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A new technique of additive prototyping filament volumetric nanostructuring based on the high-speed mechanical mixing of acrylonitrile-butadiene-styrene (ABS) copolymer granules and single-walled carbon nanotube (CNT) powder (without prior dispersion in solvents) is considered. The morphological spectra of scanning electron microscopy (SEM) images of nanostructured filament slice surfaces were obtained and characterized with the original mathematical simulation. The relations of structural changes in the "ingredient-matrix" polymer system with dielectric and mechanical properties of the ABS-based filaments were established. The supplementation of 1.5 mass.% of CNT powder to the ABS filament composition leads to the tensile strength increasing from 36 ± 2 to 42 ± 2 MPa. It is shown that the greater the average biharmonic amplitude and the morphological spectrum localization radius of the slice surfaces' SEM images, the lower the electrical resistance of the corresponding nanostructured filaments. The possibility of carbon nanotube-modified filament functional layers forming using the extrusion additive prototyping technique (FFF) on the surface of plasma-chemically modified PET substrates (for the creation of load cell elements) is experimentally demonstrated. [ABSTRACT FROM AUTHOR]

Additive manufacturing is gaining interest for printing of noble metals. In this study, aerosol jet printing was applied to fabricate traces from commercial silver nanoparticle ink. A self-built three dimensional printing machine was used without or with in-line substrate heating. A conductive traces were printed on flexible polyimide substrates. Subsequently, sintering was conducted by furnace or near-infrared source. Examination of the sample using scanning electron and atomic force microscopy revealed the existence of both micro- and nanoscale pores in the structure. Local open porosity, aerosol extensive spatter and wide porous overspray were key defects found in samples printed without substrate heating. All the features affect the properties and reliability of silver prints. In-line process heating increased the concentration of nanoparticles and limited defects formation. What is more, the width of traces decreased from 31 µm to 19 µm with simultaneous thickness increase from 1.2 to 5.5 µm due to substrate heating. The final structure was influenced by sintering method and its time. Elongated time of sintering decreased porosity and roughness of the printed traces. Nevertheless, IR sintering provided the smoothest sample surface with lowest Sa roughness of 16 nm, and significantly improved bonding of aggregates. What is more, the printed structure had a measured sheet resistance of 8.3×10−2 Ω/□. [ABSTRACT FROM AUTHOR]

We report detailed diffraction peak analysis and parameters indicative of the transition between fully amorphous microstructures and nanocrystal formation in sputter deposited thin film metallic glasses. Specifically, we fabricated ternary CuZrAg alloy films (2 µm thickness) with a large compositional gradient on flexible, X-ray transparent polymer substrates in high vacuum conditions. The combinatorial libraries were subjected to point-by-point structural (XRD synchrotron radiation) and chemical (X-ray fluorescence spectroscopy) analysis, characterizing roughly 172 alloys. A strong correlation was found between peak symmetry and width, and early stages of crystalline phase formation. These nanocrystals are difficult to detect from the evolution of the peak position. In view of current literature, our data questions the recently claimed universality of the peak width as indicator of high glass forming ability. The addition of Ag significantly improves the poor glass formation of binary CuZr (36 alloys) under identical deposition conditions, as fully amorphous alloys are found for the majority of the investigated composition space. A thorough understanding of the microstructure of CuZrAg alloys on flexible substrates is highly relevant in view of favourable antibacterial properties and potential application as coatings for biomedical surfaces.

This feature article presents recent results on the analysis of plasma/polymer interactions and the nucleation of ultra‐thin plasma films on polymeric substrates. Because of their high importance for the understanding of such processes, in situ analytical approaches of the plasma volume as well as the plasma/substrate interfaces are introduced before the findings on plasma surface chemistry. The plasma activation of polymeric substrates is divided into the understanding of fundamental processes on model substrates and the relevance of polymer surface complexity. Concerning thin film nucleation and growth, both plasma‐enhanced chemical vapor deposition and plasma‐enhanced atomic layer deposition processes as well as the combination of both processes are considered both for model substrates and technical polymers. Based on the comprehensive presentation of recent results, selective perspectives of this research field are discussed. [ABSTRACT FROM AUTHOR]

A thin-film (215 nm) of indigo dye has been deposited on a polymer substrate (polyacetate) using thermal evaporation. The structure of the prepared film has been investigated using X-ray diffraction, showing X-ray amorphous or fine nanocrystalline nature. Analysis of the absorption coefficient in the strong absorption regions shows two indirect optical transitions with energy gaps (2.45 and 1.64 eV) in addition to the energy gap of the substrate (3.5 eV). Values of the refractive index have been calculated using four different methods. The average refractive index values near the first and second absorption edges are 2.525 and 2.871, respectively. The average values of the optical dielectric constant near the two corresponding edges are 6.377 and 8.064. Furthermore, the corresponding values of the nonlinear optical susceptibilities and nonlinear refractive index are in the same order of magnitude as other promising organic materials. This recommends indigo-thin films for flexible organic electro-optical applications. [ABSTRACT FROM AUTHOR]

