Spin-casting Method Research Articles

A Stereolithography-Based Modified Spin-Casting Method for Faster Laboratory-Scale Production of Dexamethasone-Containing Dissolving Microneedle Arrays.

Microneedle arrays (MNAs) consist of a few dozens of submillimeter needles, which tend to penetrate through the stratum corneum layer of the skin and deliver hardly penetrating drugs to the systemic circulation. The application of this smart dosage form shows several advantages, such as simple use and negligible pain caused by needle punctures compared to conventional subcutaneous injections. Dissolving MNAs (DMNAs) represent a promising form of cutaneous drug delivery due to their high drug content, biocompatibility, and ease of use. Although different technologies are suitable to produce microneedle arrays (e.g., micromilling, chemical etching, laser ablation etc.), many of these are expensive or hardly accessible. Following the exponential growth of the 3D-printing industry in the last decade, high-resolution desktop printers became accessible for researchers to easily and cost-effectively design and produce microstructures, including MNAs. In this work, a low force stereolithography (LFS) 3D-printer was used to develop the dimensionally correct MNA masters for the spin-casting method. The present study aimed to develop and characterize drug-loaded DMNAs using a two-level, full factorial design for three factors focusing on the optimization of DMNA production and adequate drug content. For the preparation of DMNAs, carboxymethylcellulose and trehalose were used in certain amounts as matrices for dexamethasone sodium phosphate (DEX). Investigation of the produced DexDMNAs included mechanical analysis via texture analyzer and optical microscopy, determination of drug content and distribution with HPLC and Raman microscopy, dissolution studies via HPLC, and ex vivo qualitative permeation studies by Raman mapping. It can be concluded that a DEX-containing, mechanically stable, biodegradable DexDMNA system was successfully developed in two dosage strengths, of which both efficiently delivered the drug to the lower layers (dermis) of human skin. Moreover, the ex vivo skin penetration results support that the application of DMNAs for cutaneous drug delivery can be more effective than that of a conventional dermal gel.

Prolonged Lifespan of Superhydrophobic Thin Films and Coatings Using Recycled Polyethylene.

High-density polyethylene (HDPE) waste poses a significant environmental challenge due to its non-biodegradable nature and the vast quantities generated annually. However, conventional recycling methods are energy-intensive and often yield low-quality products. Herein, HDPE waste is upcycled into anti-aging, superhydrophobic thin films suitable for outdoor applications. A two-layer spin-casting method combined with heating-induced crosslinking is utilized to produce an exceptionally rough superhydrophobic surface, featuring a root mean square (RMS) roughness of 50 nm, an average crest height of 222 nm, an average trough depth of -264 nm, and a contact angle (CA) of 148°. To assess durability, weathering tests were conducted, revealing the films' susceptibility to degradation under harsh conditions. The films' resistance to environmental factors is improved by incorporating a UV absorber, maintaining their hydrophobic properties and mechanical strength. Our research demonstrates a sustainable method for upcycling waste into high-performance, weather-resistant, superhydrophobic films.

The Preparation and Wear Behaviors of Phenol-Formaldehyde Resin/BN Composite Coatings.

Phenolic-matrix composites possess excellent synergistic effects on mechanical and tribological properties and can be used in the aerospace, medical, and automobile industries. In this work, a series of phenol–formaldehyde resin/hexagonal boron nitride nanocomposites (PF/BNs) were in situ synthesized using an easy method. PF/BN coatings (PF/BNCs) on 316L steels were prepared through a spin-casting method. The wear behaviors of these PF/BNCs were investigated by dry sliding with steel balls. The percentage of BN, the thickness of the coating, and the heat treatment temperature affected the coefficients of friction (COFs) and wear rates of these coatings. After heat treatment at 100 °C, the tribological properties of the PF/BNCs were remarkably improved, which might be attributed to both the transformation of carbon on the worn surfaces from C-O/C=O into C=N, carbide, and other chemical bonds and the cross-linking of the prepolymers.

