High volume fabrication of laser targets using MEMS techniques

NASA Astrophysics Data System (ADS)

Spindloe, C.; Arthur, G.; Hall, F.; Tomlinson, S.; Potter, R.; Kar, S.; Green, J.; Higginbotham, A.; Booth, N.; Tolley, M. K.

2016-04-01

The latest techniques for the fabrication of high power laser targets, using processes developed for the manufacture of Micro-Electro-Mechanical System (MEMS) devices are discussed. These laser targets are designed to meet the needs of the increased shot numbers that are available in the latest design of laser facilities. Traditionally laser targets have been fabricated using conventional machining or coarse etching processes and have been produced in quantities of 10s to low 100s. Such targets can be used for high complexity experiments such as Inertial Fusion Energy (IFE) studies and can have many complex components that need assembling and characterisation with high precision. Using the techniques that are common to MEMS devices and integrating these with an existing target fabrication capability we are able to manufacture and deliver targets to these systems. It also enables us to manufacture novel targets that have not been possible using other techniques. In addition, developments in the positioning systems that are required to deliver these targets to the laser focus are also required and a system to deliver the target to a focus of an F2 beam at 0.1Hz is discussed.

Fabrication and Operation of Paper-Based Analytical Devices

NASA Astrophysics Data System (ADS)

Jiang, Xiao; Fan, Z. Hugh

2016-06-01

This review focuses on the fabrication techniques and operational components of microfluidic paper-based analytical devices (μPADs). Being low-cost, user-friendly, fast, and simple, μPADs have seen explosive growth in the literature in the last decade. Many different materials and technologies have been employed to fabricate μPADs for various applications, including those that employ patterning, the creation of physical boundaries, and three-dimensional structures. In addition to fabrication techniques, flow control and other operational components in μPADs are of great interest. These components enable μPADs to control flow rates, direct flow paths via valves, sequentially deliver reagents automatically, and display test results, all of which will make μPADs more suitable for point-of-care applications.

A new fabrication technique for back-to-back varactor diodes

NASA Technical Reports Server (NTRS)

Smith, R. Peter; Choudhury, Debabani; Martin, Suzanne; Frerking, Margaret A.; Liu, John K.; Grunthaner, Frank A.

1992-01-01

A new varactor diode process has been developed in which much of the processing is done from the back of an extremely thin semiconductor wafer laminated to a low-dielectric substrate. Back-to-back BNN diodes were fabricated with this technique; excellent DC and low-frequency capacitance measurements were obtained. Advantages of the new technique relative to other techniques include greatly reduced frontside wafer damage from exposure to process chemicals, improved capability to integrate devices (e.g. for antenna patterns, transmission lines, or wafer-scale grids), and higher line yield. BNN diodes fabricated with this technique exhibit approximately the expected capacitance-voltage characteristics while showing leakage currents under 10 mA at voltages three times that needed to deplete the varactor. This leakage is many orders of magnitude better than comparable Schottky diodes.

Fabrication Techniques and Principles for Flat Plate Antennas

DOT National Transportation Integrated Search

1973-09-01

The report documents the fabrication techniques and principles selected to produce one and ten million flat plate antennas per year. An engineering analysis of the reliability, electrical integrity, and repeatability is made, and a cost analysis summ...

Artificial submicron or nanometer speckle fabricating technique and electron microscope speckle photography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu Zhanwei; Xie Huimin; Fang Daining

2007-03-15

In this article, a novel artificial submicro- or nanometer speckle fabricating technique is proposed by taking advantage of submicro or nanometer particles. In the technique, submicron or nanometer particles were adhered to an object surface by using ultrasonic dispersing technique. The particles on the object surface can be regarded as submicro or nanometer speckle by using a scanning electronic microscope at a special magnification. In addition, an electron microscope speckle photography (EMSP) method is developed to measure in-plane submicron or nanometer deformation of the object coated with the artificial submicro or nanometer speckles. The principle of artificial submicro or nanometermore » speckle fabricating technique and the EMSP method are discussed in detail in this article. Some typical applications of this method are offered. The experimental results verified that the artificial submicro or nanometer speckle fabricating technique and EMSP method is feasible.« less

Comparative study on structural and optical properties of CdS films fabricated by three different low-cost techniques

NASA Astrophysics Data System (ADS)

Ravichandran, K.; Philominathan, P.

2009-03-01

Highly crystalline and transparent cadmium sulphide films were fabricated at relatively low temperature by employing an inexpensive, simplified spray technique using perfume atomizer (generally used for cosmetics). The structural, surface morphological and optical properties of the films were studied and compared with that prepared by conventional spray pyrolysis using air as carrier gas and chemical bath deposition. The films deposited by the simplified spray have preferred orientation along (1 0 1) plane. The lattice parameters were calculated as a = 4.138 Å and c = 6.718 Å which are well agreed with that obtained from the other two techniques and also with the standard data. The optical transmittance in the visible range and the optical band gap were found as 85% and 2.43 eV, respectively. The structural and optical properties of the films fabricated by the simplified spray are found to be desirable for opto-electronic applications.

A comparison of enhancement techniques for footwear impressions on dark and patterned fabrics.

PubMed

Farrugia, Kevin J; Bandey, Helen; Dawson, Lorna; Daéid, Niamh Nic

2013-11-01

The use of chemical enhancement techniques on porous substrates, such as fabrics, poses several challenges predominantly due to the occurrence of background staining and diffusion as well as visualization difficulties. A range of readily available chemical and lighting techniques were utilized to enhance footwear impressions made in blood, soil, and urine on dark and patterned fabrics. Footwear impressions were all prepared at a set force using a specifically built footwear rig. In most cases, results demonstrated that fluorescent chemical techniques were required for visualization as nonfluorescent techniques provided little or no contrast with the background. Occasionally, this contrast was improved by oblique lighting. Successful results were obtained for the enhancement of footwear impressions in blood; however, the enhancement of footwear impressions in urine and soil on dark and patterned fabrics was much more limited. The results demonstrate that visualization and fluorescent enhancement on porous substrates such as fabrics is possible. © 2013 American Academy of Forensic Sciences.

Accuracy of cast posts fabricated by the direct and the indirect techniques.

PubMed

Rayyan, Mohammad R; Aldossari, Roa'a A; Alsadun, Sarah F; Hijazy, Fatimah R

2016-09-01

Patterns for custom cast posts and cores can be fabricated either by the direct or the indirect technique. Which technique is more accurate is unknown. The purpose of this in vitro study was to investigate the effect of pattern fabrication technique on the accuracy of post fit. Ten intact extracted premolar teeth with a single canal and similar dimensions received root canal treatment. The teeth were sectioned 2 mm above the cementoenamel junction. A total of 20 cast post and core patterns, 2 for each tooth, were fabricated, 10 with the direct technique and 10 with the indirect technique. Patterns were cast to produce 20 cast post and cores. Each tooth was scanned using a microcomputed tomography (μCT) system with a resolution of 14.5 μm, once with the post of the direct technique and once with the post of the indirect technique. Ct analyzer software was used to calculate the overall space between the post and canal walls and the space areas in 3 different standardized sections. The Student paired t test was used to determine any significant difference in the scores of the groups. The overall space between the canal walls and posts made with the direct technique ranged between 7.86 and 17.39 mm(3), with a mean value of 12.25 mm(3), whereas with the indirect technique, the space ranged between 6.68 and 18.02 mm(3), with a mean of 11.92 mm(3). No significant differences were found between the results of either technique (P>.05). Within the limitations of this study, neither the indirect nor direct pattern fabrication technique influenced the accuracy of post fitting. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Method for Fabricating Composite Structures Using Pultrusion Processing

NASA Technical Reports Server (NTRS)

Farley, Gary L. (Inventor)

2000-01-01

A method for fabricating composite structures at a low-cost, moderate-to-high production rate. A first embodiment of the method includes employing a continuous press forming fabrication process. A second embodiment of the method includes employing a pultrusion process for obtaining composite structures. The methods include coating yarns with matrix material, weaving the yarn into fabric to produce a continuous fabric supply and feeding multiple layers of net-shaped fabrics having optimally oriented fibers into a debulking tool to form an undebulked preform. The continuous press forming fabrication process includes partially debulking the preform, cutting the partially debulked preform and debulking the partially debulked preform to form a net-shape. An electron-beam or similar technique then cures the structure. The pultrusion fabric process includes feeding the undebulked preform into a heated die and gradually debulking the undebulked preform. The undebulked preform in the heated die changes dimension until a desired cross-sectional dimension is achieved. This process further includes obtaining a net-shaped infiltrated uncured preform, cutting the uncured preform to a desired length and electron-beam curing (or similar technique) the uncured preform. These fabrication methods produce superior structures formed at higher production rates, resulting in lower cost and high structural performance.

Method for Fabricating Composite Structures Using Pultrusion Processing

NASA Technical Reports Server (NTRS)

Farley, Gary L. (Inventor)

2000-01-01

A method for fabricating composite structures at a low-cost, moderate-to-high production rate. A first embodiment of the method includes employing a continuous press forming fabrication process. A second embodiment of the method includes employing a pultrusion process for obtaining composite structures. The methods include coating yarns with matrix material, weaving the yarn into fabric to produce a continuous fabric supply and feeding multiple layers of net-shaped fabrics having optimally oriented fibers into a debulking tool to form an undebulked preform. The continuous press forming fabrication process includes partially debulking the preform, cutting the partially debulked preform and debulking the partially debulked preform to form a netshape. An electron-beam or similar technique then cures the structure. The pultrusion fabric process includes feeding the undebulked preform into a heated die and gradually debulking the undebulked preform. The undebulked preform in the heated die changes dimension until a desired cross-sectional dimension is achieved. This process further includes obtaining a net-shaped infiltrated uncured preform, cutting the uncured preform to a desired length and electronbeam curing (or similar technique) the uncured preform. These fabrication methods produce superior structures formed at higher production rates, resulting in lower cost and high structural performance.

LCD real-time mask technique for fabrication of arbitrarily shaped microstructure

NASA Astrophysics Data System (ADS)

Peng, Qinjun; Guo, Yongkang; Chen, Bo; Du, Jinglei; Xiang, Jinshan; Cui, Zheng

2002-04-01

A new technique to fabricate arbitrarily shaped microstructures by using LCD (liquid crystal display) real- time mask is reported in this paper. Its principle and design method are explained. Based on partial coherent imaging theory, the process to fabricate micro-axicon array and zigzag grating has been simulated. The experiment using a color LCD as real-time mask has been set up. Micro-axicon array and zigzag grating has been fabricated by the LCD real-time mask technique. The 3D surface relief structures were made on pan chromatic silver-halide sensitized gelatin (Kodak-131) with trypsinase etching. The pitch size of zigzag grating is 46.26micrometers . The caliber of axicon is 118.7micrometers , and the etching depth is 1.332micrometers .

Quantification of Changes in Mulberry Silk Fabrics due to Different Laundering: Using WAXS Technique

NASA Astrophysics Data System (ADS)

Parameswara, P.; Nivedita, S.; Somashekar, R.

2011-07-01

Loom finished mulberry silk fabrics (Taffeta) were machine laundered and hand laundered several times. X-ray diffractograms of pure and laundered fabrics were used to calculate microstructural parameters like average crystallite size (D) and lattice strain (Vegr) employing Williamson-Hall plot. Microstructural parameters were compared with measured mechanical properties like breaking load, tenacity, and elongation of warp yarns unraveled from fabrics. Surface morphology and texture of silk fabrics changed upon washing is evident from SEM images.

Recent Developments in Microsystems Fabricated by the Liga-Technique

NASA Technical Reports Server (NTRS)

Schulz, J.; Bade, K.; El-Kholi, A.; Hein, H.; Mohr, J.

1995-01-01

As an example of microsystems fabricated by the LIGA-technique (x-ray lithography, electroplating and molding), three systems are described and characterized: a triaxial acceleration sensor system, a micro-optical switch, and a microsystem for the analysis of pollutants. The fabrication technologies are reviewed with respect to the key components of the three systems: an acceleration sensor, and electrostatic actuator, and a spectrometer made by the LIGA-technique. Aa micro-pump and micro-valve made by using micromachined tools for molding and optical fiber imaging are made possible by combining LIGA and anisotropic etching of silicon in a batch process. These examples show that the combination of technologies and components is the key to complex microsystems. The design of such microsystems will be facilitated is standardized interfaces are available.

Technology development of fabrication techniques for advanced solar dynamic concentrators

NASA Technical Reports Server (NTRS)

Richter, Scott W.

1991-01-01

The objective of the advanced concentrator program is to develop the technology that will lead to lightweight, highly reflective, accurate, scaleable, and long lived space solar dynamic concentrators. The advanced concentrator program encompasses new and innovative concepts, fabrication techniques, materials selection, and simulated space environmental testing. Fabrication techniques include methods of fabricating the substrates and coating substrate surfaces to produce high quality optical surfaces, acceptable for further coating with vapor deposited optical films. The selected materials to obtain a high quality optical surface include microsheet glass and Eccocoat EP-3 epoxy, with DC-93-500 selected as a candidate silicone adhesive and levelizing layer. The following procedures are defined: cutting, cleaning, forming, and bonding microsheet glass. Procedures are also defined for surface cleaning, and EP-3 epoxy application. The results and analyses from atomic oxygen and thermal cycling tests are used to determine the effects of orbital conditions in a space environment.

A study for development of aerothermodynamic test model materials and fabrication technique

NASA Technical Reports Server (NTRS)

Dean, W. G.; Connor, L. E.

1972-01-01

A literature survey, materials reformulation and tailoring, fabrication problems, and materials selection and evaluation for fabricating models to be used with the phase-change technique for obtaining quantitative aerodynamic heat transfer data are presented. The study resulted in the selection of two best materials, stycast 2762 FT, and an alumina ceramic. Characteristics of these materials and detailed fabrication methods are presented.

Method for Fabricating Composite Structures Using Continuous Press Forming

NASA Technical Reports Server (NTRS)

Farley, Gary L. (Inventor)

1997-01-01

A method for fabricating composite structures at a low-cost. moderate-to-high production rate. A first embodiment of the method includes employing a continuous press forming fabrication process. A second embodiment of the method includes employing a pultrusion process for obtaining composite structures. The methods include coating yarns with matrix material, weaving the yarn into fabric to produce a continuous fabric supply and feeding multiple layers of net-shaped fabrics having optimally oriented fibers into a debulking tool to form an undebulked preform. The continuous press forming fabrication process includes partially debulking the preform, cutting the partially debulked preform and debulking the partially debulked preform to form a net-shape. An electron-beam or similar technique then cures the structure. The pultrusion fabric process includes feeding the undebulked preform into a heated die and gradually debulking the undebulked preform. The undebulked preform in the heated die changes dimension until a desired cross-sectional dimension is achieved. This process further includes obtaining a net-shaped infiltrated uncured preform, cutting the uncured preform to a desired length and electron-beam curing (or similar technique) the uncured preform. These fabrication methods produce superior structures formed at higher production rates. resulting in lower cost and high structural performance.

Optimal condition for employing an axicon-generated Bessel beam to fabricate cylindrical microlens arrays

NASA Astrophysics Data System (ADS)

Luo, Zhi; Yin, Kai; Dong, Xinran; Duan, Ji’an

2018-05-01

A numerical algorithm, modelling the transformation from a Gaussian beam to a Bessel beam, is presented for the purpose to study the optimal condition for employing an axicon-generated Bessel beam to fabricate cylindrical microlens arrays (CMLAs). By applying the numerical algorithm to simulate the spatial intensity distribution behind the axicon under different defects of a rotund-apex and different diameter ratios of an incident beam to the axicon, we find that the diffraction effects formed by the axicon edge can be almost eliminated when the diameter ratio is less than 1:2, but the spatial intensity distribution is disturbed dramatically even a few tens of microns deviation of the apex, especially for the front part of the axicon-generated Bessel beam. Fortunately, the lateral intensity profile in the rear part still maintains a desirable Bessel curve. Therefore, the rear part of the Bessel area and the less than 1:2 diameter ratio are the optimal choice for employing an axicon-generated Bessel beam to implement surface microstructures fabrication. Furthermore, by applying the optimal conditions to direct writing microstructures on fused silica with a femtosecond (fs) laser, a large area close-packed CMLA is fabricated. The CMLA presents high quality and uniformity and its optical performance is also demonstrated.

Fabrication and characterisation of ligand-functionalised ultrapure monodispersed metal nanoparticle nanoassemblies employing advanced gas deposition technique

NASA Astrophysics Data System (ADS)

Geremariam Welearegay, Tesfalem; Cindemir, Umut; Österlund, Lars; Ionescu, Radu

2018-02-01

Here, we report for the first time the fabrication of ligand-functionalised ultrapure monodispersed metal nanoparticles (Au, Cu, and Pt) from their pure metal precursors using the advanced gas deposition technique. The experimental conditions during nanoparticle formation were adjusted in order to obtain ultrafine isolated nanoparticles on different substrates. The morphology and surface analysis of the as-deposited metal nanoparticles were investigated using scanning electron microscopy, x-ray diffraction and Fourier transform infra-red spectroscopy, which demonstrated the formation of highly ordered pure crystalline nanoparticles with a relatively uniform size distribution of ∼10 nm (Au), ∼4 nm (Cu) and ∼3 nm (Pt), respectively. A broad range of organic ligands containing thiol or amine functional groups were attached to the nanoparticles to form continuous networks of nanoparticle-ligand nanoassemblies, which were characterised by scanning electron microscopy and x-ray photoelectron spectroscopy. The electrical resistance of the functional nanoassemblies deposited in the gap spacing of two microfabricated parallel Au electrodes patterned on silicon substrates ranged between tens of kΩ and tens of MΩ, which is suitable for use in many applications including (bio)chemical sensors, surface-enhanced Raman spectroscopy and molecular electronic rectifiers.

Development of a Fluid Structures Interaction Test Technique for Fabrics

NASA Technical Reports Server (NTRS)

Zilliac, Gregory G.; Heineck, James T.; Schairer, Edward T.; Mosher, Robert N.; Garbeff, Theodore Joseph

2012-01-01

Application of fluid structures interaction (FSI) computational techniques to configurations of interest to the entry, descent and landing (EDL) community is limited by two factors - limited characterization of the material properties for fabrics of interest and insufficient experimental data to validate the FSI codes. Recently ILC Dover Inc. performed standard tests to characterize the static stress-strain response of four candidate fabrics for use in EDL applications. The objective of the tests described here is to address the need for a FSI dataset for CFD validation purposes. To reach this objective, the structural response of fabrics was measured in a very simple aerodynamic environment with well controlled boundary conditions. Two test series were undertaken. The first series covered a range of tunnel conditions and the second focused on conditions that resulted in fabric panel buckling.

Development of low cost fabrication techniques for large solid rocket nozzles

NASA Technical Reports Server (NTRS)

Warga, J. J.

1971-01-01

Property measurements and fabrication characteristics were determined and the performance in subscale (Minuteman Wing 2 second stage) motors was evaluated. It was demonstrated that the incorporation of low cost fabrication techniques in a full scale 260 in. nozzle could result in savings of $149,000 when compared with an identical design using tape-wrapped components throughout.

Study on the Filament Yarns Spreading Techniques and Assessment Methods of the Electronic Fiberglass Fabric

NASA Astrophysics Data System (ADS)

Wang, Xi; Chen, Shouhui; Zheng, Tianyong; Ning, Xiangchun; Dai, Yifei

2018-03-01

The filament yarns spreading techniques of electronic fiberglass fabric were developed in the past few years in order to meet the requirements of the development of electronic industry. Copper clad laminate (CCL) requires that the warp and weft yarns of the fabric could be spread out of apart and formed flat. The penetration performance of resin could be improved due to the filament yarns spreading techniques of electronic fiberglass fabric, the same as peeling strength of CCL and drilling performance of printed circuit board (PCB). This paper shows the filament yarns spreading techniques of electronic fiberglass fabric from several aspects, such as methods and functions, also with the assessment methods of their effects.

In vitro evaluation of marginal adaptation in five ceramic restoration fabricating techniques.

PubMed

Ural, Cağri; Burgaz, Yavuz; Saraç, Duygu

2010-01-01

To compare in vitro the marginal adaptation of crowns manufactured using ceramic restoration fabricating techniques. Fifty standardized master steel dies simulating molars were produced and divided into five groups, each containing 10 specimens. Test specimens were fabricated with CAD/CAM, heat-press, glass-infiltration, and conventional lost-wax techniques according to manufacturer instructions. Marginal adaptation of the test specimens was measured vertically before and after cementation using SEM. Data were statistically analyzed by one-way ANOVA with Tukey HSD tests (a = .05). Marginal adaptation of ceramic crowns was affected by fabrication technique and cementation process (P < .001). The lowest marginal opening values were obtained with Cerec-3 crowns before and after cementation (P < .001). The highest marginal discrepancy values were obtained with PFM crowns before and after cementation. Marginal adaptation values obtained in the compared systems were within clinically acceptable limits. Cementation causes a significant increase in the vertical marginal discrepancies of the test specimens.