The last few years have seen a rapid increase in body-worn devices because these devices cover a broad spectrum of potential uses. Moreover, body-worn devices still require improvements in their flexibility, size, and weight that necessitate the development of flexible and miniature antennas. In this paper, we present a new flexible miniature antenna for body-worn devices. To ensure flexibility and comfort when the antenna is in contact with the human body, a substrate from natural rubber filled with TiO2 is developed. The miniaturization is achieved using the quadratic Koch curve. The antenna design, optimization, and characterization are performed on a human body model. The performance of the antenna is analyzed in two scenarios: (1) in- to on-body, and (2) on- to off-body wireless communications. The results show that the antenna realized the maximum telemetry range of more than 80 mm for in-body communications and more than 2 m for off-body communications. Moreover, the highest 10 g specific absorption rate value was 0.62 W/kg. These results, in addition to the antenna's compact dimensions (12 mm × 26 mm × 2.5 mm) and the low manufacturing price, make the proposed antenna an ideal candidate for health telemetry applications. [ABSTRACT FROM AUTHOR]

Electrospun fabrics have unique properties due to their uniform morphology and high surface area to volume ratio. Ultrathin nonwoven fabrics are produced for many applications: biomedical, nanosensors, tissue engineering and filtration systems. In this work, nonwoven polylactide, polylactide/natural rubber, poly-3-hydroxybutyrate, and poly-3-hydroxybutyrate/nitrile butadiene rubber fabrics were prepared by electrospinning methods. The obtained fabric samples were used as substrates for the growth of winter wheat seeds "Yubileinaya 100" (Triticum aestivum L.). The stimulating effect of polymer substrates on seed germination and plant growth was shown. The structure and properties of nonwoven agromaterials were controlled by differential scanning calorimetry, IR-spectroscopy, and optical microscopy. The mechanical properties of the obtained fabrics before and after their utilization as substrates were studied. After the wheat growing experiment, the degree of crystallinity of PHB and PHB/NBR samples decreased by 12% and they completely lost their mechanical properties. It is shown that the main factors providing the efficiency of seed growth technology on polymer substrates are the chemical nature and structure of the biodegradable matrix. [ABSTRACT FROM AUTHOR]

Indium tin oxide (ITO) is one of the most widely used semiconductor among transparent conducting oxides (TCOs) due to their electrical conductivity and optical transparency properties. Since the development of low temperature deposition methods, coating of ITO on polymer substrates especially for use in flexible electronics has been a popular topic. The existence of adequate adhesion strength between ITO and polymer is critical in producing a successful film. Nowadays, polycarbonate (PC), poly(methyl methacrylate) (PMMA) and polyethyleneterephtalate (PET) are frequently used as substrates for such coatings. However, there may be other polymeric alternatives that have a potential to be used for this purpose in the future. To evaluate these alternatives, work of adhesion (Wa ) knowledge between ITO and polymers is necessary, and it has not been handled systematically previously. In this study, the interphase interaction parameters and Wa values between ITO and various polymers were calculated based on the Dupré, Fowkes and GirifalcoGood equations. PC, PMMA, PET, polystyrene (PS), polyphenylene sulfide (PPS), Nylon 66, polypropylene (PP), polyvinylchloride (PVC), styrene-butadiene rubber (SBR), high density polyethylene (HDPE), low density polyethylene (LDPE), polyvinyl acetate (PVAc), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polytrifluoroethylene (PTrFE) and polyperfluoroalkylethyl acrylate (PPFA) were considered as substrate material. Surface free energy (SFE) components calculated by acid-base, geometric mean and harmonic mean approaches for polymeric substrates were used during the calculations. In the present study, the polymers that can be used as substrates were evaluated in terms of adhesion ability to ITO, the significance of calculation methods on Wa values were also investigated simultaneously. It was determined that the Wa between ITO and polymer substrates was directly related with the total SFE value of the polymers. [ABSTRACT FROM AUTHOR]

Polymer-supported MOFs membranes with high separation performances show great potentials in industrial purification of H 2. The key to growing defect-free and adherent MOFs layers on polymer substrates is the abundant and uniformly distributed nucleation sites on the surface of polymer substrates. Therefore, in this work, a mixed-matrix polyacrylonitrile (PAN) substrate with ZIF-8-rich seed layer (ZS-PAN) was constructed by gravity induced deposition and gradient distribution of ZIF-8 before phase inversion, then under the assistance of Tannic acid (TA), the dense and defect-free ZIF-8 membrane on flexible polymer substrate was fabricated followed by the secondary growth of ZIF-8. The EDS and SEM results of the membrane cross-section confirm the gradient distribution of ZIF-8 seeds, and the resultant membranes are defect-free. The H 2 permeance of TA-ZIF-8/ZS-PAN membrane is 953.66 GPU, and the H 2 /CO 2 selectivity is 12.09, which is 80.17 % higher than that of ZIF-8/ZS-PAN membrane without TA, exceeding the Robeson upper bound in 2008. This improved H 2 separation performance is derived from the following reasons. First, gravity-induced ZIF-8 seed deposition constructs a ZIF-8-rich seed layer on the mixed-matrix polymer substrate, which increases the nucleation sites. Second, the introduction of TA during the secondary growth process further increases the nucleation sites by hydroxyl-chelated zinc ions, both of which contribute to the dense ZIF-8 membrane. At the same time, the hydroxyl group in TA is CO 2 -philic, which can delay CO 2 permeation and improve the H 2 /CO 2 separation performance by physically adsorbing CO 2. The proposed mixed-matrix substrate by gravity induced deposition of MOFs provides a novel strategy for constructing defect-free and flexible MOFs membrane. [Display omitted] • External gravity field is utilized to induce ZIF-8 deposition. • Mixed-matrix polymer substrate is constructed with ZIF-8-rich seeds layer. • TA was used to assist ZIF-8 growth by hydroxyl-chelated zinc ions. • The TA-ZIF-8/ZS-PAN membrane is defect-free with improved H 2 separation. [ABSTRACT FROM AUTHOR]

