Minimum Layer Thickness Research Articles

Multinozzle 3D Printing of Multilayer and Thin Flexible Electronics

Multilayer flexible electronics have broad applications in the fields of sensors, biomedicine, flexible displays, etc. The existing multilayer flexible electronic manufacturing methods are complicated and usually require multiprocess and multiequipment combinations for processing; especially, it is difficult to achieve integrated manufacturing. The increase in the overall thickness of multilayer flexible electronics also limits its flexibility, stretchability, and spatial density. Herein, a method for integrated multinozzle 3D printing of multilayer flexible electronics with thin structures is proposed and a new strategy for interlayer interconnection is presented. Printing high‐viscosity stretchable silver paste on the edge of the multilayer dielectric material and avoiding microholes and vertically printed conductive micropillar structures in traditional interlayer interconnection wires are discussed. The influences of process parameters on the fabrication of multilayer and thin flexible electronics are explored, and the minimum layer thickness for the fabrication of multilayer circuits is determined. A five‐layer flexible pressure sensor and two flexible electromagnetic actuators with different coils are fabricated, and the related performance tests of the two devices are carried out. The test results demonstrate that the proposed fabrication method of flexible electronics provides a high‐efficiency, low‐cost, and simple manufacture solution for the fabrication of multilayer and thin flexible electronics.

Intereye structure–function relationship using photopic negative response in patients with glaucoma or glaucoma suspect

We evaluated the intereye structure–function relationship in glaucoma patients using photopic negative response in electroretinogram analysis. Patients with confirmed glaucoma (36 eyes, 36 patients) or suspected glaucoma (19 eyes, 19 patients) were included in this study. Electroretinogram (RETI-scan) was performed with red stimulus on blue background. Intereye comparison for 55 patients was performed between better eyes and worse eyes, which were divided based on average retinal nerve fiber layer (RNFL) thickness measured using spectral-domain optical coherence tomography. In the intereye analysis, PhNR amplitude was lower in worse eyes than in better eyes (P < 0.001). The intereye difference in PhNR amplitude was significantly correlated with intereye difference in average RNFL, as well as average or minimum ganglion cell-inner plexiform layer (GCIPL) thickness (P = 0.006, 0.044, 0.001). In patients with mean deviation ≥ − 6 dB of worse eyes, the intereye difference in PhNR amplitude was significantly associated with intereye difference in average RNFL thickness or minimum GCIPL thickness (P = 0.037, 0.007), but significant correlation was not found between mean sensitivity of visual field tests and structural parameters. In conclusion, PhNR performed well with regard to intereye structure–function association in glaucoma patients, especially at the early stage.

Armor Layer Uniformity and Thickness in Stationary Conditions with Steady Uniform Flow

The continuous movement of riverbed particles due to turbulent flow determines the stability of non-cohesive riverbeds and banks during riverbed and bank erosion and sedimentation. This study emulated the stable channel design by deriving the low maintenance cost of the channel through bed protection by an armor layer. The study investigated the effects of shear stress and grain size uniformity to determine the minimum non-cohesive armor layer thickness for the stability of riverbeds under steady uniform flow conditions. Experiments were conducted with four different discharges, five armor material gradations, and five bed-slope variations in a full-scale flume. We observed and recorded the behaviors of the five gradations of armor materials for given discharges and bed slopes. Eighty data points were recorded and analyzed. The hydraulic analysis of the flow along with the soil mechanics analysis of the armor materials was done. The soil mechanic analysis was particularly focused on the uniformity coefficient of the armor layer, Cu, to derive the armor layer equation. However, for the manageability of the study, we set the limit of the Cu between 3.0 and 6.0. From the viewpoint of non-erodibility, a wider Cu value indicated a thinner armor layer. Variables that govern the armor layer thickness and the layer thickness itself were derived and proposed. The variables, namely Cu, shear stress (t0 and tc), and mean diameter of the bed load and armor materials (Db50 and Da50). Our results show that these variables governed the thickness of the armor layer, and this is expected to contribute to the design of stable natural channels, which can minimize the cost of irrigation canal maintenance and development. Doi: 10.28991/CEJ-2022-08-06-01 Full Text: PDF

