Variation Of Layer Thickness Research Articles

Biocompatibility of variable thicknesses of a novel directly printed aligner in orthodontics

Direct printed aligners (DPAs) offer benefits like the ability to vary layer thickness within a single DPA and to 3D print custom-made removable orthodontic appliances. The biocompatibility of appliances made from Tera Harz TA-28 (Graphy Inc., Seoul, South Korea) depends on strict adherence to a standardized production and post-production protocol, including UV curing. Our aim was to evaluate whether design modifications that increase layer thickness require a longer UV curing time to ensure biocompatibility. Specimens with varying layer thickness were printed to high accuracy using Tera Harz TA-28 and the Asiga MAX 3D printer (Asiga SPS ™ technology, Sydney, Australia). UV curing durations were set at 20, 30 and 60 min. Cytotoxicity was evaluated using the AlamarBlue assay on human gingival fibroblasts. Cell viability decreased with increasing specimen thickness (significant for 2 mm [p < 0.001], 4 mm [p < 0.0001], and 6 mm [p < 0.01]) under the manufacturer-recommended 20-min UV curing. Extending the curing time did not improve cell viability. However, cell viability never decreased by more than 30%, meeting EN ISO 10993-5 standards for non-cytotoxicity. The standard 20-minute UV curing protocol ensures the biocompatibility and patient safety of Tera Harz TA-28 for material thicknesses up to 6 mm.

Spectroscopic Ellipsometry and Correlated Studies of AlGaN-GaN HEMTs Prepared by MOCVD

A series of AlGaN/GaN high-electron-mobility transistor (HEMT) structures, with an AlN thin buffer, GaN thick layer and Al0.25Ga0.75N layer (13–104 nm thick), is prepared by metal–organic chemical vapor deposition and investigated via multiple techniques. Spectroscopic ellipsometry (SE) and temperature-dependent measurements and penetrative analyses have achieved significant understanding of these HEMT structures. Bandgaps of AlGaN and GaN are acquired via SE-deduced relationships of refraction index n and extinguish coefficient k vs. wavelength λ in a simple but straightforward way. The optical constants of n and k, and the energy gap Eg of AlGaN layers, are found slightly altered with the variation in AlGaN layer thickness. The Urbach energy EU at the AlGaN and GaN layers are deduced. High-resolution X-ray diffraction and calculations determined the extremely low screw dislocation density of 1.6 × 108 cm−2. The top AlGaN layer exhibits a tensile stress influenced by the under beneath GaN and its crystalline quality is improved with the increase in thickness. Comparative photoluminescence (PL) experiments using 266 nm and 325 nm two excitations reveal and confirm the 2DEG within the AlGaN-GaN HEMT structures. DUV (266 nm) excitation Raman scattering and calculations acquired carrier concentrations in compatible AlGaN and GaN layers.

Increasing the sensitivity of Love wave MSAW sensors by magnetoelastic layer thickness variation

Abstract Increasing the magnetic field sensitivity is one of the major challenges in the study of magnetic surface acoustic wave (MSAW) sensors. In this paper, Love wave MSAW sensors are investigated in a Transmissive Single Port Delay Line (TSP-DL) configuration, on ZnO (700 nm)/Y-X LiNbO3. CoFeB (100 nm) or CoFeB(100 nm)/SiO2(3 nm)/CoFeB(100 nm) sensitive magnetoelastic layers are placed in the acoustic path between two electrically connected interdigital transducers. The fundamental Love wave on ZnO(700 nm)/ Y-X LiNbO3 presents a high electromechanical coupling coefficient (K 2), resulting in a high signal amplitude, which is favorable for delay lines performances. Additionally, shear waves are highly sensitive to the magnetic field due to the large ΔG effect in the magnetoelastic layers. A maximum frequency shift of 0.36% was achieved using a CoFeB(100 nm)/SiO2(3 nm)/CoFeB(100 nm) stack as the sensitive layer, with a high maximum magnetic sensitivity of 3630 ppm mT−1 (1482 kHz mT−1 at 410 MHz). This sensitivity is among the highest reported in the literature on magnetic SAW sensors.