HR MAS NMR, dielectric impedance and XRD characterization of polyethylene oxide films for structural phase transitions

The amorphous/crystalline phase transition behavior of PEO films prepared by spin casting method was studied. According to X-ray diffraction (DELTA) analysis, PEO film has a semicrystalline nature at room temperature. The amorphous to crystalline nature of PEO increases with temperature until reaching an amorphous state at 333 K. 1H NMR spectra of PEO in the temperatures between 298 K and 323 K exhibit two main peaks at around 1.132 ppm and 3.174 ppm with very different widths, where the narrow component can be assigned to the mobile polymer chains in the amorphous phase, whereas the broad component is assigned to the more rigid molecules in the crystalline phase. The calculated activation energies from the Arrhenius fit of the Γ1 data of the crystalline and amorphous phases are comparable and found to be 0.252 eV and 0.221 eV, respectively. Form fitting dielectric loss (ε″) and the electrical modulus (M″) data with the Havriliak-Negami model with addition of the electrical conductivity term in the case of ε″, it was deduced that the inverse relaxation time (τ−1), dielectric strength (Δε) and electrical conductivity (σ) follow an Arrhenius-like behavior plot versus reciprocal temperature.

Multi-Bit Biomemristic Behavior for Neutral Polysaccharide Dextran Blended with Chitosan

Natural biomaterials applicable for biomemristors have drawn prominent attention and are of benefit to sustainability, biodegradability, biocompatibility, and metabolism. In this work, multi-bit biomemristors based on the neutral polysaccharide dextran were built using the spin-casting method, which was also employed to explore the effect of dextran on the ternary biomemristic behaviors of dextran–chitosan nanocomposites. The doping of 50 wt% dextran onto the bio-nanocomposite optimized the ratio of biomemristance in high-, intermediate-, and low-resistance states (105:104:1). The interaction between dextran and chitosan (hydrogen-bond network) was verified by Fourier transform infrared (FTIR) and Raman spectroscopy analysis; through this interaction, protons derived from the self-dissociation of water may migrate under the electric field, and so proton conduction may be the reason for the ternary biomemristic behaviors. Observations from X-ray diffraction (XRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) analysis displayed that the 50 wt% dextran/50 wt% chitosan nanocomposite had the greatest amorphous ratio as well as the highest decomposition and peak transition temperatures in comparison with the other three dextran–chitosan nanocomposites. This work lays the foundation for neutral biomaterials applied to green ultra-high-density data-storage systems.

Cs incorporation via sequential deposition for stable and scalable organometal halide perovskite solar cells

In this study, uniform Cs distribution in an organometal halide perovskite (OHP) film was achieved via sequential deposition method entailing the dissolution of Cs compounds in dimethyl formamide (DMF) with inorganic components, as opposed to using isopropyl alcohol with organic components, and the thermal stability and crystallinity of the OHP film were enhanced by improving the structural stability through Cs incorporation. Additionally, the device performance and thermal stability of OHP solar cells were enhanced by Cs incorporation, which led to fewer defect sites and the suppression of defect generation in OHP films, as confirmed by optical and electrical analysis, improving the overall film quality. The sequential deposition method was more amenable to scaling up than the anti-solvent assisted one-step spin-casting method, as demonstrated by the sequential deposition of the OHP film uniformly over a substrate with size of 8 cm × 8 cm. The uniformly sequentially deposited OHP film was used to create a large-area 1 cm 2 OHP solar cell, which exhibited a high power conversion efficiency (PCE) of 16.77%. Further scalability of the sequentially deposited OHP solar cell was confirmed by highly uniform device performances by three cells on a single substrate with a negligible PCE standard deviation of 0.94%. • The uniform Cs distribution in OHP film is achieved via sequential deposition. • The thermal stability of the OHP film increased through Cs incorporation. • The performance and stability of the PeSCs is improved. • Uniform OHP film with large size is successfully fabricated by sequential deposition. • A p-i-n PeSCs with a size of 1 cm 2 was successfully fabricated.