Metal oxide nanocomposites (MON) have gained significant attention in the literature for the possibility of improving the optical and electronic properties of the hybrid material, compared to its pristine constituent oxides. These superior properties have been observed for TiO2 — based MON, which exhibit improved structural stability and photoactivity in environmental decontamination processes. In addition, the use of polymer membrane-supported MON is preferable to prevent further aggregation of particles, increase the surface area of the semiconductor in contact with the contaminant, and enable material reuse without considerable efficiency loss. In this work, V 5+-doped TiO 2 / WO 3   MON nanostructures were prepared by the sintering process at 500 °C and supported in electrospun fiber membranes for application as photocatalyst devices. Microstructural characterization of the samples was performed by XRD, SEM, EDS, Raman, and DSC techniques. The reflectance spectra showed that the bandgap of the MON was progressively decreased (3.20 to 2.11 eV) with the V5+ ions doping level increase. The fiber-supported MON showed photoactivity for rhodamine B dye degradation using visible light. In addition, the highest photodegradation efficiency was noted for the systems with 5 wt% vanadium oxide dispersed in the fibers (92% dye degradation in 120 min of exposure to the light source), with recyclability of the composite material for use in new photocatalysis cycles. The best results are directly related to the microstructure, lower bandgap and aggregation of metal oxide nanocomposite in the electrospun membrane, compared to the support-free MON. [ABSTRACT FROM AUTHOR]

This paper examines the simulation, design, and fabrication of a nano-particle silver microheater. COMSOL Multiphysics is used to simulate the microheater of an area of 720 × 720 μm 2 . Different stages of the microheater fabrication process are discussed. The size of the cartridge used is 10 pL and the nozzle diameter was 50 μ m . The drop spacing was chosen to be 45 μ m after testing several different values. Controlled printing of Ag ink was reached by setting the tickle control frequency to 8 kHz and cartridge print height to 0.4 mm. The nozzle temperature was set at ambient temperature. The inkjet printed microheater is of same area and track and gap widths of 110 μ m . The measured resistance of the microheater, 119 Ω, is approximately equal to the simulated resistance of 100 Ω. It was observed that the temperature at the center of the heater reaches up to 250 °C. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ag significantly improves the glass forming ability of CuZr thin films on flexible polymer substrates. • Co-sputtered CuZrAg alloys are fully amorphous over a large composition range. • Important parameters for crystalline phase identification are XRD peak width and symmetry. • Significant microstructural changes are hardly detectable in the XRD peak position. • Correlation length calculated from XRD analysis does not correlate with glass formation. We report detailed diffraction peak analysis and parameters indicative of the transition between fully amorphous microstructures and nanocrystal formation in sputter deposited thin film metallic glasses. Specifically, we fabricated ternary CuZrAg alloy films (2 µm thickness) with a large compositional gradient on flexible, X-ray transparent polymer substrates in high vacuum conditions. The combinatorial libraries were subjected to point-by-point structural (XRD synchrotron radiation) and chemical (X-ray fluorescence spectroscopy) analysis, characterizing roughly 172 alloys. A strong correlation was found between peak symmetry and width, and early stages of crystalline phase formation. These nanocrystals are difficult to detect from the evolution of the peak position. In view of current literature, our data questions the recently claimed universality of the peak width as indicator of high glass forming ability. The addition of Ag significantly improves the poor glass formation of binary CuZr (36 alloys) under identical deposition conditions, as fully amorphous alloys are found for the majority of the investigated composition space. A thorough understanding of the microstructure of CuZrAg alloys on flexible substrates is highly relevant in view of favourable antibacterial properties and potential application as coatings for biomedical surfaces. [ABSTRACT FROM AUTHOR]

The electro-mechanical behaviors of transparent conductive oxide film on polymer substrate are of great concern because they would greatly affect the stability and lifespan of the corresponding devices. In this paper, indium tin oxide (ITO) films with different thicknesses were deposited on a polycarbonate (PC) sheet; meanwhile, in situ electrical resistance, in situ scanning electron microscopy and profilometry were employed to record the electrical resistance, morphologies and residual stress in order to investigate the fracture behavior and electrical-mechanical properties of ITO films under uniaxial tension loading. The electrical resistance changes, crack initiation, crack propagation and crack density evolution of ITO films were systematically characterized by in situ tests. Three fracture stages of ITO films were summarized: Ⅰ crack initiation, Ⅱ crack propagation, Ⅲ crack saturation and delamination. The crack initiation and electrical failure in a thinner ITO film occurred at relatively higher applied tensile strain; namely, the ductility of the film decreased as the film thickness increased. Residual compressive stress was recorded in the ITO films deposited on PC at room temperature and increased as the film thickness increased. Intrinsic crack initiation strain (CIS*) showed an opposite thickness dependence to residual strain (εr); the increase in residual compressive strain was counteracted by the decrease of intrinsic cohesion, leading to an overall decrease in effective crack initiation strain (CIS) when the film thickness increased. In addition, integrated with a formulated mechanics model and the analysis of the three fracture stages under tension, the fracture toughness and interfacial shear strength were quantitatively determined. As the film thickness increased (in the range of 50~500 nm), the fracture toughness decreased and the films were more prone to crack, whereas the interfacial shear strength increased and the films were less likely to delaminate. [ABSTRACT FROM AUTHOR]