Numerical Analysis of Concrete Overlays on Flexible Pavements

Due to the proven durability and long-term performance of Portland cement concrete (PCC) surfaces, rehabilitation of hot-mix asphalt (HMA) pavements with PCC overlays has been widely considered in the past 15 years (Cable 2005). In this study, a number of finite element models of conventional HMA pavements overlaid by a jointed plain concrete pavement (JPCP) were analyzed to measure and assess the effects of asphalt layer and concrete slab thickness variations, as well as changes in the asphalt layer and subgrade mechanical properties, on the service life of the overlaid pavement.

Anatomy-driven segmentation of parafoveal optical coherence tomography (OCT) measures may improve associations with clinical outcomes in multiple sclerosis.

Previous investigations on optical coherence tomography (OCT) in multiple sclerosis (MS) focused on generalizable macular and peri-papillary regions without considering the anatomic variations of the retinal layer thickness. This study aimed to assess the utility of parafoveal retinal layer thickness measured by OCT, underscoring its relationships with clinical outcomes in MS. In this cross-sectional study, 214 people with MS (pwMS) and 57 age- and sex-matched healthy controls (HCs) were enrolled. Spectral domain OCT evaluation using 1, 3, 6mm Early Treatment Diabetic Retinopathy Study grid were conducted. The macular and parafoveal thickness (excluding the 1mm foveal/umbo contribution) of the retinal nerve fiber layer (RNFL), ganglion cell-inner plexiform layer (GCIPL), ganglion cell layer (GCL), inner plexiform layer (IPL), and the peri-papillary RNFL (pRNFL) were measured. Multivariable step-wise logistic, linear and generalized estimating equation (GEE) regression models were used to assess the association between the OCT parameters and clinical MS outcomes. The parafoveal RNFL thickness (d = 0.27, p = 0.023), GCL (d = 0.87, p < 0.001), IPL (d = 0.82, p < 0.001), and GCIPL (d = 0.85, p < 0.001) were all significantly lower in pwMS than HCs. Optic neuritis history [odds ratio (OR) = 0.84, p < 0.001] and progressive MS (PMS) status (OR = 0.92, p < 0.001) were bothbest predicted by parafoveal GCL. The Expanded Disability Status Scale (EDSS) was associated with the parafoveal thickness of GCL (standardized β = -0.472, p < 0.001) and pRNFL (standardized β = 0.187, p = 0.021). The parafoveal GCL thickness as predictor of MS disability was also confirmed by the GEE models. This investigation supports the potential use of parafoveal OCT segmentation as an alternative assessment method in detecting neuroinflammatory and neurodegenerative processes in MS. Averaging of the parafoveal retinal layer thickness into the OCT measures may increase the sensitivity of the standard macular OCT segmentation outcomes. Further studies should aim at exploring the reproducibility of this OCT outcome and its longitudinal responsiveness.

Optimizing UHPC Layers to Improve Punching Shear Performance in Concrete Slabs

Flat slabs supported by columns without beams are widely used in construction owing to their economy and efficiency. However, brittle punching shear failure at slab–column connections can cause progressive collapse. UHPC has a higher tensile strength than NSC and, when appropriately reinforced with steel fibers, exhibits strain hardening after initial cracking. These properties make Ultra-High-Performance Concrete (UHPC) ideal for durable, thin, low-cost bridge decking and heavily loaded elements and an excellent choice for improving slab–column connections that have experienced punched shear failure. This study explores the impact of UHPC layers on the punching shear behavior of reinforced concrete slabs. Sixteen slab specimens were tested with variations in UHPC layer thickness, placement, and column shape. Results demonstrate that incorporating UHPC layers significantly enhances punching shear resistance, increasing ultimate load capacity by 27–91% compared to reference specimens. Notably, thicker UHPC layers (75 mm) and bottom-placed layers exhibited superior performance in terms of ductility and toughness. Square columns outperformed circular ones in resisting punching shear. Additionally, thicker layers reduced initial stiffness, while debonding issues in 25 mm layers adversely affected structural performance. This research provides valuable insights for optimizing UHPC configurations to improve the punching shear resistance of concrete slabs, offering promising solutions for high-load structures in modern construction.