Solid-State and Super Solidus Liquid Phase Sintering of 4340 Steel SLM Powders Shaped by Fused Filament Fabrication

4340 steel powders were processed with an additive manufacturing process using the FFF (Fused Filament Fabrication) technique. A composite filament was developed to print samples and study the effect of the bed and nozzle temperatures on its physical and microstructural properties. The printed samples were debinded and sintered by: Solid State (SS) at 1300 °C or SLPS (Supersolidus Liquid Phase Sintering) at 1420 °C. Metallography and scanning electron microscopy (SEM) identified the microstructure and phases. The hardness of the sintered samples was measured with the Vickers method. The SLPS process contributes to better densification and volume contraction; however, it promotes geometrical distortion of the samples compared to the SS samples. The microstructure of the sintered samples consists of ferrite situated in the original austenite grain and bainite. The sintering mechanism significantly influenced the hardness of the samples. Finally, a part was designed, printed, debinded, and sintered with the aim of studying the maximum inclination angle, the minimum vertical and horizontal holes, and the minimum vertical layer thickness, which can be obtained through the whole process.

Design of Cylindrical Surrounding Double-Gate MOSFET With Fabrication Steps Using a Layer-by-Layer Approach

The semiconductors with nanometer-scale are subjected to various patterns and scaling using the latest technology. The most widely used methods are top-down approaches in the design of complex heterostructures. The top-down approach involves the photolithography to ion sequentially beaming of the materials. In this context, the alternative layer-by-layer approach with cylindrical structures has been discussed and supported by the subsequent results to make Cylindrical Surrounding Double-Gate (CSDG) MOSFETs in this research work. This method involves the making of cylindrical structures with high-resolution morphological structures of CSDG MOSFETs. The process has been described in detail to design the CSDG MOSFETs with high-ƙ dielectric materials to make them suitable for low-frequency RF applications. The fast modulation of the Single Nano Wire (SNW) has been adopted for complex heterostructure modeling. The high-ƙ dielectric materials are placed in between the spacer and the gate material to overcome the Short Channel Effects (SCEs). This method produces symmetrical and concentric cylindrical structures of the CSDG MOSFETs with suitable layers. The minimum layer thickness achieved is about 10 nm axial length along with the core of the SNW. This gives enough insight for the proposed cylindrical structure to fabricate over the core of 2DEG. In this type of structure development, many cylindrical structures with various properties can be designed. The parameters focused on the cylindrical structure will be periodic, non-periodic, symmetric, asymmetric structures, and gaps/dots of nanometer scale. This innovative method introduces the method of designing the symmetric CSDG MOSFET concerning the center core. In this work, the authors focus on the suitable novel technique of designing cylindrical structures with unique dimensions and physical properties using various semiconductor materials.

Precision and trueness of maxillary crowded models produced by 2 vat photopolymerization 3-dimensional printing techniques

This cross-sectional study aimed to analyze the precision and trueness of dental models produced using 2 rapid prototyping 3-dimensional printers. A digital crowded maxillary arch with a T-shaped base and 2 hemispheres of 2.5mm radius was printed 10 times with a stereolithography apparatus (SLA) and digital light processing (DLP) in the highest precision and minimum layer thickness (z-resolution) mode. The copies were scanned using the D710 3Shape desktop scanner and assessed for precision and trueness via arch superimpositions and hemisphere measurements. Mann-Whitney U tests were used to compare trueness and precision among printers. Hemisphere radius was compared with the reference measurement and between 3-dimensional printers using 1 sample and independent Student t tests, respectively (α=0.05). The root mean square values of arch superimpositions showed statistically significant differences between the 2 techniques, both for precision (P=0.011): SLA (46.8μm±13.5); DLP (111.1μm±71.9), and trueness (P=0.015): SLA (61.1μm±9.8); DLP (99.8μm±47.2). The color map model analysis indicated greater distortion on premolar and molar surfaces, with a higher range of contraction on the SLA and both contraction and expansion on the DLP. Anterior and posterior hemisphere radius registered increased values with DLP (1.7% and 0.49%) and reduced values with SLA (0.6% and 0.7%); however, only the anterior SLA hemispheres revealed a significant decrease from the reference value (P=0.037). In this study, the SLA printer was significantly different from the DLS printer, with the highest precision and trueness.

