Thin Sheet Materials Research Articles

Fabrication of Electrochemical Biosensor for Cholesterol Using CNT-Gold Nanohybrid Buckypaper

An electrochemical biosensor for cholesterol has been developed based on carbon nanaotube and gold nanoparticle hybrid materials. A free standing buckypaper electrode composed of functionalized multiwallled carbon nanotubes (MWCNT) and gold nanoparticles (AuNP) has been used as electrode in an electrochemical biosensor for cholesterol. Carbon nanotubes (CNTs) have been recognized as one of the most promising electrode materials[1,2] due to their high chemical stability, good electrical conductivity, and tubular structure . On the other hand gold nanoparticles exhibit quantum size effects leading to unique optical, electronic and catalytic properties. AuNPs enhance the electrode conductivity and facilitate the electron transfer, thus improving the analytical sensitivity and selectivity[3]. Due to their compatibility with biolmoecules gold nanoparticles are widely used in medical diagnosis area. The combination of AuNPs and CNTs creates a new nanohybrid material with the integrated properties of the two components. This nanohybrid material can offer new opportunities for the development of biosensors with high analytical performance. In this work we have created a thin sheet of nanohybrid material, commonly known as buckypaper( thickness~50-60micron). Buckyppaer shows better electrochemical signal [4] compared to the dispersion formed by MWCNT and gold nanoparticles. We have reported that work earlier [4]with respect to several biomolecules such as tyrosine, tryptophan, myoglobin and glucose[5]. Due to the enhanced surface area, engineered CNT buckyppaer shows much enhanced signal and higher sensitivity. For this cholesterol biosensor, Cholesterol oxidase has been immobized on AuNP modified buckypaper. In addition to that buckypaper with carboxyl functionality was also modified by 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide, (EDC) and N-hydroxy succinimide(NHS) and after this activation cholesterol oxidase was immobilized. These two series of Buckypaers were used as electrodes. biosensor. Cholesterol was dissolved in 10mM tritobn X and different solution of cholesterol were made using 0.1 M phosphate buffer solution. Cyclic voltametry, amperometry and differential pulse voltammetry techniques wesr used to study the electrochemical behavior of this biosensor and to determine the sensitivity. Above figures show DPV results and the calibration plot obtained for cholesterol solution concentration ranging from from 0.2-1mM/L using AuNP –MWCNT hybrid buckypaper/. A detection limit obtained was 3 mmole/L which is higher than many reported biosensors based on other CNT dispersion based biosensors.

In-plane biaxial compression and tension testing of thin sheet materials

Detailed experimental data on the behavior of textured sheet metals under compressive loading is important to describe their tension–compression asymmetry. This is particularly needed for materials that exhibit a strength-differential effect, or in cases where the Bauschinger effect occurs. So far, there is no systematic work describing the third quadrant in the 2D stress space under biaxial compressive loading. This paper presents a new device for biaxial, compressive in-plane testing of thin sheets. Biaxial and uniaxial compression experiments are carried out in the strain controlled device, analyzing the behavior of deep drawing steel sheets with and without skin-pass treatment. Moreover, in order to allow for the experimental description of the yield surfaces, biaxial tensile tests are performed. Detailed numerical validations and experimental strain analysis both for the new specimen for biaxial compressive testing and for the cruciform specimen for biaxial tensile testing show that reasonably homogeneous strain distributions can be achieved. The combined experimental and numerical method presented here allows to evaluate the tension–compression asymmetry of thin sheet materials. The results for the skin-passed condition clearly exhibit a tension–compression asymmetry, which highlights the necessity of biaxial compression tests already in the as-received material condition. The biaxial compression test opens a pathway to a more detailed analysis of the flow behavior of thin sheets under biaxial compression loading.