Retention of denture bases fabricated by three different processing techniques – An in vivo study

PubMed Central

Chalapathi Kumar, V. H.; Surapaneni, Hemchand; Ravikiran, V.; Chandra, B. Sarat; Balusu, Srilatha; Reddy, V. Naveen

2016-01-01

Aim: Distortion due to Polymerization shrinkage compromises the retention. To evaluate the amount of retention of denture bases fabricated by conventional, anchorized, and injection molding polymerization techniques. Materials and Methods: Ten completely edentulous patients were selected, impressions were made, and master cast obtained was duplicated to fabricate denture bases by three polymerization techniques. Loop was attached to the finished denture bases to estimate the force required to dislodge them by retention apparatus. Readings were subjected to nonparametric Friedman two-way analysis of variance followed by Bonferroni correction methods and Wilcoxon matched-pairs signed-ranks test. Results: Denture bases fabricated by injection molding (3740 g), anchorized techniques (2913 g) recorded greater retention values than conventional technique (2468 g). Significant difference was seen between these techniques. Conclusions: Denture bases obtained by injection molding polymerization technique exhibited maximum retention, followed by anchorized technique, and least retention was seen in conventional molding technique. PMID:27382542

Novel technique for fabrication of multi-layered microcoils in microelectromechanical systems (MEMS) applications

NASA Astrophysics Data System (ADS)

Chang, Hung-Pin; Qian, Jiangyuan; Bachman, Mark; Congdon, Philip; Li, Guann-pyng

2002-07-01

A novel planarization technique, compressive molding planarization (CMP) is developed for implementation of a multi-layered micro coil device. Applying CMP and other micromachining techniques, a multi-layered micro coil device has been designed and fabricated, and its use in the magnetic micro actuators for hard disk drive applications has been demonstrated, showing that it can produce milli-Newton of magnetic force suitable for driving a micro actuator. The novel CMP technique can be equally applicable in other MEMS devices fabrication to ease the process integration for the complicated structure.

Advanced Materials and Fabrication Techniques for the Orion Attitude Control Motor

NASA Technical Reports Server (NTRS)

Gorti, Sridhar; Holmes, Richard; O'Dell, John; McKechnie, Timothy; Shchetkovskiy, Anatoliy

2013-01-01

Rhenium, with its high melting temperature, excellent elevated temperature properties, and lack of a ductile-to-brittle transition temperature (DBTT), is ideally suited for the hot gas components of the ACM (Attitude Control Motor), and other high-temperature applications. However, the high cost of rhenium makes fabricating these components using conventional fabrication techniques prohibitive. Therefore, near-net-shape forming techniques were investigated for producing cost-effective rhenium and rhenium alloy components for the ACM and other propulsion applications. During this investigation, electrochemical forming (EL-Form ) techniques were evaluated for producing the hot gas components. The investigation focused on demonstrating that EL-Form processing techniques could be used to produce the ACM flow distributor. Once the EL-Form processing techniques were established, a representative rhenium flow distributor was fabricated, and samples were harvested for material properties testing at both room and elevated temperatures. As a lower cost and lighter weight alternative to an all-rhenium component, rhenium- coated graphite and carbon-carbon were also evaluated. The rhenium-coated components were thermal-cycle tested to verify that they could withstand the expected thermal loads during service. High-temperature electroforming is based on electrochemical deposition of compact layers of metals onto a mandrel of the desired shape. Mandrels used for electro-deposition of near-net shaped parts are generally fabricated from high-density graphite. The graphite mandrel is easily machined and does not react with the molten electrolyte. For near-net shape components, the inner surface of the electroformed part replicates the polished graphite mandrel. During processing, the mandrel itself becomes the cathode, and scrap or refined refractory metal is the anode. Refractory metal atoms from the anode material are ionized in the molten electrolytic solution, and are deposited

Development of a Direct Fabrication Technique for Full-Shell X-Ray Optics

NASA Technical Reports Server (NTRS)

Gubarev, M.; Kolodziejczak, J. K.; Griffith, C.; Roche, J.; Smith, W. S.; Kester, T.; Atkins, C.; Arnold, W.; Ramsey, B.

2016-01-01

Future astrophysical missions will require fabrication technology capable of producing high angular resolution x-ray optics. A full-shell direct fabrication approach using modern robotic polishing machines has the potential for producing high resolution, light-weight and affordable x-ray mirrors that can be nested to produce large collecting area. This approach to mirror fabrication, based on the use of the metal substrates coated with nickel phosphorous alloy, is being pursued at MSFC. The design of the polishing fixtures for the direct fabrication, the surface figure metrology techniques used and the results of the polishing experiments are presented.

Investigation of low-cost fabrication of ablative heat shields

NASA Technical Reports Server (NTRS)

Massions, V. P.; Mach, R. W.

1973-01-01

The fabrication, testing, and evaluation of materials and techniques employed in the fabrication of ablative heat shield panels are described. Results of this effort show projected reductions in labor man-hours for dielectric curing of panels when compared to panels molded in a steam-heated press. In addition, panels were fabricated with more than one density within the cross-section. These dual-density panels show significant weight and cost reduction potentials.

Comparison of marginal and internal adaptation of copings fabricated from three different fabrication techniques: An in vitro study.

PubMed

Arora, Aman; Yadav, Avneet; Upadhyaya, Viram; Jain, Prachi; Verma, Mrinalini

2018-01-01

The purpose of this study was to compare the marginal and internal adaptation of cobalt-chromium (Co-Cr) copings fabricated from conventional wax pattern, three-dimensional (3D)-printed resin pattern, and laser sintering technique. A total of thirty copings were made, out of which ten copings were made from 3D-printed resin pattern (Group A), ten from inlay wax pattern (Group B), and ten copings were obtained from direct metal laser sintering (DMLS) technique (Group C). All the thirty samples were seated on their respective dies and sectioned carefully using a laser jet cutter and were evaluated for marginal and internal gaps at the predetermined areas using a stereomicroscope. The values were then analyzed using one-way ANOVA test and post hoc Bonferroni test. One-way ANOVA showed lowest mean marginal discrepancy for DMLS and highest value for copings fabricated from inlay wax. The values for internal discrepancy were highest for DMLS (169.38) and lowest for 3D-printed resin pattern fabricated copings (133.87). Post hoc Bonferroni test for both marginal and internal discrepancies showed nonsignificant difference when Group A was compared to Group B ( P > 0.05) and significant when Group A was compared with Group C ( P < 0.05). Group B showed significant difference ( P < 0.05) when compared with Group C. Marginal and internal discrepancies of all the three casting techniques were within clinically acceptable values. Marginal fit of DMLS was superior as compared to other two techniques, whereas when internal fit was evaluated, conventional technique showed the best internal fit.

Pedagogical Techniques Employed by the Television Show "MythBusters"

NASA Astrophysics Data System (ADS)

Zavrel, Erik

2016-11-01

"MythBusters," the long-running though recently discontinued Discovery Channel science entertainment television program, has proven itself to be far more than just a highly rated show. While its focus is on entertainment, the show employs an array of pedagogical techniques to communicate scientific concepts to its audience. These techniques include: achieving active learning, avoiding jargon, employing repetition to ensure comprehension, using captivating demonstrations, cultivating an enthusiastic disposition, and increasing intrinsic motivation to learn. In this content analysis, episodes from the show's 10-year history were examined for these techniques. "MythBusters" represents an untapped source of pedagogical techniques, which science educators may consider availing themselves of in their tireless effort to better reach their students. Physics educators in particular may look to "MythBusters" for inspiration and guidance in how to incorporate these techniques into their own teaching and help their students in the learning process.

Fit Analysis of Different Framework Fabrication Techniques for Implant-Supported Partial Prostheses.

PubMed

Spazzin, Aloísio Oro; Bacchi, Atais; Trevisani, Alexandre; Farina, Ana Paula; Dos Santos, Mateus Bertolini

2016-01-01

This study evaluated the vertical misfit of implant-supported frameworks made using different techniques to obtain passive fit. Thirty three-unit fixed partial dentures were fabricated in cobalt-chromium alloy (n = 10) using three fabrication methods: one-piece casting, framework cemented on prepared abutments, and laser welding. The vertical misfit between the frameworks and the abutments was evaluated with an optical microscope using the single-screw test. Data were analyzed using one-way analysis of variance and Tukey test (α = .05). The one-piece casted frameworks presented significantly higher vertical misfit values than those found for framework cemented on prepared abutments and laser welding techniques (P < .001 and P < .003, respectively). Laser welding and framework cemented on prepared abutments are effective techniques to improve the adaptation of three-unit implant-supported prostheses. These techniques presented similar fit.

Balloon fabrics made of Goldbeater's skins

NASA Technical Reports Server (NTRS)

Chollet, L

1922-01-01

Goldbeater's skin, which is the prepared outside membrane of the large intestine of an ox, is examined as a balloon fabric and details of how goldbeater's skin is prepared for use are provided. The construction techniques employed by Germany, France, and England are all discussed.

Development of nano-fabrication technique utilizing self-organizational behavior of point defects induced by ion irradiation

NASA Astrophysics Data System (ADS)

Nitta, Noriko; Taniwaki, Masafumi

2006-04-01

The present authors proposed a novel nano-fabrication technique that is able to arrange the fine cells orderly, based on their finding in GaSb implanted at a low temperature. In this article, first the experimental results that anomalous cellular structure was formed in GaSb by ion implantation is introduced and the self-organizational formation mechanism of the structure is described. Next a nano-fabrication technique that utilizes focused ion beam is described. This technique consists of two procedures, i.e. the formation process of the voids array and the development of the initial array to ordered cellular structure. Finally, the nano-fabrication is actually performed by this technique and their results are reported. Fabrication succeeded in structures where the dot (cell) interval was 100 nm or larger. The minimum ion dose for initial voids which develops to the ordered cellular structure is evaluated. It is also shown that the substrate temperature during implantation is an essential parameter for this technique.

Comparison of the fit of cast gold crowns fabricated from the digital and the conventional impression techniques

PubMed Central

Jeon, Young-Chan; Jeong, Chang-Mo

2017-01-01

PURPOSE The purpose of this study was to compare the fit of cast gold crowns fabricated from the conventional and the digital impression technique. MATERIALS AND METHODS Artificial tooth in a master model and abutment teeth in ten patients were restored with cast gold crowns fabricated from the digital and the conventional impression technique. The forty silicone replicas were cut in three sections; each section was evaluated in nine points. The measurement was carried out by using a measuring microscope and I-Soultion. Data from the silicone replica were analyzed and all tests were performed with α-level of 0.05. RESULTS 1. The average gaps of cast gold crowns fabricated from the digital impression technique were larger than those of the conventional impression technique significantly. 2. In marginal and internal axial gap of cast gold crowns, no statistical differences were found between the two impression techniques. 3. The internal occlusal gaps of cast gold crowns fabricated from the digital impression technique were larger than those of the conventional impression technique significantly. CONCLUSION Both prostheses presented clinically acceptable results with comparing the fit. The prostheses fabricated from the digital impression technique showed more gaps, in respect of occlusal surface. PMID:28243386

Electroless-plating technique for fabricating thin-wall convective heat-transfer models

NASA Technical Reports Server (NTRS)

Avery, D. E.; Ballard, G. K.; Wilson, M. L.

1984-01-01

A technique for fabricating uniform thin-wall metallic heat-transfer models and which simulates a Shuttle thermal protection system tile is described. Two 6- by 6- by 2.5-in. tiles were fabricated to obtain local heat transfer rates. The fabrication process is not limited to any particular geometry and results in a seamless thin-wall heat-transfer model which uses a one-wire thermocouple to obtain local cold-wall heat-transfer rates. The tile is relatively fragile because of the brittle nature of the material and the structural weakness of the flat-sided configuration; however, a method was developed and used for repairing a cracked tile.

Smart fabric sensors and e-textile technologies: a review

NASA Astrophysics Data System (ADS)

Castano, Lina M.; Flatau, Alison B.

2014-05-01

This paper provides a review of recent developments in the rapidly changing and advancing field of smart fabric sensor and electronic textile technologies. It summarizes the basic principles and approaches employed when building fabric sensors as well as the most commonly used materials and techniques used in electronic textiles. This paper shows that sensing functionality can be created by intrinsic and extrinsic modifications to textile substrates depending on the level of integration into the fabric platform. The current work demonstrates that fabric sensors can be tailored to measure force, pressure, chemicals, humidity and temperature variations. Materials, connectors, fabric circuits, interconnects, encapsulation and fabrication methods associated with fabric technologies prove to be customizable and versatile but less robust than their conventional electronics counterparts. The findings of this survey suggest that a complete smart fabric system is possible through the integration of the different types of textile based functional elements. This work intends to be a starting point for standardization of smart fabric sensing techniques and e-textile fabrication methods.

Highly efficient tandem organic light-emitting devices employing an easily fabricated charge generation unit

NASA Astrophysics Data System (ADS)

Yang, Huishan; Yu, Yaoyao; Wu, Lishuang; Qu, Biao; Lin, Wenyan; Yu, Ye; Wu, Zhijun; Xie, Wenfa

2018-02-01

We have realized highly efficient tandem organic light-emitting devices (OLEDs) employing an easily fabricated charge generation unit (CGU) combining 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile with ultrathin bilayers of CsN3 and Al. The charge generation and separation processes of the CGU have been demonstrated by studying the differences in the current density-voltage characteristics of external-carrier-excluding devices. At high luminances of 1000 and 10000 cd/m2, the current efficiencies of the phosphorescent tandem device are about 2.2- and 2.3-fold those of the corresponding single-unit device, respectively. Simultaneously, an efficient tandem white OLED exhibiting high color stability and warm white emission has also been fabricated.

Rapid Prototyping Technique for the Fabrication of Millifluidic Devices for Polymer Formulations

NASA Astrophysics Data System (ADS)

Cabral, Joao; Harrison, Christopher; Eric, Amis; Karim, Alamgir

2003-03-01

We describe a rapid prototyping technique for the fabrication of 600 micron deep fluidic channels in a solvent-resistant polymeric matrix. Using a conventional illumination source, a laser-jet printed mask, and a commercially available thioelene-based adhesive, we demonstrate the fabrication of fluidic channels which are impervious to a wide range of solvents. The fabrication of channels with this depth by conventional lithography would be both challenging and time-consuming. We demonstrate two lithography methods: one which fabricates channels sealed between glass plates (closed face) and one which fabricates structures on a single plate (open-faced). Furthermore, we demonstrate that this technology can be used to fabricate channels with a depth which varies linearly with distance. The latter is completely compatible with silicone replication technniques. Additionally, we demonstrate that siloxane-based elastomer molds of these channels can be readily made for aqueous applications. Applications to on-line phase mapping of polymer solutions (PEO-Water-Salt) and off line phase separation studies will be discussed.

Fabrication of fixed implant prostheses using function bite impression technique (FBI technique).

PubMed

Suzuki, Yasunori; Shimpo, Hidemasa; Ohkubo, Chikahiro; Kurtz, Kenneth S

2012-10-01

The patient was partially edentulous, lacking both the first mandibular molars. The FBI and the conventional impression technique were used for the fabrication of implant-fixed prosthesis replacing the right and left molars, respectively. In the FBI technique, the definitive impression was made under occlusal force and functionally generated path (FGP) recording at the same time. The right and left occlusal contact areas were compared after completing the implant-fixed prosthesis rehabilitation. It has been suggested that accuracy of the impression and maxillomandibular registration is necessary to ensure a satisfactory long-term clinical outcome. The transfer of the exact position of the implants to the working cast is even more important because implants lack the mobility of natural teeth. There are displacement differences between implants and natural teeth under occlusal force. The FBI technique may compensate for this difference in accuracy. Using the FBI technique, a precise prosthesis could be produced by completing simultaneously the maxillomandibular registration, impression and FGP. Copyright © 2012 Japan Prosthodontic Society. All rights reserved.

Method for Fabricating Composite Structures Including Continuous Press Forming and Pultrusion Processing

NASA Technical Reports Server (NTRS)

Farley, Gary L. (Inventor)

1995-01-01

A method for fabricating composite structures at a low-cost, moderate-to-high production rate is disclosed. A first embodiment of the method includes employing a continuous press forming fabrication process. A second embodiment of the method includes employing a pultrusion process for obtaining composite structures. The methods include coating yarns with matrix material, weaving the yarn into fabric to produce a continuous fabric supply, and feeding multiple layers of net-shaped fabrics having optimally oriented fibers into a debulking tool to form an undebulked preform. The continuous press forming fabrication process includes partially debulking the preform, cutting the partially debulked preform, and debulking the partially debulked preform to form a netshape. An electron-beam or similar technique then cures the structure. The pultrusion fabric process includes feeding the undebulked preform into a heated die and gradually debulking the undebulked preform. The undebulked preform in the heated die changes dimension until a desired cross-sectional dimension is achieved. This process further includes obtaining a net-shaped infiltrated uncured preform, cutting the uncured preform to a desired length, and electron-beam curing (or similar technique) the uncured preform. These fabrication methods produce superior structures formed at higher production rates, resulting in lower cost and high structural performance.

Fabrication of thorium bearing carbide fuels

DOEpatents

Gutierrez, Rueben L.; Herbst, Richard J.; Johnson, Karl W. R.

1981-01-01

Thorium-uranium carbide and thorium-plutonium carbide fuel pellets have been fabricated by the carbothermic reduction process. Temperatures of 1750.degree. C. and 2000.degree. C. were used during the reduction cycle. Sintering temperatures of 1800.degree. C. and 2000.degree. C. were used to prepare fuel pellet densities of 87% and >94% of theoretical, respectively. The process allows the fabrication of kilogram quantities of fuel with good reproducibility of chemicals and phase composition. Methods employing liquid techniques that form carbide microspheres or alloying-techniques which form alloys of thorium-uranium or thorium-plutonium suffer from limitation on the quantities processed of because of criticality concerns and lack of precise control of process conditions, respectively.

Fabric phase sorptive extraction: Two practical sample pretreatment techniques for brominated flame retardants in water.

PubMed

Huang, Guiqi; Dong, Sheying; Zhang, Mengfei; Zhang, Haihan; Huang, Tinglin

2016-09-15

Sample pretreatment is the critical section for residue monitoring of hazardous pollutants. In this paper, using the cellulose fabric as host matrix, three extraction sorbents such as poly (tetrahydrofuran) (PTHF), poly (ethylene glycol) (PEG) and poly (dimethyldiphenylsiloxane) (PDMDPS), were prepared on the surface of the cellulose fabric. Two practical extraction techniques including stir bar fabric phase sorptive extraction (stir bar-FPSE) and magnetic stir fabric phase sorptive extraction (magnetic stir-FPSE) have been designed, which allow stirring of fabric phase sorbent during the whole extraction process. In the meantime, three brominated flame retardants (BFRs) [tetrabromobisphenol A (TBBPA), tetrabromobisphenol A bisallylether (TBBPA-BAE), tetrabromobisphenol A bis(2,3-dibromopropyl)ether (TBBPA-BDBPE)] in the water sample were selected as model analytes for the practical evaluation of the proposed two techniques using high-performance liquid chromatography (HPLC). Moreover, various experimental conditions affecting extraction process such as the type of fabric phase, extraction time, the amount of salt and elution conditions were also investigated. Due to the large sorbent loading capacity and unique stirring performance, both techniques possessed high extraction capability and fast extraction equilibrium. Under the optimized conditions, high recoveries (90-99%) and low limits of detection (LODs) (0.01-0.05 μg L(-1)) were achieved. In addition, the reproducibility was obtained by evaluating the intraday and interday precisions with relative standard deviations (RSDs) less than 5.1% and 6.8%, respectively. The results indicated that two pretreatment techniques were promising and practical for monitoring of hazardous pollutants in the water sample. Due to low solvent consumption and high repeated use performance, proposed techniques also could meet green analytical criteria. Copyright © 2016 Elsevier Ltd. All rights reserved.

Fabrication of advanced electrochemical energy materials using sol-gel processing techniques

NASA Technical Reports Server (NTRS)

Chu, C. T.; Chu, Jay; Zheng, Haixing

1995-01-01

Advanced materials play an important role in electrochemical energy devices such as batteries, fuel cells, and electrochemical capacitors. They are being used as both electrodes and electrolytes. Sol-gel processing is a versatile solution technique used in fabrication of ceramic materials with tailored stoichiometry, microstructure, and properties. The application of sol-gel processing in the fabrication of advanced electrochemical energy materials will be presented. The potentials of sol-gel derived materials for electrochemical energy applications will be discussed along with some examples of successful applications. Sol-gel derived metal oxide electrode materials such as V2O5 cathodes have been demonstrated in solid-slate thin film batteries; solid electrolytes materials such as beta-alumina for advanced secondary batteries had been prepared by the sol-gel technique long time ago; and high surface area transition metal compounds for capacitive energy storage applications can also be synthesized with this method.

Combined fabrication technique for high-precision aspheric optical windows

NASA Astrophysics Data System (ADS)

Hu, Hao; Song, Ci; Xie, Xuhui

2016-07-01

Specifications made on optical components are becoming more and more stringent with the performance improvement of modern optical systems. These strict requirements not only involve low spatial frequency surface accuracy, mid-and-high spatial frequency surface errors, but also surface smoothness and so on. This presentation mainly focuses on the fabrication process for square aspheric window which combines accurate grinding, magnetorheological finishing (MRF) and smoothing polishing (SP). In order to remove the low spatial frequency surface errors and subsurface defects after accurate grinding, the deterministic polishing method MRF with high convergence and stable material removal rate is applied. Then the SP technology with pseudo-random path is adopted to eliminate the mid-and-high spatial frequency surface ripples and high slope errors which is the defect for MRF. Additionally, the coordinate measurement method and interferometry are combined in different phase. Acid-etched method and ion beam figuring (IBF) are also investigated on observing and reducing the subsurface defects. Actual fabrication result indicates that the combined fabrication technique can lead to high machining efficiency on manufaturing the high-precision and high-quality optical aspheric windows.