A Hybrid Data-Driven Machine Learning Framework for Predicting the Impact Resistance of Composite Armor

Composite armor plays a crucial role as the primary defense against high-velocity impacts from fragments and projectiles. However, balancing the need for lightweight structures with the requirement for robust protection remains a significant engineering challenge. Traditional approaches for predicting the protective performance of armor typically involve a combination of experimental testing and numerical simulations, both of which can be resource-intensive and costly. In contrast, data-driven methods combined with machine learning have demonstrated the potential to significantly reduce both time and economic costs, highlighting their substantial advantages in various engineering domains. Unfortunately, a mature machine learning framework for predicting the performance of multilayer composite armor against high-velocity impacts from large fragments has yet to be established. In this paper, a novel data-driven framework for predicting the ballistic performance of composite armor using a hybrid model of Support Vector Machine and Deep Neural Network was established. This framework employed hyperparameter optimization to enhance predictive performance, yielding a model with excellent accuracy. The proposed model was adaptable to multilayered armor with varying layer thicknesses, enabling rapid predictions of armor penetration, residual projectile kinetic energy, and armor deformation.

Infrared imaging with visible light in microfluidic devices: the water absorption barrier.

Infrared spectro-microscopy is a powerful technique for analysing chemical maps of cells and tissues for biomedical and clinical applications, yet the strong water absorption in the mid-infrared region is a challenge to overcome, as it overlaps with the spectral fingerprints of biological components. Microfluidic chips offer ultimate control over the water layer thickness and are increasingly used in infrared spectro-microscopy. However, the actual impact of the water layer thickness on the instrument's performance is often left to the experimentalist's intuition and the peculiarities of specific instruments. Aiming to experimentally test the amount of absorption introduced by water with varying layer thicknesses, we fabricated a set of microfluidic devices with three controlled chamber thicknesses, each comprising a simple test pattern made of a well-known photoresist SU-8. We employed two infrared spectro-microscopy methods for measurements. The first method involves using a standard FTIR microscope with a benchtop infrared light source. The second method is a quantum infrared microscopy technique, where infrared imaging is achieved by detecting correlated photons in the visible range. We demonstrated that both methods enable the measurement of the absorption spectrum in the mid-IR region, even in the presence of up to a 30 μm thick water layer on top of a sample pattern. Additionally, the Q-IR technique offers practical advantages over synchrotron-based FTIR, such as reduced complexity, cost, and ease of operation.

Angle-independent topological interface states in one-dimensional photonic crystal heterostructures containing hyperbolic metamaterials.

Topological interface states (TISs), known for their distinctive capabilities in manipulating electromagnetic waves, have attracted significant interest. However, in conventional all-dielectric one-dimensional photonic crystal (1DPC) heterostructures, TISs strongly depend on incident angle, which limits their practical applications. Here, we realize an angle-independent TIS in 1DPC heterostructures containing hyperbolic metamaterials (HMMs) for transverse magnetic polarized waves. We begin with the design of two kinds of angle-independent photonic bandgaps (PBGs) in two 1DPCs with symmetric unit cells based on the phase-variation compensation effect. From the Zak phases of the upper and lower bands, the topological properties of PBGs in two 1DPCs are different. By harnessing different topological properties, we can realize an angle-independent TIS in the heterostructure composed of these two 1DPCs. Moreover, we further discover that the angle-independent property of the TIS is robust against the layer thickness variation due to topological protection, making the experimental realization of the angle-independent TISs more feasible. It is noted that the TISs still depend on the incident angle under transverse electric polarized waves since the iso-frequency curve of the HMM is a circle. Empowered by the polarization-dependent property of the TIS, we design a wide-angle polarization selector with an operating angle range up to 45.9°. Our work provides a viable route to realizing angle-independent TISs with substantial angular tolerances under current experimental conditions, which facilitates the design of optical devices including polarizers, filters, and sensors with robustness against disorder.