Tailoring the Composition and Structure of Nb-, Si-, and B-Doped Mo-Based Composite Materials in the Self-Propagating High-Temperature Synthesis Metallurgy Process

We have examined for the first time the feasibility of producing cast Nb-, Si-, and B-doped Mo-based composite materials by a spin-casting self-propagating high-temperature synthesis metallurgy method and obtained new results regarding control over their composition and structure. In synthesis, we used combinations of a highly exothermic (MoO3/Nb2O5/Al/Si/B) and a low-exothermic (Mo/Nb/Si/B) composition. We have assessed the effect of the ratio of the ratio of the highly exothermic and low-exothermic compositions (α) and acceleration (a) on the composition and structure of the cast composite materials. The mixtures have been shown to be capable of combustion at up to 80% low-exothermic composition. The combustion products have cast form in the range 0 ≤ α ≤ 65%. At α in the range from 0 to 40% and accelerations from 40g to 400g, the combustion products have the form of a two-layer ingot: the lower layer (Mo–Nb–Si–B) consists of the required product and the upper layer (Al2O3) is a slag product. The optimal parameters for the preparation of cast Mo–Nb–Si–B materials are α = 20–30% and a > 100g.

Preferentially oriented Fe-doped CaCu3Ti4O12 films with high dielectric constant and low dielectric loss deposited on LaAlO3 and NdGaO3 substrates

The colossal dielectric constant of calcium copper titanate (CCTO) thin films is generally accompanied by high dielectric losses which limit its potential for electronic miniaturization. Strategies for reducing the dielectric loss while keeping large dielectric constants are needed for various electrical applications of CCTO. This work aims to reduce the loss by means of doping preferentially oriented CCTO films with Fe3+ ions. Highly oriented undoped and Fe-doped calcium copper titanate (Fe-doped CCTO) thin films were fabricated by synthesizing CCTO on LaAlO3(100) and NdGaO3(100) substrates via a sol-gel spin casting method. The films with different Fe-doping concentrations (0, 1.6 and 2.6 wt%) were structurally and chemically characterized via energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. X-Ray Diffraction (XRD) patterns confirmed that our doped CCTO films had a cubic perovskite structure with well-defined preferential orientations of (h00) and (hh0) on LAO and NGO substrates, respectively. Preferentially oriented films having room temperature dielectric constants on the order of 1000 in conjunction with values of loss tangent smaller than 0.012 in the frequency range of 50 Hz-2 MHz were achieved. Temperature dependence of the dielectric constant and loss tangent revealed that Fe-doping decreased the dielectric loss via the lowering of the electrical conduction through CCTO grains.

Ultrathin, Large-Area Membrane Diffusion Cell for pH-Dependent Simultaneous Dissolution and Absorption Studies.

Preclinical evaluation of modern oral dosage forms requires more advanced in vitro devices as the trend of selecting low solubility, high permeability compounds for commercial development continues. Current dissolution methodologies may not always be suitable for such compounds due to excessive fluid volume, high fluid shear rates, heterogeneity of shear rates, suboptimal fluid flow, and, ultimately, the lack of absorption ability (Gray The Science of USP 1 and 2 Dissolution: Present Challenges and Future Relevance; Pharmaceutical Research, 2009; Vol. 26; pp 1289-1302). Herein, a new dissolution apparatus is introduced in combination with an ultrathin, semipermeable polymer membrane that mimics human passive absorption for lipophilic compounds. The ultrathin large-area polydimethylsiloxane (PDMS) membrane (UTLAM) absorption system is designed to mimic the dissolution and passive transcellular diffusion process representing the oral absorption pathway. A simple spin-casting method was developed to fabricate the ultrathin highly uniform membranes. To minimize membrane resistance to diffusion and maximize transport across the polymer membrane, 10-40 μm PDMS membranes were successfully prepared. A new diffusion cell was designed and tested to support the UTLAM and incorporates a hydrofoil impeller for more desirable hydrodynamics and mixing, using ibuprofen as a model weak acidic drug. UTLAM permeability was sufficiently high that the aqueous boundary layer contributed to the overall permeability of the system. This diffusion cell system demonstrated that, when the aqueous diffusion layer contributes to the overall resistance to transport, the pH at which absorption is 50% of maximum (pH50%) shifts from the pKa to higher values, demonstrating why weak acid drugs can exhibit high absorption at pH's significantly greater than their pKa. High rates of transport across the UTLAM are possible for drugs with high partition coefficients (i.e., BCS II compounds even under mostly ionized conditions), and PDMS UTLAMs may be tailored to simulate human intestinal passive absorption rates.

Biomemristic Behavior for Water-Soluble Chitosan Blended with Graphene Quantum Dot Nanocomposite.