Protection of extreme ultraviolet lithography masks. II. Showerhead flow mitigation of nanoscale particulate contamination

An analysis is presented of a method to protect the reticle (mask) in an extreme ultraviolet (EUV) mask inspection tool using a showerhead plenum to provide a continuous flow of clean gas over the surface of a reticle. The reticle is suspended in an inverted fashion (face down) within a stage/holder that moves back and forth over the showerhead plenum as the reticle is inspected. It is essential that no particles of 10-nm diameter or larger be deposited on the reticle during inspection. Particles can originate from multiple sources in the system, and mask protection from each source is explicitly analyzed. The showerhead plate has an internal plenum with a solid conical wall isolating the aperture. The upper and lower surfaces of the plate are thin flat sheets of porous-metal material. These porous sheets form the top and bottom showerheads that supply the region between the showerhead plate and the reticle and the region between the conical aperture and the Optics Zone box with continuous flows of clean gas. The model studies show that the top showerhead provides robust reticle protection from particles of 10-nm diameter or larger originating from the Reticle Zone and from plenum surfaces contaminated by exposure to the Reticle Zone. Protection is achieved with negligible effect on EUV transmission. The bottom showerhead efficiently protects the reticle from nanoscale particles originating from the Optics Zone. With similar mass flow rates from the two showerheads, this system provides efficient protection even when a significant overpressure exists between the Optics Zone and the Reticle Zone. Performance is insensitive to the fraction of incident particles that sticks to walls, the accommodation coefficient, the aperture geometry, and the gas pressure. The showerheads also protect the aperture (and therefore the Optics Zone) during mask loading and unloading. Commercially available porous-metal media have properties suitable for these showerheads at the required flow rates. The benefits of the approach compared to a conceptual EUV pellicle are described.

Heterojunctions of model CdTe/CdSe mixtures

We report on the strain behavior of compound mixtures of model group II–VI semiconductors. We use the Stillinger–Weber Hamiltonian that we recently introduced, specifically developed to model binary mixtures of group II–VI compounds such as CdTe and CdSe. We employ molecular dynamics simulations to examine the behavior of thin sheets of material, bilayers of CdTe and CdSe. The lattice mismatch between the two compounds leads to a strong bending of the entire sheet, with about a 0.5 to 1° deflection between neighboring planes. To analyze bilayer bending, we introduce a simple one-dimensional model and use energy minimization to find the angle of deflection. The analysis is equivalent to a least-squares straight line fit. We consider the effects of bilayers which are asymmetric with respect to the thickness of the CdTe and CdSe parts. From this we learn that the bending can be subdivided into four kinds depending on the compressive/tensile nature of each outer plane of the sheet. We use this approach to directly compare our findings with experimental results on the bending of CdTe/CdSe rods. To reduce the effects of the lattice mismatch we explore diffuse interfaces, where we mix (i.e. alloy) Te and Se, and estimate the strain response.

Multi-layer stencil creation from images

A stencil is a thin sheet of material, such as paper, plastic, or metal, with certain patterns cut from it. Applying a pigment through the cut-out holes produces a design on an underlying surface. Using multiple overlapping stencil layers, artists can create intricate, yet reproducible imagery on a variety of surfaces. Traditionally, artists have to design not only the final appearance, but also each individual stencil layer. A stencil layer needs to be connected, geometrically simple, and physically stable. Taking all these constraints into account during the design process is difficult and unintuitive even for skilled artists.In this paper, we propose a system which separates the artistic design stage from the complex and tedious task of stencil creation. For a given user design, our algorithm automatically generates a set of stencil layers satisfying all required properties. The task is formulated as a constrained energy optimization problem and solved efficiently. Experiments, including a user study, are carried out to examine the complete algorithm as well as each individual step.

FDTD Formulation for Graphene Modeling Based on Piecewise Linear Recursive Convolution and Thin Material Sheets Techniques

A finite-difference time-domain formulation based on piecewise linear recursive convolution method and on thin material sheets technique is developed for modeling terahertz graphene antennas and some other photonic components. The graphene sheets are modeled by specific recursive equations obtained for tangential electric field components, allowing one to easily apply voltage or current sources between the sheets. The effective conductivity of graphene sheets in Yee's three-dimensional lattice is calculated and used in simulations. A bow-tie-like geometry is investigated, aiming at resonance tuning. The developed numerical formulation is validated by comparison of results to data published in literature.

Gap Bridging Ability in Laser Beam Welding of Thin Aluminum Sheets

Abstract The applicability of laser welding processes with its specific advantages, such as low distortion or production efficiency, is often limited when joining thin-walled aluminum components due to small gap bridging ability. To overcomethis limit, a novel approach is presented using filler wire and a highly focused laser beam oscillation transverse to the welding direction. In the present work, the process development for welding in butt-joint configuration is shown. For this purpose, the influence of the welding speed, wire feed speed and beam oscillation parameters on wire melting behavior and on the welding result is presented. A process window for joining thin sheet material of 1 mm thickness with 1 mm joint gap is shown, and allowable tolerances for laser, wire and gap misalignment are investigated. Furthermore, the reached gap bridging ability of 1.9 mm for a constant gapand 3.15 mm for an opening gap configuration is shown in dependence of the utilized aluminum alloys.

