Layer Setup Research Articles

Design of experiment evaluation of sputtered thin film platinum surface metallization on alumina substrate for implantable conductive structures.

Reliability and reproducibility of implants and their fabrication are highly depending on the assembly and packaging procedures. Individual fabrication skills like soldering introduce inaccuracies and should be avoided as much as possible. Screen printing is often utilized for the metallization of ceramics. Using platinum/gold (Pt/Au) paste liquidus diffusion leads to a low adhesion strength of the Pt/Au pads after soldering. As an alternative, sputtering of thin film surface metallization was investigated. However, this alternative comes with a huge amount of different layer and parameter setups. In order to keep the amount of experiments and data acquisition in a reasonable magnitude, the Design of Experiment (DoE) evaluation displays a powerful tool. We found an optimal layer setup that maximizes the adhesion strength of the layer, while simultaneously minimizing the sheet resistance and removing the dependency of soldering time.

Flexible electronics-compatible non-enzymatic glucose sensing via transparent CuO nanowire networks on PET films

Diabetic individuals need simple, accurate, and cost effective means by which to independently assess their glucose levels in a non-invasive way. In this work, a sensor based on randomly oriented CuO nanowire networks supported by a polyethylene terephthalate thin film is evaluated as a flexible, transparent, non-enzymatic glucose sensing system analogous to those envisioned for future wearable diagnostic devices. The amperometric sensing characteristics of this type of device architecture are evaluated both before and after bending, with the system’s glucose response, sensitivity, lower limit of detection, and effect of applied bias being experimentally determined. The obtained data shows that the sensor is capable of measuring changes in glucose levels within a physiologically relevant range (0–12 mM glucose) and at lower limits of detection (0.05 mM glucose at +0.6 V bias) consistent with patient tears and saliva. Unlike existing studies utilizing a conductive backing layer or macroscopic electrode setup, this sensor demonstrates a percolation network-like trend of current versus glucose concentration. In this implementation, controlling the architectural details of the CuO nanowire network could conceivably allow the sensor’s sensitivity and optimal sensing range to be tuned. Overall, this work shows that integrating CuO nanowires into a sensor architecture compatible with transparent, flexible electronics is a promising avenue to realizing next generation wearable non-enzymatic glucose diagnostic devices.

Droplet dynamics and fine-scale structure in a shearless turbulent mixing layer with phase changes

Three-dimensional direct numerical simulations of a shearless mixing layer in a small fraction of the cloud–clear air interface are performed to study the response of an ensemble of cloud water droplets to the turbulent entrainment of clear air into a cloud filament. The main goal of this work is to understand how mixing of cloudy and clear air evolves as turbulence and thermodynamics interact through phase changes, and how the cloud droplets respond. In the main simulation case, mixing proceeds between a higher level of turbulence in the cloudy filament and a lower level of turbulence in the clear air environment – the typical shearless mixing layer set-up. Fluid turbulence is driven solely by buoyancy, which incorporates feedbacks from the temperature, the vapour content and the liquid water content fields. Two different variations on the core set of shearless mixing layer simulations are discussed, a simulation in a larger domain and a simulation with the same turbulence level inside the filament and its environment. Overall, it is found that, as evaporation occurs for the droplets that enter subsaturated clear air regions, buoyancy comes to dominate the subsequent evolution of the mixing layer. The buoyancy feedback leads initially to downdraughts at the cloudy–clear air interface and to updraughts in the bulk regions. The strength of the turbulence after initial transients depends on the domain size, showing that the range of scales is an important parameter in the shearless mixing layer set-up. In contrast, the level of turbulence in the clear air is found to have little effect on the evolution of the mixing process. The distributions of cloud water droplet size, supersaturation at the droplet positions and vertical velocity are more sensitive to domain size than to the details of the turbulence profile, suggesting that the evolution of cloud microphysics is more sensitive to large-scale as opposed to small-scale properties of the flow.