Bionanocomposite has promising biomemristic behaviors for data storage inspired by a natural biomaterial matrix. Carboxylated chitosan (CCS), a water-soluble derivative of chitosan avoiding the acidic salt removal, has better biodegradability and bioactivity, and is able to absorb graphene quantum dots (GQDs) employed as charge-trapping centers. In this investigation, biomemristic devices based on water-soluble CCS:GQDs nanocomposites were successfully achieved with the aid of the spin-casting method. The promotion of binary biomemristic behaviors for Ni/CCS:GQDs/indium-tin-oxide (ITO) was evaluated for distinct weight ratios of the chemical components. Fourier transform infrared spectroscopy, Raman spectroscopy (temperature dependence), thermogravimetric analyses and scanning electron microscopy were performed to assess the nature of the CCS:GQDs nanocomposites. The fitting curves on the experimental data further confirmed that the conduction mechanism might be attributed to charge trapping–detrapping in the CCS:GQDs nanocomposite film. Advances in water-soluble CCS-based electronic devices would open new avenues in the biocompatibility and integration of high-performance biointegrated electronics.

Novel low‐dielectric‐constant fluorine‐functionalized polysulfone with outstanding comprehensive properties

AbstractIn this work, a series of fluorine‐functionalized polysulfone (F‐PSU) copolymers with intrinsic low dielectric constants (low ε) are reported, which are derived from the polycondensation reaction of 4,4′‐dichlorophenyl sulfone with bisphenol A and bisphenol F (BPF) compounds. The resulting F‐PSU copolymers show high glass transition temperatures (Tg) varying from 187 to 201 °C and are thermally stable up to 500 °C under an N2 atmosphere. The introduction of BPF units into the PSU copolymers imparts enhanced hydrophobic properties to the F‐PSU films with increased water contact angle values from 66.2° to 93.7°. Moreover, the dielectric constant and dielectric loss of the F‐PSU (sample V) film are as low as 2.2 and 0.003 at 1 kHz, respectively. Interestingly, the dielectric properties are relatively stable to near the glass transition temperature, which is because of the existence of BPF structures in the molecular backbone. Furthermore, the F‐PSU copolymers are soluble in common solvents and can be readily fabricated into flexible transparent films by the spin casting method. © 2020 Society of Chemical Industry

Surface morphological, optical and electrical characterization of methylammonium lead bromide perovskite (CH3NH3PbBr3) thin film

Hybrid halide perovskites (CH3NH3PbX3; X=F, Cl, Br and I) have been emerging as innovative candidates in the development of optoelectronic devices. In this paper, a methylammonium lead bromide (CH3NH3PbBr3) perovskite-based heterojunction device of architecture FTO/PEDOT:PSS/CH3NH3PbBr3/PC61BM/Al has been fabricated using a low-cost spin casting method. PEDOT:PSS and PC61BM layers serve as the hole transport layer (HTL) and the electron transport layer (ETL), respectively. The photoluminescence and absorbance spectrum of perovskite have been determined with an extracted band gap using a Tauc plot. The electrical characterization of the device has been carried out using current-voltage and impedance measurements. A dark current measurement reveals low leakage current, which can be attributed to the blocking effect of the PEDOT:PSS and PC61BM layers. The photocurrent generation in the device has been explained by the energy level diagram, and the role of the ETL and HTL identified. The device exhibits the ideality factor 2.37 in the dark and 1.79 under illumination. The parameters show good correlation with the I–V results.

Elaboration and thermal annealing of the optical properties of the thin films of meta-PPV copolymer

The meta-PPV copolymer was prepared by the condensation of the diphosphonium chloride of meta-xylene with dialdehyde of vanillin. Meta-PPV thin films were successfully deposited on glass substrates by spin casting method. The polycrystalline structure of the films was confirmed using X-ray diffraction (XRD) analysis, and also XRD was utilized to compute the grain size and dislocation. Surface morphology was characterized by using photomicroscope and scanning electron microscopy. Fourier-transform infrared spectroscopy was used to verify the presence of the absorbance bands. The optical absorption measurement revealed direct-allowed electronic transition with band gaps 3.3 eV and 2.85 eV for as-deposited and annealed films, respectively. The redshift of the band gap and related optical constant after annealing was assigned to the change in configuration and conformation of copolymer chains. Thermal annealing leads to the reduction in PL efficiencies and redshift of single peak which attributed to band-to-band transition.