Fabrication of composite propfan blades for a cruise missile wind tunnel model

NASA Technical Reports Server (NTRS)

Fite, E. Brian

1993-01-01

This report outlines the procedures that were employed in fabricating prototype graphite-epoxy composite prop fan blades. These blades were used in wind tunnel tests that investigated prop fan propulsion system interactions with a missile airframe in order to study the feasibility of an advanced-technology-propfan-propelled missile. Major phases of the blade fabrication presented include machining of the master blade, mold fabrication, ply cutting and assembly, blade curing, and quality assurance. Specifically, four separate designs were fabricated, 18 blades of each geometry, using the same fabrication technique for each design.

High T(sub c) superconductors fabricated by plasma aerosol mist deposition technique

NASA Technical Reports Server (NTRS)

Wang, X. W.; Vuong, K. D.; Leone, A.; Shen, C. Q.; Williams, J.; Coy, M.

1995-01-01

We report new results on high T(sub c) superconductors fabricated by a plasma aerosol mist deposition technique, in atmospheric environment. Materials fabricated are YBaCuO, BiPbSrCaCuO, BaCaCuO precursor films for TlBaCaCuO, and other buffers such as YSZ. Depending on processing conditions, sizes of crystallites and/or particles are between dozens of nano-meters and several micrometers. Superconductive properties and other material characteristics can also be tailored.

The longitudinal offset technique for apodization of coupled resonator optical waveguide devices: concept and fabrication tolerance analysis.

PubMed

Doménech, José David; Muñoz, Pascual; Capmany, José

2009-11-09

In this paper, a novel technique to set the coupling constant between cells of a coupled resonator optical waveguide (CROW) device, in order to tailor the filter response, is presented. The technique is demonstrated by simulation assuming a racetrack ring resonator geometry. It consists on changing the effective length of the coupling section by applying a longitudinal offset between the resonators. On the contrary, the conventional techniques are based in the transversal change of the distance between the ring resonators, in steps that are commonly below the current fabrication resolution step (nm scale), leading to strong restrictions in the designs. The proposed longitudinal offset technique allows a more precise control of the coupling and presents an increased robustness against the fabrication limitations, since the needed resolution step is two orders of magnitude higher. Both techniques are compared in terms of the transmission esponse of CROW devices, under finite fabrication resolution steps.

Comparison of quartz crystallographic preferred orientations identified with optical fabric analysis, electron backscatter and neutron diffraction techniques.

PubMed

Hunter, N J R; Wilson, C J L; Luzin, V

2017-02-01

Three techniques are used to measure crystallographic preferred orientations (CPO) in a naturally deformed quartz mylonite: transmitted light cross-polarized microscopy using an automated fabric analyser, electron backscatter diffraction (EBSD) and neutron diffraction. Pole figure densities attributable to crystal-plastic deformation are variably recognizable across the techniques, particularly between fabric analyser and diffraction instruments. Although fabric analyser techniques offer rapid acquisition with minimal sample preparation, difficulties may exist when gathering orientation data parallel with the incident beam. Overall, we have found that EBSD and fabric analyser techniques are best suited for studying CPO distributions at the grain scale, where individual orientations can be linked to their source grain or nearest neighbours. Neutron diffraction serves as the best qualitative and quantitative means of estimating the bulk CPO, due to its three-dimensional data acquisition, greater sample area coverage, and larger sample size. However, a number of sampling methods can be applied to FA and EBSD data to make similar approximations. © 2016 The Authors Journal of Microscopy © 2016 Royal Microscopical Society.

Comparison of denture tooth movement between CAD-CAM and conventional fabrication techniques.

PubMed

Goodacre, Brian J; Goodacre, Charles J; Baba, Nadim Z; Kattadiyil, Mathew T

2018-01-01

Data comparing the denture tooth movement of computer-aided design and computer-aided manufacturing (CAD-CAM) and conventional denture processing techniques are lacking. The purpose of this in vitro study was to compare the denture tooth movement of pack-and-press, fluid resin, injection, CAD-CAM-bonded, and CAD-CAM monolithic techniques for fabricating dentures to determine which process produces the most accurate and reproducible prosthesis. A total of 50 dentures were evaluated, 10 for each of the 5 groups. A master denture was fabricated and milled from prepolymerized poly(methyl methacrylate). For the conventional processing techniques (pack-and-press, fluid resin, and injection) a polyvinyl siloxane putty mold of the master denture was made in which denture teeth were placed and molten wax injected. The cameo surface of each wax-festooned denture was laser scanned, resulting in a standard tessellation language (STL) format file. The CAD-CAM dentures included 2 subgroups: CAD-CAM-bonded teeth in which the denture teeth were bonded into the milled denture base and CAD-CAM monolithic teeth in which the denture teeth were milled as part of the denture base. After all specimens had been fabricated, they were hydrated for 24 hours, and the cameo surface laser scanned. The preprocessing and postprocessing scan files of each denture were superimposed using surface-matching software. Measurements were made at 64 locations, allowing evaluation of denture tooth movement in a buccal, lingual, mesial-distal, and occlusal direction. The use of median and interquartile range values was used to assess accuracy and reproducibility. Levene and Kruskal-Wallis analyses of variance were used to evaluate differences between processing techniques (α=.05). The CAD-CAM monolithic technique was the most accurate, followed by fluid resin, CAD-CAM-bonded, pack-and-press, and injection. CAD-CAM monolithic technique was the most reproducible, followed by pack-and-press, CAD

Microfluidic-based photocatalytic microreactor for environmental application: a review of fabrication substrates and techniques, and operating parameters.

PubMed

Das, Susmita; Srivastava, Vimal Chandra

2016-06-08

Photochemical technology with microfluidics is emerging as a new platform in environmental science. Microfluidic technology has various advantages, like better mixing and a shorter diffusion distance for the reactants and products; and uniform distribution of light on the photocatalyst. Depending on the material type and related applications, several fabrication techniques have been adopted by various researchers. Microreactors have been prepared by various techniques, such as lithography, etching, mechanical microcutting technology, etc. Lithography can be classified into photolithography, soft lithography and X-ray lithography techniques whereas the etching process is divided into wet etching (chemical etching) and dry etching (plasma etching) techniques. Several substrates, like polymers, such as polydimethyl-siloxane (PDMS), polymethyle-methacrylate (PMMA), hydrogel, etc.; metals, such as stainless steel, titanium foil, etc.; glass, such as silica capillary, glass slide, etc.; and ceramics have been used for microchannel fabrication. During degradation in a microreactor, the degradation efficiency is affected by few important parameters such as flow rate, initial concentration of the target compound, microreactor dimensions, light intensity, photocatalyst structure and catalyst support. The present paper discusses and critically reviews fabrication techniques and substrates used for microchannel fabrication and critical operating parameters for organics, especially dye degradation in the microreactor. The kinetics of degradation has also been discussed.

Evaluation of Three Different Processing Techniques in the Fabrication of Complete Dentures.

PubMed

Chintalacheruvu, Vamsi Krishna; Balraj, Rajasekaran Uttukuli; Putchala, Lavanya Sireesha; Pachalla, Sreelekha

2017-06-01

The objective of the present study is to compare the effectiveness of three different processing techniques and to find out the accuracy of processing techniques through number of occlusal interferences and increase in vertical dimension after denture processing. A cross-sectional study was conducted on a sample of 18 patients indicated for complete denture fabrication was selected for the study and they were divided into three subgroups. Three processing techniques, compression molding and injection molding using prepolymerized resin and unpolymerized resin, were used to fabricate dentures for each of the groups. After processing, laboratory-remounted dentures were evaluated for number of occlusal interferences in centric and eccentric relations and change in vertical dimension through vertical pin rise in articulator. Data were analyzed using statistical test ANOVA and SPSS software version 19.0 by IBM was used. Data obtained from three groups were subjected to one-way ANOVA test. After ANOVA test, results with significant variations were subjected to post hoc test. Number of occlusal interferences with compression molding technique was reported to be more in both centric and eccentric positions as compared to the two injection molding techniques with statistical significance in centric, protrusive, right lateral nonworking, and left lateral working positions ( P < 0.05). Mean vertical pin rise (0.52 mm) was reported to more in compression molding technique as compared to injection molding techniques, which is statistically significant ( P < 0.001). Within the limitations of this study, injection molding techniques exhibited less processing errors as compared to compression molding technique with statistical significance. There was no statistically significant difference in processing errors reported within two injection molding systems.

Fabrication of single domain GdBCO bulk superconductors by a new modified TSIG technique

NASA Astrophysics Data System (ADS)

Yang, W. M.; Zhi, X.; Chen, S. L.; Wang, M.; Li, J. W.; Ma, J.; Chao, X. X.

2014-01-01

Single domain GdBCO bulk superconductors have been fabricated with new and traditional solid phases by a top seeded infiltration and growth (TSIG) process technique. In the conventional TSIG process, three types of powders, such as Gd2BaCuO5, GdBa2Cu3O7-x and Ba3Cu5O8, must be prepared, but in our new modified TSIG technique, only BaCuO2 powders are required during the fabrication of the single domain GdBCO bulk superconductors. The solid phase used in the conventional process is Gd2BaCuO5 instead of the solid phase (Gd2O3 + BaCuO2) utilized in the new process. The liquid phase used in the conventional process is a mixture of (GdBa2Cu3O7-x + Ba3Cu5O8), and the liquid phase in the new process is a mixture of (Gd2O3 + 10BaCuO2 + 6CuO). Single domain GdBCO bulk superconductors have been fabricated with the new solid and liquid phases. The levitation force of the GdBCO bulk samples fabricated by the new solid phase is 28 N, which is slightly higher than that of the samples fabricated using the conventional solid phases (26 N). The microstructure and the levitation force of the samples indicate that this new method can greatly simplify the fabrication process, introduce nanometer-sized flux centers, improve the levitation force and working efficiency, and greatly reduce the cost of fabrication of single domain GdBCO bulk superconductors by the TSIG process.

Marginal adaptation and CAD-CAM technology: A systematic review of restorative material and fabrication techniques.

PubMed

Papadiochou, Sofia; Pissiotis, Argirios L

2018-04-01

The comparative assessment of computer-aided design and computer-aided manufacturing (CAD-CAM) technology and other fabrication techniques pertaining to marginal adaptation should be documented. Limited evidence exists on the effect of restorative material on the performance of a CAD-CAM system relative to marginal adaptation. The purpose of this systematic review was to investigate whether the marginal adaptation of CAD-CAM single crowns, fixed dental prostheses, and implant-retained fixed dental prostheses or their infrastructures differs from that obtained by other fabrication techniques using a similar restorative material and whether it depends on the type of restorative material. An electronic search of English-language literature published between January 1, 2000, and June 30, 2016, was conducted of the Medline/PubMed database. Of the 55 included comparative studies, 28 compared CAD-CAM technology with conventional fabrication techniques, 12 contrasted CAD-CAM technology and copy milling, 4 compared CAD-CAM milling with direct metal laser sintering (DMLS), and 22 investigated the performance of a CAD-CAM system regarding marginal adaptation in restorations/infrastructures produced with different restorative materials. Most of the CAD-CAM restorations/infrastructures were within the clinically acceptable marginal discrepancy (MD) range. The performance of a CAD-CAM system relative to marginal adaptation is influenced by the restorative material. Compared with CAD-CAM, most of the heat-pressed lithium disilicate crowns displayed equal or smaller MD values. Slip-casting crowns exhibited similar or better marginal accuracy than those fabricated with CAD-CAM. Cobalt-chromium and titanium implant infrastructures produced using a CAD-CAM system elicited smaller MD values than zirconia. The majority of cobalt-chromium restorations/infrastructures produced by DMLS displayed better marginal accuracy than those fabricated with the casting technique. Compared with copy

Method of fabricating porous silicon carbide (SiC)

NASA Technical Reports Server (NTRS)

Shor, Joseph S. (Inventor); Kurtz, Anthony D. (Inventor)

1995-01-01

Porous silicon carbide is fabricated according to techniques which result in a significant portion of nanocrystallites within the material in a sub 10 nanometer regime. There is described techniques for passivating porous silicon carbide which result in the fabrication of optoelectronic devices which exhibit brighter blue luminescence and exhibit improved qualities. Based on certain of the techniques described porous silicon carbide is used as a sacrificial layer for the patterning of silicon carbide. Porous silicon carbide is then removed from the bulk substrate by oxidation and other methods. The techniques described employ a two-step process which is used to pattern bulk silicon carbide where selected areas of the wafer are then made porous and then the porous layer is subsequently removed. The process to form porous silicon carbide exhibits dopant selectivity and a two-step etching procedure is implemented for silicon carbide multilayers.

Characterization of Natural Dyes and Traditional Korean Silk Fabric by Surface Analytical Techniques.

PubMed

Lee, Jihye; Kang, Min Hwa; Lee, Kang-Bong; Lee, Yeonhee

2013-05-15

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) and X-ray photoelectron spectroscopy (XPS) are well established surface techniques that provide both elemental and organic information from several monolayers of a sample surface, while also allowing depth profiling or image mapping to be carried out. The static TOF-SIMS with improved performances has expanded the application of TOF-SIMS to the study of a variety of organic, polymeric and biological materials. In this work, TOF-SIMS, XPS and Fourier Transform Infrared (FTIR) measurements were used to characterize commercial natural dyes and traditional silk fabric dyed with plant extracts dyes avoiding the time-consuming and destructive extraction procedures necessary for the spectrophotometric and chromatographic methods previously used. Silk textiles dyed with plant extracts were then analyzed for chemical and functional group identification of their dye components and mordants. TOF-SIMS spectra for the dyed silk fabric showed element ions from metallic mordants, specific fragment ions and molecular ions from plant-extracted dyes. The results of TOF-SIMS, XPS and FTIR are very useful as a reference database for comparison with data about traditional Korean silk fabric and to provide an understanding of traditional dyeing materials. Therefore, this study shows that surface techniques are useful for micro-destructive analysis of plant-extracted dyes and Korean dyed silk fabric.

Characterization of Natural Dyes and Traditional Korean Silk Fabric by Surface Analytical Techniques

PubMed Central

Lee, Jihye; Kang, Min Hwa; Lee, Kang-Bong; Lee, Yeonhee

2013-01-01

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) and X-ray photoelectron spectroscopy (XPS) are well established surface techniques that provide both elemental and organic information from several monolayers of a sample surface, while also allowing depth profiling or image mapping to be carried out. The static TOF-SIMS with improved performances has expanded the application of TOF-SIMS to the study of a variety of organic, polymeric and biological materials. In this work, TOF-SIMS, XPS and Fourier Transform Infrared (FTIR) measurements were used to characterize commercial natural dyes and traditional silk fabric dyed with plant extracts dyes avoiding the time-consuming and destructive extraction procedures necessary for the spectrophotometric and chromatographic methods previously used. Silk textiles dyed with plant extracts were then analyzed for chemical and functional group identification of their dye components and mordants. TOF-SIMS spectra for the dyed silk fabric showed element ions from metallic mordants, specific fragment ions and molecular ions from plant-extracted dyes. The results of TOF-SIMS, XPS and FTIR are very useful as a reference database for comparison with data about traditional Korean silk fabric and to provide an understanding of traditional dyeing materials. Therefore, this study shows that surface techniques are useful for micro-destructive analysis of plant-extracted dyes and Korean dyed silk fabric. PMID:28809257

Fabrication of channeled scaffolds with ordered array of micro-pores through microsphere leaching and indirect Rapid Prototyping technique.

PubMed

Tan, J Y; Chua, C K; Leong, K F

2013-02-01

Advanced scaffold fabrication techniques such as Rapid Prototyping (RP) are generally recognized to be advantageous over conventional fabrication methods in terms architectural control and reproducibility. Yet, most RP techniques tend to suffer from resolution limitations which result in scaffolds with uncontrollable, random-size pores and low porosity, albeit having interconnected channels which is characteristically present in most RP scaffolds. With the increasing number of studies demonstrating the profound influences of scaffold pore architecture on cell behavior and overall tissue growth, a scaffold fabrication method with sufficient architectural control becomes imperative. The present study demonstrates the use of RP fabrication techniques to create scaffolds having interconnected channels as well as controllable micro-size pores. Adopted from the concepts of porogen leaching and indirect RP techniques, the proposed fabrication method uses monodisperse microspheres to create an ordered, hexagonal closed packed (HCP) array of micro-pores that surrounds the existing channels of the RP scaffold. The pore structure of the scaffold is shaped using a single sacrificial construct which comprises the microspheres and a dissolvable RP mold that were sintered together. As such, the size of pores as well as the channel configuration of the scaffold can be tailored based on the design of the RP mold and the size of microspheres used. The fabrication method developed in this work can be a promising alternative way of preparing scaffolds with customized pore structures that may be required for specific studies concerning cell-scaffold interactions.

Evaluation of Three Different Processing Techniques in the Fabrication of Complete Dentures

PubMed Central

Chintalacheruvu, Vamsi Krishna; Balraj, Rajasekaran Uttukuli; Putchala, Lavanya Sireesha; Pachalla, Sreelekha

2017-01-01

Aims and Objectives: The objective of the present study is to compare the effectiveness of three different processing techniques and to find out the accuracy of processing techniques through number of occlusal interferences and increase in vertical dimension after denture processing. Materials and Methods: A cross-sectional study was conducted on a sample of 18 patients indicated for complete denture fabrication was selected for the study and they were divided into three subgroups. Three processing techniques, compression molding and injection molding using prepolymerized resin and unpolymerized resin, were used to fabricate dentures for each of the groups. After processing, laboratory-remounted dentures were evaluated for number of occlusal interferences in centric and eccentric relations and change in vertical dimension through vertical pin rise in articulator. Data were analyzed using statistical test ANOVA and SPSS software version 19.0 by IBM was used. Results: Data obtained from three groups were subjected to one-way ANOVA test. After ANOVA test, results with significant variations were subjected to post hoc test. Number of occlusal interferences with compression molding technique was reported to be more in both centric and eccentric positions as compared to the two injection molding techniques with statistical significance in centric, protrusive, right lateral nonworking, and left lateral working positions (P < 0.05). Mean vertical pin rise (0.52 mm) was reported to more in compression molding technique as compared to injection molding techniques, which is statistically significant (P < 0.001). Conclusions: Within the limitations of this study, injection molding techniques exhibited less processing errors as compared to compression molding technique with statistical significance. There was no statistically significant difference in processing errors reported within two injection molding systems. PMID:28713763

A TEMPLATE-BASED FABRICATION TECHNIQUE FOR SPATIALLY-DESIGNED POLYMER MICRO/NANOFIBER COMPOSITES

PubMed Central

Naik, Nisarga; Caves, Jeff; Kumar, Vivek; Chaikof, Elliot; Allen, Mark G.

2013-01-01

This paper reports a template-based technique for the fabrication of polymer micro/nanofiber composites, exercising control over the fiber dimensions and alignment. Unlike conventional spinning-based methods of fiber production, the presented approach is based on micro-transfer molding. It is a parallel processing technique capable of producing fibers with control over both in-plane and out-of-plane geometries, in addition to packing density and layout of the fibers. Collagen has been used as a test polymer to demonstrate the concept. Hollow and solid collagen fibers with various spatial layouts have been fabricated. Produced fibers have widths ranging from 2 µm to 50 µm, and fiber thicknesses ranging from 300 nm to 3 µm. Also, three-dimensionality of the process has been demonstrated by producing in-plane serpentine fibers with designed arc lengths, out-of-plane wavy fibers, fibers with focalized particle encapsulation, and porous fibers with desired periodicity and pore sizes. PMID:24533428

A Novel Bio-carrier Fabricated Using 3D Printing Technique for Wastewater Treatment

PubMed Central

Dong, Yang; Fan, Shu-Qian; Shen, Yu; Yang, Ji-Xiang; Yan, Peng; Chen, You-Peng; Li, Jing; Guo, Jin-Song; Duan, Xuan-Ming; Fang, Fang; Liu, Shao-Yang

2015-01-01

The structure of bio-carriers is one of the key operational characteristics of a biofilm reactor. The goal of this study is to develop a series of novel fullerene-type bio-carriers using the three-dimensional printing (3DP) technique. 3DP can fabricate bio-carriers with more specialized structures compared with traditional fabrication processes. In this research, three types of fullerene-type bio-carriers were fabricated using the 3DP technique and then compared with bio-carrier K3 (from AnoxKaldnes) in the areas of physicochemical properties and biofilm growth. Images acquired by 3D profiling and SEM indicated that the surface roughness of the 3DP bio-carrier was greater than that of K3. Furthermore, contact angle data indicated that the 3DP bio-carriers were more hydrophilic than K3. The biofilm on the 3DP bio-carriers exhibited higher microbial activity and stronger adhesion ability. These findings were attributed to excellent mass transfer of the substrate (and oxygen) between the vapour-liquid-solid tri-phase system and to the surface characteristics. It is concluded that the novel 3DP fullerene-type bio-carriers are ideal carriers for biofilm adherence and growth. PMID:26202477

A Novel Bio-carrier Fabricated Using 3D Printing Technique for Wastewater Treatment.

PubMed

Dong, Yang; Fan, Shu-Qian; Shen, Yu; Yang, Ji-Xiang; Yan, Peng; Chen, You-Peng; Li, Jing; Guo, Jin-Song; Duan, Xuan-Ming; Fang, Fang; Liu, Shao-Yang

2015-07-23

The structure of bio-carriers is one of the key operational characteristics of a biofilm reactor. The goal of this study is to develop a series of novel fullerene-type bio-carriers using the three-dimensional printing (3DP) technique. 3DP can fabricate bio-carriers with more specialized structures compared with traditional fabrication processes. In this research, three types of fullerene-type bio-carriers were fabricated using the 3DP technique and then compared with bio-carrier K3 (from AnoxKaldnes) in the areas of physicochemical properties and biofilm growth. Images acquired by 3D profiling and SEM indicated that the surface roughness of the 3DP bio-carrier was greater than that of K3. Furthermore, contact angle data indicated that the 3DP bio-carriers were more hydrophilic than K3. The biofilm on the 3DP bio-carriers exhibited higher microbial activity and stronger adhesion ability. These findings were attributed to excellent mass transfer of the substrate (and oxygen) between the vapour-liquid-solid tri-phase system and to the surface characteristics. It is concluded that the novel 3DP fullerene-type bio-carriers are ideal carriers for biofilm adherence and growth.

