglomeration of the particles during ultrasonic spray coating. It is also demonstrated that with ultrasonic spray coating it is possible to deposit an eco-friendly, water-based nanoparticle ink into layers with desired thickness and morphology. [ABSTRACT FROM AUTHOR]

Nanostructured aluminium (Al) doped cadmium oxide (CdO) films with highly electrical conductivity and optical transparency have been deposited for the first time on soda-lime glass substrates preheated at 250 °C by ultrasonic spray coating technique. The aluminium dopant content in the CdO film was changed from 0 to 5 at%. The influencing of Al doping on the structural, morphological, electrical and optical properties of the CdO nanostructured films has been investigated. Atomic force microscopy study showed the grain size of the films is an order of nanometers, and it decreases with increase in Al dopant content. All the films having cubic structure with a lattice parameter 4.69 Å were determined via X ray diffraction analysis. The optical band gap value of the films, obtained by optical absorption, was found to increase with Al doping. Electrical studies exhibited mobility, carrier concentration and resistivity of the film strongly dependent on the doping content. It has been evaluated that optical band gap, and grain size of the nanostructured CdO film could be modified by Al doping. [ABSTRACT FROM AUTHOR]

In this work the ultrasonic spray coating technique is introduced as an alternative wet solution process for the deposition of the (Super Yellow) light-emitting layer for polymer light-emitting diodes (PLEDs). An investigation on the use of this coating technique in ambient conditions is performed and a comparison with spin coated PLEDs in inert atmosphere is made. Uniform low roughness thin films with a typical thickness of 80 nm are obtained by varying the polymer–solvent mixture and spray coater parameters. PLEDs are produced and reach a luminous power efficacy in the order of 10 lm/W. Through the use of various optical and analytical techniques it is demonstrated that the applied ultrasonic atomization has no noteworthy influence on the original properties of the polymer and on the resulting PLED’s efficacy. Ultrasonic spray coating is therefore a viable deposition technique for the production of PLEDs. [ABSTRACT FROM AUTHOR]

This paper reports use of an ultrasonic-spray for producing low Pt loadings membrane electrode assemblies (MEAs) with the catalyst coated substrate (CCS) fabrication technique. The main MEA sub-components (catalyst, membrane and gas diffusion layer (GDL)) are supplied from commercial manufacturers. In this study, high temperature (HT) MEAs with phosphoric acid (PA)-doped poly(2,5-benzimidazole) (AB–PBI) membrane are fabricated and tested under 160 °C, hydrogen and air feed 100 and 250 cc min −1 and ambient pressure conditions. Four different Pt loadings (from 0.138 to 1.208 mg cm −2 ) are investigated in this study. The experiment data are determined by in-situ electrochemical methods such as polarization curve, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The high Pt loading MEA exhibits higher performance at high voltage operating conditions but lower performances at peak power due to the poor mass transfer. The Pt loading 0.350 mg cm −2 GDE performs the peak power density and peak cathode mass power to 0.339 W cm −2 and 0.967 W mg Pt −1 , respectively. This work presents impressive cathode mass power and high fuel cell performance for high temperature proton exchange membrane fuel cells (HT-PEMFCs) with low Pt loadings. [ABSTRACT FROM AUTHOR]

Advanced porous separators with thin selective skin layers to reduce the hydrogen permeation are developed for applications in alkaline water electrolysis. A thin skin layer based on crosslinked polyvinyl alcohol (cPVA) is fabricated on a porous substrate by a facile and scalable ultrasonic spray coating process. As the number of ultrasonic spraying cycles increases, the resulting separator demonstrates a decrease in the large-diameter pore fraction, an increase in the bubble-point pressure, and a reduction in the hydrogen permeability without a significant increase in the areal resistance. As a result, the optimized separator with a cPVA skin layer combines a low ionic resistance of 0.267 Ω cm2, a high bubble point pressure of 2.71 bar, and a low hydrogen permeability of 1.12 × 10−11 mol cm−2 s−1 bar−1. The electrolytic cell assembled with cPVAZ-30 achieves current densities of 861 mA cm−2 and 1890 mA cm−2 at 2.0 V and 2.6 V, respectively, in a 30 wt% KOH electrolyte solution at 80 °C. [Display omitted] • Selective porous separator with thin skin layer is prepared using ultrasonic spray. • Introducing thin skin layer significantly improved gas barrier properties. • Electrolysis cell assembled with the cPVAZ separator achieves good performance. [ABSTRACT FROM AUTHOR]