Comparative characterization of quasi-static and cyclic deformation behavior of glass fiber-reinforced polyurethane (GFR-PU) and epoxy (GFR-EP)

Abstract Glass fiber-reinforced polymers (GFRP) are highly suitable for use in transportation industry in order to achieve the targets of energy and resource efficiency. In this context, due to its high specific strength, GFR-epoxy (GFR-EP) has already been implemented in a wide range of applications. However, in cases of energy efficiency and damage tolerance, GFR-EP shows disadvantages compared to GFR-polyurethane (GFR-PU). The aim of this study is the comparative characterization of the quasi-static and cyclic deformation behavior of GFR-PU and GFR-EP with similar layer setup. The mechanical properties have been investigated in instrumented tensile, interlaminar shear strength and compression after impact tests. In addition, the tests were combined with varying temperatures (−30 °C, RT, +70 °C) with respect to aerospace applications to determine the material property development under low and elevated temperatures. In cyclic investigations, the fatigue properties have been estimated by resource-efficient multiple step tests and validated in constant amplitude tests. Hysteresis and temperature measurements were applied in order to investigate the damage processes. It could be shown that polyurethane exhibits improved damage tolerance by significantly reducing delamination area under impact loading, whereas epoxy leads to optimized properties under elevated temperature. Furthermore, epoxy generally underlines higher capabilities under cyclic loading, which is due to void content of polyurethane.

Hydro-geophysical techniques for safe exploitation of the fresh groundwater resources in coastal area

Vertical disposition of the freshwater aquifer lens and their progressive change on lateral scale are relevant to understand the short circuiting of fresh and saline water at coastal areas. Since, half of the world population dwells within 50 km of coast line, the freshwater aquifers at coast are deteriorating at alarming rate. There are well-defined water well construction plans for coastal aquifer management, but mostly fails while execution due to lack of precise knowledge of subsurface lithological layer setup. In the present study, an attempt has been made to investigate such precise information about subsurface lithological layer setup to protect the freshwater resources at coastal area, applying noninvasive hydro-geophysical technique. Integrated electrical parameters, hydrochemistry, topography, and water table assessment have been applied to decipher the geometry of freshwater lens at Cuddalore coast, India. Results show in this study (1) the electrical resistivity (ρ) 1–10 Ω-m of subsurface formation, electrical conductivity (σ) 30,891 µS/cm of groundwater, and water table 1.55 m above mean sea level (MSL) confirms the zone of effluent contamination; (2) the zone showing ρ = 1–10 Ω-m, σ = 6172 µS/cm, water table 6.46 m below MSL is attributed to the saline water intrusion; (3) freshwater formations are identified in beach ridges underlain by clay layers with ρ = 30–60 Ω-m, σ = 453 µS/cm and water table above MSL; and (4) water well design is proposed to tap the freshwater aquifers avoiding vertical short circuiting of saline and freshwater.

IDENTIFICATION OF LAYERS DISTRIBUTION IN THE COMPOSITE COUPON USING FINITE ELEMENT METHOD AND THREE POINT BENDING TEST

Abstract The main objective of the study is to develop experimentally validated FE model and perform numerical analysis of layered composites made by hand lay-up techniques during tension and bending test. The research object is glass - polyester laminate made of four unidirectional layers. In order to validate the numerical models experimental test were performed. Due to the very different stiffness modulus in tension and bending loading the material properties obtained from standard test are not suitable to apply in numerical model. Significantly different behaviour compared to experimental test was obtained for tree point bending where the numerical model becomes too stiff. Simple coupons, relatively easy to manufacture presented in the paper have very low quality. The differences in actual and theoretical bending stiffness (obtained from tension stiffness) exceed 70%. In order to represent the actual structure the layers of the composite were divided by resin layers and also additional resin layer at the top and bottom of the model were defined. Single stage optimization process was used to adjust the material layout. After layer set-up modification very significant improvement can be seen for flexural behaviour

Development of a Highly Stressed Bladed Rotor Made of a CFRP Using the Tailored Fiber Placement Technology