Pedagogical Techniques Employed by the Television Show "MythBusters"

ERIC Educational Resources Information Center

Zavrel, Erik

2016-01-01

"MythBusters," the long-running though recently discontinued Discovery Channel science entertainment television program, has proven itself to be far more than just a highly rated show. While its focus is on entertainment, the show employs an array of pedagogical techniques to communicate scientific concepts to its audience. These…

Method of fabricating reflection-mode EUV diffraction elements

DOEpatents

Naulleau, Patrick P.

2002-01-01

Techniques for fabricating a well-controlled, quantized-level, engineered surface that serves as substrates for EUV reflection multilayer overcomes problems associated with the fabrication of reflective EUV diffraction elements. The technique when employed to fabricate an EUV diffraction element that includes the steps of: (a) forming an etch stack comprising alternating layers of first and second materials on a substrate surface where the two material can provide relative etch selectivity; (b) creating a relief profile in the etch stack wherein the relief profile has a defined contour; and (c) depositing a multilayer reflection film over the relief profile wherein the film has an outer contour that substantially matches that of the relief profile. For a typical EUV multilayer, if the features on the substrate are larger than 50 nm, the multilayer will be conformal to the substrate. Thus, the phase imparted to the reflected wavefront will closely match that geometrically set by the surface height profile.

Adhesion of perfume-filled microcapsules to model fabric surfaces.

PubMed

He, Yanping; Bowen, James; Andrews, James W; Liu, Min; Smets, Johan; Zhang, Zhibing

2014-01-01

The retention and adhesion of melamine formaldehyde (MF) microcapsules on a model fabric surface in aqueous solution were investigated using a customised flow chamber technique and atomic force microscopy (AFM). A cellulose film was employed as a model fabric surface. Modification of the cellulose with chitosan was found to increase the retention and adhesion of microcapsules on the model fabric surface. The AFM force-displacement data reveal that bridging forces resulting from the extension of cellulose chains dominate the adhesion between the microcapsule and the unmodified cellulose film, whereas electrostatic attraction helps the microcapsules adhere to the chitosan-modified cellulose film. The correlation between results obtained using these two complementary techniques suggests that the flow chamber device can be potentially used for rapid screening of the effect of chemical modification on the adhesion of microparticles to surfaces, reducing the time required to achieve an optimal formulation.

Fabrication of superconducting MgB2 nanostructures by an electron beam lithography-based technique

NASA Astrophysics Data System (ADS)

Portesi, C.; Borini, S.; Amato, G.; Monticone, E.

2006-03-01

In this work, we present the results obtained in fabrication and characterization of magnesium diboride nanowires realized by an electron beam lithography (EBL)-based method. For fabricating MgB2 thin films, an all in situ technique has been used, based on the coevaporation of B and Mg by means of an e-gun and a resistive heater, respectively. Since the high temperatures required for the fabrication of good quality MgB2 thin films do not allow the nanostructuring approach based on the lift-off technique, we structured the samples combining EBL, optical lithography, and Ar milling. In this way, reproducible nanowires 1 μm long have been obtained. To illustrate the impact of the MgB2 film processing on its superconducting properties, we measured the temperature dependence of the resistance on a nanowire and compared it to the original magnesium diboride film. The electrical properties of the films are not degraded as a consequence of the nanostructuring process, so that superconducting nanodevices may be obtained by this method.

EML Array fabricated by SAG technique monolithically integrated with a buried ridge AWG multiplexer

NASA Astrophysics Data System (ADS)

Xu, Junjie; Liang, Song; Zhang, Zhike; An, Junming; Zhu, Hongliang; Wang, Wei

2017-06-01

We report the fabrication of a ten channel electroabsorption modulated DFB laser (EML) array. Different emission wavelengths of the laser array are obtained by selective area growth (SAG) technique, which is also used for the integration of electroabsorption modulators (EAM) with the lasers. An arrayed waveguide grating (AWG) combiner is integrated monolithically with the laser array by butt-joint regrowth (BJR) technique. A buried ridge waveguide structure is adopted for the AWG combiner. A self aligned fabrication procedure is adopted for the fabrication of the waveguide structure of the device to eliminate the misalignment between the laser active waveguide and the passive waveguide. A Ti thin film heater is integrated for each laser in the array. With the help of the heaters, ten laser emissions with 1.8 nm channel spacing are obtained. The integrated EAM has a larger than 11 dB static extinction ratios and larger than 8 GHz small signal modulation bandwidths. The light power collected in the output waveguide of the AWG is larger than -13 dBm for each wavelength.

Low cost batch fabrication of microdevices using ultraviolet light-emitting diode photolithography technique

NASA Astrophysics Data System (ADS)

Lee, Neam Heng; Swamy, Varghese; Ramakrishnan, Narayanan

2016-01-01

Solid-state technology has enabled the use of light-emitting diodes (LEDs) in lithography systems due to their low cost, low power requirement, and higher efficiency relative to the traditional mercury lamp. Uniform irradiance distribution is essential for photolithography to ensure the critical dimension (CD) of the feature fabricated. However, light illuminated from arrays of LEDs can have nonuniform irradiance distribution, which can be a problem when using LED arrays as a source to batch-fabricate multiple devices on a large wafer piece. In this study, the irradiance distribution of an UV LED array was analyzed, and the separation distance between light source and mask optimized to obtain maximum irradiance uniformity without the use of a complex lens. Further, employing a diffuser glass enhanced the fabrication process and the CD loss was minimized to an average of 300 nm. To assess the performance of the proposed technology, batch fabrication of surface acoustic wave devices on lithium niobate substrate was carried out, and all the devices exhibited identical insertion loss of -18 dB at a resonance frequency of 39.33 MHz. The proposed low-cost UV lithography setup can be adapted in academic laboratories for research and teaching on microdevices.

A review of computer-aided design/computer-aided manufacture techniques for removable denture fabrication.

PubMed

Bilgin, Mehmet Selim; Baytaroğlu, Ebru Nur; Erdem, Ali; Dilber, Erhan

2016-01-01

The aim of this review was to investigate usage of computer-aided design/computer-aided manufacture (CAD/CAM) such as milling and rapid prototyping (RP) technologies for removable denture fabrication. An electronic search was conducted in the PubMed/MEDLINE, ScienceDirect, Google Scholar, and Web of Science databases. Databases were searched from 1987 to 2014. The search was performed using a variety of keywords including CAD/CAM, complete/partial dentures, RP, rapid manufacturing, digitally designed, milled, computerized, and machined. The identified developments (in chronological order), techniques, advantages, and disadvantages of CAD/CAM and RP for removable denture fabrication are summarized. Using a variety of keywords and aiming to find the topic, 78 publications were initially searched. For the main topic, the abstract of these 78 articles were scanned, and 52 publications were selected for reading in detail. Full-text of these articles was gained and searched in detail. Totally, 40 articles that discussed the techniques, advantages, and disadvantages of CAD/CAM and RP for removable denture fabrication and the articles were incorporated in this review. Totally, 16 of the papers summarized in the table. Following review of all relevant publications, it can be concluded that current innovations and technological developments of CAD/CAM and RP allow the digitally planning and manufacturing of removable dentures from start to finish. As a result according to the literature review CAD/CAM techniques and supportive maxillomandibular relationship transfer devices are growing fast. In the close future, fabricating removable dentures will become medical informatics instead of needing a technical staff and procedures. However the methods have several limitations for now.

A review of computer-aided design/computer-aided manufacture techniques for removable denture fabrication

PubMed Central

Bilgin, Mehmet Selim; Baytaroğlu, Ebru Nur; Erdem, Ali; Dilber, Erhan

2016-01-01

The aim of this review was to investigate usage of computer-aided design/computer-aided manufacture (CAD/CAM) such as milling and rapid prototyping (RP) technologies for removable denture fabrication. An electronic search was conducted in the PubMed/MEDLINE, ScienceDirect, Google Scholar, and Web of Science databases. Databases were searched from 1987 to 2014. The search was performed using a variety of keywords including CAD/CAM, complete/partial dentures, RP, rapid manufacturing, digitally designed, milled, computerized, and machined. The identified developments (in chronological order), techniques, advantages, and disadvantages of CAD/CAM and RP for removable denture fabrication are summarized. Using a variety of keywords and aiming to find the topic, 78 publications were initially searched. For the main topic, the abstract of these 78 articles were scanned, and 52 publications were selected for reading in detail. Full-text of these articles was gained and searched in detail. Totally, 40 articles that discussed the techniques, advantages, and disadvantages of CAD/CAM and RP for removable denture fabrication and the articles were incorporated in this review. Totally, 16 of the papers summarized in the table. Following review of all relevant publications, it can be concluded that current innovations and technological developments of CAD/CAM and RP allow the digitally planning and manufacturing of removable dentures from start to finish. As a result according to the literature review CAD/CAM techniques and supportive maxillomandibular relationship transfer devices are growing fast. In the close future, fabricating removable dentures will become medical informatics instead of needing a technical staff and procedures. However the methods have several limitations for now. PMID:27095912

Nanoscale fabrication using single-ion impacts

NASA Astrophysics Data System (ADS)

Millar, Victoria; Pakes, Chris I.; Cimmino, Alberto; Brett, David; Jamieson, David N.; Prawer, Steven D.; Yang, Changyi; Rout, Bidhudutta; McKinnon, Rita P.; Dzurak, Andrew S.; Clark, Robert G.

2001-11-01

We describe a novel technique for the fabrication of nanoscale structures, based on the development of localized chemical modification caused in a PMMA resist by the implantation of single ions. The implantation of 2 MeV He ions through a thin layer of PMMA into an underlying silicon substrate causes latent damage in the resist. On development of the resist we demonstrate the formation within the PMMA layer of clearly defined etched holes, of typical diameter 30 nm, observed using an atomic force microscope employing a carbon nanotube SPM probe in intermittent-contact mode. This technique has significant potential applications. Used purely to register the passage of an ion, it may be a useful verification of the impact sites in an ion-beam modification process operating at the single-ion level. Furthermore, making use of the hole in the PMMA layer to perform subsequent fabrication steps, it may be applied to the fabrication of self-aligned structures in which surface features are fabricated directly above regions of an underlying substrate that are locally doped by the implanted ion. Our primary interest in single-ion resists relates to the development of a solid-state quantum computer based on an array of 31P atoms (which act as qubits) embedded with nanoscale precision in a silicon matrix. One proposal for the fabrication of such an array is by phosphorous-ion implantation. A single-ion resist would permit an accurate verification of 31P implantation sites. Subsequent metalisation of the latent damage may allow the fabrication of self-aligned metal gates above buried phosphorous atoms.

Fabrication techniques for superconducting readout loops

NASA Technical Reports Server (NTRS)

Payne, J. E.

1982-01-01

Procedures for the fabrication of superconducting readout loops out of niobium on glass substrates were developed. A computer program for an existing fabrication system was developed. Both positive and negative resist procedures for the production of the readout loops were investigated. Methods used to produce satisfactory loops are described and the various parameters affecting the performance of the loops are analyzed.

Fatigue Life of Titanium Alloys Fabricated by Additive Layer Manufacturing Techniques for Dental Implants

NASA Astrophysics Data System (ADS)

Chan, Kwai S.; Koike, Marie; Mason, Robert L.; Okabe, Toru

2013-02-01

Additive layer deposition techniques such as electron beam melting (EBM) and laser beam melting (LBM) have been utilized to fabricate rectangular plates of Ti-6Al-4V with extra low interstitial (ELI) contents. The layer-by-layer deposition techniques resulted in plates that have different surface finishes which can impact significantly on the fatigue life by providing potential sites for fatigue cracks to initiate. The fatigue life of Ti-6Al-4V ELI alloys fabricated by EBM and LBM deposition techniques was investigated by three-point testing of rectangular beams of as-fabricated and electro-discharge machined surfaces under stress-controlled conditions at 10 Hz until complete fracture. Fatigue life tests were also performed on rolled plates of Ti-6Al-4V ELI, regular Ti-6Al-4V, and CP Ti as controls. Fatigue surfaces were characterized by scanning electron microscopy to identify the crack initiation site in the various types of specimen surfaces. The fatigue life data were analyzed statistically using both analysis of variance techniques and the Kaplan-Meier survival analysis method with the Gehan-Breslow test. The results indicate that the LBM Ti-6Al-4V ELI material exhibits a longer fatigue life than the EBM counterpart and CP Ti, but a shorter fatigue life compared to rolled Ti-6Al-4V ELI. The difference in the fatigue life behavior may be largely attributed to the presence of rough surface features that act as fatigue crack initiation sites in the EBM material.

Modified Powder-in-Tube Technique Based on the Consolidation Processing of Powder Materials for Fabricating Specialty Optical Fibers

PubMed Central

Auguste, Jean-Louis; Humbert, Georges; Leparmentier, Stéphanie; Kudinova, Maryna; Martin, Pierre-Olivier; Delaizir, Gaëlle; Schuster, Kay; Litzkendorf, Doris

2014-01-01

The objective of this paper is to demonstrate the interest of a consolidation process associated with the powder-in-tube technique in order to fabricate a long length of specialty optical fibers. This so-called Modified Powder-in-Tube (MPIT) process is very flexible and paves the way to multimaterial optical fiber fabrications with different core and cladding glassy materials. Another feature of this technique lies in the sintering of the preform under reducing or oxidizing atmosphere. The fabrication of such optical fibers implies different constraints that we have to deal with, namely chemical species diffusion or mechanical stress due to the mismatches between thermal expansion coefficients and working temperatures of the fiber materials. This paper focuses on preliminary results obtained with a lanthano-aluminosilicate glass used as the core material for the fabrication of all-glass fibers or specialty Photonic Crystal Fibers (PCFs). To complete the panel of original microstructures now available by the MPIT technique, we also present several optical fibers in which metallic particles or microwires are included into a silica-based matrix. PMID:28788176

A Comparison of Fabrication Techniques for Hollow Retroreflectors

NASA Technical Reports Server (NTRS)

Preston, Alix; Merkowitz, Stephen

2014-01-01

Despite the wide usage of hollow retroreflectors, there is limited literature involving their fabrication techniques and only two documented construction methods could be found. One consists of an adjustable fixture that allows for the independent alignment of each mirror, while the other consists of a modified solid retroreflector that is used as a mandrel. Although both methods were shown to produce hollow retroreflectors with arcsecond dihedral angle errors, a comparison and analysis of each method could not be found which makes it difficult to ascertain which method would be better suited to use for precision-aligned retroreflectors. Although epoxy bonding is generally the preferred method to adhere the three mirrors, a relatively new method known as hydroxide-catalysis bonding (HCB) presents several potential advantages over epoxy bonding. HCB has been used to bond several optical components for space-based missions, but has never been applied for construction of hollow retroreflectors. In this paper we examine the benefits and limitations of each bonding fixture as well as present results and analysis of hollow retroreflectors made using both epoxy and HCB techniques.

The design and fabrication of two portal vein flow phantoms by different methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yunker, Bryan E., E-mail: bryan.yunker@ucdenver.edu; Lanning, Craig J.; Shandas, Robin

2014-02-15

Purpose: This study outlines the design and fabrication techniques for two portal vein flow phantoms. Methods: A materials study was performed as a precursor to this phantom fabrication effort and the desired material properties are restated for continuity. A three-dimensional portal vein pattern was created from the Visual Human database. The portal vein pattern was used to fabricate two flow phantoms by different methods with identical interior surface geometry using computer aided design software tools and rapid prototyping techniques. One portal flow phantom was fabricated within a solid block of clear silicone for use on a table with Ultrasound ormore » within medical imaging systems such as MRI, CT, PET, or SPECT. The other portal flow phantom was fabricated as a thin walled tubular latex structure for use in water tanks with Ultrasound imaging. Both phantoms were evaluated for usability and durability. Results: Both phantoms were fabricated successfully and passed durability criteria for flow testing in the next project phase. Conclusions: The fabrication methods and materials employed for the study yielded durable portal vein phantoms.« less

Fabrication of a highly sensitive penicillin sensor based on charge transfer techniques.

PubMed

Lee, Seung-Ro; Rahman, M M; Sawada, Kazuaki; Ishida, Makoto

2009-03-15

A highly sensitive penicillin biosensor based on a charge-transfer technique (CTTPS) has been fabricated and demonstrated in this paper. CTTPS comprised a charge accumulation technique for penicilloic acid and H(+) ions perception system. With the proposed CTTPS, it is possible to amplify the sensing signals without external amplifier by using the charge accumulation cycles. The fabricated CTTPS exhibits excellent performance for penicillin detection and exhibit a high-sensitivity (47.852 mV/mM), high signal-to-noise ratio (SNR), large span (1445 mV), wide linear range (0-25 mM), fast response time (<3s), and very good reproducibility. A very lower detection limit of about 0.01 mM was observed from the proposed sensor. Under optimum conditions, the proposed CTTPS outstripped the performance of the widely used ISFET penicillin sensor and exhibited almost eight times greater sensitivity as compared to ISFET (6.56 mV/mM). The sensor system is implemented for the measurement of the penicillin concentration in penicillin fermentation broth.

New technique to fabricate an immediate surgical obturator restoring the defect in original anatomical form.

PubMed

Patil, Pravinkumar G

2011-08-01

The presence of oral cancer can necessitate the surgical removal of all or part of the maxilla, leaving the patient with a defect compromising the oral cavity's integrity and function. The immediate postoperative restoration of esthetics, deglutition, and speech shortens recovery time in the hospital and expedites the patient's return to the community as a functioning member. This article describes a simple technique to fabricate an immediate surgical obturator by restoring the patient's original dentition and facial and palatal tissue form. An immediate obturator fabricated with this technique supports soft tissues after surgery and minimizes scar contracture and disfigurement and thus may have a positive effect on the patient's psychology. © 2011 by The American College of Prosthodontists.

Application of Statistical Quality Control Techniques to Detonator Fabrication: Feasibility Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jones, J. Frank

1971-05-20

A feasibility study was performed on the use of process control techniques which might reduce the need for a duplicate inspection by production inspection and quality control inspection. Two active detonator fabrication programs were selected for the study. Inspection areas accounting for the greatest percentage of total inspection costs were selected by applying "Pareto's Principle of Maldistribution." Data from these areas were then gathered and analyzed by a process capabiltiy study.

Effect of fabrication technique on direct methanol fuel cells designed to operate at low airflow

NASA Technical Reports Server (NTRS)

Valdez, T. I.; Narayanan, S. R.

2002-01-01

This study investigates the effects of catalyst ink constituents and MEA fabrication techniques on improving cell performance. Particular attention was focused on increasing the overall cell efficiency.

[Fabrication and in vivo implantation of ligament-bone composite scaffolds based on three-dimensional printing technique].

PubMed

Zhang, Wenyou; He, Jiankang; Li, Xiang; Liu, Yaxiong; Bian, Weiguo; Li, Dichen; Jin, Zhongmin

2014-03-01

To solve the fixation problem between ligament grafts and host bones in ligament reconstruction surgery by using ligament-bone composite scaffolds to repair the ligaments, to explore the fabrication method for ligament-bone composite scaffolds based on three-dimensional (3-D) printing technique, and to investigate their mechanical and biological properties in animal experiments. The model of bone scaffolds was designed using CAD software, and the corresponding negative mould was created by boolean operation. 3-D printing techinique was employed to fabricate resin mold. Ceramic bone scaffolds were obtained by casting the ceramic slurry in the resin mould and sintering the dried ceramics-resin composites. Ligament scaffolds were obtained by weaving degummed silk fibers, and then assembled with bone scaffolds and bone anchors. The resultant ligament-bone composite scaffolds were implanted into 10 porcine left anterior cruciate ligament rupture models at the age of 4 months. Mechanical testing and histological examination were performed at 3 months postoperatively, and natural anterior cruciate ligaments of the right sides served as control. Biomechanical testing showed that the natural anterior cruciate ligament of control group can withstand maximum tensile force of (1 384 +/- 181) N and dynamic creep of (0.74 +/- 0.21) mm, while the regenerated ligament-bone scaffolds of experimental group can withstand maximum tensile force of (370 +/- 103) N and dynamic creep of (1.48 +/- 0.49) mm, showing significant differences (t = 11.617, P = 0.000; t = 2.991, P = 0.020). In experimental group, histological examination showed that new bone formed in bone scaffolds. A hierarchical transition structure regenerated between ligament-bone scaffolds and the host bones, which was similar to the structural organizations of natural ligament-bone interface. Ligament-bone composite scaffolds based on 3-D printing technique facilitates the regeneration of biomimetic ligament

Contact-eutectic-lens fabrication technique

NASA Technical Reports Server (NTRS)

Allen, F. G.; Yue, A. S.; Yu, J. G.

1975-01-01

Method enables use of crystal or semiconductor materials with selective spectral-response characteristics (ultraviolet, visible, or infrared wavelengths) in fabrication of contact lenses, reading glasses, and photographic processing equipment.

Employing lighting techniques during on-orbit operations

NASA Technical Reports Server (NTRS)

Wheelwright, Charles D.; Toole, Jennifer R.