The effects of double-shell organic interfaces on the dielectric and energy storage properties of the P(VDF-CTFE)/BT@HBP@PDA-Ag nanocomposite films

Abstract In order to improve the interfacial compatibility of PVDF-based nanocomposites, the BaTiO3 (BT) nanoparticles are coated successively using double-shell layers of hyperbranched polyamide polyamide (HBP) and polydopamine (PDA). Subsequently, the BT particles with an organic double-shell structure is compound to a dielectric poly (vinylidene fluoride-chlorotrifluoroethylene) (P(VDF-CTFE)), and the flexible 0–3P(VDF-CTFE)/BT@HBP@PDA-Ag nanocomposites films with ∼20 μm in thickness are obtained using spin-casting method. The results of FTIR, TEM and SEM indicate that the good interfacial compatibility of the composites favors the dispersion of coated BT particles in the P(VDF-CTFE) matrix. Consequently, the P(VDF-CTFE)/BT@HBP@PDA-Ag nanocomposites film shows a large dielectric permittivity (er ∼ 40) with depressed dielectric loss tangent at a low frequency of 0.1 Hz. In addition, a high electrical displacement of 5.6 μC/cm2 and a large discharged energy density of 7.0 J/cm3 are obtained in this nanocomposite film due to the together contributions of ionic polarization of BT and the penetration effect of electrons. Considering its relative low dielectric loss, the double-shell coating on the inorganic particles in the polymer/ceramic composite film provides an effective way of interfacial fabricating for the high dielectric and energy storage performance.

Electrically Controllable Single-Point Covalent Functionalization of Spin-Cast Carbon-Nanotube Field-Effect Transistor Arrays

Single-point-functionalized carbon-nanotube field-effect transistors (CNTFETs)have been used to sense conformational changes and binding events in protein and nucleic acid structures fromintrinsic molecular charge. The key to utilizing thesedevices as single-molecule sensors is the ability to attach a single probe molecule to an individual device. In contrast, with noncovalent attachment approaches such as those based on van der Waals interactions, covalent attachment approaches generally deliver higher stability but have traditionally been more difficult to control, resulting in low yield. Here, we present a single-point-functionalization method for CNTFET arrays based on electrochemical control of a diazonium reaction to create sp3 defects, combined with a scalable spin-casting method for fabricating large arrays of devices on arbitrary substrates. Attachment of probe DNA to the functionalized device enables single-molecule detection of DNA hybridization withcomplementary target, verifying the single-point functionalization. Overall, this method enablessingle-point defect generation with 80% yield.

Correlation of Band Electronic Structure to Efficiency in Perovskite Solar Cells with Vanadium Oxide Buffers

Over the past few years, solar cells with an organo metal halide perovskite structure have been well studied and attracted attention due to their excellent basic properties such as diffusion length of long charge carriers, good electrical properties, and light absorption coefficient, as well as easy and inexpensive solution processability. According to the efficiency chart, perovskite solar cells have achieved efficiencies of 22.1% in 2016 through rapid development with efficiency starting at 3.8%. However, despite these high efficiencies, one of the biggest problems of perovskite solar cells is the low stability and reliability of the devices in the atmosphere. For commercialization of perovskite solar cells, it is necessary to analyze and improve stability and efficiency. In the structure of the device, the electron transporting layer (ETL) and the hole transporting layer (HTL) transport charges, respectively, and mainly organic materials are used. The stability of the device can be enhanced by inserting a charge transporting layer of an inorganic material such as NiOx, ZnO, and VOx, which is superior in stability to organic materials such as PEDOT: PSS and Spiro-OMeTAD. Among them, p-type VOx with wide bandgap is used as HTL and can replace PEDOT: PSS. It is also important to note that in such a stacked heterojunction solar cell structure, band bending occurs due to different band gaps. Due to the non-optimization of conduction band offset (CBO) and valence band offset (VBO) at the interface between the absorption layer and the charge transport layer, it is possible to secure a smooth movement path of electrons and holes, and conversely, recombination of electrons and holes can be a cause of reduction in efficiency. Perovskite solar cells are also attracting attention as a strategy for improving efficiency at the interface between the charge transporting layer and the absorber layer. In this study, the efficiency difference and electronic structure analysis were carried out in planar heterojunction structure with ITO/VOx/Perovskite/PCBM/ZnO/Al structure fabricated by two process methods. The VOx buffer layer was deposited by vacuum deposition using RF magnetron sputtering and spin casting method. The VBM and core levels at the interface were measured using optical bandgap and depth profile x-ray photoelectron spectroscopy. After that, CBO and VBO values were derived from the calculations and the mechanism of electron and hole transport was clarified. As a result, it has been confirmed that the perovskite solar cell fabricated by the RF sputter process has an efficiency of about 13% and the device manufactured by the spin casting method has an efficiency of about 8%, and the reason for the difference efficiency is explained in relation to the electronic band structure.