Increasing the rotational frequency of bladed rotors used in turbomachinery leads to their increased efficiency and performance. Especially for turbomolecular pumps, this would allow either higher compression rates or smaller pump dimensions. The maximal rotational frequency is focused on the structural strength of the construction and the material used. Due to their high density, specific strength, and stiffness in the fiber direction, carbon-fiberreinforced plastics (CFRPs) seem to be ideal for such an application. The highly orthotropic material behavior of CFRPs demands new approaches in terms of their manufacturing and dimensioning. As a new approach, a rotor with 17 blades in a blade-integrated disk construction (BLISK) made of a CFRP, allowing a 35% higher burst speed than a bladed rotor made of a high-strength aluminum alloy, was developed. An appropriate fiber layout has to reflect the rotational symmetry, which demands either a radial or tangential fiber orientation. Therefore, the Tailored Fiber Placement (TFP) technology was used, which allows a high flexibility for the fiber layout. For consolidation, resin infiltration was performed using a modified vacuum-assisted process, and the final geometry was generated employing a milling machine. A radius-dependent layer setup of tangential and radial fibers was chosen to maximize the burst speed by using an adapted finite-element analysis. Additionally, a numerical modal analysis and a numerical failure analysis were performed. Finally, the theoretical results were verified on manufactured rotors by an experimental modal analysis and burst tests, where experimental data showed a good coincidence with numerical results.

Utilization of natural and artificial adsorbents in the mitigation of arsenic leached from hydrothermally altered rock

We have developed the adsorption-layer system for the simple and effective disposal of excavated rocks containing hazardous pollutants like arsenic (As). In this study, adsorption properties of natural and artificial materials including their performance in an actual altered rock-adsorption layer setup were evaluated. The adsorption of As[V] and As[III] onto all adsorbents fitted well with the Langmuir isotherm, indicating monolayer adsorption and progressive saturation of adsorption sites. All adsorbents were capable of As[V] and As[III] sequestration, but As[V] was more strongly adsorbed than As[III] based on the Langmuir isotherm. Also, artificial adsorbents were more efficient per unit weight than the natural adsorbent. Using the Langmuir isotherms and sequential extraction results, appropriate adsorbent dosages were estimated and then applied to an actual altered rock-adsorption layer column setup. The leaching concentration of As was lowered below 10μg/L throughout the experiment regardless of the kind of adsorbent used. This suggests that the adsorption-layer system is a promising alternative to special landfills in the disposal of excavated rocks enriched with As.

Optimal layer setup generation in layered manufacturing with a given error constraint

This paper introduces a new tolerance-based method to generate the optimum layer setup required to build layered manufacturing (LM) end-user parts for maximized efficiency. To achieve this, the deviation between the final polished LM part geometry and the original design model is formulated and controlled. Minimum build time is then realized through optimization of the thickness and position of each layer with respect to the design and final polished part geometry in order to minimize the number of layers to be used. Current LM layer setup methods target the intermediate or raw layered model, generated directly by an LM machine. By not considering the complete LM build process as well as the final polished part geometry, the involved layer setup problem cannot be correctly formulated and solved. Overly conservative layer thickness is then chosen, causing more layers than necessary to be used and greatly compromised efficiency. To achieve maximized efficiency, this work proposed a method based on error compensation and minimization. It has been applied to solving for the optimum layer setup necessary to allow the final polished physical part to meet the user-specified tolerance limit for the design model. Case studies have been performed and the results have validated that the presented method is able to minimize the number of layers for constructing an LM part while controlling the maximum error for tolerance conformance.

Micropumps operated by swelling and shrinking of temperature-sensitive hydrogels

This paper describes two types of polymeric micropumps based on the temperature-sensitive hydrogel poly(N-isopropylacrylamide). The gel actuators are realised as photopolymerised patterns and microgels. They are electrothermically controlled by resistive heating elements. The diffusion-based micropump contains a photopatterned monolithic actuator, which is placed within the pump chamber, and provides a valveless single layer set-up. The diffusion micropump is intended for low performance applications and can operate in two modes: peristaltic or pulsatile. The maximum operating parameters are a flow rate of 2.8 +/- 0.35 microl min(-1) and a back pressure of 1.28 kPa. The second type, a displacement pump, provides a higher performance (maximal 4.5 microl min(-1) and 15 kPa). The pump comprises a microgel-based actuator, which is placed within a separate actuator layer, and active microvalves. The specific features of the design and performance of the pumps are discussed.