Optimization and characterization of a PCF-based SPR sensor for enhanced sensitivity and reliability in diverse chemical and biological applications

This paper presents the meticulous design and characterization of a photonic crystal fiber (PCF)-based surface plasmon resonance (SPR) sensor, analyzed using finite element method (FEM) simulations. The sensor’s superior performance is demonstrated by its exceptional sensitivity to minute changes in the refractive index (RI) of various analytes. The optimized structure reveals a peak resonance at 0.78898 µm with a maximum confinement loss of 546.34 dB/cm. Detailed investigations show resonance wavelength red shifts of up to 0.93% with a 5% increase in air hole diameter and blue shifts of up to 0.88% with a 5% decrease. Additionally, variations in the plasmonic gold layer thickness result in resonance shifts of up to 0.76% longer or 0.87% shorter wavelengths. The sensor achieves remarkable wavelength sensitivity (WS) of up to 13,000 nm/RIU and amplitude sensitivity (AS) of up to 1538.90RIU−1, underscoring its high precision in detecting analyte concentration changes. The design’s robustness against fabrication errors, evidenced by minimal variations in resonance characteristics, highlights its practical reliability. Furthermore, the use of a polynomial regression model with an R2 value near unity accurately approximates the relationship between resonance wavelength and analyte RI, ensuring precise sensing capabilities without overfitting. Comparative analysis with existing designs confirms the sensor’s superior performance, rendering it highly suitable for a wide range of applications, including biosensing of glucose, water contaminated by cholera germs, mucosa of the human intestine, important components of human blood, and detection of chemicals like acetone, ethanol, benzene, propanol, glycerol, and expired transformer oil.

Impact of insulating layer thickness variation on IGZO-based thin-film transistor performance

Abstract This paper highlights the thin film transistors used in the latest applications and devices. The working principle of thin film transistors with various device structures can be used to fabricate thin film transistors. Progress in the latest materials that are being used in applications like LCDs, sensors, RFID tags, Displays, etc The remarkable characteristics of Indium-Gallium-Zinc Oxide (IGZO) thin films, for instance, their transparency and high mobility, have generated significant interest in the application part of Thin-Film Transistors (TFTs). Simulating the functioning of a-IGZO TFTs over Silvaco [Atlas] TCAD Tool, four distinct insulators [SiO2, Si3N4, HfO2, and Al2O3] are taken into consideration by adjusting insulator thicknesses and measuring the overall current density.

Shock Activation Mechanism of Aluminum Nano-Particles outside High Explosives

Abstract Adding aluminum nanoparticles (ANPs) to explosive charges can effectively increase the total explosion energy and work capacity. A novel explosive charge was researched where ANPs were placed outside the high explosive. And the shock activation mechanism for the ANPs was proposed. The proposed shock activation mechanism suggests that under shock loadings, ANPs ignite due to the combined effects of shock work and plastic work. To investigate this mechanism, four turns of explosion experiments were conducted with varying layer thicknesses of ANPs in an enclosed space. The quasi-static pressure was measured to characterize the activation efficiency of the ANPs. The experimental results revealed that the reaction degree of the ANPs ranged from 55.9% to 67.2%, indicating that ANPs reached a relatively high reaction degree despite being placed outside the high explosives. Furthermore, the reaction degree decreased monotonically from 67.2% to 55.9% as the Al layer thickness increased from 1.3% to 6.3% of the explosive diameter. This observation suggests that the activation efficiency of the ANPs decreased with increasing layer thickness. These experimental findings show that the shock activation mechanism can effectively explain the activation of ANPs placed outside of explosives. The proposed shock activation mechanism is indeed valid and provides a promising approach to enhance the explosion energy and work capacity by incorporating ANPs in the charge configuration.