Determination of thermal contact conductance between thin metal sheets of battery tabs

A novel method combining experimental test and heat transfer modeling was developed to determine the thermal contact conductance (TCC) between thin metal sheets as a function of contact pressures. In the experiment, thin metal samples were sandwiched between one white light transparent and one infrared (IR) transparent glass disks pressed together under different pressure levels. The metal stack was then heated up from the white light transparent side by an intense short pulse of flash light. The temperature transient on the other side was measured by an IR camera. To obtain a value of TCC, two separate experiments having different layers of thin sheet materials were performed and the values of maximum temperature rise were measured. Numerical heat transfer modeling was used to calculate the temperature evolution in the stack-up comprised of metal layers sandwiched between two glass disks. The heat transfer calculation results showed that TCC had a strong correlation to the ratio of maximum temperature rise between the two experiment configurations, but it was insensitive to the variations of other thermal properties. Thus, for a given pair of metal sheets in contact, a unique correlation between the TCC and the ratio of temperature rise was established using the heat transfer calculation. Such correlation allows the direct determination of the TCC value from the ratio of the experimentally measured temperature rise. The TCC between three types of thin metal sheets (i.e., 0.2-mm-thick Al, 0.2-mm-thick Cu and 0.9-mm-thick Cu) were measured and compared with the available literature data.

Energy Absorption of Thin-Walled Square Tubes With a Prefolded Origami Pattern—Part I: Geometry and Numerical Simulation

Thin-walled tubes subjected to axial crushing have been extensively employed as energy absorption devices in transport vehicles. Conventionally, they have a square or rectangular section, either straight or tapered. Dents are sometimes added to the surface in order to reduce the initial buckling force. This paper presents a novel thin-walled energy absorption device known as the origami crash box that is made from a thin-walled tube of square cross section whose surface is prefolded according to a developable origami pattern. The prefolded surface serves both as a type of geometric imperfection to lower the initial buckling force and as a mode inducer to trigger a collapse mode that is more efficient in terms of energy absorption. It has been found out from quasi-static numerical simulation that a new collapse mode referred to as the completed diamond mode, which features doubled traveling plastic hinge lines compared with those in conventional square tubes, can be triggered, leading to higher energy absorption and lower peak force than those of conventional ones of identical weight. A parametric study indicates that for a wide range of geometric parameters the origami crash box exhibits predictable and stable collapse behavior, with an energy absorption increase of 92.1% being achieved in the optimum case. The origami crash box can be stamped out of a thin sheet of material like conventional energy absorption devices without incurring in-plane stretching due to the developable surface of the origami pattern. The manufacturing cost is comparable to that of existing thin-walled crash boxes, but it absorbs a great deal more energy during a collision.

Efficient Algorithm for the Evaluation of the Physical Optics Scattering by NURBS Surfaces With Relatively General Boundary Condition

An adaptive integration algorithm is presented for the computation of the Physical Optics (PO) electric and magnetic field scattered by electrically large objects modeled by Non-Uniform Rational B-Splines (NURBS). The algorithm is the customization of a more general-purpose result that has been recently published. By using a unique formulation both impenetrable (e.g., impedance surfaces, coated conductors) as well as transparent thin sheet materials (e.g., thin dielectric panels, or frequency selective surfaces) are treated, via their Fresnel reflection and transmission coefficients. The PO radiation integral is evaluated over the NURBS parametric domain. Since most of the computer-aided geometric design (CAGD) tools are based on NURBS, the proposed algorithm allows a straightforward electromagnetic analysis of the structures by exploiting the standard available geometrical description, with no need of generating new geometrical models. Furthermore, the proposed adaptive sampling requires a number of integration points that is found to be drastically smaller than that resulting from standard Nyquist-based sampling integration algorithms. Such reduction of the sampling points is achieved by resorting to high-frequency technique concepts and allows a significant reduction of the CPU computational burden. Therefore the algorithm is efficient and particulary suitable for the electromagnetic characterization of real-life electrically large objects.