UV Nanoimprint Lithography: Geometrical Impact on Filling Properties of Nanoscale Patterns.

Ultraviolet (UV) Nanoimprint Lithography (NIL) is a replication method that is well known for its capability to address a wide range of pattern sizes and shapes. It has proven to be an efficient production method for patterning resist layers with features ranging from a few hundred micrometers and down to the nanometer range. Best results can be achieved if the fundamental behavior of the imprint resist and the pattern filling are considered by the equipment and process parameters. In particular, the material properties and pattern size and shape play a crucial role. For capillary force-driven filling behavior it is important to understand the influencing parameters and respective failure modes in order to optimize the processes for reliable full wafer manufacturing. In this work, the nanoimprint results obtained for different pattern geometries are compared with respect to pattern quality and residual layer thickness: The comprehensive overview of the relevant process parameters is helpful for setting up NIL processes for different nanostructures with minimum layer thickness.

An Analytical Model for Liquid and Gas Diffusion Layers in Electrolyzers and Fuel Cells

The diffusion layer is a crucial part of most fuel cells and electrolyzers. We analytically solve a simplified set of visco-capillary equations for the gas and liquid saturation profiles inside such layers. Contrary to existing numerical simulations, this approach allows us to obtain general scaling relations. We derive simple explicit equations for the limiting current density associated with reactant starvation, flooding, and membrane dehydration, including the effect of fluid properties, contact angle, tortuosity, and the pore size distribution. This is the first explicit, extensive and thorough analytical modeling framework for the two-phase transport in an electrochemical cell that provides useful insights into the performance characteristics of the diffusion layer. A more even pore size distribution generally allows higher currents. Explicit expressions for the minimum pore size and maximum layer thickness show that modern diffusion layers are typically well-designed.

Study on Heat Transfer in Self-Excited Oscillation with Backflow Vortex Disturbance Effect

The fluid motion characteristics have an important influence on the evolution of the backflow vortex near the pipe wall. The instantaneous velocity and instantaneous temperature of the outlet flow channel section, the shear stress of the outlet flow channel wall, the boundary layer thickness, and the Nusselt number under different ratios of the upstream and downstream pipe diameter are studied at the inlet pressure of 12,000 Pa, using the large eddy simulation numerical method. The research results show that a pulsating flow is presented in the outlet channel of the self-excited oscillation chamber, and a backflow vortex can be formed near the wall of the outlet channel. The heat exchange between the fluid near the wall and the wall is accelerated due to the backflow vortex. The thickness of the boundary layer near the wall first decreases and then increases when the ratio of the upstream and downstream pipe diameters of the self-excited oscillation chamber is 1 to 1.8, whereas the heat transfer efficiency first increases and then decreases. The minimum boundary layer thickness is 0.385 mm. The maximum comprehensive evaluation factor is 1.23 when the is 1.5. The total heat exchange efficiency increases by 23%.

Assessment on surface integrity of AISI 304 steel during powder mixed electrical discharge machining

The effect of mixing molybdenum-di-sulphide (MoS2) powder particle into the dielectric medium of electrical discharge machining is analysed. The duty factor and MoS2 powder particle size were taken as input parameters. Duty factor is varied at 2, 6, 10 and two different size of MoS2 powder particles 40 µm, 90 nm were used. The significance of input parameters on crater, globules, and recast layer thickness were analysed. Peak current 6 A, discharge duration 300 µs, gap voltage 80 V, powder concentration 1 g/l, and a continuous ultrasonic vibration to dielectric fluid were maintained constant throughout the experiments. For both sizes of MoS2 powder particle, small size crater and minimum global appendages generated on the surface machined at duty factor 2. Compared to 40 μm size powder, more MoS2 powder particles gets deposit on the machined surface and minimum recast layer thickness is achieved while using 90 nm size powder into dielectric medium.