Heat reflecting optical filter based on zero-order diffraction

We present a solar control technique based on zero-order diffraction instead of thin-film interference. Such zero-order filters consist of a thin layer with a high index of refraction (e.g. TiO 2) which is structured to form a zero-order grating. The thickness of the layer is a few hundred nano-meters or less. The structuring can be done by embossing and the deposition of the high index layer e.g. by evaporation. Thus the technique is well suited for large area production even in roll-to-roll processes. Advantages of this technique are the low production costs due to the simple layer setup, the high speed processes and the lack of cost intensive materials like ITO.

Effect of the reinforcement bar arrangement on the efficiency of electrochemical chloride removal technique applied to reinforced concrete structures

This paper reports on the research done to find out the effect that different bar arrangements may have on the efficiency of the electrochemical chloride removal (ECR) technique when applied to a reinforced concrete structural member. Five different types of bar arrangements were considered, corresponding to typical structural members such as columns (with single and double bar reinforcing), slabs, beams and footings. ECR was applied in several steps. We observe that the extraction efficiency depends on the reinforcing bar arrangement. A uniform layer set-up favours chloride extraction. Electrochemical techniques were also used to estimate the reinforcing bar corrosion states, as well as measure the corrosion potential, and instant corrosion rate based on the polarization resistance technique. After ECR treatment, a reduction in the corrosion levels is observed falling short of the depassivation threshold.

Three-Dimensional Dynamics of the Subsurface Countercurrents and Equatorial Thermostad. Part II: Influence of the Large-Scale Ventilation and of Equatorial Winds

Sensitivity tests are performed to assess the respective influences of the large-scale ventilation and of the near-equatorial winds on the dynamics of the the subsurface countercurrents (SCCs) and thermostad. They show that the intensity of the inertial jets is a function of the potential vorticity (PV) values at subduction and that stronger jets are favored by low PV injection, forced in the authors’ framework either by a deep mixed layer at subduction and/or by an injection of PV at lower latitudes. Such circumstances lead to a strong meridional shoaling of the thermocline near the equator. The resulting inertial jets occur at about 3 8N in the western part of the basin and are the poleward limit of a near-0 PV region and of an equatorial thermostad. A necessary condition for the existence of inertial jets is that the equatorial wind fetch is large enough, otherwise only weak time-mean eastward currents are produced by a nonlinear rectification of instability waves farther away from the equator. The presence of a North Equatorial Countercurrent does not constitute a barrier for equatorward motions within the lower thermocline, and inertial jets are still controlled by the meridional slope of the SSCs’ layer setup through the establishment of tropical PV pools predicted by ventilation theory.

STEP-based feature recognition for manufacturing cost optimization

This paper proposes to integrate feature recognition and process planning in the machining domain. The input part is analyzed to produce a set of setups which might be needed to manufacture the part. Then, a two-layered search strategy is adopted, where a node of the upper layer corresponds to a specific setup, and a node of the lower layer corresponds to a specific process for a feature. For each visited setup node, tool database is consulted in order to generate manufacturable features, feature dependencies are established, and the lower layer search is invoked. The lower layer computes an optimal machining sequence and its manufacturing cost. Then, the control gets returned to the upper layer. Together with the manufacturing cost computed at the lower layer, setup cost analysis guides the upper layer's setup space search. Eventually, a setup sequence is generated where an optimal machining sequence is determined per each setup. The system presented in this paper uses STEP as input and output formats, and therefore can be ported to arbitrary CAD and planning systems.

X-ray diffraction and reflectivity analysis of GaAs/InGaAsfree-standing trapezoidal quantum wires

Combined x-ray diffraction and reflectivity experiments have beenperformed on free-standing trapezoidal GaAs/InGaAs quantum wires using aconventional x-ray tube. Interpreting the intensity distribution around (004)by curve simulation of the extracted coherent grating truncation rods on thebasis of a semikinematical diffraction theory (DWBA) the shape and geometricparameters as well as the strain within the wires could be determined takingthe results of a finite element calculation of the atomic displacements intoaccount. The map of the coplanar x-ray reflectivity around (000), as well asthe intensity profiles of the coherent grating truncation rods, locatedequidistantly around the specularly reflected beam, have been recorded inorder to estimate the roughness properties of the sample interfaces as well asthe wire shape and layer set-up without the influence of strain. Allsmall-angle as well as wide-angle scattering experimental results went in tothe mutually consistent estimate of the sample properties. The experimentsperformed for a conventional x-ray tube supply a parameter set comparable incompleteness and precision to that obtained from similar samples byinterpreting synchrotron experiments.