초기 이방성 SUS409L 박판재의 직사각 컵 성형을 위한 다단 디프드로잉 공정 적용에 관한 수치적 연구

Recently, electric vehicles and hybrid cars are being promoted as alternatives to reduce automobile emissions. Generally, thin sheet materials such as aluminum alloy AA300X and cold-rolled steel sheet such as JIS-G-3141 are used for the container for the lithium-ion secondary batteries. In this study, a multi-stage deep drawing process is used to produce a rectangular cup from thin stainless steel sheet material, SUS409L, with an initial blank thickness of 0.4mm for the battery container application. Numerical simulations of the first through the fifth stages for the multi-stage deep drawing with thin SUS409L sheet were conducted using LS-Dyna3D Implicit/Explicit. Special consideration was given to the deformation characteristics due to the normal anisotropy of the sheet material. The numerical simulations were conducted with both isotropic properties and the anisotropic properties of the initial blank material. An unexpected forming failure, barreling in the bottom region of the deep drawn rectangular cup, was observed. This failure mode can be avoided by additional ironing thickness control during the process.

In-situ EBSD study of the active slip systems and lattice rotation behavior of surface grains in aluminum alloy during tensile deformation

This paper reports an in-situ study of the plastic deformation behavior of surface grains in a polycrystalline aluminum alloy, in particular the active slip systems and lattice rotation, by means of the electron backscattered diffraction method. The experimental analysis is conducted at a spatial resolution of 1μm, thus allowing detailed analysis at subgrain levels, enabling elucidation of fine details of the deformation process that are not commonly seen in the literature. It is found that the grains rotate gradually with increasing strain during tensile deformation. The lattice rotation, in terms of both rotation path and rotation rate, is highly inhomogeneous both among the grains and within individual grains, leading to the formation of subgrains. The rotation behavior can be adequately described by the activation of slip systems with the maximum and second maximum Schmid factors. The number of independent slip systems in surface grains is much fewer than that in interior grains, as predicted by crystal plasticity theories. The lattice rotation rate is also heterogeneous among grains and subregions and for different deformation stages. The differences in rotation rate provide another mechanism for the accommodation of plastic strains and for the creation of subgrains. These findings are of importance for the mechanical processing of thin sheet materials or the deformation behavior of miniature components, where the majority of grains are on the surfaces.

Determination of the characteristics of crack resistance for unidirectional glass-reinforced plastics

We determine the characteristics of crack resistance of thin-sheet composite orthotropic polymeric materials by using the fields of displacements and strains in the process zone constructed by the method of digital correlation of speckle images. It is shown that, for fibrous unidirectional composites in the complex stressed state, the fracture energy and critical stresses depend on the angle between the orientation of the notch and the direction of reinforcement.

The forming limit diagram of ferritic stainless steel sheets: Experiments and modeling

The forming limit diagrams (FLDs) of two ferritic stainless steel sheets of thicknesses 1 and 0.1mm were determined experimentally. For the 0.1mm thick sheet, the modified Marciniak test and the conventional ASTM standard test were used for the FLD determination. However, the latter produced wrinkles and buckles on the sheet specimens and undesired fractures for some strain paths. The results showed that the modified Marciniak test is a more robust method for the FLD determination of thin sheet materials. Nevertheless, in spite of the issues associated with the ASTM standard test for the low thickness sheet, the FLDs determined by the two methods led to similar results. In addition to the experimental approach, the FLD was predicted using a modification of the Parmar–Mellor–Chakrabarty (PMC) model, which incorporates the effect of surface roughness. A non-quadratic anisotropic yield function, Yld2000-2d was implemented in this model to represent the anisotropy of the sheet metals. The FLD predicted with the conventional M–K (Marciniak–Kuczyński) and the modified PMC models were compared to the FLD determined experimentally. The FLD calculated with this modified model was in better agreement with the measured data than that computed with the M–K model for both thin and thick sheets.