The last few years have seen a rapid increase in body-worn devices because these devices cover a broad spectrum of potential uses. Moreover, body-worn devices still require improvements in their flexibility, size, and weight that necessitate the development of flexible and miniature antennas. In this paper, we present a new flexible miniature antenna for body-worn devices. To ensure flexibility and comfort when the antenna is in contact with the human body, a substrate from natural rubber filled with TiO2 is developed. The miniaturization is achieved using the quadratic Koch curve. The antenna design, optimization, and characterization are performed on a human body model. The performance of the antenna is analyzed in two scenarios: (1) in- to on-body, and (2) on- to off-body wireless communications. The results show that the antenna realized the maximum telemetry range of more than 80 mm for in-body communications and more than 2 m for off-body communications. Moreover, the highest 10 g specific absorption rate value was 0.62 W/kg. These results, in addition to the antenna’s compact dimensions (12 mm × 26 mm × 2.5 mm) and the low manufacturing price, make the proposed antenna an ideal candidate for health telemetry applications.

Nanocrystals have exhibited unique optoelectronic properties and demonstrated a wide range of applications in light-emitting devices, semiconductor devices and solar cell devices. However, previous studies usually deposit nanocrystal films on traditional rigid substrates, limiting their applications in large-scale, direct-deposited flexible device fabrication processes, such as roll-to-roll printing process. Here, we report a direct deposition method for lead sulfide (PbS) nanocrystal films on flexible polymer substrates. By adding triethanolamine-coordinated Pb precursors to the reaction system to enhance the adhesion to the substrate and controlling the precursor ratios, we obtained high-quality flexible PbS films. The film is composed of octahedral PbS nanocrystals with preferred (111) orientation. The optical band gap of the nanocrystal films can be tuned from 1.32 eV to 1.60 eV by adjusting the ratio of the precursors, and an ideal band gap of 1.4 eV for single-junction solar cells was also obtained when Pb to S ratio reaches 1.4:1. More importantly, the flexible PbS films exhibit high charge carrier mobility of up to 25 cm2 V − 1  s − 1 , which is comparable to that of PbS films grown on traditional rigid substrates (e.g. silicon wafers or glasses). To our knowledge, this mobility is also the highest for PbS fabricated directly on flexible substrates. Our study provides a new approach for the preparation of low-cost and roll-to-roll processable nanocrystal films for future flexible optoelectronic devices. [ABSTRACT FROM AUTHOR]

Exchange-coupled spin valves based on ferromagnetic alloys CoFeNi and antiferromagnetic alloy FeMn are obtained on flexible polyimide substrates by magnetron sputtering. The magnetoresistive properties of films and microstrips of spin valves are measured at various degrees of bending deformation of the sample. The behavior of the dependence of the deformation sensitivity of the spin valve on the interaction between the magnetic layers and on the arrangement of the anisotropy axes with respect to the deformation vector is characterized. It is found that the deformation sensitivity decreases with an increase in the interval between the fields of magnetization reversal of the free and fixed layers in the spin valve. [ABSTRACT FROM AUTHOR]

A spray coating technique is an excellent method for surface metallization and ceramic deposition to widen the application fields of irreplaceable engineering polymers. In this study, Al metallization and Al2O3 deposition on thermoplastic-polymers (polycarbonate, polyimide) and a thermosetting-polymer composite (carbon fiber reinforced epoxy) were conducted via atmospheric plasma spray (APS). Due to the susceptibility of polymers to thermal or mechanical damage, precise process control is required. It was shown that the engineering temperature range critically determines the process window of thermoplastic-polymers. An Al2O3 coating can be fabricated on polymers via an Al bond coat. Like a heat sink, the Al buffer layer enables polymers to endure process heating. In low thermally resistant polycarbonate (PC), only a low plasma energy source could be applied. Additionally, vaporization induced by Al droplet contact was a clear reason of the unstable weak interface between the coating and substrate. The coatings fabricated on polyimide (PI) substrates generally showed a continuous and clean interface with a moderate adhesion property. In the case of carbon fiber reinforced epoxy (CFRP), it is believed that carbon fibers acted as a heat sink such that considerable thermal damage of CFRP was not observed and there was not delamination of the coatings. However, fracturing of carbon fibers and epoxy resin by grit-blasting (surface pre-treatment) made the surface unstable. This led to the worst adhesion characteristics between the coating and CFRP substrate. It was demonstrated that because the available temperature range and surface condition are very sensitive compared to conventional metal substrates, advanced surface pre-treatment, precise process optimization, and additional cooling are required for successful deposition. [ABSTRACT FROM AUTHOR]

Metal oxide nanocomposites (MON) have gained significant attention in the literature for the possibility of improving the optical and electronic properties of the hybrid material, compared to its pristine constituent oxides. These superior properties have been observed for TiO2 — based MON, which exhibit improved structural stability and photoactivity in environmental decontamination processes. In addition, the use of polymer membrane-supported MON is preferable to prevent further aggregation of particles, increase the surface area of the semiconductor in contact with the contaminant, and enable material reuse without considerable efficiency loss. In this work, V5+-doped TiO2/WO3 MON nanostructures were prepared by the sintering process at 500 °C and supported in electrospun fiber membranes for application as photocatalyst devices. Microstructural characterization of the samples was performed by XRD, SEM, EDS, Raman, and DSC techniques. The reflectance spectra showed that the bandgap of the MON was progressively decreased (3.20 to 2.11 eV) with the V5+ ions doping level increase. The fiber-supported MON showed photoactivity for rhodamine B dye degradation using visible light. In addition, the highest photodegradation efficiency was noted for the systems with 5 wt% vanadium oxide dispersed in the fibers (92% dye degradation in 120 min of exposure to the light source), with recyclability of the composite material for use in new photocatalysis cycles. The best results are directly related to the microstructure, lower bandgap and aggregation of metal oxide nanocomposite in the electrospun membrane, compared to the support-free MON.