Molecular Combing of a Flexible Polymer Chain by Simple Spin-Casting.

If polymer chains could be fixed on a substrate as a fully elongated chain, a procedure known as “molecular combing”, the chain structure could be analyzed more precisely than has been possible with the characterization techniques available today. Although the molecular combing of a rigid biomolecule, DNA, has been attained for the mapping of genetic information, that of flexible chains has never been achieved as yet. We show here that poly(n-nonyl acrylate) (PNA) can be molecularly combed on mica by a simple spin-casting method, and that the chain lengths were in good agreement with that of the all-trans conformation. One of the key factors for successful molecular combing was found to be the weak adsorption of PNA on mica, indicating that flexible polymers may be molecularly combed by adjusting their affinity to the substrate. The molecular combing of polymer chains may open a new way not only to characterize the chain structures more precisely but also to fabricate new nanomaterials based on polymers.

Optical properties of Rhodamine B Dye mixed with Polyvinylpyrrolidone (PVP ) as a matrix

In the present work, the spin casting method has been utilized for preparing different concentrations of Rhodamine B (Rh B) (5%,10% and 15%) mixed with a transparent polymer Polyvinylpyrrolidone (PVP) as a matrix. The spectral characteristics of the prepared samples are studied by absorption, transmission, reflection (the wavelength region from 300 nm to 900 nm) and fluorescence spectroscopy (the wavelength region from 550 nm to 800 nm). The calculated Stokes shift between the absorption and emission of Rh.B reflects the displacement in potential surface between the ground and the excited states. The analysis of the spectral behavior of the absorption coefficient in the absorption region reveals an direct allowed transition with a band gap of 2.07 eV . The values of some important parameters (refractive index n and extinction coefficient K ) of polymer thin film are determined from these spectra.

Corrosion resistance and adhesion strength of a spin-assisted layer-by-layer assembled coating on AZ31 magnesium alloy

A polyvinylpyrrolidone (PVP)/polyacrylic acid (PAA) layer-by-layer (LbL) assembled composite coating with a multilayer structure for the corrosion protection of AZ31 magnesium alloy was prepared by a novel spin-casting method. The microstructure and composition of this coating were investigated by means of SEM, XRD and FT-IR measurements. Moreover, electrochemical, immersion and scratch tests in vitro were performed to measure the corrosion performance and the adhesion strength. These results indicated that the (PVP/PAA)10 composite coating with defect-free, dense and uniform morphologies could be successfully deposited on the surface of magnesium alloy. The coating had excellent corrosion resistance and adhesion strength.

Performance Improvement of p-Channel Tin Monoxide Transistors With a Solution-Processed Zirconium Oxide Gate Dielectric

This letter reports the fabrication of p-channel tin monoxide (SnO) thin-film transistors (TFTs) with a high-permittivity zirconium oxide (ZrO2) gate insulator film, which were prepared by a low-cost spin-cast method. The spin-cast ZrO2 dielectrics exhibit a low leakage current density of $4.5 \times 10^{{\textsf {-8}}}$ A/cm2 at 1 MV/cm. Introducing the ZrO2 dielectric in top-type SnO TFTs allows for a reduction in the driving gate voltage range from 80 to 10 V, as compared with devices with a thermal SiO2 gate insulator. Additionally, a high field-effect mobility of 2.5 cm2/Vs and an $I_{{ \mathrm{\scriptscriptstyle ON} / \mathrm{\scriptscriptstyle OFF}}}$ of $3 \times 10^{{\textsf {3}}}$ were preserved.