Surface Kinetics and Uniformity Issues in Low-Temperature Epitaxy of Sige and Si:P Layers

Fabrication of the modern Si/SiGe-based devices normally necessitates the application of reduced temperatures (in the range about 550-750 °C) during the growth, which imposes significant kinetic limitations. As a result, the growth rate, layer composition, and dopant incorporation show high sensitivity to the process parameters and even small temperature non-uniformities over the wafer may result in considerable variation of the SiGe layer thickness and composition.In the growth of Si:P layers, the intrinsic Si growth kinetics is supplemented with the influence of the P concentration on the Si:P growth rate that may differ significantly as compared to the undoped Si despite P incorporation in concentrations of 0.1 % and even lower. In addition, the trend of the growth rate variation (increase or decrease) is different at the atmospheric and reduced operating pressures.Under all these inputs, control of the thickness and composition uniformity over the 300 mm wafer becomes challenging and should involve the adjustment of both temperature distribution and process parameters, including zonal distribution of the gas flow rates.To approach the solution of this problem, we have developed models of SiGe growth from SiH4/SiH2Cl2 (DCS) and GeH4 as well as Si:P growth from DCS and PH3 in the atmosphere of hydrogen with possible addition of HCl. The models account for high coverages of the surface with the adsorbed H2 and HCl, resulting in the growth limitation by low density of the free adsorption sites (kinetically limited growth mode). In case of SiGe, the model accounts also for the dependencies of surface kinetic parameters on the Ge concentration in the layer.The models were carefully verified using numerous experimental data on the layer growth rate and composition versus temperature and precursor flow rates. Calculations with the developed models reproduce the effect and facilitate interpretation of the following experimentally observed trends: higher growth rate and lower Ge concentration at elevated temperatures and the opposite tendency at a higher HCl supply. This behavior is explained in terms of stronger kinetic limitations for the Si part of the alloy that weaken with the temperature increase and contribution of the added HCl to the surface site blocking.The strong and non-monotonic dependence of Si:P growth rate on the PH3 supply is attributed to the competition between the adsorbed HCl and P-containing species. Addition of PH3 to the reactive gas mixture results, on the one hand, in additional coverage of the surface with these species but, on the other hand, in removal of the adsorbed HCl from the surface due to its interaction with these species, followed by the formation of volatile products.Next, the developed approaches have been applied to the detailed modeling of the process in widely used industrial reactors to address the uniformity issue in dependence of the operating parameters and reactor settings. In particular, variation of the uniformity for different temperature distributions over the wafer and gas injection parameters will be discussed. Also, conclusions are made on the relative sensitivity of the thickness and composition to possible non-uniformities of the wafer temperature and details of species transport inside the reactor. Figure 1

Electrochemical Modeling of a Commercial Polymer Electrolyte Fuel Cell Using 3-D Micro-Computed Tomography

Challenges remain with the accurate modeling and optimization of gas transport in polymer electrolyte membrane fuel cells (PEMFCs) due to the complexity of calculating transport across the relevant domains and structures in a fuel cell. Each cell comprises two bipolar plates (BPPs) compressed around a membrane electrode assembly (MEA). The bipolar plates (BPPs) are a multifunctional component having flow fields with mm-sized features designed for reactant delivery and heat and water management. The MEA comprises a 5-layer structure with microporous catalyst and gas diffusion layers (GDLs) on either side of a proton exchange membrane (PEM). Actual cell designs are further constrained by their materials, and manufacturing cost and speed.Prior work primarily focuses on modeling the flow fields in metal BPPs as idealized geometries, neglecting the inherent curvature introduced during the stamping manufacturing process and the compression and thickness variation of the MEA layers. To create high-performance cells, it is necessary to understand the detailed interaction of the BPPs and MEAs in practical, manufactured fuel cell stacks.In this work, a compressed short stack of unit cells from a decommissioned commercial fuel cell electric vehicle (FCEV) was resolved in three dimensions (3-D) using a micro-computed tomography instrument (micro-CT) capable of imaging large samples (up to 30 cm). Representative images from across the cell domains are shown in Figure 1. The 3-D images were subsequently segmented and meshed for computational fluid dynamics (CFD) modeling. Simulations of transport and electrochemical phenomena were performed using commercial CFD software using custom codes. Simulation results were used to assess the performance of a mesh-type cathode flow field design with secondary flows as well as the impact of compression, and stamped plate curvature. The results highlight the significant impact of the induced convective transport in the gas diffusion layers (GDLs) has on the performance of a practical fuel cell.Acknowledgements: This material is based upon work supported by Plug Power Incorporated.Figure Collage: Left – 3D Micro-CT Images of the BPPs and components of an MEA, Center - Meshing faces, Right – Relative Humidity Profile Figure 1