A submicrometer-thick molecular sieve zeolite nanosheet laminated (ZNL) membrane has been synthesized on macroporous polyvinylidene fluoride (PVDF) substrate via the simplistic vacuum filtration-coating method. The membrane has been demonstrated with extraordinary water flux (∼11 kg/m2·h) and salt rejection (∼99.9%) in pervaporation (PV) desalination of a multicomponent brine with 22 wt % of total dissolved salts (TDS) including Li+, Na+, K+, Mg2+, Cl–, and SO42–, etc. The desalination of high-salinity brines is critical to treatment and beneficial use of many industrial produced waters. The large aspect ratios (>100) and preferable b-orientation of the densely layered nanosheets make the solution dewatering rate surpass the ion diffusion rates in the nanoscale internanosheet spaces. This unique transport behavior effectively prevents the dissolved salts from migrating through the ZNL layer and stabilizes the water flux and ion rejection rates. The supported multilayered ZNL membrane, which is interlocked by the substrate-type PVDF binder, exhibits structure and performance stability in PV desalination of high-TDS brines. [ABSTRACT FROM AUTHOR]

Although in-situ monitoring of electrical resistance of polymer-supported thin films during a mechanical test is frequently used, the impact of the magnitude of electric current on material behavior in such experiments remained unknown. Here, we report on cyclic straining of polymer-supported gold metallization lines under direct current of different magnitudes. Fatigue damage in form of localized extrusions becomes more pronounced with increasing current as a result of Joule heat and material softening. After a critical current value is reached, crack propagation results in a local decrease of line cross-section leading to thermal runaway and open circuit failure. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Organic light-emitting diodes (OLEDs) are widely commercialized in the display market due to many advantages such as wide color gamut, outstanding flexibility, and high contrast ratio. However, the performance of OLED is often hindered by the refractive index differences between the anode, substrate, and air, leading to inefficient light out-coupling from the device. In this study, we designed a polymer substrate incorporated with barium titanium oxide (BaTiO3) nanoparticles (NPs) with high refractive index to function as a bifunctional scattering substrate for efficiency enhancement of OLEDs. Fine-tuning the concentration of BaTiO3 NPs enables direct control of the refractive index and optical scattering of the substrate. The results show that the luminance efficiency and external quantum efficiency of OLED employing BaTiO3 embedded substrate are approximately 1.6 times higher than its pristine counterpart. Evidently, the nanocomposite polymer substrate demonstrated herein could serve as an efficient light out-coupling medium for flexible OLEDs. [ABSTRACT FROM AUTHOR]

An azobenzene derivative containing a dimethylchlorosilane end group was chemically attached to a flexible polymer substrate to create permanent photo alignment layer. The commercially obtained polymer substrate (overhead projector film) was characterised and found to contain cellulose acetate as the main component. Surface functionalization of the substrate was confirmed through X-ray photoelectron spectroscopy (XPS), attenuated total reflectance fourier transform infrared (ATR-FTIR) spectroscopy, water contact angle (CA) and atomic force microscopy (AFM) techniques. Photo-isomerisation behaviour of the azo-layer on the polymer substrate was additionally confirmed by UV-diffuse reflection spectroscopy (UV-DRS). Further, the azo-modified flexible substrate was analysed for the orientation of the bulk liquid crystal (LC) sample and tuning the LC orientation by utilising photo-switching behaviour of the azo-layer on the substrate. [ABSTRACT FROM AUTHOR]

An approach toward designing and building of a compact, low-profile, wideband, unidirectional, and conformal imaging antenna for electromagnetic (EM) head imaging systems is presented. The approach includes the realization of a custom-made flexible high-permittivity dielectric substrate to achieve a compact sensing antenna. The developed composite substrate is built using silicon-based poly-di-methyl-siloxane (PDMS) matrix and microscale of aluminium oxide (Al2O3) and graphite (G) powders. Al2O3 and G powders are used as fillers with different weight-ratio to manipulate and control the dielectric properties of the substrate for attaining better matched with the human head and reducing antenna’s physical size while keeping the PDMS flexibility feature. Using the custom-made substrate, a compact, wideband, and unidirectional on-body matched antenna for wearable EM head imaging system is realized. The antenna is configured as a multi-slot planar structure with four shorting pins, working as electric and magnetic dipoles at different frequency bands. The measured reflection coefficient (S11) shows an operating frequency band of 1–4.3 GHz. The time-average power density and the amplitude of the received signal inside the MRI-based realistic head phantom demonstrate a unidirectional propagation and high-fidelity factor (FF) of more than 90%. An array of 13 antennas are fabricated and tested on a realistic 3-D head phantom to verify the imaging capability of the proposed antenna. The reconstructed images of different targets inside the head phantom demonstrate the possibility of utilizing the conformal antenna arrays to detect and locate abnormality inside the brain using multistatic delay-multiply-and-sum beamforming algorithm. [ABSTRACT FROM AUTHOR]