Influence of Process Parameters on the Microstructural Characteristics and Mechanical Properties of Recast Layer Thickness Coating on Die Steel Machined Surface after Electrical Discharge Machining

The surface layer machined after electrical discharge machining (EDM) is different from it after traditional methods, and studying the surface layer structure machined by this method will contribute significantly to the selection of finishing methods. In this study, the surface layer of SKD61 steel after EDM using copper (Cu) electrode was analyzed. Technological parameters including discharge current (Ie), pulse on time (Ton), pulse off time (Tof), and voltage (Ue) were used in the study. The minimum recast layer thickness (RLT) was determined using the Taguchi method. The results showed that Ie, Ton, and Tof were significant influences on RLT, and Ue was insignificant. Minimum, value of RLT = 3.72 µm at process parameters Ie = 1 A, Ton = 50 µs, Tof = 12 µs, and Ue = 30 V. The machined surface layer after EDM is inconsistent with the workability of the product, and it should be removed from the machined surface.

Parametric Influence of Process Parameters on the Wear Rate of 3D Printed Polylactic Acid Specimens

Fused deposition modeling (FDM) is a 3D printing technique that prints thermoplastic layer by layer. Various parameters affect the properties of the final printed object. The exact identification of variation in the properties of the printed object is still a very popular issue among the researchers. In the present work, an effort has been made to identify the parametric influence of layer thickness, infill density, print speed and extruder temperature on the wear behavior of the printed specimens. The specimens of polylactic acid (PLA) have been printed using Fused Deposition Modeling (FDM). The combinations of input parameters during the fabrication have been considered as per the Taguchi L16 Orthogonal Array. Moreover, to identify the parametric influence on wear, mathematical modeling has been done using regression and artificial neural networks. The results show that the average percentage variation in predicted experimental values for regression and ANN models are, 5.04% and 1.94%, respectively. Moreover, for minimum wear layer thickness should be kept between 0.28- 0.34mm. Similarly, infill density, print speed, and extruder temperature should be between 70-72, 125-175mm/s and 195-202 degree, respectively.

Experimental investigation and parametric optimisation of the hole-circularity and recast layer during the laser trepan drilling

ABSTRACT Re-solidified layer of molten metal during laser trepan drilling of Inconel-718 is a serious concern. Re-solidification affects the dimensional stability and geometrical features. Many scientific efforts have been reported for understanding and minimising the re-solidification layer (recast layer) thickness in laser cutting and percussion drilling operations. However till date, limited scientific work has been reported concerning recast layer formation during the laser trepanning of Inconel-718. In the present work, a methodology has been proposed for reducing the recast layer formation during the laser trepanning of Inconel-718. For understanding and achieving minimum recast layer thickness with better circularity, series of laser trepanning experiments have been performed on a thin sheet of Inconel-718. Recast layer thickness and hole- circularity are measured for each laser trepan drilled hole followed by the development of mathematical models using response surface methodology. The developed mathematical models are optimised with the help of multi-objective genetic algorithm to ascertain the optimum trepan drilling parameters. The obtained values of optimum parameters are validated by conducting more experiments. From validation experiments, it has been found that the obtained range of input parameters is significant, and the heat affected zone can be controlled using the proposed methodology.