Development of a hydroforming setup for deep drawing of square cups with variable blank holding force technique

Sheet hydroforming is a process that uses fluid pressure for deformation of a blank into a die cavity of desired shape. This process has high potential to manufacture complex auto body and other sheet metal parts. Successful production of parts using hydroforming mainly depends on design aspects of tooling as well as control of important process parameters such as closing force or blank holding force (BHF) and variation of fluid pressure with time. An experimental setup has been designed and developed for hydroforming of square cups from thin sheet materials. Square cups have been deep drawn using constant and variable BHF techniques. A methodology has been established to determine the variable BHF path for successful hydroforming of the cups with the assistance of programmable logic controller and data acquisition system. Finite element (FE) simulations have also been carried out to predict formability with both of these techniques. It has been found that it is possible to achieve better formability in terms of minimum corner radius and thinning in the case of variable BHF technique than in the case of constant BHF technique (constant force during forming and calibration). The results of FE analysis have been found to be in good agreement with experimental data.

An Investigation On Deformation-Based Surface Texturing

Surface textures have various applications, such as friction/wear reduction and light absorbing enhancement. Deformation-based surface texturing has the potential of economically creating micro-scale surface textures over a large surface area. A novel desktop surface texturing system is proposed for efficiently and economically fabricating microchannels on the surface of thin sheet material for microfluid and friction/wear reduction applications. Both the experimental and numerical studies were employed to analyze the problems of the flatness of the textured sheet, the uniform of the channel depth and pile-ups built up during the surface texturing process. The results demonstrated a clear relationship between relative velocity of the upper and lower rolls and the flatness of the textured sheet and the final profile of the microchannels.

Cohesive crack modelling of thin sheet material exhibiting anisotropy, plasticity and large-scale damage evolution

The crack tip region in notched structures generally exhibit damage evolution before ultimate failure occurs. In some materials, the damaged regions may reach considerable sizes prior to structural collapse. In this work, a cohesive crack model suitable for static fracture mechanics analysis of thin sheet materials exhibiting anisotropy, plasticity, and large-scale damage evolution was developed. The material parameters of the model were calibrated solely by tensile testing of unnotched test specimens. The predictive capability of the model was verified by comparisons with experiments on notched test specimens with different crack sizes. The predictions of failure were shown to be in excellent agreement with the experiments.

Modeling of mixed-mode crack growth in ductile thin sheets under combined in-plane and out-of-plane loading

This paper describes a modeling approach for analyzing mixed-mode crack growth events in ductile thin-sheet materials under large deformation and combined in-plane and out-of-plane loading conditions. The remote mixed-mode I/III loading leads to local mixed-mode I/II/III fields near the crack front. Making use of full-field surface deformation measurements, finite element models of mixed-mode I/III stable tearing events in thin-sheet specimens have been developed. Model predictions have been compared with experimental measurements (a) just prior to initial crack growth and (b) during stable tearing crack growth. Analyses of curvilinear crack growth events are carried out using a nodal release option or a local re-meshing option and using a generalized CTOD parameter with experimentally measured critical CTOD values. Results of this study suggest that the modeling approach can be employed to numerically re-construct experimental crack growth events in thin plate specimens. This offers a viable means of analyzing and understanding the mixed-mode crack growth events and provides a tool for further investigations of 3D crack front fields (which are otherwise unavailable experimentally) and for the study of fracture criteria for stable tearing events.

Blueprinting nematic glass: Systematically constructing and combining active points of curvature for emergent morphology

Much recent progress has been made in the study of nematic solids, both glassy and elastomeric, particularly in the realm of stress-free, defect-driven deformation in thin sheets of material. In this paper we consider a subset of texture domains in nematic glasses that are simple to synthesize, and explore the ways that these simple domains may be compatibly combined to yield analogs of the traditional smooth disclination defect textures seen in standard liquid crystals. We calculate the deformation properties of these constructed textures, and show that, subject to the compatibility constraints of the construction, these textures may be further combined to achieve shape blueprinting of three-dimensional structures from flat sheets.

On the formation of vacancies by edge dislocation dipole annihilation in fatigued copper

Fatigue experiments on copper have shown that vacancy production leads to the evolution of extrusions, which are the preferred sites for fatigue crack initiation. However, experimental, analytical and numerical results for the critical edge-dislocation dipole annihilation distance vastly differ. This study performs molecular statics and molecular dynamics simulations at elevated temperature to investigate the discrepancies in annihilation distance. Vacancy forming edge dislocation dipoles are stable if their spacing exceeds 2 lattice spacings. If the dislocation dipole is perpendicular to the free surface in a thin sheet of material, jogs on edge dislocations lead to dipole annihilation. Our main conclusion is that dislocation generation, glide and stable edge dislocation dipoles are sufficient to lead to that extrusion growth, which results in fatigue crack initiation.