Inorganic thin films on polymer substrates have enhanced functionalities in electronic, packaging, and energy conservation applications. Nevertheless, establishing a robust interfacial bond between the thin film and substrate remains a significant challenge. Polymer substrates inherently possess unique properties, and this review compares the changes observed in aliphatic and aromatic polymers after ion and plasma treatments. The analysis also reveals various factors from the substrate that can influence by the treatments. Additionally, process parameters of the treatment, such as process gas, energy of ion and plasma species, and treatment duration are critical to determine effects of treatment to the polymer substrates. Factors affecting interfacial bonding between inorganic thin film and polymer substrate and residual stress generated in the thin film-substrate system have been systematically reviewed. Furthermore, a significant focus of this review is placed on the impact of weathering effects, such as sunlight with UV irradiation, humidity, and temperature, on the durability of thin film-polymer substrate system and typical thin film adhesion quality characterization techniques. • Review on the effects of polymer substrate to ion and plasma treatment. • Both ion and plasma treatments require optimization for different machine configurations and applications. • Interfacial bonding between inorganic thin film can improve by inducing surface roughness and hydrophilicity to some extent. • Intrinsic stress of thin film-substrate system and weathering effect during service lifetime led to coating failure. • Adhesion between thin film and inorganic coating is a complex phenomenon to be explained by only any one of the factors. [ABSTRACT FROM AUTHOR]

Direct writing of cobalt/cobalt oxide composites has attracted attention for its potential use in catalysts and detectors in microsensors. In this study, cobalt-based composite patterns were selectively formed on glass, polyethylene naphthalate (PEN), and polyethylene terephthalate (PET) substrates via the femtosecond laser reductive sintering of Co3O4 nanoparticles in an ambient atmosphere. A Co3O4 nanoparticle ink, including the nanoparticles, ethylene glycol as a reductant, and polyvinylpyrrolidone as a dispersant, was spin-coated onto the substrates. Near-infrared femtosecond laser pulses were then focused and scanned across the ink films to form the patterns. The non-sintered nanoparticles were subsequently removed from the substrate. The resulting sintered patterns were found to be made up of Co/CoO composites on the glass substrates, utilizing various pulse energies and scanning speeds, and the Co/CoO/Co3O4 composites were fabricated on both the PEN and PET substrates. These results suggest that the polymer substrates with low thermal resistance react with the ink during the reductive sintering process and oxidize the patterns more easily compared with the patterns on the glass substrates. Such a direct writing technique of cobalt/cobalt oxide composites is useful for the spatially selective printing of catalysts and detectors in functional microsensors.

The feasibility of depositing aluminum onto thermoplastic substrates via cold spray (CS) was investigated. Dense coatings of 7075 Al and CP Al (commercial purity) were achieved on three substrates—polyetheretherketone (PEEK), polyetherimide (PEI), and acrylonitrile butadiene styrene (ABS) using an iterative optimization process. 7075 Al deposition yielded low deposition efficiencies (DEs) and low thicknesses but high adhesive strengths, while CP Al deposition led to high DEs and thicknesses but relatively low adhesive strengths. PEEK and PEI were more suitable substrates for cold spray than ABS, which suffered from surface erosion and substrate distortion. Two key factors were identified that influenced the DE and adhesive strength of the coating. The first factor was the bond layer, the initial few particle layers that fused with the substrate to allow subsequent buildup. The bond layer was influenced by the substrate hardness, yield strength, glass transition temperature, and impact strength, as well as the differences in thermal expansion coefficients of Al and the polymer substrates. The second factor was the CS process parameters selected, as the bond layer and the build-up layers may require different process conditions in order to optimize both bonding strength and coating strength, respectively. [ABSTRACT FROM AUTHOR]

Abstract Graphene possesses excellent mechanical strength and chemical inertness with high intrinsic carrier mobility and superior flexibility making them exceptional candidates for optoelectronic applications. Graphene quantum dots (GQDs) derived from graphene domains have been widely explored to study their photoluminescence properties which can be tuned by size. GQDs are biocompatible, low cytotoxic, strongly luminescent and disperse well in polar and non-polar solvents showing bright promise for the integration into devices for bioimaging, light emitting and photovoltaic applications. In the present study, graphene quantum dots were synthesized by an electrochemical cyclic voltammetry technique using reduced graphene oxide (rGO). GQDs have been incorporated into binder free TiO 2 paste and studied as a photoelectrode material fabricated on ITO/PEN substrates for flexible dye sensitised solar cells (DSSCs). DSSC based on GQDs-TiO 2 exhibited open circuit output potential difference (V oc) of 0.73 V, and short circuit current density (J sc) of 11.54 mA cm−2 with an increment in power conversion efficiency by 5.48%, when compared with those with DSSC build with just a TiO 2 photoanode (open-circuit output potential difference (V oc) of 0.68 V and short circuit density (J sc) of 10.67 mA cm−2). The results have been understood in terms of increased charge extraction and reduced recombination losses upon GQDs incorporation. Graphical abstract Image 10376 Highlights • GQDs were prepared by electrochemical cyclic voltammetry technique using reduced graphene oxide as starting precursor. • GQDs-TiO 2 films are prepared by doctor blade method. • The GQDs-TiO 2 based flexible polymer DSSC exhibited good photo conversion parameters. • Further modification in the GQDs-TiO 2 film preparation can lead GQDs as a promising material in hybrid photovoltaics. [ABSTRACT FROM AUTHOR]