1991-01-01

As a result of past space missions and evaluations, many procedures have been established and shown to be prudent applications for use in present and future space environment scenarios. However, recent procedures to employ the use of robotics to assist crewmembers in performing tasks which require viewing remote and obstructed locations have led to a need to pursue alternative methods to assist in these operations. One of those techniques which is under development entails incorporating the use of suitable lighting aids/techniques with a closed circuit television (CCTV) camera/monitor system to supervise the robotics operations. The capability to provide adequate lighting during grappling, deploying, docking and berthing operations under all on-orbit illumination conditions is essential to a successful mission. Using automated devices such as the Remote Manipulator System (RMS) to dock and berth a vehicle during payload retrieval, under nighttime, earthshine, solar, or artificial illumination conditions can become a cumbersome task without first incorporating lighting techniques that provide the proper target illumination, orientation, and alignment cues. Studies indicate that the use of visual aids such as the CCTV with a pretested and properly oriented lighting system can decrease the time necessary to accomplish grappling tasks. Evaluations have been and continue to be performed to assess the various on-orbit conditions in order to predict and determine the appropriate lighting techniques and viewing angles necessary to assist crewmembers in payload operations.

Employing lighting techniques during on-orbit operations

NASA Astrophysics Data System (ADS)

Wheelwright, Charles D.; Toole, Jennifer R.

As a result of past space missions and evaluations, many procedures have been established and shown to be prudent applications for use in present and future space environment scenarios. However, recent procedures to employ the use of robotics to assist crewmembers in performing tasks which require viewing remote and obstructed locations have led to a need to pursue alternative methods to assist in these operations. One of those techniques which is under development entails incorporating the use of suitable lighting aids/techniques with a closed circuit television (CCTV) camera/monitor system to supervise the robotics operations. The capability to provide adequate lighting during grappling, deploying, docking and berthing operations under all on-orbit illumination conditions is essential to a successful mission. Using automated devices such as the Remote Manipulator System (RMS) to dock and berth a vehicle during payload retrieval, under nighttime, earthshine, solar, or artificial illumination conditions can become a cumbersome task without first incorporating lighting techniques that provide the proper target illumination, orientation, and alignment cues. Studies indicate that the use of visual aids such as the CCTV with a pretested and properly oriented lighting system can decrease the time necessary to accomplish grappling tasks. Evaluations have been and continue to be performed to assess the various on-orbit conditions in order to predict and determine the appropriate lighting techniques and viewing angles necessary to assist crewmembers in payload operations.

Advanced fabrication techniques for hydrogen-cooled engine structures

NASA Technical Reports Server (NTRS)

Buchmann, O. A.; Arefian, V. V.; Warren, H. A.; Vuigner, A. A.; Pohlman, M. J.

1985-01-01

Described is a program for development of coolant passage geometries, material systems, and joining processes that will produce long-life hydrogen-cooled structures for scramjet applications. Tests were performed to establish basic material properties, and samples constructed and evaluated to substantiate fabrication processes and inspection techniques. Results of the study show that the basic goal of increasing the life of hydrogen-cooled structures two orders of magnitude relative to that of the Hypersonic Research Engine can be reached with available means. Estimated life is 19000 cycles for the channels and 16000 cycles for pin-fin coolant passage configurations using Nickel 201. Additional research is required to establish the fatigue characteristics of dissimilar-metal coolant passages (Nickel 201/Inconel 718) and to investigate the embrittling effects of the hydrogen coolant.

Transparent optically vanadium dioxide thermochromic smart film fabricated via electrospinning technique

NASA Astrophysics Data System (ADS)

Lu, Yuan; Xiao, Xiudi; Cao, Ziyi; Zhan, Yongjun; Cheng, Haoliang; Xu, Gang

2017-12-01

The monoclinic phase vanadium dioxide VO2 (M) based transparent thermochromic smart films were firstly fabricated through heat treatment of opaque VO2-based composite nanofibrous mats, which were deposited on the glass substrate via electrospinning technique. Noteworthily, the anti-oxidation property of VO2 smart film was improved due to inner distribution of VO2 in the polymethylmethacrylate (PMMA) nanofibers, and the composite mats having water contact angle of 165° determined itself good superhydrophobic property. Besides, PMMA nanofibrous mats with different polymer concentrations demonstrated changeable morphology and fiber diameter. The VO2 nanoparticles having diameter of 30-50 nm gathered and exhibited ellipse-like or belt-like structure. Additionally, the solar modulation ability of PMMA-VO2 composite smart film was 6.88% according to UV-Vis-NIR spectra. The research offered a new notion for fabricating transparent VO2 thermochromic material.

A Novel Technique for Performing PID Susceptibility Screening during the Solar Cell Fabrication Process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oh, Jaewon; Dahal, Som; Dauksher, Bill

2016-11-21

Various characterization techniques have historically been developed in order to screen potential induced degradation (PID)-susceptible cells, but those techniques require final solar cells. We present a new characterization technique for screening PID-susceptible cells during the cell fabrication process. Illuminated Lock-In Thermography (ILIT) was used to image PID shunting of the cell without metallization and clearly showed PID-affected areas. PID-susceptible cells can be screened by ILIT, and the sample structure can advantageously be simplified as long as the sample has the silicon nitride antireflection coating and an aluminum back surface field.

Comparative evaluation of marginal fit and axial wall adaptability of copings fabricated by metal laser sintering and lost-wax technique: An in vitro study.

PubMed

Gaikwad, Bhushan Satish; Nazirkar, Girish; Dable, Rajani; Singh, Shailendra

2018-01-01

The present study aims to compare and evaluate the marginal fit and axial wall adaptability of Co-Cr copings fabricated by metal laser sintering (MLS) and lost-wax (LW) techniques using a stereomicroscope. A stainless steel master die assembly was fabricated simulating a prepared crown; 40 replicas of master die were fabricated in gypsum type IV and randomly divided in two equal groups. Group A coping was fabrication by LW technique and the Group B coping fabrication by MLS technique. The copings were seated on their respective gypsum dies and marginal fit was measured using stereomicroscope and image analysis software. For evaluation of axial wall adaptability, the coping and die assembly were embedded in autopolymerizing acrylic resin and sectioned vertically. The discrepancies between the dies and copings were measured along the axial wall on each halves. The data were subjected to statistical analysis using unpaired t -test. The mean values of marginal fit for copings in Group B (MLS) were lower (24.6 μm) than the copings in Group A (LW) (39.53 μm), and the difference was statistically significant ( P < 0.05). The mean axial wall discrepancy value was lower for Group B (31.03 μm) as compared with Group A (54.49 μm) and the difference was statistically significant ( P < 0.05). The copings fabricated by MLS technique had better marginal fit and axial wall adaptability in comparison with copings fabricated by the LW technique. However, the values of marginal fit of copings fabricated that the two techniques were within the clinically acceptable limit (<50 μm).

Novel fabrication technique for improving the figure-of-merit of thermoelectric materials

NASA Technical Reports Server (NTRS)

Beaty, J. S.; Masters, R.; Vandersande, J. W.; Wood, C.

1989-01-01

Reduction of the thermal conductivity of thermoelectric materials in order to improve the figure of merit and, hence, the conversion efficiency is discussed. A novel fabrication technique that reduces the thermal conductivity without too adverse an effect on the electrical properties is reported. This is achieved by producing an oxygen-free, very-fine-grain SiGe alloy with very small (on the order of 50 A) precipitates.

Fabrication of gas turbine water-cooled composite nozzle and bucket hardware employing plasma spray process

DOEpatents

Schilke, Peter W.; Muth, Myron C.; Schilling, William F.; Rairden, III, John R.

1983-01-01

In the method for fabrication of water-cooled composite nozzle and bucket hardware for high temperature gas turbines, a high thermal conductivity copper alloy is applied, employing a high velocity/low pressure (HV/LP) plasma arc spraying process, to an assembly comprising a structural framework of copper alloy or a nickel-based super alloy, or combination of the two, and overlying cooling tubes. The copper alloy is plamsa sprayed to a coating thickness sufficient to completely cover the cooling tubes, and to allow for machining back of the copper alloy to create a smooth surface having a thickness of from 0.010 inch (0.254 mm) to 0.150 inch (3.18 mm) or more. The layer of copper applied by the plasma spraying has no continuous porosity, and advantageously may readily be employed to sustain a pressure differential during hot isostatic pressing (HIP) bonding of the overall structure to enhance bonding by solid state diffusion between the component parts of the structure.

Improved ceramic slip casting technique. [application to aircraft model fabrication

NASA Technical Reports Server (NTRS)

Buck, Gregory M. (Inventor); Vasquez, Peter (Inventor)

1993-01-01

A primary concern in modern fluid dynamics research is the experimental verification of computational aerothermodynamic codes. This research requires high precision and detail in the test model employed. Ceramic materials are used for these models because of their low heat conductivity and their survivability at high temperatures. To fabricate such models, slip casting techniques were developed to provide net-form, precision casting capability for high-purity ceramic materials in aqueous solutions. In previous slip casting techniques, block, or flask molds made of plaster-of-paris were used to draw liquid from the slip material. Upon setting, parts were removed from the flask mold and cured in a kiln at high temperatures. Casting detail was usually limited with this technique -- detailed parts were frequently damaged upon separation from the flask mold, as the molded parts are extremely delicate in the uncured state, and the flask mold is inflexible. Ceramic surfaces were also marred by 'parting lines' caused by mold separation. This adversely affected the aerodynamic surface quality of the model as well. (Parting lines are invariably necessary on or near the leading edges of wings, nosetips, and fins for mold separation. These areas are also critical for flow boundary layer control.) Parting agents used in the casting process also affected surface quality. These agents eventually soaked into the mold, the model, or flaked off when releasing the case model. Different materials were tried, such as oils, paraffin, and even an algae. The algae released best, but some of it remained on the model and imparted an uneven texture and discoloration on the model surface when cured. According to the present invention, a wax pattern for a shell mold is provided, and an aqueous mixture of a calcium sulfate-bonded investment material is applied as a coating to the wax pattern. The coated wax pattern is then dried, followed by curing to vaporize the wax pattern and leave a shell

A microelectromechanical accelerometer fabricated using printed circuit processing techniques

NASA Astrophysics Data System (ADS)

Rogers, J. E.; Ramadoss, R.; Ozmun, P. M.; Dean, R. N.

2008-01-01

A microelectromechanical systems (MEMS) capacitive-type accelerometer fabricated using printed circuit processing techniques is presented. A Kapton polymide film is used as the structural layer for fabricating the MEMS accelerometer. The accelerometer proof mass along with four suspension beams is defined in the Kapton polyimide film. The proof mass is suspended above a Teflon substrate using a spacer. The deflection of the proof mass is detected using a pair of capacitive sensing electrodes. The top electrode of the accelerometer is defined on the top surface of the Kapton film. The bottom electrode is defined in the metallization on the Teflon substrate. The initial gap height is determined by the distance between the bottom electrode and the Kapton film. For an applied external acceleration (normal to the proof mass), the proof mass deflects toward or away from the fixed bottom electrode due to inertial force. This deflection causes either a decrease or increase in the air-gap height thereby either increasing or decreasing the capacitance between the top and the bottom electrodes. An example PCB MEMS accelerometer with a square proof mass of membrane area 6.4 mm × 6.4 mm is reported. The measured resonant frequency is 375 Hz and the Q-factor in air is 0.52.

Method of fabrication of electrodes and electrolytes

DOEpatents

Jankowski, Alan F.; Morse, Jeffrey D.

2004-01-06

Fuel cell stacks contain an electrolyte layer surrounded on top and bottom by an electrode layer. Porous electrodes are prepared which enable fuel and oxidant to easily flow to the respective electrode-electrolyte interface without the need for high temperatures or pressures to assist the flow. Rigid, inert microspheres in combination with thin-film metal deposition techniques are used to fabricate porous anodes, cathodes, and electrolytes. Microshperes contained in a liquid are randomly dispersed onto a host structure and dried such that the microsperes remain in position. A thin-film deposition technique is subsequently employed to deposit a metal layer onto the microsperes. After such metal layer deposition, the microspheres are removed leaving voids, i.e. pores, in the metal layer, thus forming a porous electrode. Successive repetitions of the fabrication process result in the formation of a continuous fuel cell stack. Such stacks may produce power outputs ranging from about 0.1 Watt to about 50 Watts.

UV-transmitting step-index fluorophosphate glass fiber fabricated by the crucible technique

NASA Astrophysics Data System (ADS)

Galleani, Gustavo; Ledemi, Yannick; de Lima Filho, Elton Soares; Morency, Steeve; Delaizir, Gaëlle; Chenu, Sébastien; Duclere, Jean René; Messaddeq, Younes

2017-02-01

In this study, we report on the fabrication process of highly pure step-index fluorophosphate glass optical fibers by a modified crucible technique. High-purity fluorophosphate glasses based on 10 mol% of barium metaphosphate and 90 mol% of metal fluorides (AlF3sbnd CaF2sbnd MgF2sbnd SrF2) have been studied in order to produce step-index optical fibers transmitting in the deep-ultraviolet (DUV) region. The characteristic temperatures, viscosity around softening temperature and optical transmission in the UV-visible region of the prepared bulk glasses were characterized in a first step. The selected glass compositions were then used to prepare core-cladding optical preforms by using a modified built-in casting technique. While uncontrolled crystallization of the fiber was observed during the preform stretching by using the conventional method, we successfully obtained crystal-free fiber by using a modified crucible technique. In this alternative approach, the produced core-cladding preforms were inserted into a home-designed fused silica crucible assembly and heated at 643 °C to allow glass flowing throughout the crucible, preventing the formation of crystals. Single index fluorophosphate glass fibers were fabricated following the same process as well. The optical attenuation at 244 nm and in the interval 350-1750 nm was measured on both single index and step-index optical fibers. Their potential for using in DUV applications is discussed.

Fabrication of a Bronze Age Sword using Ancient Techniques

NASA Astrophysics Data System (ADS)

Sapiro, David; Webler, Bryan

2016-12-01

A khopesh was cast and forged for the TMS 2016 Bladesmithing Symposium. The khopesh was the first sword style, originating during the Bronze Age in the Near East. The manufacturing process used in this study closely followed Bronze Age techniques to determine the plausibility of open mold casting coupled with cold work and annealing cycles. Forging and annealing cycles substantially increased blade strength and diminished intergranular δ-phase inclusions. While a functional blade was not completed due to casting defects, the process gives valuable insight into the effort required to fabricate a khopesh during the Bronze Age. Forging and annealing cycles following casting were necessary to produce the mechanical properties desired in a sword.

Development of an Electron-capture Technique Specific for Explosives Detection

DOT National Transportation Integrated Search

1974-07-01

This document contains information on the design, fabrication, and testing of a prototype detector specific for explosives which employs electron-capture sensors. The technique used exploits the observation that the electronegative vapors from explos...

Parallel fabrication of macroporous scaffolds.

PubMed

Dobos, Andrew; Grandhi, Taraka Sai Pavan; Godeshala, Sudhakar; Meldrum, Deirdre R; Rege, Kaushal

2018-07-01

Scaffolds generated from naturally occurring and synthetic polymers have been investigated in several applications because of their biocompatibility and tunable chemo-mechanical properties. Existing methods for generation of 3D polymeric scaffolds typically cannot be parallelized, suffer from low throughputs, and do not allow for quick and easy removal of the fragile structures that are formed. Current molds used in hydrogel and scaffold fabrication using solvent casting and porogen leaching are often single-use and do not facilitate 3D scaffold formation in parallel. Here, we describe a simple device and related approaches for the parallel fabrication of macroporous scaffolds. This approach was employed for the generation of macroporous and non-macroporous materials in parallel, in higher throughput and allowed for easy retrieval of these 3D scaffolds once formed. In addition, macroporous scaffolds with interconnected as well as non-interconnected pores were generated, and the versatility of this approach was employed for the generation of 3D scaffolds from diverse materials including an aminoglycoside-derived cationic hydrogel ("Amikagel"), poly(lactic-co-glycolic acid) or PLGA, and collagen. Macroporous scaffolds generated using the device were investigated for plasmid DNA binding and cell loading, indicating the use of this approach for developing materials for different applications in biotechnology. Our results demonstrate that the device-based approach is a simple technology for generating scaffolds in parallel, which can enhance the toolbox of current fabrication techniques. © 2018 Wiley Periodicals, Inc.

Ultrasound-Induced Organogel Formation Followed by Thin Film Fabrication via Simple Doctor Blading Technique for Field-Effect Transistor Applications.

PubMed

Xu, Jiaju; Wang, Yulong; Shan, Haiquan; Lin, Yiwei; Chen, Qian; Roy, V A L; Xu, Zongxiang

2016-07-27

We demonstrate doctor blading technique to fabricate high performance transistors made up of printed small molecular materials. In this regard, we synthesize a new soluble phthalocyanine, tetra-n-butyl peripheral substituted copper(II) phthalocaynine (CuBuPc), that can easily undergo gel formation upon ultrasonic irradiation, leading to the formation of three-dimensional (3D) network composed of one-dimensional (1D) nanofibers structure. Finally, taking the advantage of thixotropic nature of the CuBuPc organogel, we use the doctor blade processing technique that limits the material wastage for the fabrication of transistor devices. Due to the ultrasound induced stronger π-π interaction, the transistor fabricated by doctor blading based on CuBuPc organogel exhibits significant increase in charge carrier mobility in comparison with other solution process techniques, thus paving a way for a simple and economically viable preparation of electronic circuits.

Design, Fabrication and Levitation Experiments of a Micromachined Electrostatically Suspended Six-Axis Accelerometer

PubMed Central

Cui, Feng; Liu, Wu; Chen, Wenyuan; Zhang, Weiping; Wu, Xiaosheng

2011-01-01

A micromachined electrostatically suspended six-axis accelerometer, with a square plate as proof mass housed by a top stator and bottom stator, is presented. The device structure and related techniques concerning its operating principles, such as calculation of capacitances and electrostatic forces/moments, detection and levitation control of the proof mass, acceleration measurement, and structural parameters design, are described. Hybrid MEMS manufacturing techniques, including surface micromachining fabrication of thin film electrodes and interconnections, integration fabrication of thick nickel structures about 500 μm using UV-LIGA by successful removal of SU-8 photoresist mold, DRIE of silicon proof mass in thickness of 450 μm, microassembly and solder bonding, were employed to fabricate this prototype microdevice. A levitation experiment system for the fabricated microaccelerometer chip is introduced, and levitation results show that fast initial levitation within 10 ms and stable full suspension of the proof mass have been successfully demonstrated. PMID:22247662

Metal-ceramic bond strength between a feldspathic porcelain and a Co-Cr alloy fabricated with Direct Metal Laser Sintering technique.

PubMed

Dimitriadis, Konstantinos; Spyropoulos, Konstantinos; Papadopoulos, Triantafillos

2018-02-01

The aim of the present study was to record the metal-ceramic bond strength of a feldspathic dental porcelain and a Co-Cr alloy, using the Direct Metal Laser Sintering technique (DMLS) for the fabrication of metal substrates. Ten metal substrates were fabricated with powder of a dental Co-Cr alloy using DMLS technique (test group) in dimensions according to ISO 9693. Another ten substrates were fabricated with a casing dental Co-Cr alloy using classic casting technique (control group) for comparison. Another three substrates were fabricated using each technique to record the Modulus of Elasticity ( E ) of the used alloys. All substrates were examined to record external and internal porosity. Feldspathic porcelain was applied on the substrates. Specimens were tested using the three-point bending test. The failure mode was determined using optical and scanning electron microscopy. The statistical analysis was performed using t-test. Substrates prepared using DMLS technique did not show internal porosity as compared to those produced using the casting technique. The E of control and test group was 222 ± 5.13 GPa and 227 ± 3 GPa, respectively. The bond strength was 51.87 ± 7.50 MPa for test group and 54.60 ± 6.20 MPa for control group. No statistically significant differences between the two groups were recorded. The mode of failure was mainly cohesive for all specimens. Specimens produced by the DMLS technique cover the lowest acceptable metal-ceramic bond strength of 25 MPa specified in ISO 9693 and present satisfactory bond strength for clinical use.

Fabrication of metal nanoelectrodes by interfacial reactions.

PubMed

Zhu, Xinyu; Qiao, Yonghui; Zhang, Xin; Zhang, Sensen; Yin, Xiaohong; Gu, Jing; Chen, Ye; Zhu, Zhiwei; Li, Meixian; Shao, Yuanhua

2014-07-15

Despite great improvements in the past decades, the controllable fabrication of metal nanoelectrodes still remains very challenging. In this work, a simple and general way to fabricate metal nanoelectrodes (Ag, Au, and Pt) is developed. On the basis of interfacial reactions at nano-liquid/liquid interfaces supported at nanopipettes, the nanoparticles can be formed in situ and have been used to block the orifices of pipettes to make nanoelectrodes. The effect of the driving force for interfacial reaction at the liquid/liquid interface, the ratio of redox species in organic and aqueous phases, and the surface charge of the inner wall of a pipette have been studied. The fabricated nanoelectrodes have been characterized by scanning electron microscopy (SEM) and electrochemical techniques. A silver electrode with about 10 nm in radius has been employed as the scanning electrochemical microscopy (SECM) probe to explore the thickness of a water/nitrobenzene (W/NB) interface, and this value is equal to 0.8 ± 0.1 nm (n = 5). This method of fabrication of nanoelectrodes can be extended to other metal or semiconductor electrodes.

Managing age discrimination: an examination of the techniques used when seeking employment.

PubMed

Berger, Ellie D

2009-06-01

This article examines the age-related management techniques used by older workers in their search for employment. Data are drawn from interviews with individuals aged 45-65 years (N = 30). Findings indicate that participants develop "counteractions" and "concealments" to manage perceived age discrimination. Individuals counteract employers' ageist stereotypes by maintaining their skills and changing their work-related expectations and conceal age by altering their résumés, physical appearance, and language used. This research suggests that there is a need to reexamine the hiring practices of employers and to improve legislation in relation to their accountability.