The ultrasonic spray-coating process (USCP) has been proved to be desirable to fabricate the perovskite solar cells (PSCs) at high volume, especially for the three-dimensional perovskites. In this work, we extend this technique to the fabrication of two-dimensional (2D) PSCs due to a series of advantages of 2D PSCs, including long-term stability and excellent electrical properties. we apply this high-throughput deposition technology with an ultrasonic spray-coating system for forming the 2D perovskite which provides more possibility for the lab-to-fab translation. Due to the difference of crystal structure between 2D and 3D perovskites, the process of film formation is diverse which requires extra optimization to produce 2D perovskites in large scale. By comparing the perovskite quality deposited with different film deposition methods, we find layer-by-layer deposition method can provide a better film quality and more controllable film formation process. Hence, with this deposition method, we use USCP to realize an efficient batch production, obtaining an optimized power conversion efficiency of 10.5%, which is slightly lower than that (12.2%) of spin-coating processed samples. Moreover, devices based on USCP exhibit comparable long-term stability with the spin-coated devices. This report provides a promising alternative for the producing the 2D perovskite devices with high-throughput way. [Display omitted] • Ultrasonic spray-coating technique is used to deposit 2D perovskite film with desirable film quality. • Depositing 2D perovskite with ultrasonic spray-coating process can obtain high-throughput yield. • Long-term stability can be ensured based on this efficient fabrication method. • Two-step method is proved more suitable for the ultrasonic spray-coating technique. [ABSTRACT FROM AUTHOR]

Spray coating is an industrially mature technique used to deposit thin films that combines high throughput with the ability to coat nonplanar surfaces. Here, we explore the use of ultrasonic spray coating to fabricate perovskite solar cells (PSCs) over rigid, nonplanar surfaces without problems caused by solution dewetting and subsequent "run-off". Encouragingly, we find that PSCs can be spray-coated using our processes onto glass substrates held at angles of inclination up to 45° away from the horizontal, with such devices having comparable power conversion efficiencies (up to 18.3%) to those spray-cast onto horizontal substrates. Having established that our process can be used to create PSCs on surfaces that are not horizontal, we fabricate devices over a convex glass substrate, with devices having a maximum power conversion efficiency of 12.5%. To our best knowledge, this study represents the first demonstration of a rigid, curved perovskite solar cell. The integration of perovskite photovoltaics onto curved surfaces will likely find direct applications in the aerospace and automotive sectors.

Abstract: This paper reports use of an ultrasonic spray for producing ultra-low Pt load membrane electrode assemblies (MEAs) with the catalyst coated membrane (CCM) fabrication technique. Anode Pt loading optimization and rough cathode Pt loading were investigated in the first stage of this research. Accurate cathode Pt coating with catalyst ink using the ultrasonic spray method was investigated in the second stage. It was found that 0.272 mgPt/cm2 showed the best observed performance for a 33 wt% Nafion CCM when it was ultrasonically spray coated with SGL 24BC, a Sigracet manufactured gas diffusion layer (GDL). Two different loadings (0.232 and 0.155 mgPt/cm2) exposed to 600 mA/cm2 showed cathode power mass densities of 1.69 and 2.36 W/mgPt, respectively. This paper presents impressive cathode mass power density and high fuel cell performance using air as the oxidant and operated at ambient pressure. [Copyright &y& Elsevier]