Nowadays, a lot of flexible and lightweight devices are needed in some electronics applications. In this paper, zinc oxide (ZnO) films were deposited on flexible Teflon substrates by radio frequency (RF) magnetron sputtering, and the influence of Ar pressure on the structure, residual stress and photoluminescence (PL) spectra properties was also studied. The results show that all the films have a polycrystalline microstructure with dominated (002) orientation. The best (002) c-axis orientation and largest grain size are observed in the films deposited at highest Ar pressure of 4Pa. It is found that all the ZnO films exhibit compressive stress. At lower Ar pressure, the stress is very small and increases with the increasing Ar pressure from 0.5 Pa to 1.5 Pa. However, at higher pressure, the stress decreases abruptly as Ar pressure increases from 2.0 Pa to 4.0 Pa. All samples have presented road deep-level (DL) emission in the visible range between 450 nm and 500 nm. The UV emission can only be found in the films with smaller stress. Furthermore, the intensity of the UV emission and visible luminescence is weaker in the films deposited at lower Ar pressure compared with those at higher pressure. The best (002) c-axis orientation and the deduction of the stress in the films deposited at 4Pa are believed to be associated with more efficient UV PL emission. Another possible reason for the strong UV emission in the films of 4.0 Pa may be ascribed to the larger grains. [ABSTRACT FROM AUTHOR]

Flexible thin film photovoltaic devices have been a way of interest for researchers through the last decade. Creating suitable ultrathin films of any material is necessary for the realization of flexible systems. Therefore, the current study aims to study the impact of the thickness of the Boron sub-phthalocyanine chloride B(SubPc)Cl deposited on flexible Polyacetate (PA) as a polymer substrate. The structural properties of B(SubPc)Cl/PA with different thicknesses have been investigated using XRD and AFM. The investigated samples show an amorphous characterization with grain size slightly changed from 107 to 131 nm for thicknesses of 76 and 300 nm respectively, which is affected by the effect of the thickness. The optical transmission and absorption were studied in the spectral range of 300–2500 nm where the characteristic bands of a metallic phthalocyanine known as B and Q bands were observed in this range of the spectrum. The dispersion parameters, optical dielectric, SELF, and VELF for B(SubPc)Cl/PA were calculated and interpreted. Also, by using Tauc's extrapolation, the optical energy gap (E g) was calculated. The E g has values of 1.76 and 3.19 for a thickness of 76 nm which increased by increasing the film thickness. The nonlinear optical properties of B(SubPc)Cl/PA have been investigated, and the values obtained showed a high nonlinear optical response. The research outcomes candidate B(SubPc)Cl/PA for optoelectronics applications such as solar cells, sensors, and nonlinear optical devices. [ABSTRACT FROM AUTHOR]

In this paper, a simple fabrication process for SU-8 in-plane micro electro-mechanical systems (MEMS) structures, called “border-bulk micromachining”, is introduced. It aims to enhance the potential of SU-8 MEMS structures for applications such as low-cost/disposable microsystems and wearable MEMS. The fabrication process is robust and uses only four processing steps to fabricate SU-8 in-plane MEMS structures, simplifying the fabrication flow in comparison with other reported attempts. The whole fabrication process has been implemented on copper-polyimide composites. A new processing method enables the direct, laser-based micromachining of polyimide in a practical way, bringing in extra processing safety and simplicity. After forming the polymeric in-plane MEMS structures through SU-8 lithography, a copper wet etching masked by the SU-8 structure layers is carried out. After the wet etching, fabricated in-plane MEMS structures are suspended within an open window on the substrate, similar to the final status of in-plane MEMS devices made from industrial silicon micromachining methods (such as SOIMUMPS). The last step of the fabrication flow is a magnetron sputtering of aluminum. The border-bulk micromachining process has been experimentally evaluated through the fabrication and the characterization of simple in-plane electrically actuated MEMS test structures. The characterization results of these simple test structures have verified the following process qualities: controllability, reproducibility, predictability and general robustness.

The miniaturization of electronics has been following Moore's Law for decades and has resulted in the development of sequentially evolutionized multifunctional nanoengineered devices. The conventional electronic devices are processed over planar hierarchically nanopatterned substrates having mechanical rigidity and stiffness which limit the degree of utility due to its inability to interface with soft curvilinear morphology, brittle nature, and inferior optical transparency. However, flexible substrates assembled over polymeric framework would, therefore, play a key role by offering light weighted thin film architecture, wearability, improved optical transparency, and morphological configuration to curvilinearity. The flexibility of substrate is defined when the material is processed such that individual component complies to a comparable degree of bending without deterioration of electronic/optoelectronic performance. Since the fabricated structure is pliable, the mechanical integrity of the structure governs the electromechanical performance of flexible electronic devices. The structure may undergo delamination, which occurs due to the stress field gradient developed due to the coefficient of thermal expansion, thereby generating a built-in strain potentially capable of breaking the adhering bonds. This article provides a consolidated review of numerous processing techniques to fabricate flexible electronics ranging from printing, sol-gel, chemical vapor deposition to chemical synthesis route, etc. and their applications in thin-film transistors, solar cells, sensors, health monitoring e-skins, optical devices, etc. along with a theoretical mechanical two layer film substrate model. [ABSTRACT FROM AUTHOR]