Exploring the effect of layer thickness on the elastoplastic properties of the constituent materials of CrN/CrAlN multilayer coatings: a nanoindentation and finite element-based investigation

This paper aims to assess the effect of layer thickness on the elastoplastic properties of the constituent materials of multilayer coating systems, as well as on the stress and strain fields in the vicinity of the coating/substrate interface. A methodology based on a trust-region reflective optimization algorithm, integrated with finite element analysis of the nanoindentation process, is employed to extract the elastoplastic properties of the distinct layers, constituting multilayer coating. This approach is validated on a CrN/CrAlN multilayer coating systems with varying layer thicknesses from 1 to 0.35 µm, by which Young's modulus (E), yield stress (σy), and work hardening exponent (n) of each individual coating material layer were obtained. The results revealed a reduction in the hardness and Young's modulus of either CrN, or CrAlN coating layer as the layer thickness decreased. Finite element analysis of the nanoindentation process demonstrated that decreasing the coating layer thickness leads to an increase in the plastic deformation within the coatings, which reduces the stress concentration in this area. The simulation results suggest that an optimum thickness of 0.5 μm of CrAlN and CrN monolayer materials would improve the adhesion properties of CrN/CrAlN multilayer coatings.

Wall-mounted circular cylinder flows

The flow over wall-mounted circular cylinders is influenced by variations in aspect ratio, Reynolds number, and boundary layer thickness, all of which affect the vortical structures in the wake. In this study, we conducted direct numerical simulations and data-driven techniques, including proper orthogonal decomposition (POD) and dynamic mode decomposition, to examine vortical flows behind wall-mounted circular cylinders with aspect ratios of 4, 8, and 12 at Reynolds numbers ranging from 60 to 800, based on cylinder diameter. The incoming boundary layer thickness varied from 0.05 to 0.25. Our findings reveal that a thicker boundary layer promotes the development of low-frequency symmetric vortical structures along the wall surface, suppressing antisymmetric wake shedding. Consequently, the induced upwashing motion of the flow behind the cylinder pushes the wake shedding region closer to the free-end side, facilitating quadrupole mean streamwise vortices. The wake shedding frequency is significantly altered as the symmetric low-frequency mode intensifies along the boundary. POD analysis demonstrates the coexistence of symmetric and antisymmetric vortical structures in the wake region. The presence of either antisymmetric or symmetric wake shedding is determined by the dominant frequency in the instantaneous flow. These findings substantiate previous conjectures about the simultaneous presence of symmetric and antisymmetric wake shedding modes and enhance our understanding of vortical flows around wall-mounted circular cylinders.

Impact of Summer Air Temperature on Water and Solute Transport on a Permafrost‐Affected Slope in West Greenland

AbstractIn Arctic landscapes, the active layer forms a near‐surface aquifer on top of the permafrost where water and nutrients are available for plants or subject to downslope transport. Warmer summer air temperatures can increase the thickness of the active layer and alter the partitioning of water into evapotranspiration and discharge by increasing the potential evapotranspiration, the depth to the water table, and changing the flow paths but the interacting processes are poorly understood. In this study, a numerical model for surface‐ and subsurface cryo‐hydrology is calibrated based on field observations from a discontinue permafrost area in West Greenland considered sensitive to future climate changes. The validated model is used to simulate the effect of three summers with contrasting temperature regimes to quantify the variations in the active layer thickness, the resulting changes in the water balance, and the implications on solute transport. We find that an increase of summer air temperature by1.6°C, under similar precipitation can increase the active layer thickness by 0.25 m, increase evapotranspiration by 5%, and reduce the total discharge compared to a colder summer by 9%. Differences in soil moisture and evapotranspiration between upslope and downslope were amplified in a warm summer. These hydrological differences impact solute transport which is 1.6 times faster in a cold summer. Surprisingly, we note that future warmer summer with increase in permafrost thaw may not necessary lead to an increase in discharge along a hill slope with underlying permafrost.