[Display omitted] • Ultrasonic spray coating system is used for fabrication of pure PVDF films with high piezoelectric coefficient (d 33 = 48 pm/V). • Highly crystalline (56%) PVDF films with predominant β phase for flexible and transparent engineering devices are achieved without post processing. • Uniformity and roughness (<50 nm) of the PVDF films strongly affects their piezoelectric properties. • We proved that the ultrasonic spray coating method is capable of producing large-scale, low-cost PVDF films in a single step. Piezoelectric Poly (vinylidene fluoride) (PVDF) films with high flexibility are a suitable and promising replacement for rigid ceramic piezoelectric materials. However, for this purpose, enhancing piezoelectric properties and adopting an industrial fabrication method are of great importance. In this study, 5–9 µm thick PVDF films were fabricated by a nozzle-less ultrasonic spray coating (USC) system, followed by an annealing process at 100 °C. By applying proper spraying parameters, we could obtain highly uniform films with large d 33 values (48 pm/V) and 56% crystallinity. Results show that the uniformity of the films plays an important role in the final piezoelectric properties. Thus, ultrasonic spray coating method can be used for fabrication of large-scale piezoelectric films with no need for poling or stretching processes. [ABSTRACT FROM AUTHOR]

Biodegradable materials are widely used in drug delivery at present. Blending polymers with complementary properties has become a promising strategy to tune drug release. In this study, the effects of poly(D, L-lactic acid) (PDLLA) and poly(L-lactide-co-ε-caprolactone) (PLCL) blend films on the in vitro release kinetics of sirolimus were investigated. Herein, a series of PDLLA/PLCL blend films with different ratios were prepared by the ultrasonic spray technology and in vitro release tests of these polymer films were carried out in phosphate buffered saline (PBS). Release profiles showed biphasic release pattern: the initial rapid release (phase I) and stable release (phase II) and more PLCL resulted in earlier and faster sirolimus release, with more cumulative drug release observed. The release rate could be tuned by adjusting the ratio of PLCL to PDLLA in blend films, but they may not be a simple linear proportional relationship. Moreover, in vitro sirolimus release kinetics from these blend films were analyzed using mathematical models. This work can provide a feasible way for tuning drug release in polymer matrices under a blend strategy and improve the design of coating films in drug delivery systems. [ABSTRACT FROM AUTHOR]

The performance of spray-coated polymer solar cells could be largely improved via morphologies and phase optimization by solvent engineering. However, there is still a lack of fundamental knowledge and know-how in controlling blend morphology by using various solvents. Here, the effect of adding low polar benzene and non-halogen benzene derivatives with triple symmetric molecular has been systematically investigated and discussed. It is found that the triple symmetric non-halogen benzene could promote the formation of preferential face-on molecule orientation for PBDB-T-2Cl:IT4F films by grazing incidence wide-angle X-ray scattering. The X-ray photoelectron spectroscopy shows that PBDB-T-2Cl could be transported to the surface of the blend film during drying process. A 3D opt-digital microscope shows that triple symmetric non-halogen benzene could also improve the morphologies of active layers by reducing the coffee ring or other micro-defects. Due to the appropriate vapor pressures, devices with mixing 20% benzene or the triple symmetric non-halogen in spray solution could significantly improve the device performance. Device prepared using 20% 1,3,5-trimethylbenzene (TMB) and 80% chlorobenzene (CB) mixture solvent has the best morphology and phase structure, and the power conversion efficiency (PCE) of the device was increased nearly 60 to 10.21% compared with the device using CB as the only solvent., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Tang, Tang, Bai, Hu, Yan, Li and Cheng.)

Advanced applications in optics, for example, Faraday isolators, demand for complex magneto‐plasmonic nanostructures which exhibit large Faraday rotation. These structures is fabricated by a Layer‐by‐Layer approach, albeit this being a slow technique. Here, the ultrasonic spray coating as a promising alternative method toward the formation of hybrid magneto‐plasmonic structures is pioneered by the authors. Ultrasonic spray coating is a stable, fast, and tunable mass production method applied in this work to deposit gold and iron oxide nanoparticles. Altering multiple deposition parameters give the spray coating technique a large amount of control over the coverage. Optical and magneto‐optical properties, layer formation and surface coverage of single and hybrid layers with increasing thickness and number of layers are studied and compared to samples synthesized by Layer‐by‐Layer deposition. Ultrasonic spray coating paves the way to the widespread application of innovative and versatile hybrid magnetic‐plasmonic nanocomposites. In this work, the authors pioneer ultrasonic spray coating as a new technique to fabricate plasmonic nanomaterials suitable for Faraday rotation. Comparing it to a layer‐by‐layer approach allows for an attractive mix of chemistry and engineering. After synthesis, the material is characterized using UV‐Vis spectroscopy, scanning electron microscopy, atomic force microscopy, and Faraday rotation is measured. [ABSTRACT FROM AUTHOR]