Experimental investigation of initial yield surfaces of solid foams and their evolution under subsequent loading

Metal foams exhibit excellent characteristics suitable for a variety of light weight construction applications, based on outstanding specific mechanical properties and the ability to provide a nearly constant force during energy absorption. All components are subjected to multiaxial stress states during the application. In order to ensure a safe design, yield surfaces constitute the fundamental basis for simulations. The determination of yield surfaces for metal foams is a complex challenge. In the literature yield surfaces have been usually simulated using model assumptions and rarely experimentally validated. The present contribution provides a comprehensive representation of experimentally determined yield surfaces for open-cell nickel/polyurethane (Ni/PU) hybrid metal foams. For the first time in the literature, the effect of different nickel coating thicknesses on the shape of the yield surface is systematically examined. Determining the yield surface parameters as function of the effective foam density allows for a prediction of the minimum layer thickness required for any complex loading condition. Furthermore, the development of the post-yield surfaces under increasing strain is investigated. Post-yield surfaces provide reliable information about the mechanical material behaviour under applied multiaxial stress after a certain pre-damage.

On the suppression of oscillatory circulation inside an evaporating bi-component drop through acoustic streaming

The present study investigates the effect of acoustics on the oscillatory internal circulation of evaporating methanol – water drops. The circulation is termed oscillatory when a periodic boosting and deceleration of flow is observed. The acoustic signal generated, is a sine wave of different frequencies at constant amplitude, with and without added white noise. Minimum acoustic boundary layer thickness and maximum evaporation rate are observed at lowest acoustic frequency of 30 Hz, with and without, added white noise. The evaporation rate is enhanced for all volume fractions (vf) of methanol when compared to the absence of acoustics. It is observed that the oscillation frequency for a given drop decreases when subjected to an acoustic field, and is lowest at 30 Hz for all drops tested. The presence of intense acoustic streaming around the evaporating drop creates large velocity gradients on the drop surface due to higher air entrainment from the surroundings at low acoustic frequencies, sweeping out more amount of evaporated mass from the surrounding of drop and augmenting the heat and mass transfer from the drop surface. Further, the higher rate of air entrainment into the drop, (i) suppresses the oscillatory behavior of internal circulation and (ii) breakup of the circulation ligaments. The breakup of circulation ligaments accelerates the circulation velocity which results in enhancement of the evaporation rate. The enhanced evaporation raises solutal Marangoni and Rayleigh convection, and again forces the circulation to be steadier.

Stability Analysis of Minimum Broken Top Layer Thickness of Rock Drilling Chamber in a Mining Site Based on Midas/GTS

The determination of the reasonable thickness of the top layer of the large- diameter deep-hole stope is one of the important process parameters that must be considered in the high-stage mining recovery. The thickness of the top layer can ensure that the large-diameter deep-hole stope is not easy to collapse after the formation of the empty zone. To ensure the stability of the rock drilling chamber. According to the similar mine experience and mechanical model, the scientific and reasonable top-level safety thickness range is calculated. The three-dimensional numerical simulation of MIDAS/GTS is used to verify and optimize the stability of different top layer thicknesses. From the perspective of displacement and stress, comprehensive simulation analysis is carried out. After comprehensive comparison of angles, the optimal thickness of the top layer is determined to be 9 m.

Microstructural Evolution and Mechanical Behavior of Cu/Nb Multilayer Composites Processed by Accumulative Roll Bonding

Cu/Nb multilayer composites with minimum individual layer thicknesses of ≈2.8 μm are achieved by accumulative roll bonding (ARB). The microstructural evolution and mechanical properties of these composites are investigated with different layer thicknesses after ARB processing. The results show that there is no visible interfacial reaction between the Cu and Nb layers, and the kernel average misorientation (KAM) distributions in electron backscatter diffraction (EBSD) maps remain in steady state during the third to seventh ARB cycles. The tensile testing results demonstrate that the yield strength increases with decreasing layer thickness in Cu/Nb multilayer composites. A simultaneous increase of strength and elongation is achieved by regulating the laminated structures. Microstructure and fracture analysis indicate that the simultaneous increase of strength and elongation is attributable to the high density of bimetal interfaces, which act as a barrier for dislocation mobility and crack propagation.