Topology transition description of horseshoe vortex system in juncture flows with velocity characteristic lines

Particle image velocimetry and numerical simulation results of juncture flows were analyzed to parametrically investigate topology transition. The vortex system evolutions from non-vortex to multi-vortex with variations in obstacle bluntness, obstacle width, flow velocity and boundary layer thickness are discussed from the perspective of velocity characteristic lines. The velocity characteristic lines of u=0, v=0, and ∇2v=0 are adopted to describe the vortex system evolution. The motions of the characteristic lines with juncture flow parameters are described in detail, and the corresponding reflections of the vortex system patterns are illustrated. A panoramic picture of the development of velocity characteristic lines corresponding to the HSV topology transition from a non-vortex to a multi-vortex system with variations in the juncture flow parameter is established. Two methods for determining the attachment/separation pattern of the most upstream singularity are proposed. One method is based on the number of intersections of the u=0 and v=0 velocity characteristic curve lines, and the other is based on the relative positions of the most upstream feet of the u=0 and v=0 loop curves with both feet attached to the wall.

In vitro assessment of corrosion, antibacterial properties, and degradation behavior of zirconia-coated polyetheretherketone (PEEK)

The medical industry often uses ceramic and polymeric coatings to safeguard metal substrates. However, more investigation is required to explore the implementation of ceramic coatings on polymer substrates and to determine their degradation and in vitro characteristics. This work involves applying zirconia coating onto the 3D-printed PEEK polymer substrate using the RF magnetron sputtering technique. With varying layer thickness and printing speed parameters, PEEK samples (S1, S2, S3, and S4) were 3D printed and coated with zirconia. The coated and uncoated samples were immersed in Fusayama artificial saliva solution for 30 days. Following immersion in artificial saliva, this study examined the corrosion of 3D-printed PEEK samples with and without coatings. Elemental mapping, field emission scanning electron microscopy, and X-ray photoelectron spectroscopy were employed to evaluate sample morphology and estimate the binding energy of possible compounds generated in the artificial saliva solution. In vitro assessments such as antibacterial studies were performed against E. coli and S. aureus, and cytotoxic analysis was performed using Human Wharton’s jelly-derived mesenchymal stem cells (WJ-MSCs) to determine cell proliferation. The results indicated that sample S3, printed with 0.15 mm layer thickness and 20 mm/s print speed coated with zirconia showed a better degradation rate of 9.01% whereas the other three samples S1, S2, and S4 coated with zirconia showed deterioration rates of 36.4%, 33% and 16% respectively. Sample S3 showed a better antibacterial activity as biofilm formation was absent and also showed cell viability of about 79% and hence can be considered as a viable option for dental applications.

The Influence of Thickness and Spectral Properties of Green Color-Emitting Polymer Thin Films on Their Implementation in Wearable PLED Applications.

A systematic investigation of optical, electrochemical, photophysical, and electrooptical properties of printable green color-emitting polymer (poly(9,9-dioctylfluorene-alt-bithiophene)) (F8T2) and spiro-copolymer (SPG-01T) was conducted to explore their potentiality as an emissive layer for wearable polymer light-emitting diode (PLED) applications. We compared the two photoactive polymers in terms of their spectral characteristics and color purity, as these are the most critical factors for wearable lighting sources and optical sensors. Low-cost, solution-based methods and facile architecture were applied to produce rigid and flexible light-emitting devices with high luminance efficiencies. Emission bandwidths, color coordinates, operational characteristics, and luminance were also derived to evaluate the device's stability. The tuning of emission's spectral features by layer thickness variation was realized and was correlated with the interplay between H-aggregates and J-aggregates formations for both conjugated polymers. Finally, we applied the functional green light-emitting PLED devices based on the two studied materials for the detection of Rhodamine 6G. It was determined that the optical detection of the R6G photoluminescence is heavily influenced by the emission spectrum characteristics of the PLED and changes in the thickness of the active layer.