Comparative Accuracy of Facial Models Fabricated Using Traditional and 3D Imaging Techniques.

PubMed

Lincoln, Ketu P; Sun, Albert Y T; Prihoda, Thomas J; Sutton, Alan J

2016-04-01

The purpose of this investigation was to compare the accuracy of facial models fabricated using facial moulage impression methods to the three-dimensional printed (3DP) fabrication methods using soft tissue images obtained from cone beam computed tomography (CBCT) and 3D stereophotogrammetry (3D-SPG) scans. A reference phantom model was fabricated using a 3D-SPG image of a human control form with ten fiducial markers placed on common anthropometric landmarks. This image was converted into the investigation control phantom model (CPM) using 3DP methods. The CPM was attached to a camera tripod for ease of image capture. Three CBCT and three 3D-SPG images of the CPM were captured. The DICOM and STL files from the three 3dMD and three CBCT were imported to the 3DP, and six testing models were made. Reversible hydrocolloid and dental stone were used to make three facial moulages of the CPM, and the impressions/casts were poured in type IV gypsum dental stone. A coordinate measuring machine (CMM) was used to measure the distances between each of the ten fiducial markers. Each measurement was made using one point as a static reference to the other nine points. The same measuring procedures were accomplished on all specimens. All measurements were compared between specimens and the control. The data were analyzed using ANOVA and Tukey pairwise comparison of the raters, methods, and fiducial markers. The ANOVA multiple comparisons showed significant difference among the three methods (p < 0.05). Further, the interaction of methods versus fiducial markers also showed significant difference (p < 0.05). The CBCT and facial moulage method showed the greatest accuracy. 3DP models fabricated using 3D-SPG showed statistical difference in comparison to the models fabricated using the traditional method of facial moulage and 3DP models fabricated from CBCT imaging. 3DP models fabricated using 3D-SPG were less accurate than the CPM and models fabricated using facial moulage and CBCT

Digital versus conventional techniques for pattern fabrication of implant-supported frameworks.

PubMed

Alikhasi, Marzieh; Rohanian, Ahmad; Ghodsi, Safoura; Kolde, Amin Mohammadpour

2018-01-01

The aim of this experimental study was to compare retention of frameworks cast from wax patterns fabricated by three different methods. Thirty-six implant analogs connected to one-piece abutments were divided randomly into three groups according to the wax pattern fabrication method ( n = 12). Computer-aided design/computer-aided manufacturing (CAD/CAM) milling machine, three-dimensional printer, and conventional technique were used for fabrication of waxing patterns. All laboratory procedures were performed by an expert-reliable technician to eliminate intra-operator bias. The wax patterns were cast, finished, and seated on related abutment analogs. The number of adjustment times was recorded and analyzed by Kruskal-Wallis test. Frameworks were cemented on the corresponding analogs with zinc phosphate cement and tensile resistance test was used to measure retention value. One-way analysis of variance (ANOVA) and post hoc Tukey tests were used for statistical analysis. Level of significance was set at P < 0.05. The mean retentive values of 680.36 ± 21.93 N, 440.48 ± 85.98 N, and 407.23 ± 67.48 N were recorded for CAD/CAM, rapid prototyping, and conventional group, respectively. One-way ANOVA test revealed significant differences among the three groups ( P < 0.001). The post hoc Tukey test showed significantly higher retention for CAD/CAM group ( P < 0.001), while there was no significant difference between the two other groups ( P = 0.54). CAD/CAM group required significantly more adjustments ( P < 0.001). CAD/CAM-fabricated wax patterns showed significantly higher retention for implant-supported cement-retained frameworks; this could be a valuable help when there are limitations in the retention of single-unit implant restorations.

A novel 2D silicon nano-mold fabrication technique for linear nanochannels over a 4 inch diameter substrate

PubMed Central

Yin, Zhifu; Qi, Liping; Zou, Helin; Sun, Lei

2016-01-01

A novel low-cost 2D silicon nano-mold fabrication technique was developed based on Cu inclined-deposition and Ar+ (argon ion) etching. With this technique, sub-100 nm 2D (two dimensional) nano-channels can be etched economically over the whole area of a 4 inch n-type <100> silicon wafer. The fabricating process consists of only 4 steps, UV (Ultraviolet) lithography, inclined Cu deposition, Ar+ sputter etching, and photoresist & Cu removing. During this nano-mold fabrication process, we investigated the influence of the deposition angle on the width of the nano-channels and the effect of Ar+ etching time on their depth. Post-etching measurements showed the accuracy of the nanochannels over the whole area: the variation in width is 10%, in depth it is 11%. However, post-etching measurements also showed the accuracy of the nanochannels between chips: the variation in width is 2%, in depth it is 5%. With this newly developed technology, low-cost and large scale 2D nano-molds can be fabricated, which allows commercial manufacturing of nano-components over large areas. PMID:26752559

Communication methods and production techniques in fixed prosthesis fabrication: a UK based survey. Part 2: Production techniques

PubMed Central

Berry, J.; Nesbit, M.; Saberi, S.; Petridis, H.

2014-01-01

Aim The aim of this study was to identify the communication methods and production techniques used by dentists and dental technicians for the fabrication of fixed prostheses within the UK from the dental technicians' perspective. This second paper reports on the production techniques utilised. Materials and methods Seven hundred and eighty-two online questionnaires were distributed to the Dental Laboratories Association membership and included a broad range of topics, such as demographics, impression disinfection and suitability, and various production techniques. Settings were managed in order to ensure anonymity of respondents. Statistical analysis was undertaken to test the influence of various demographic variables such as the source of information, the location, and the size of the dental laboratory. Results The number of completed responses totalled 248 (32% response rate). Ninety percent of the respondents were based in England and the majority of dental laboratories were categorised as small sized (working with up to 25 dentists). Concerns were raised regarding inadequate disinfection protocols between dentists and dental laboratories and the poor quality of master impressions. Full arch plastic trays were the most popular impression tray used by dentists in the fabrication of crowns (61%) and bridgework (68%). The majority (89%) of jaw registration records were considered inaccurate. Forty-four percent of dental laboratories preferred using semi-adjustable articulators. Axial and occlusal under-preparation of abutment teeth was reported as an issue in about 25% of cases. Base metal alloy was the most (52%) commonly used alloy material. Metal-ceramic crowns were the most popular choice for anterior (69%) and posterior (70%) cases. The various factors considered did not have any statistically significant effect on the answers provided. The only notable exception was the fact that more methods of communicating the size and shape of crowns were utilised for

An Alternate Vista in Rehabilitation of Cranial Defects: Combining Digital and Manual Techniques to Fabricate a Hybrid Cranioplast.

PubMed

Kaur, Harsimran; Nanda, Aditi; Koli, Dheeraj; Verma, Mahesh; Singh, Hukum; Bishnoi, Ishu; Pathak, Pooja; Gupta, Ankur

2015-06-01

The desired features of a cranioplast include providing an acceptable contour, continuity with the remaining skull (marginal adaptation), improvising the aesthetic outcome, providing a strengthened prosthesis to avoid fracture in case of repeat trauma, and protecting the remaining neurological structures. Combining digital and manual techniques to fabricate a hybrid polymethylmethacrylate cranioplast during the rehabilitation of a pediatric patient with cranial defect has been described. Utilization of digital techniques (rapid prototyping to obtain skull analog) and manual (hand) sculpting of the prosthesis strengthened with glass fiber enabled the authors to fabricate a hybrid cranioplast. Satisfactory outcome was achieved.

Metal-ceramic bond strength between a feldspathic porcelain and a Co-Cr alloy fabricated with Direct Metal Laser Sintering technique

PubMed Central

Spyropoulos, Konstantinos

2018-01-01

PURPOSE The aim of the present study was to record the metal-ceramic bond strength of a feldspathic dental porcelain and a Co-Cr alloy, using the Direct Metal Laser Sintering technique (DMLS) for the fabrication of metal substrates. MATERIALS AND METHODS Ten metal substrates were fabricated with powder of a dental Co-Cr alloy using DMLS technique (test group) in dimensions according to ISO 9693. Another ten substrates were fabricated with a casing dental Co-Cr alloy using classic casting technique (control group) for comparison. Another three substrates were fabricated using each technique to record the Modulus of Elasticity (E) of the used alloys. All substrates were examined to record external and internal porosity. Feldspathic porcelain was applied on the substrates. Specimens were tested using the three-point bending test. The failure mode was determined using optical and scanning electron microscopy. The statistical analysis was performed using t-test. RESULTS Substrates prepared using DMLS technique did not show internal porosity as compared to those produced using the casting technique. The E of control and test group was 222 ± 5.13 GPa and 227 ± 3 GPa, respectively. The bond strength was 51.87 ± 7.50 MPa for test group and 54.60 ± 6.20 MPa for control group. No statistically significant differences between the two groups were recorded. The mode of failure was mainly cohesive for all specimens. CONCLUSION Specimens produced by the DMLS technique cover the lowest acceptable metal-ceramic bond strength of 25 MPa specified in ISO 9693 and present satisfactory bond strength for clinical use. PMID:29503711

Direct single-layered fabrication of 3D concavo convex patterns in nano-stereolithography

NASA Astrophysics Data System (ADS)

Lim, T. W.; Park, S. H.; Yang, D. Y.; Kong, H. J.; Lee, K. S.

2006-09-01

A nano-surfacing process (NSP) is proposed to directly fabricate three-dimensional (3D) concavo convex-shaped microstructures such as micro-lens arrays using two-photon polymerization (TPP), a promising technique for fabricating arbitrary 3D highly functional micro-devices. In TPP, commonly utilized methods for fabricating complex 3D microstructures to date are based on a layer-by-layer accumulating technique employing two-dimensional sliced data derived from 3D computer-aided design data. As such, this approach requires much time and effort for precise fabrication. In this work, a novel single-layer exposure method is proposed in order to improve the fabricating efficiency for 3D concavo convex-shaped microstructures. In the NSP, 3D microstructures are divided into 13 sub-regions horizontally with consideration of the heights. Those sub-regions are then expressed as 13 characteristic colors, after which a multi-voxel matrix (MVM) is composed with the characteristic colors. Voxels with various heights and diameters are generated to construct 3D structures using a MVM scanning method. Some 3D concavo convex-shaped microstructures were fabricated to estimate the usefulness of the NSP, and the results show that it readily enables the fabrication of single-layered 3D microstructures.

Curved grating fabrication techniques for concentric-circle grating, surface-emitting semiconductor lasers

NASA Technical Reports Server (NTRS)

Jordan, Rebecca H.; King, Oliver; Wicks, Gary W.; Hall, Dennis G.; Anderson, Erik H.; Rooks, Michael J.

1993-01-01

We describe the fabrication and operational characteristics of a novel, surface-emitting semiconductor laser that makes use of a concentric-circle grating to both define its resonant cavity and to provide surface emission. A properly fabricated circular grating causes the laser to operate in radially inward- and outward-going circular waves in the waveguide, thus, introducing the circular symmetry needed for the laser to emit a beam with a circular cross-section. The basic circular-grating-resonator concept can be implemented in any materials system; an AlGaAs/GaAs graded-index, separate confinement heterostructure (GRINSCH), single-quantum-well (SQW) semiconductor laser, grown by molecular beam epitaxy (MBE), was used for the experiments discussed here. Each concentric-circle grating was fabricated on the surface of the AlGaAs/GaAs semiconductor laser. The circular pattern was first defined by electron-beam (e-beam) lithography in a layer of polymethylmethacrylate (PMMA) and subsequently etched into the semiconductor surface using chemically-assisted (chlorine) ion-beam etching (CAIBE). We consider issues that affect the fabrication and quality of the gratings. These issues include grating design requirements, data representation of the grating pattern, and e-beam scan method. We provide examples of how these techniques can be implemented and their impact on the resulting laser performance. A comparison is made of the results obtained using two fundamentally different electron-beam writing systems. Circular gratings with period lambda = 0.25 microns and overall diameters ranging from 80 microns to 500 microns were fabricated. We also report our successful demonstration of an optically pumped, concentric-circle grating, semiconductor laser that emits a beam with a far-field divergence angle that is less than one degree. The emission spectrum is quite narrow (less than 0.1 nm) and is centered at wavelength lambda = 0.8175 microns.

CAD/CAM machining Vs pre-sintering in-lab fabrication techniques of Y-TZP ceramic specimens: Effects on their mechanical fatigue behavior.

PubMed

Zucuni, C P; Guilardi, L F; Fraga, S; May, L G; Pereira, G K R; Valandro, L F

2017-07-01

This study evaluated the effects of different pre-sintering fabrication processing techniques of Y-TZP ceramic (CAD/CAM Vs. in-lab), considering surface characteristics and mechanical performance outcomes. Pre-sintered discs of Y-TZP ceramic (IPS e.max ZirCAD, Ivoclar Vivadent) were produced using different pre-sintering fabrication processing techniques: Machined- milling with a CAD/CAM system; Polished- fabrication using a cutting device followed by polishing (600 and 1200 SiC papers); Xfine- fabrication using a cutting machine followed by grinding with extra-fine diamond bur (grit size 30 μm); Fine- fabrication using a cutting machine followed by grinding with fine diamond bur (grit size 46 μm); SiC- fabrication using a cutting machine followed by grinding with 220 SiC paper. Afterwards, the discs were sintered and submitted to roughness (n=35), surface topography (n=2), phase transformation (n=2), biaxial flexural strength (n=20), and biaxial flexural fatigue strength (fatigue limit) (n=15) analyses. No monoclinic-phase content was observed in all processing techniques. It can be observed that obtaining a surface with similar characteristics to CAD/CAM milling is essential for the observation of similar mechanical performance. On this sense, grinding with fine diamond bur before sintering (Fine group) was the best mimic protocol in comparison to the CAD/CAM milling. Copyright © 2017 Elsevier Ltd. All rights reserved.

Thermorheological characteristics and comparison of shape memory polymers fabricated by novel 3D printing technique

NASA Astrophysics Data System (ADS)

Hassan, Rizwan Ul; Jo, Soohwan; Seok, Jongwon

The feasibility of fabrication of shape memory polymers (SMPs) was investigated using a customized 3-dimensional (3D) printing technique with an excellent resolution that could be less than 100 microns. The thermorheological effects of SMPs were adjusted by contact and non-contact triggering, which led to the respective excellent shape recoveries of 100% and 99.89%. Thermogravimetric analyses of SMPs resulted in a minor weight loss, thereby revealing good thermal stability at higher temperatures. The viscoelastic properties of SMPs were measured using dynamic mechanical analyses, exhibiting increased viscous and elastic characteristics. Mechanical strength, thermal stability and viscoelastic properties, of the two SMPs were compared [di(ethylene) glycol dimethacrylate (DEGDMA) and poly (ethylene glycol) dimethacrylate (PEGDMA)] to investigate the shape memory behavior. This novel 3D printing technique can be used as a promising method for fabricating smart materials with increased accuracy in a cost-effective manner.

CCD research. [design, fabrication, and applications

NASA Technical Reports Server (NTRS)

Gassaway, J. D.

1976-01-01

The fundamental problems encountered in designing, fabricating, and applying CCD's are reviewed. Investigations are described and results and conclusions are given for the following: (1) the development of design analyses employing computer aided techniques and their application to the design of a grapped structure; (2) the role of CCD's in applications to electronic functions, in particular, signal processing; (3) extending the CCD to silicon films on sapphire (SOS); and (4) all aluminum transfer structure with low noise input-output circuits. Related work on CCD imaging devices is summarized.

Digital versus conventional techniques for pattern fabrication of implant-supported frameworks

PubMed Central

Alikhasi, Marzieh; Rohanian, Ahmad; Ghodsi, Safoura; Kolde, Amin Mohammadpour

2018-01-01

Objective: The aim of this experimental study was to compare retention of frameworks cast from wax patterns fabricated by three different methods. Materials and Methods: Thirty-six implant analogs connected to one-piece abutments were divided randomly into three groups according to the wax pattern fabrication method (n = 12). Computer-aided design/computer-aided manufacturing (CAD/CAM) milling machine, three-dimensional printer, and conventional technique were used for fabrication of waxing patterns. All laboratory procedures were performed by an expert-reliable technician to eliminate intra-operator bias. The wax patterns were cast, finished, and seated on related abutment analogs. The number of adjustment times was recorded and analyzed by Kruskal–Wallis test. Frameworks were cemented on the corresponding analogs with zinc phosphate cement and tensile resistance test was used to measure retention value. Statistical Analysis Used: One-way analysis of variance (ANOVA) and post hoc Tukey tests were used for statistical analysis. Level of significance was set at P < 0.05. Results: The mean retentive values of 680.36 ± 21.93 N, 440.48 ± 85.98 N, and 407.23 ± 67.48 N were recorded for CAD/CAM, rapid prototyping, and conventional group, respectively. One-way ANOVA test revealed significant differences among the three groups (P < 0.001). The post hoc Tukey test showed significantly higher retention for CAD/CAM group (P < 0.001), while there was no significant difference between the two other groups (P = 0.54). CAD/CAM group required significantly more adjustments (P < 0.001). Conclusions: CAD/CAM-fabricated wax patterns showed significantly higher retention for implant-supported cement-retained frameworks; this could be a valuable help when there are limitations in the retention of single-unit implant restorations. PMID:29657528

Technique to verify the accuracy of a definitive cast before the fabrication of a fixed dental prosthesis.

PubMed

Farah, Ra'fat I; Alshabi, Abdullah M

2016-09-01

This report describes a straightforward technique for verifying the accuracy of a definitive cast by using a maximal intercuspation record fabricated from polyvinyl siloxane occlusal registration material. This precise verification method detects inaccurate casts before the dental prosthesis is fabricated, thus saving chairside and laboratory time while reducing the number of costly prosthesis remakes. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Fabricating fiber Bragg gratings with two phase masks based on reconstruction-equivalent-chirp technique.

PubMed

Gao, Liang; Chen, Xiangfei; Xiong, Jintian; Liu, Shengchun; Pu, Tao

2012-01-30

Based on reconstruction-equivalent-chirp (REC) technique, a novel solution for fabricating low-cost long fiber Bragg gratings (FBGs) with desired properties is proposed and initially studied. A proof-of-concept experiment is demonstrated with two conventional uniform phase masks and a submicron-precision translation stage, successfully. It is shown that the original phase shift (OPS) caused by phase mismatch of the two phase masks can be compensated by the equivalent phase shift (EPS) at the ±1st channels of sampled FBGs, separately. Furthermore, as an example, a π phase-shifted FBG of about 90 mm is fabricated by using these two 50mm-long uniform phase masks based on the presented method.

Analytical and experimental evaluation of techniques for the fabrication of thermoplastic hologram storage devices

NASA Technical Reports Server (NTRS)

Rogers, J. W.

1975-01-01

The results of an experimental investigation on recording information on thermoplastic are given. A description was given of a typical fabrication configuration, the recording sequence, and the samples which were examined. There are basically three configurations which can be used for the recording of information on thermoplastic. The most popular technique uses corona which furnishes free charge. The necessary energy for deformation is derived from a charge layer atop the thermoplastic. The other two techniques simply use a dc potential in place of the corona for deformation energy.

Rapid prototype fabrication processes for high-performance thrust cells

NASA Technical Reports Server (NTRS)

Hunt, K.; Chwiedor, T.; Diab, J.; Williams, R.

1994-01-01

The Thrust Cell Technologies Program (Air Force Phillips Laboratory Contract No. F04611-92-C-0050) is currently being performed by Rocketdyne to demonstrate advanced materials and fabrication technologies which can be utilized to produce low-cost, high-performance thrust cells for launch and space transportation rocket engines. Under Phase 2 of the Thrust Cell Technologies Program (TCTP), rapid prototyping and investment casting techniques are being employed to fabricate a 12,000-lbf thrust class combustion chamber for delivery and hot-fire testing at Phillips Lab. The integrated process of investment casting directly from rapid prototype patterns dramatically reduces design-to-delivery cycle time, and greatly enhances design flexibility over conventionally processed cast or machined parts.

Plasmonic nanoparticle lithography: Fast resist-free laser technique for large-scale sub-50 nm hole array fabrication

NASA Astrophysics Data System (ADS)

Pan, Zhenying; Yu, Ye Feng; Valuckas, Vytautas; Yap, Sherry L. K.; Vienne, Guillaume G.; Kuznetsov, Arseniy I.

2018-05-01

Cheap large-scale fabrication of ordered nanostructures is important for multiple applications in photonics and biomedicine including optical filters, solar cells, plasmonic biosensors, and DNA sequencing. Existing methods are either expensive or have strict limitations on the feature size and fabrication complexity. Here, we present a laser-based technique, plasmonic nanoparticle lithography, which is capable of rapid fabrication of large-scale arrays of sub-50 nm holes on various substrates. It is based on near-field enhancement and melting induced under ordered arrays of plasmonic nanoparticles, which are brought into contact or in close proximity to a desired material and acting as optical near-field lenses. The nanoparticles are arranged in ordered patterns on a flexible substrate and can be attached and removed from the patterned sample surface. At optimized laser fluence, the nanohole patterning process does not create any observable changes to the nanoparticles and they have been applied multiple times as reusable near-field masks. This resist-free nanolithography technique provides a simple and cheap solution for large-scale nanofabrication.

Microgroove fabrication with excimer laser ablation techniques for optical fiber array alignment purposes

NASA Astrophysics Data System (ADS)

Naessens, Kris; Van Hove, An; Coosemans, Thierry; Verstuyft, Steven; Vanwassenhove, Luc; Van Daele, Peter; Baets, Roel G.