Activation energies in organic light emitting diodes comprising ohmic contacts both for electron and hole injection

The lowest obtainable operating voltage for organic light emitting diodes (OLEDs) utilising a predefined organic layer setup can only be achieved with ohmic contacts both for electron and hole injection. We have investigated dark current transients of unipolar single-layer samples, and we have found ohmic contacts both for hole injection at indium tin oxide (ITO)/4,4′,4″-tris{ N-(1-naphtyl)- N-phenylamino}-triphenylamine (1-Naphdata) interfaces and for electron injection at 8-hydroxyquinoline aluminum (Alq 3)/LiF/Al interfaces. Therefore, the properties of OLEDs comprising these two interfaces are governed only by bulk material properties and internal organic/organic interfaces. In order to identify the dominating mechanisms concerning the temperature-dependent behaviour of prototypical double layer OLEDs, we have measured (with respect to the applied electric field) the activation energies of the charge carrier mobility and of the steady state current density in 1-Naphdata (holes) and Alq 3 (electrons), the activation energies of the steady state current density and of the luminance in OLEDs comprising an 1-Naphdata/Alq 3 heterojunction, plus the activation energy of the luminance onset. These experimentally activation energies are discussed with respect to device performance in the typical operating temperature range of flat panel displays including implications for further device optimisation.

Electron injection and transport in 8-hydroxyquinoline aluminum

We have measured the current–voltage characteristics and device efficiency of organic light emitting diodes (OLEDs) based on 8-hydroxyquinoline aluminum (Alq 3) in combination with several cathode layer setups. The electron injection properties of cathode metals evaporated under high vacuum (HV) and ultra-high vacuum (UHV) conditions are compared. Further, cathodes incorporating a thin layer of lithium fluoride, which is covered with a metal capping layer, are investigated. It will be shown that aluminum is an outstanding capping metal and significantly improves both electron injection and device efficiency. Quasi-static and transient current–voltage measurements on single-layer devices will be presented. It will be demonstrated that cathodes, comprising 0.2 nm LiF and aluminum, are able to sustain space charge limited currents in Alq 3. Additionally, the efficiency and lifetime data of multi-layer devices using this cathode layer setup are discussed.

Electrochemical characterization of new thianthrene-containing polymers and their application in LEDs

Four novel thianthrene-containing polymers were investigated by cyclovoltammetric measurement. The redox behavior of these materials is compared with the chemical structure, and the oxidation behavior reveals that these polymers are suitable hole transport layers for electronical devices. The polymers were used in single and double layer set-up as light emitting diodes (LEDs). The diodes were characterized by electroluminescence, photoluminescence and absorption spectroscopy. Due to the chemical structure, blue, green and white emitting LEDs were accomplished.

Computer simulations of pore growth in silicon

The dynamics of pore formation in silicon was studied by computer simulation. Porous structures were generated by a Monte Carlo algorithm that controlled the motion of an ensemble of electronic holes on a two-dimensional square lattice. Hole motion was biased to the nearest pore tip in order to simulate local electric-field effects corresponding to the depletion layer setup in n-type silicon. Several morphological characteristics seen in porous silicon were seen in the simulation: highly directional pores, steady-state pore spacing, and a smooth pore front. The pore spacing and the degree of sidebranching depended on the concentration of holes and the magnitude of the bias. The simulation trends are analogous to the pore morphologies seen in n-type silicon.

X-Ray Study of Non-Periodic Si/SiGe Multilayers

ABSTRACTX-ray diffraction is applied for the assessment of structural data such as lattice mismatch and layer thickness of MBE grown Si/Si1−xGex heterobipolar transistor and double-barrier resonant-tunneling structures. Rocking curves from the former structure show distinct features which are obviously correlated to the individual layer parameters. The diffraction profile of the resonant tunneling structure is not only more complicated because of the larger number of parameters but also due to the strong interference effects resulting from the layer set-up. For a determination of the structural parameters a comparison of the experimental diffraction pattern with simulated rocking curves is performed.