A key engineering parameter of thin coatings is their stiffness. Stiffness characterization of ultrathin coatings with a nanometer scale thickness is experimentally challenging. In this work, three feasible methods have been used to estimate the Young’s modulus of metal coatings on polymer films. The methods are: (1) nanoindentation, (2) strain-induced elastic buckling and (3) peak-force measurements integrated in atomic force microscopy. The samples were prepared by atomic layer deposition of TiO2 (6 and 20 nm thick) and mixed oxides of TiO2 and Al2O3 (4 and 20 nm thick). The differences in estimated Young’s modulus are interpreted in terms of the underlying assumptions and test conditions. Their specific advantages and drawbacks are also compared and discussed. In particular, the nanoindentation necessitates a sufficiently sharp indenter tip to make localized measurements dominated by the coating. The strain-induced elastic buckling method is simple in practice, but showed a large scatter due to variation in local coating thickness and irregular deformation patterns. The stiffness characterization using atomic force microscopy gave the most consistent results, due to a sharp tip with a radius comparable to the thinnest coating thickness. All methods gave a higher Young’s modulus for the TiO2 coating than for the mixed oxide coating, with a variation within one order of magnitude between the methods. [ABSTRACT FROM AUTHOR]

Highly flexible lead zirconate titanate, Pb(Zr,Ti)O 3 (PZT), thin films have been realized by an all chemical process on a plastic substrate. The procedure is composed of three steps: the first one is the PZT deposition on aluminium thin substrate, the second step corresponds to the bonding PZT thin film to a polymer layer and the final step is the aluminium substrate etching. Diffractions and microscopy techniques were used to check the quality of the new PZT/polymer composite structure. Polarization hysteresis and permittivity measurements were also performed to determine the electrical characteristics of the composite. These results demonstrate that the recently developed PZT/polymer thin films are very attractive for both bending actuation and sensing as well as for low frequency vibrating energy harvesting applications. [ABSTRACT FROM AUTHOR]

Miniature power sources are needed for a variety of applications, including implantable medical devices, remote microsensors and transmitters, “smart” cards, and Internet of things (IoT) systems. Today's rechargeable lithium-ion batteries - with the best performance on the subject of energy density and with a reasonably good power efficiency - dominate the consumer market. Insufficient areal energy density from thin-film planar microbatteries has inspired a search for three-dimensional microbatteries (3DMB) with the use of low cost and efficient micro- and nano-scale materials and techniques. The exclusive capabilities of the 3D-printing technology enable the design of different shapes and high-surface-area structures, which no other manufacturing method can easily do. We present a novel, quasi-solid rechargeable 3D microbattery assembled on a 3D-printed perforated polymer substrate (3DPS) with interconnected channels formed through XYZ planes. Simple and inexpensive electrophoretic-deposition routes are applied for the fabrication of all the thin-film active-material layers of the microbattery. With the advantage of thin films, which conformally follow all the contours of the 3D substrate and are composed of nanosize electrode materials, like modified Lithium Iron Phosphate (LFP, Lithium Titanate (LTO), and original polymer-in-ceramic electrolyte, our 3D microbatteries offer high reversible specific capacity and high pulse-power capability. [ABSTRACT FROM AUTHOR]

MgF2 coating solutions were solvothermally treated at 160 °C for different time periods, this procedure induced crystallization and particle growth. Antireflection coatings prepared on glass from these solutions were compared to films derived from untreated precursor material. Ellipsometric porosimetry (EP) was employed to characterize structural features of coatings on glass as function of annealing temperature. Based on precursor solutions that had undergone solvothermal treatment antireflective coatings with a peak transparency exceeding 99% were prepared on PMMA substrates.Solvothermal treatment of MgF2 precursor solutions results in crystallization of particles that can directly be applied to PMMA substrates for λ/4 antireflective films. [ABSTRACT FROM AUTHOR]

The solvent‐provoked formation and evolution of thin film buckling‐delamination on a compliant substrate have been studied. The film surface is observed by an optical microscope showing a remarkable dynamic buckling‐delamination development and a subsequent stable branched‐straight state. It is revealed that the initiation, propagation, and the resulting patterns of film buckles are strongly dependent on the solvent type, film stress, interfacial adhesion, and film thickness. The buckling could be controlled further by a reasonable chemical solvent configuration and used to provide useful information for the pattern creation on polymer systems in diverse fields, such as micro/nanofabrication and optics. [ABSTRACT FROM AUTHOR]

Twisting monotonic and fatigue experiments were conducted on multi-layered films of Ag-alloy based indium tin oxide (ITO) deposited on polyethylene terephthalate (PET). In the twisting tests, crack development and electrical resistance were monitored in situ . Cracks initiated at an angle of 39° ± 1.7° and propagated towards the direction of the sample length. Two sets of experiments were performed; the first set of experiments was conducted to study the effect of twisting angle and temperature on the film's electromechanical performance. The other set of experiments was conducted to study the effect of temperature in the absence of cyclic twisting deformation. The change in electrical resistance increased with number of twisting cycles and twisting angle. In addition, the highest change in electrical resistance was observed for samples subjected to cyclic fatigue at 100 °C, which is attributed to crack growth and oxidation of the Ag-alloy layer. The cracks were observed to initiate not only from coating defects but also from edge defects. Development of cracks is accelerated due to the combined effects of the external repeated stress and temperature. Therefore, it is suggested that controlling temperature when using ITO/Ag-alloy/ITO thin film under mechanical stress is important for electrical device performance; temperatures in both fabrication and use should not exceed 50 °C. [ABSTRACT FROM AUTHOR]