2000-11-01

Currently, an ever increasing need for bandwidth, compactness and efficiency characterizes the world of interconnect and data communication. This tendency has already led to serial links being gradually replaced by parallel optical interconnect solutions. However, as the maximum capacity for the latter will be reached in the near future, new approaches are required to meet demand. One possible option is to switch to 2D parallel implementations of fiber arrays. In this paper we present the fabrication of a 2D connector for coupling a 4x8 array of plastic optical fibers to RCLED or VCSEL arrays. The connector consists primarily of dedicated PMMA plates in which arrays of 8 precisely dimensioned grooves at a pitch of 250 micrometers are introduced. The trenches are each 127 micrometers deep and their width is optimized to allow fixation of plastic optical fibers. We used excimer laser ablation for prototype fabrication of these alignment microstructures. In a later stage, the plates can be replicated using standard molding techniques. The laser ablation technique is extremely well suited for rapid prototyping and proves to be a versatile process yielding high accuracy dimensioning and repeatability of features in a wide diversity of materials. The dependency of the performance in terms of quality of the trenches (bottom roughness) and wall angle on various parameters (wavelength, energy density, pulse frequency and substrate material) is discussed. The fabricated polymer sheets with grooves are used to hold optical fibers by means of a UV-curable adhesive. In a final phase, the plates are stacked and glued in order to realize the 2D-connector of plastic optical fibers for short distance optical interconnects.

Techniques employed for detection of hot particles in the marine environment.

PubMed

Pillsbury, G D

2007-09-01

During the decommissioning of the Maine Yankee nuclear plant, several methods were developed and employed to survey for hot particles in the marine environment surrounding the site. The methods used and the sensitivities achieved in the search for environmentally dispersed particles during the various decommissioning activities performed are described in detail. Surveys were performed on dry soil, exposed marine sediment and submerged marine sediment. Survey techniques ranged from the use of the basic NaI detector coupled to a count rate meter to an intrinsic germanium detector deployed in a submarine housing coupled to a multi-channel analyser. The initial surveys consisted of collecting samples of marine sediment, spreading them out over a 1 m2 surface in a thin layer, and scanning the deposited sediment by hand using a 5 cm by 5 cm NaI detector coupled to a standard count rate meter. This technique was later replaced by walkover scans with the 5 cm by 5 cm NaI detector moved in a serpentine pattern over the sediment surface. By coupling the detector to a 'smart meter', an alarm set point could be used to alert the surveyor to the presence of a particle within the instrument's field of view. A similar technique, with the detector mounted in a watertight housing secured to the end of a pole, was also employed to scan underwater locations. The most sensitive method developed for performing underwater surveys was the use of the intrinsic germanium detector placed in a submarine housing. Detailed descriptions of the methods employed and the results obtained are presented. This work demonstrates that there are several approaches to surveying for discrete particles in the marine environment and the relative merits of each are considered.

Characterization and fabrication of target materials for RIB generation

NASA Astrophysics Data System (ADS)

Welton, R. F.; Janney, M. A.; Mueller, P. E.; Ortman, W. K.; Rauniyar, R.; Stracener, D. W.; Williams, C. L.

2001-07-01

This report discusses two techniques developed at the Oak Ridge National Laboratory (ORNL) that are employed for the fabrication and characterization of targets used in the production of Radioactive Ion Beams (RIBs). First, our method of in-house fabrication of uranium carbide targets is discussed. We have found that remarkably uniform coatings of UC2 can be formed on the microstructure of porous C matrices. The technique has been used to form UC2 layers on highly thermally conductive graphitic foams. Targets fabricated in this fashion have been tested under low-intensity proton bombardment and yields of selected radioactive species are reported. This report also describes an off-line test stand for the investigation of effusive and diffusive transport in RIB target/ion sources. Permeation rates of gases and vapors passing through a high temperature membrane or through an effusive channel constructed from the material under investigation are recorded. Diffusion coefficients and adsorption enthalpies, which characterize the interaction of RIB species with materials of the target/ion source, are extracted from the time profile of the recorded data. Examples of diffusion, effusion, and conductance measurements are provided.

3D printed electromagnetic transmission and electronic structures fabricated on a single platform using advanced process integration techniques

NASA Astrophysics Data System (ADS)

Deffenbaugh, Paul Issac

3D printing has garnered immense attention from many fields including in-office rapid prototyping of mechanical parts, outer-space satellite replication, garage functional firearm manufacture, and NASA rocket engine component fabrication. 3D printing allows increased design flexibility in the fabrication of electronics, microwave circuits and wireless antennas and has reached a level of maturity which allows functional parts to be printed. Much more work is necessary in order to perfect the processes of 3D printed electronics especially in the area of automation. Chapter 1 shows several finished prototypes of 3D printed electronics as well as newly developed techniques in fabrication. Little is known about the RF and microwave properties and applications of the standard materials which have been developed for 3D printing. Measurement of a wide variety of materials over a broad spectrum of frequencies up to 10 GHz using a variety of well-established measurement methods is performed throughout chapter 2. Several types of high frequency RF transmission lines are fabricated and valuable model-matched data is gathered and provided in chapter 3 for future designers' use. Of particular note is a fully 3D printed stripline which was automatically fabricated in one process on one machine. Some core advantages of 3D printing RF/microwave components include rapid manufacturing of complex, dimensionally sensitive circuits (such as antennas and filters which are often iteratively tuned) and the ability to create new devices that cannot be made using standard fabrication techniques. Chapter 4 describes an exemplary fully 3D printed curved inverted-F antenna.

3D printing of polypropylene using the fused filament fabrication technique

NASA Astrophysics Data System (ADS)

Silva, A. F.; Carneiro, O. S.; Gomes, R.

2017-10-01

This work addresses the potential of polypropylene, neat (PP) and reinforced with short glass fibers (GRPP), as a candidate for the Fused Filament Fabrication (FFF)-based 3D printing technique. The entire production chain was evaluated, i.e., starting with PP and GRPP pellets, filaments were produced by extrusion and test samples were printed in different process conditions (different layers' thicknesses, deposition orientation and infill) with the in-house produced filaments. This strategy enabled a true comparison between parts printed (FFF) with parts manufactured by compression molding (CM), using exactly the same grade of raw material.

Preliminary fabrication and characterization of electron beam melted Ti-6Al-4V customized dental implant.

PubMed

Ramakrishnaiah, Ravikumar; Al Kheraif, Abdulaziz Abdullah; Mohammad, Ashfaq; Divakar, Darshan Devang; Kotha, Sunil Babu; Celur, Sree Lalita; Hashem, Mohamed I; Vallittu, Pekka K; Rehman, Ihtesham Ur

2017-05-01

The current study was aimed to fabricate customized root form dental implant using additive manufacturing technique for the replacement of missing teeth. The root form dental implant was designed using Geomagic™ and Magics™, the designed implant was directly manufactured by layering technique using ARCAM A2™ electron beam melting system by employing medical grade Ti-6Al-4V alloy powder. Furthermore, the fabricated implant was characterized in terms of certain clinically important parameters such as surface microstructure, surface topography, chemical purity and internal porosity. Results confirmed that, fabrication of customized dental implants using additive rapid manufacturing technology offers an attractive method to produce extremely pure form of customized titanium dental implants, the rough and porous surface texture obtained is expected to provide better initial implant stabilization and superior osseointegration.

Microporous Poly(L-Lactic Acid) Membranes Fabricated by Polyethylene Glycol Solvent-Cast/Particulate Leaching Technique

PubMed Central

Selvam, Shivaram; Chang, Wenji V.; Nakamura, Tamako; Samant, Deedar M.; Thomas, Padmaja B.; Trousdale, Melvin D.; Mircheff, Austin K.; Schechter, Joel E.

2009-01-01

With the eventual goal of developing a tissue-engineered tear secretory system, we found that primary lacrimal gland acinar cells grown on solid poly(L-lactic acid) (PLLA) supports expressed the best histiotypic morphology. However, to be able to perform vectorial transport functions, epithelia must be supported by a permeable substratum. In the present study, we describe the use of a solvent-cast/particulate leaching technique to fabricate microporous PLLA membranes (mpPLLAm) from PLLA/polyethylene glycol blends. Scanning electron microscopy revealed pores on both the air-cured (∼4 μm) and glass-cured sides (<2 μm) of the mpPLLAm. Diffusion studies were performed with mpPLLAm fabricated from 57.1% PLLA/42.9% polyethylene glycol blends to confirm the presence of channelized pores. The data reveal that glucose, L-tryptophan, and dextran (a high molecular weight glucose polymer) readily permeate mpPLLAm. Diffusion of the immunoglobulin G through the mpPLLAm decreased with time, suggesting the possible adsorption and occlusion of the pores. Cells cultured on the mpPLLAm (57.1/42.9 wt%) grew to subconfluent monolayers but retained histiotypic morphological and physiological characteristics of lacrimal acinar cells in vivo. Our results suggest that mpPLLAm fabricated using this technique may be useful as a scaffold for a bioartificial lacrimal gland device. PMID:19260769

Systems and Methods for Fabricating Objects Including Amorphous Metal Using Techniques Akin to Additive Manufacturing

NASA Technical Reports Server (NTRS)

Hofmann, Douglas (Inventor)

2017-01-01

Systems and methods in accordance with embodiments of the invention fabricate objects including amorphous metals using techniques akin to additive manufacturing. In one embodiment, a method of fabricating an object that includes an amorphous metal includes: applying a first layer of molten metallic alloy to a surface; cooling the first layer of molten metallic alloy such that it solidifies and thereby forms a first layer including amorphous metal; subsequently applying at least one layer of molten metallic alloy onto a layer including amorphous metal; cooling each subsequently applied layer of molten metallic alloy such that it solidifies and thereby forms a layer including amorphous metal prior to the application of any adjacent layer of molten metallic alloy; where the aggregate of the solidified layers including amorphous metal forms a desired shape in the object to be fabricated; and removing at least the first layer including amorphous metal from the surface.

Development of improved electroforming technique. [for fabricating regeneratively cooled thrust chambers

NASA Technical Reports Server (NTRS)

Mccandles, L. C.; Davies, L. G.

1973-01-01

Techniques were studied to reinforce or strengthen electroformed nickel to allow a fuller utilization of electroforming as a reliable and low cost fabrication technique for regenerately cooled thrust chambers. Techniques for wire wrapping while electrodepositing were developed that can result in a structurally strong wall with less weight than a conventional electroformed wall. Also a technique of codepositing submicron sized THO2 particles with the nickel to form a dispersion strengthened structure was evaluated. The standard nickel cylinders exhibited an average hoop strength of 80,000 psi with a yield strength of 65,000 psi and a modulus of 25.6 x 10 to the 6th power psi. The as produced dispersion strengthened nickel showed a hoop strength of 97,000 psi with a yield strength of 67,000 psi. This is an increase of 17,000 psi or 21% over the standard nickel hoop strength. The wire wrapping cylinders showed an increased strength over the standard nickel test samples of 26,000 to 66,800 psi which is in the range of 26 to 104% increase in strength over the base standard nickel. These latter test results are indicative of a volume percent wire reinforcement from 15 to 31. The measured hoop strengths agree with calculated composite strengths based upon rule of mixtures.

Fabrication of high-transmission microporous membranes by proton beam writing-based molding technique

NASA Astrophysics Data System (ADS)

Wang, Liping; Meyer, Clemens; Guibert, Edouard; Homsy, Alexandra; Whitlow, Harry J.

2017-08-01

Porous membranes are widely used as filters in a broad range of micro and nanofluidic applications, e.g. organelle sorters, permeable cell growth substrates, and plasma filtration. Conventional silicon fabrication approaches are not suitable for microporous membranes due to the low mechanical stability of thin film substrates. Other techniques like ion track etching are limited to the production of randomly distributed and randomly orientated pores with non-uniform pore sizes. In this project, we developed a procedure for fabricating high-transmission microporous membranes by proton beam writing (PBW) with a combination of spin-casting and soft lithography. In this approach, focused 2 MeV protons were used to lithographically write patterns consisting of hexagonal arrays of high-density pillars of few μm size in a SU-8 layer coated on a silicon wafer. After development, the pillars were conformably coated with a thin film of poly-para-xylylene (Parylene)-C release agent and spin-coated with polydimethylsiloxane (PDMS). To facilitate demolding, a special technique based on the use of a laser-cut sealing tape ring was developed. This method facilitated the successful delamination of 20-μm thick PDMS membrane with high-density micropores from the mold without rupture or damage.

Fabrication of microgrooves with excimer laser ablation techniques for plastic optical fiber array alignment purposes

NASA Astrophysics Data System (ADS)

Naessens, Kris; Van Hove, An; Coosemans, Thierry; Verstuyft, Steven; Ottevaere, Heidi; Vanwassenhove, Luc; Van Daele, Peter; Baets, Roel G.

2000-06-01

Laser ablation is extremely well suited for rapid prototyping and proves to be a versatile technique delivering high accuracy dimensioning and repeatability of features in a wide diversity of materials. In this paper, we present laser ablation as a fabrication method for micro machining in of arrays consisting of precisely dimensioned U-grooves in dedicated polycarbonate and polymethylmetacrylate plates. The dependency of the performance on various parameters is discussed. The fabricated plates are used to hold optical fibers by means of a UV-curable adhesive. Stacking and gluing of the plates allows the assembly of a 2D connector of plastic optical fibers for short distance optical interconnects.

Managing Age Discrimination: An Examination of the Techniques Used when Seeking Employment

ERIC Educational Resources Information Center

Berger, Ellie D.

2009-01-01

Purpose: This article examines the age-related management techniques used by older workers in their search for employment. Design and Methods: Data are drawn from interviews with individuals aged 45-65 years (N = 30). Results: Findings indicate that participants develop "counteractions" and "concealments" to manage perceived age discrimination.…

AlGaInAs EML having high extinction ratios fabricated by identical epitaxial layer technique

NASA Astrophysics Data System (ADS)

Deng, Qiufang; Guo, Lu; Liang, Song; Sun, Siwei; Xie, Xiao; Zhu, Hongliang; Wang, Wei

2018-04-01

AlGaInAs electroabsorption-modulated lasers (EMLs) fabricated by identical epitaxial layer technique are demonstrated. The EML device shows an infinite characteristic temperature when the temperature ranges from 20 oC to 30 oC. The integrated modulator has static extinction ratios of larger than 20 dB at a reverse bias voltage of - 2 V. The small signal modulation bandwidth of the modulator is larger than 11 GHz. At 10 Gb/s data modulation, the dynamic extinction ratio is about 9.5 dB in a back to back test configuration. Because only a simple fabrication procedure is needed, our EMLs are promising low cost light sources for optical fiber transmission applications.

Development and fabrication of patient-specific knee implant using additive manufacturing techniques

NASA Astrophysics Data System (ADS)

Zammit, Robert; Rochman, Arif

2017-10-01

Total knee replacement is the most effective treatment to relief pain and restore normal function in a diseased knee joint. The aim of this research was to develop a patient-specific knee implant which can be fabricated using additive manufacturing techniques and has reduced wear rates using a highly wear resistant materials. The proposed design was chosen based on implant requirements, such as reduction in wear rates as well as strong fixation. The patient-specific knee implant improves on conventional knee implants by modifying the articulating surfaces and bone-implant interfaces. Moreover, tribological tests of different polymeric wear couples were carried out to determine the optimal materials to use for the articulating surfaces. Finite element analysis was utilized to evaluate the stresses sustained by the proposed design. Finally, the patient-specific knee implant was successfully built using additive manufacturing techniques.

Federal and State Employment Laws. Module Number 11. Work Experience Program Modules. Coordination Techniques Series.

ERIC Educational Resources Information Center

Kidney, John

This self-instructional module, the eleventh in a series of 16 on techniques for coordinating work experience programs, deals with federal and state employment laws. Addressed in the module are federal and state employment laws pertaining to minimum wage for student learners, minimum wage for full-time students, unemployment insurance, child labor…

Two-dimensional designed fabrication of subwavelength grating HCG mirror on silicon-on-insulator

NASA Astrophysics Data System (ADS)

Huang, Shen-Che; Hong, Kuo-Bin; Lu, Tien-Chang; He, Sailing

2016-03-01

We designed and fabricated a two dimensional high contrast subwavelength grating (HCG) mirrors. The computer-aided software was employed to verify the structural parameters including grating periods and filling factors. From the optimized simulation results, the designed HCG structure has a wide reflection stopband (reflectivity (R) >90%) of over 200 nm, which centered at telecommunication wavelength. The optimized HCG mirrors were fabricated by electron beam lithography and inductively coupled plasma process technique. The experimental result was almost consistent with calculated data. This achievement should have an impact on numerous photonic devices helpful attribution to the integrated HCG VCSELs in the future.

Fabrication of phonon-based metamaterial structures using focused ion beam patterning

NASA Astrophysics Data System (ADS)

Bassim, Nabil D.; Giles, Alexander J.; Ocola, Leonidas E.; Caldwell, Joshua D.

2018-02-01

The focused ion beam (FIB) is a powerful tool for rapid prototyping and machining of functional nanodevices. It is employed regularly to fabricate test metamaterial structures but, to date, has been unsuccessful in fabricating metamaterial structures with features at the nanoscale that rely on surface phonons as opposed to surface plasmons because of the crystalline damage that occurs with the collision cascade associated with ion sputtering. In this study, we employ a simple technique of protecting the crystalline substrate in single-crystal 4H-SiC to design surface phonon polariton-based optical resonance structures. By coating the material surface with a thin film of chromium, we have placed a material of high sputter resistance on the surface, which essentially absorbs the energy in the beam tails. When the beam ultimately punches through the Cr film, the hard walls in the film have the effect of channeling the beam to create smooth sidewalls. This demonstration opens the possibility of further rapid-prototyping of metamaterials using FIB.

Marginal and internal adaptation of ceramic crown restorations fabricated with CAD/CAM technology and the heat-press technique.

PubMed

Mously, Hisham A; Finkelman, Matthew; Zandparsa, Roya; Hirayama, Hiroshi

2014-08-01

The accuracy of chairside computer-aided design and computer-aided manufacturing (CAD/CAM) restorations is questionable, and the effect of the die spacer settings is not well stated in the literature. The purpose of the study was to evaluate the marginal and internal adaptation of E4D crowns fabricated with different spacer thicknesses and to compare these crowns with those fabricated with the heat-press technique. The E4D system was used to fabricate 30 crowns for the first 3 groups, with different spacer thickness settings: 30 μm, 60 μm, and 100 μm. In the fourth group, 10 lithium disilicate crowns were fabricated with the heat-press technique. The occlusal gap, axial gap, vertical marginal gap, and absolute marginal discrepancy were evaluated by x-ray microtomography. Statistical significance was assessed with the Kruskal-Wallis test (α=.05). For post hoc analyses, the Mann-Whitney U test was used alongside the Bonferroni correction for multiple comparisons (α=.008). Within the CAD/CAM groups, the 30-μm spacer thickness resulted in the lowest median axial gap (90.04 μm), whereas the 60-μm spacer thickness resulted in the lowest median occlusal gap (152.39 μm). The median marginal gap values of the CAD/CAM-60 group (49.35 μm) and CAD/CAM-100 group (46.65 μm) were lower than those of the CAD/CAM-30 group (55.18 μm). No significant differences among the CAD/CAM groups were observed for absolute marginal discrepancy. The heat-press group had significantly different values than those of the CAD/CAM groups. The spacer thickness and fabrication technique affected the adaptation of ceramic crowns. The heat-press group yielded the best marginal and internal crown adaptation results. The 30- or 60-μm spacer settings are recommended for the E4D CAD/CAM system. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Fabrication of enzyme-degradable and size-controlled protein nanowires using single particle nano-fabrication technique

PubMed Central

Omichi, Masaaki; Asano, Atsushi; Tsukuda, Satoshi; Takano, Katsuyoshi; Sugimoto, Masaki; Saeki, Akinori; Sakamaki, Daisuke; Onoda, Akira; Hayashi, Takashi; Seki, Shu

2014-01-01

Protein nanowires exhibiting specific biological activities hold promise for interacting with living cells and controlling and predicting biological responses such as apoptosis, endocytosis and cell adhesion. Here we report the result of the interaction of a single high-energy charged particle with protein molecules, giving size-controlled protein nanowires with an ultra-high aspect ratio of over 1,000. Degradation of the human serum albumin nanowires was examined using trypsin. The biotinylated human serum albumin nanowires bound avidin, demonstrating the high affinity of the nanowires. Human serum albumin–avidin hybrid nanowires were also fabricated from a solid state mixture and exhibited good mechanical strength in phosphate-buffered saline. The biotinylated human serum albumin nanowires can be transformed into nanowires exhibiting a biological function such as avidin–biotinyl interactions and peroxidase activity. The present technique is a versatile platform for functionalizing the surface of any protein molecule with an extremely large surface area. PMID:24770668

Fabrication of a metal-ceramic crown to fit an existing partial removable dental prosthesis using ceramic pressed to metal technique: a clinical report

PubMed Central

Seo, Jae-Min

2014-01-01

Fabricating a crown to retrofit an existing abutment tooth for a partial removable dental prosthesis (PRDP) is one of the most time-consuming and labor-intensive clinical procedures. In particular, when the patient is concerned with esthetic aspects of restoration, the task of fabricating becomes more daunting. Many techniques for the fabrication of all-metallic or metal-ceramic crowns have been discussed in the literature. This article was aimed to describe a simple fabrication method in which a retrofitting crown was fabricated for a precise fit using a ceramic-pressed-to-metal system. PMID:25006389

Evaluation of metal-ceramic bond characteristics of three dental Co-Cr alloys prepared with different fabrication techniques.