Study of material characteristics in laser trepan drilling of ZTA

Zirconia Toughened Alumina (ZTA) ceramic is used to make distinct components of aerospace, military and biomedical industries which require suitable machining method free of mechanical forces. Recent researchers reveal that Laser Beam Machining has diverse potential to overcome machining difficulty of structural ceramics. But to enhance the durability and performance of these components, study of material properties became essential after laser machining because this process involves intense heat or thermal energy. Present study investigates the material characteristics of laser trepanned ZTA plate with the aim to explore the effects of process parameters on recast layer thickness, microcrack width and microhardness. The outcome of study may be helpful in setting the processing regime for laser trepanning of ZTA ceramic which may furnish the products with minimum recast layer thickness and microcrack width along with minimum change in microhardness. The experimental results show that lower pulse width or trepanning speed, and higher air pressure reduce the recast layer thickness and microcrack width.

Surface integrity in grinding of C-250 maraging steel with resin-bonded and electroplated CBN grinding wheels

Maraging steels are widely used in the aerospace industry for the manufacture of precision parts. However, surface integrity of ground maraging steels has received little attention. In order to explore the surface integrity of ground maraging steels and help contribute to develop the strategy of grinding these steels, surface integrity components such as roughness, surface defects, microstructure, and residual stresses in grinding of C-250 maraging steel (3J33) were studied. Grinding experiments were performed using resin-bonded and electroplated CBN grinding wheels with two different grain size (180# and 320#) abrasives in the cases of dry and wet grinding conditions. The results show that under the dry grinding conditions, the electroplated CBN grinding wheel is more suitable for grinding of C-250 maraging steel than the resin-bonded CBN grinding wheel. Compressive residual stress depth profiles (maximum value is up to − 200 Mpa in grinding direction), a good surface finish (Ra = 0.56 μm), and a minimum deformation layer thickness (less than 2 μm) can be achieved when dry grinding using the electroplated CBN grinding wheel with 320# grit size. Under the wet grinding conditions, benefitting from the fact that the cooling lubricant is more effective in improving the grinding performance of the resin-bonded CBN grinding wheel than in improving that of the electroplated CBN grinding wheel, the resin-bonded CBN grinding wheel achieved similar surface integrity to the electroplated CBN wheel in grinding of C-250 maraging steel.

Efficacy of N95 amplitude of pattern electroretinogram measured from baseline to N95 trough in the traumatic optic neuropathy.

To investigate the utility of selected pattern electroretinogram (PERG) parameters-including N95 amplitude and N95/P50 ratio, and a BL-N95 amplitude-in the analysis of visual function(s) and for predicting changes in retinal ganglion cell structures in traumatic optic neuropathy. A retrospective, observational case series performed at a single center. Forty-four eyes from 36 patients diagnosed with optic neuropathy were included. A BL-N95 amplitude was defined as the amplitude measured from baseline to the trough of N95. PERG and pattern visual evoked potential (pVEP) measures were acquired within 1week after onset of optic neuropathies. To compare functional and anatomical changes, mean temporal peripapillary retinal nerve fiber layer (pRNFL) and average and minimum ganglion cell-inner plexiform layer (GC-IPL) thicknesses were measured using optical coherence tomography. Thirty-six patients (20 men, 16 women; mean age 37.5 ± 17.6years) were evaluated. The BL-N95 amplitude was significantly smaller than the N95 amplitude (1.01 ± 0.56μV and 2.45 ± 1.02μV, respectively; p < 0.0001). Both the N95 (r = - 0.38, p = 0.010) and BL-N95 r = - 0.32, p = 0.029) amplitudes were significantly correlated with visual acuity. Although P100 latency was not correlated with all PERG parameters, the N95 (r = 0.32, p = 0.032) and BL-N95 (r = 0.41, p = 0.005) amplitudes demonstrated a positive correlation with P100 amplitude in pVEP. PERG parameters, including the N95 and BL-N95 amplitudes, and N95/P50 ratio, were not correlated with pRNFL thickness in optical coherence tomography. Only the BL-N95 amplitude demonstrated a significant correlation with GC-IPL. The BL-N95 amplitude-measured from baseline to the trough of N95-was valuable in the analysis of visual function(s) and for predicting changes in retinal ganglion cell structures in traumatic optic neuropathy.