A novel two-dimensional (2D) heterojunction photoelectrode composed of WO 3 and (Er,W):BiVO 4 is proposed for water oxidation with efficient photoinduced charge carrier separation and transfer. Er stoichiometric along with W nonstoichiometric codoping was introduced to simultaneously manage vacancy creation during substitutional doping, enhance light absorption, and reduce overall impedance. It was found that Er 3+ is substituted at the Bi 3+ sites in the BiVO 4 lattice to provide expanded light absorption from 400 to 680 nm. The fabricated WO 3 /(Er,W):BiVO 4 electrode shows photocurrent densities of 4.1 and 7.2 mA cm -2 at 1.23 and 2.3 V (vs reversible hydrogen electrode, RHE), respectively, under a 1 sun illumination in K 2 HPO 4 electrolyte. This electrode has shown remarkably high charge separation efficiency of 93% at 1.23 V (vs RHE). With the addition of a standard surface catalyst (i.e., Co-Pi), the WO 3 /(Er,W):BiVO 4 /Co-Pi electrode exhibits the highest photocurrent of 5.6 ± 0.3 mA cm -2 at 1.23 V (vs RHE), nearing the theoretical limit (i.e., 7.5 mA cm -2 ) while retaining 98% of the photoelectrochemical cell performance after 3 h. By concomitantly doping the Bi 3+ and V 5+ sites to enhance absorption, this study demonstrates for the first time a planar WO 3 /BiVO 4 heterojunction that reaches 88% of the record-high performance of its nanostructured counterpart. Through a detailed characterization of the electrodes, it is concluded that the stoichiometric Er and nonstoichiometric W codoping extend light absorption region and improve charge separation efficiency by reducing bulk resistance. The photoactive materials with 2D morphology were synthesized using a facile ultrasonic spray-coating technique without any complex process steps and thus it can be scaled for commercial development.

Substrate heating is the most common method for controlling crystallization during spray coating. However, due to poor controllability during substrate heating, the sprayed films have variable thicknesses and rich pores, which limit the efficiency of the device. Here, hot air blowing was applied to spray coating to promote the crystallization of perovskite films under ambient conditions. Upon employing a hot air blowing method that stimulated uniformly distributed nuclei growth, the pinhole-free and thickness-controllable perovskite film was prepared. This enabled more reproducible high-quality perovskite films to achieve a power conversion efficiency of 13.5% and obtain a stabilized power output of >12% in ambient conditions.

Thin polycrystalline films of the solar absorber copper-zinc-tin-sulfide (CZTS) were formed by annealing coatings deposited on molybdenum-coated soda lime glass via ultrasonic spraying of aerosol droplets from colloidal CZTS nanocrystal dispersions. Production of uniform continuous nanocrystal coatings with ultrasonic spraying requires that the evaporation time is longer than the aerosol flight time from the spray nozzle to the substrate such that the aerosol droplets still have low enough viscosity to smooth the impact craters that form on the coating surface. In this work, evaporation was slowed by adding a high boiling point cosolvent, cyclohexanone, to toluene as the dispersing liquid. We analyzed, quantitatively, the effects of the solvent composition on the aerosol and coating drying dynamics using an aerosol evaporation model. Annealing coatings in sulfur vapor converts them into polycrystalline films with micrometer size grains, but the grains form continuous films only when Na is present during annealing to enhance grain growth. Continuous films are easier to form when the average nanocrystal size is 15 nm: using larger nanocrystals (e.g., 20 nm) sacrifices film continuity.