PubMed

Wang, Hongmei; Feng, Qing; Li, Ning; Xu, Sheng

2016-12-01

Limited information is available regarding the metal-ceramic bond strength of dental Co-Cr alloys fabricated by casting (CAST), computer numerical control (CNC) milling, and selective laser melting (SLM). The purpose of this in vitro study was to evaluate the metal-ceramic bond characteristics of 3 dental Co-Cr alloys fabricated by casting, computer numerical control milling, and selective laser melting techniques using the 3-point bend test (International Organization for Standardization [ISO] standard 9693). Forty-five specimens (25×3×0.5 mm) made of dental Co-Cr alloys were prepared by CAST, CNC milling, and SLM techniques. The morphology of the oxidation surface of metal specimens was evaluated by scanning electron microscopy (SEM). After porcelain application, the interfacial characterization was evaluated by SEM equipped with energy-dispersive spectrometry (EDS) analysis, and the metal-ceramic bond strength was assessed with the 3-point bend test. Failure type and elemental composition on the debonding interface were assessed by SEM/EDS. The bond strength was statistically analyzed by 1-way ANOVA and Tukey honest significant difference test (α=.05). The oxidation surfaces of the CAST, CNC, and SLM groups were different. They were porous in the CAST group but compact and irregular in the CNC and SLM groups. The metal-ceramic interfaces of the SLM and CNC groups showed excellent combination compared with those of the CAST group. The bond strength was 37.7 ±6.5 MPa for CAST, 43.3 ±9.2 MPa for CNC, and 46.8 ±5.1 MPa for the SLM group. Statistically significant differences were found among the 3 groups tested (P=.028). The debonding surfaces of all specimens exhibited cohesive failure mode. The oxidation surface morphologies and thicknesses of dental Co-Cr alloys are dependent on the different fabrication techniques used. The bond strength of all 3 groups exceed the minimum acceptable value of 25 MPa recommended by ISO 9693; hence, dental Co-Cr alloy

Fabrication of magnetic bubble memory overlay

NASA Technical Reports Server (NTRS)

1973-01-01

Self-contained magnetic bubble memory overlay is fabricated by process that employs epitaxial deposition to form multi-layered complex of magnetically active components on single chip. Overlay fabrication comprises three metal deposition steps followed by subtractive etch.

A new method of fabricating a blend scaffold using an indirect three-dimensional printing technique.

PubMed

Jung, Jin Woo; Lee, Hyungseok; Hong, Jung Min; Park, Jeong Hun; Shim, Jung Hee; Choi, Tae Hyun; Cho, Dong-Woo

2015-11-03

Due to its simplicity and effectiveness, the physical blending of polymers is considered to be a practical strategy for developing a versatile scaffold having desirable mechanical and biochemical properties. In the present work, an indirect three-dimensional (i3D) printing technique was proposed to fabricate a 3D free-form scaffold using a blend of immiscible materials, such as polycaprolactone (PCL) and gelatin. The i3D printing technique includes 3D printing of a mold and a sacrificial molding process. PCL/chloroform and gelatin/water were physically mixed to prepare the blend solution, which was subsequently injected into the cavity of a 3D printed mold. After solvent removal and gelatin cross-linking, the mold was dissolved to obtain a PCL-gelatin (PG) scaffold, with a specific 3D structure. Scanning electron microscopy and Fourier transform infrared spectroscopy analysis indicated that PCL masses and gelatin fibers in the PG scaffold homogenously coexisted without chemical bonding. Compression tests confirmed that gelatin incorporation into the PCL enhanced its mechanical flexibility and softness, to the point of being suitable for soft-tissue engineering, as opposed to pure PCL. Human adipose-derived stem cells, cultured on a PG scaffold, exhibited enhanced in vitro chondrogenic differentiation and tissue formation, compared with those on a PCL scaffold. The i3D printing technique can be used to blend a variety of materials, facilitating 3D scaffold fabrication for specific tissue regeneration. Furthermore, this convenient and versatile technique may lead to wider application of 3D printing in tissue engineering.

A microcomputed tomography evaluation of the marginal fit of cobalt-chromium alloy copings fabricated by new manufacturing techniques and alloy systems.

PubMed

Kim, Eun-Ha; Lee, Du-Hyeong; Kwon, Sung-Min; Kwon, Tae-Yub

2017-03-01

Although new digital manufacturing techniques are attracting interest in dentistry, few studies have comprehensively investigated the marginal fit of fixed dental prostheses fabricated with such techniques. The purpose of this in vitro microcomputed tomography (μCT) study was to evaluate the marginal fit of cobalt-chromium (Co-Cr) alloy copings fabricated by casting and 3 different computer-aided design and computer-aided manufacturing (CAD-CAM)-based processing techniques and alloy systems. Single Co-Cr metal crowns were fabricated using 4 different manufacturing techniques: casting (control), milling, selective laser melting, and milling/sintering. Two different commercial alloy systems were used for each fabrication technique (a total of 8 groups; n=10 for each group). The marginal discrepancy and absolute marginal discrepancy of the crowns were determined with μCT. For each specimen, the values were determined from 4 different regions (sagittal buccal, sagittal lingual, coronal mesial, and coronal distal) by using imaging software and recorded as the average of the 4 readings. For each parameter, the results were statistically compared with 2-way analysis of variance and appropriate post hoc analysis (using Tukey or Student t test) (α=.05). The milling and selective laser melting groups showed significantly larger marginal discrepancies than the control groups (70.4 ±12.0 and 65.3 ±10.1 μm, respectively; P<.001), whereas the milling/sintering groups exhibited significantly smaller values than the controls (P=.004). The milling groups showed significantly larger absolute marginal discrepancy than the control groups (137.4 ±29.0 and 139.2 ±18.9 μm, respectively; P<.05). In the selective laser melting and milling/sintering groups, the absolute marginal discrepancy values were material-specific (P<.05). Nonetheless, the milling/sintering groups yielded statistically comparable (P=.935) or smaller (P<.001) absolute marginal discrepancies to the control

V/sub 3/Ga wire fabricated by the modified jelly roll technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gubser, D.U.; Francavilla, T.L.; Pande, C.S.

V/sub 3/Ga wire has been fabricated by the modified jelly roll technique for the first time. Critical current densities in magnetic fields to 22 T, critical magnetic fields, and superconducting transition temperatures are reported for this wire as a function of reaction temperature for forming the interfacial V/sub 3/Ga layer. Superconducting properties of the reacted wire are optimized for reaction temperatures between 550--580 /sup 0/C. With a reaction temperature of 580 /sup 0/C, the overall (noncopper) current density of the wire is over 10/sup 4/ amp/cm/sup 2/ at 19 T.

Radio frequency diodes and circuits fabricated via adhesion lithography (Conference Presentation)

NASA Astrophysics Data System (ADS)

Georgiadou, Dimitra G.; Semple, James; Wyatt-Moon, Gwenhivir; Anthopoulos, Thomas D.

2016-09-01

The commercial interest in Radio Frequency Identification (RFID) tags keeps growing, as new application sectors, spanning from healthcare to electronic article surveillance (EAS) and personal identification, are constantly emerging for these types of electronic devices. The increasing demand for the so-called "smart labels" necessitates their high throughput manufacturing, and indeed on thin flexible substrates, that will reduce the cost and render them competitive to the currently widely employed barcodes. Adhesion Lithography (a-Lith) is a novel patterning technique that allows the facile high yield fabrication of co-planar large aspect ratio (<100,000) metal electrodes separated by a sub-20 nm gap on large area substrates of any type. Deposition of high mobility semiconductors from their solution at low, compatible with plastic substrates, temperatures and application of specific processing protocols can dramatically improve the performance of the fabricated Schottky diodes. It will be shown that in this manner both organic and inorganic high speed diodes and rectifiers can be obtained, operating at frequencies much higher than the 13.56 MHz benchmark, currently employed in passive RFID tags and near filed communications (NFC). This showcases the universality of this method towards fabricating high speed p- and n-type diodes, irrespective of the substrate, simply based on the extreme downscaling of key device dimensions obtained in these nanoscale structures. The potential for scaling up this technique at low cost, combined with the significant performance optimisation and improved functionality that can be attained through intelligent material selection, render a-Lith unique within the field of plastic electronics.

A novel method of fabricating carbon nanotubes-polydimethylsiloxane composite electrodes for electrocardiography.

PubMed

Liu, Benyan; Chen, Yingmin; Luo, Zhangyuan; Zhang, Wenzan; Tu, Quan; Jin, Xun

2015-01-01

Polymer-based flexible electrodes are receiving much attention in medical applications due to their good wearing comfort. The current fabrication methods of such electrodes are not widely applied. In this study, polydimethylsiloxane (PDMS) and conductive additives of carbon nanotubes (CNTs) were employed to fabricate composite electrodes for electrocardiography (ECG). A three-step dispersion process consisting of ultrasonication, stirring, and in situ polymerization was developed to yield homogenous CNTs-PDMS mixtures. The CNTs-PDMS mixtures were used to fabricate CNTs-PDMS composite electrodes by replica technology. The influence of ultrasonication time and CNT concentration on polymer electrode performance was evaluated by impedance and ECG measurements. The signal amplitude of the electrodes prepared using an ultrasonication time of 12 h and CNT content of 5 wt% was comparable to that of commercial Ag/AgCl electrodes. The polymer electrodes were easily fabricated by conventional manufacturing techniques, indicating a potential advantage of reduced cost for mass production.

Fabrication of nanowire channels with unidirectional alignment and controlled length by a simple, gas-blowing-assisted, selective-transfer-printing technique.

PubMed

Kim, Yong-Kwan; Kang, Pil Soo; Kim, Dae-Il; Shin, Gunchul; Kim, Gyu Tae; Ha, Jeong Sook

2009-03-01

A printing-based lithographic technique for the patterning of V(2)O(5) nanowire channels with unidirectional orientation and controlled length is introduced. The simple, directional blowing of a patterned polymer stamp with N(2) gas, inked with randomly distributed V(2)O(5) nanowires, induces alignment of the nanowires perpendicular to the long axis of the line patterns. Subsequent stamping on the amine-terminated surface results in the selective transfer of the aligned nanowires with a controlled length corresponding to the width of the relief region of the polymer stamp. By employing such a gas-blowing-assisted, selective-transfer-printing technique, two kinds of device structures consisting of nanowire channels and two metal electrodes with top contact, whereby the nanowires were aligned either parallel (parallel device) or perpendicular (serial device) to the current flow in the conduction channel, are fabricated. The electrical properties demonstrate a noticeable difference between the two devices, with a large hysteresis in the parallel device but none in the serial device. Systematic analysis of the hysteresis and the electrical stability account for the observed hysteresis in terms of the proton diffusion in the water layer of the V(2)O(5) nanowires, induced by the application of an external bias voltage higher than a certain threshold voltage.

Nanoimprint lithography for nanodevice fabrication

NASA Astrophysics Data System (ADS)

Barcelo, Steven; Li, Zhiyong

2016-09-01

Nanoimprint lithography (NIL) is a compelling technique for low cost nanoscale device fabrication. The precise and repeatable replication of nanoscale patterns from a single high resolution patterning step makes the NIL technique much more versatile than other expensive techniques such as e-beam or even helium ion beam lithography. Furthermore, the use of mechanical deformation during the NIL process enables grayscale lithography with only a single patterning step, not achievable with any other conventional lithography techniques. These strengths enable the fabrication of unique nanoscale devices by NIL for a variety of applications including optics, plasmonics and even biotechnology. Recent advances in throughput and yield in NIL processes demonstrate the potential of being adopted for mainstream semiconductor device fabrication as well.

The role of rapid solidification processing in the fabrication of fiber reinforced metal matrix composites

NASA Technical Reports Server (NTRS)

Locci, Ivan E.; Noebe, Ronald D.

1989-01-01

Advanced composite processing techniques for fiber reinforced metal matrix composites require the flexibility to meet several widespread objectives. The development of uniquely desired matrix microstructures and uniformly arrayed fiber spacing with sufficient bonding between fiber and matrix to transmit load between them without degradation to the fiber or matrix are the minimum requirements necessary of any fabrication process. For most applications these criteria can be met by fabricating composite monotapes which are then consolidated into composite panels or more complicated components such as fiber reinforced turbine blades. Regardless of the end component, composite monotapes are the building blocks from which near net shape composite structures can be formed. The most common methods for forming composite monotapes are the powder cloth, foil/fiber, plasma spray, and arc spray processes. These practices, however, employ rapid solidification techniques in processing of the composite matrix phase. Consequently, rapid solidification processes play a vital and yet generally overlooked role in composite fabrication. The future potential of rapid solidification processing is discussed.

A novel porous scaffold fabrication technique for epithelial and endothelial tissue engineering.

PubMed

McHugh, Kevin J; Tao, Sarah L; Saint-Geniez, Magali

2013-07-01

Porous scaffolds have the ability to minimize transport barriers for both two- (2D) and three-dimensional tissue engineering. However, current porous scaffolds may be non-ideal for 2D tissues such as epithelium due to inherent fabrication-based characteristics. While 2D tissues require porosity to support molecular transport, pores must be small enough to prevent cell migration into the scaffold in order to avoid non-epithelial tissue architecture and compromised function. Though electrospun meshes are the most popular porous scaffolds used today, their heterogeneous pore size and intense topography may be poorly-suited for epithelium. Porous scaffolds produced using other methods have similar unavoidable limitations, frequently involving insufficient pore resolution and control, which make them incompatible with 2D tissues. In addition, many of these techniques require an entirely new round of process development in order to change material or pore size. Herein we describe "pore casting," a fabrication method that produces flat scaffolds with deterministic pore shape, size, and location that can be easily altered to accommodate new materials or pore dimensions. As proof-of-concept, pore-cast poly(ε-caprolactone) (PCL) scaffolds were fabricated and compared to electrospun PCL in vitro using canine kidney epithelium, human colon epithelium, and human umbilical vein endothelium. All cell types demonstrated improved morphology and function on pore-cast scaffolds, likely due to reduced topography and universally small pore size. These results suggest that pore casting is an attractive option for creating 2D tissue engineering scaffolds, especially when the application may benefit from well-controlled pore size or architecture.

Digital evaluation of absolute marginal discrepancy: A comparison of ceramic crowns fabricated with conventional and digital techniques.

PubMed

Liang, Shanshan; Yuan, Fusong; Luo, Xu; Yu, Zhuoren; Tang, Zhihui

2018-04-05

Marginal discrepancy is key to evaluating the accuracy of fixed dental prostheses. An improved method of evaluating marginal discrepancy is needed. The purpose of this in vitro study was to evaluate the absolute marginal discrepancy of ceramic crowns fabricated using conventional and digital methods with a digital method for the quantitative evaluation of absolute marginal discrepancy. The novel method was based on 3-dimensional scanning, iterative closest point registration techniques, and reverse engineering theory. Six standard tooth preparations for the right maxillary central incisor, right maxillary second premolar, right maxillary second molar, left mandibular lateral incisor, left mandibular first premolar, and left mandibular first molar were selected. Ten conventional ceramic crowns and 10 CEREC crowns were fabricated for each tooth preparation. A dental cast scanner was used to obtain 3-dimensional data of the preparations and ceramic crowns, and the data were compared with the "virtual seating" iterative closest point technique. Reverse engineering software used edge sharpening and other functional modules to extract the margins of the preparations and crowns. Finally, quantitative evaluation of the absolute marginal discrepancy of the ceramic crowns was obtained from the 2-dimensional cross-sectional straight-line distance between points on the margin of the ceramic crowns and the standard preparations based on the circumferential function module along the long axis. The absolute marginal discrepancy of the ceramic crowns fabricated using conventional methods was 115 ±15.2 μm, and 110 ±14.3 μm for those fabricated using the digital technique was. ANOVA showed no statistical difference between the 2 methods or among ceramic crowns for different teeth (P>.05). The digital quantitative evaluation method for the absolute marginal discrepancy of ceramic crowns was established. The evaluations determined that the absolute marginal discrepancies were

Polyurethane-acrylate-based hydrophobic film: Facile fabrication, characterization, and application

NASA Astrophysics Data System (ADS)

Park, Jongsung; Nguyen, Bui Quoc Huy; Kim, Ji-Kwan; Shanmugasundaram, Arunkumar; Lee, Dong-Weon

2018-06-01

Polyurethane-acrylate (PUA) is a versatile UV-curable polymer with a short curing time at room temperature, whose surface structure can be flexibly modified by applying various micropatterns. In this paper, we propose a facile and cost-effective fabrication method for the continuous production of an optically transparent PUA-based superhydrophobic thin film. Poly(dimethylsiloxane) (PDMS) was employed as a soft mold for the fabrication of PUA films through the roll-to-roll technique. In addition, nanosilica was spray-coated onto the PUA surface to further improve the hydrophobicity. The fabricated PUA thin film showed the highest static water contact angle (WCA) of ∼140°. The high durability of the PUA film was also demonstrated through mechanical impacting tests. Furthermore, only ∼2% of voltage loss was observed in the solar panel covered with the PUA-based superhydrophobic film. These obtained results indicate the feasibility of applying the film as a protective layer in applications requiring a high transparency and a self-cleaning effect.

Comparison the Marginal and Internal Fit of Metal Copings Cast from Wax Patterns Fabricated by CAD/CAM and Conventional Wax up Techniques.

PubMed

Vojdani, M; Torabi, K; Farjood, E; Khaledi, Aar

2013-09-01

Metal-ceramic crowns are most commonly used as the complete coverage restorations in clinical daily use. Disadvantages of conventional hand-made wax-patterns introduce some alternative ways by means of CAD/CAM technologies. This study compares the marginal and internal fit of copings cast from CAD/CAM and conventional fabricated wax-patterns. Twenty-four standardized brass dies were prepared and randomly divided into 2 groups according to the wax-patterns fabrication method (CAD/CAM technique and conventional method) (n=12). All the wax-patterns were fabricated in a standard fashion by means of contour, thickness and internal relief (M1-M12: representative of CAD/CAM group, C1-C12: representative of conventional group). CAD/CAM milling machine (Cori TEC 340i; imes-icore GmbH, Eiterfeld, Germany) was used to fabricate the CAD/CAM group wax-patterns. The copings cast from 24 wax-patterns were cemented to the corresponding dies. For all the coping-die assemblies cross-sectional technique was used to evaluate the marginal and internal fit at 15 points. The Student's t- test was used for statistical analysis (α=0.05). The overall mean (SD) for absolute marginal discrepancy (AMD) was 254.46 (25.10) um for CAD/CAM group and 88.08(10.67) um for conventional group (control). The overall mean of internal gap total (IGT) was 110.77(5.92) um for CAD/CAM group and 76.90 (10.17) um for conventional group. The Student's t-test revealed significant differences between 2 groups. Marginal and internal gaps were found to be significantly higher at all measured areas in CAD/CAM group than conventional group (p< 0.001). Within limitations of this study, conventional method of wax-pattern fabrication produced copings with significantly better marginal and internal fit than CAD/CAM (machine-milled) technique. All the factors for 2 groups were standardized except wax pattern fabrication technique, therefore, only the conventional group results in copings with clinically acceptable

Gold nanoparticles mediated coloring of fabrics and leather for antibacterial activity.

PubMed

Velmurugan, Palanivel; Shim, Jaehong; Bang, Keuk-Soo; Oh, Byung-Taek

2016-07-01

Metal gold nanoparticles (AuNPs) were synthesized in situ onto leather, silk and cotton fabrics by three different modules, including green, chemical, and a composite of green and chemical synthesis. Green synthesis was employed using Ginkgo biloba Linn leaf powder extract and HAuCl4 with the fabrics, and chemical synthesis was done with KBH4 and HAuCl4. For composite synthesis, G. biloba extract and KBH4 were used to color and embed AuNPs in the fabrics. The colored fabrics were tested for color coordination and fastness properties. To validate the green synthesis of AuNPs, various instrumental techniques were used including UV-Vis spectrophotometry, HR-TEM, FTIR, and XRD. The chemical and composite methods reduce Au(+) onto leather, silk and cotton fabrics upon heating, and alkaline conditions are required for bonding to fibers; these conditions are not used in the green synthesis protocol. FE-SEM image revealed the binding nature of the AuNPs to the fabrics. The AuNPs that were synthesized in situ on the fabrics were tested against a skin pathogen, Brevibacterium linens using LIVE/DEAD BacLight Bacterial Viability testing. This study represents an initial route for coloring and bio-functionalization of various fabrics with green technologies, and, accordingly, should open new avenues for innovation in the textile and garment sectors. Copyright © 2016 Elsevier B.V. All rights reserved.

Characterization of a Viking Blade Fabricated by Traditional Forging Techniques

NASA Astrophysics Data System (ADS)

Vo, H.; Frazer, D.; Bailey, N.; Traylor, R.; Austin, J.; Pringle, J.; Bickel, J.; Connick, R.; Connick, W.; Hosemann, P.

2016-12-01

A team of students from the University of California, Berkeley, participated in a blade-smithing competition hosted by the Minerals, Metals, and Materials Society at the TMS 2015 144th annual meeting and exhibition. Motivated by ancient forging methods, the UC Berkeley team chose to fabricate our blade from historical smithing techniques utilizing naturally-occurring deposits of iron ore. This approach resulted in receiving the "Best Example of a Traditional Blade Process/Ore Smelting Technique" award for our blade named "Berkelium." First, iron-enriched sand was collected from local beaches. Magnetite (Fe3O4) was then extracted from the sand and smelted into individual high- and low-carbon steel ingots. Layers of high- and low-carbon steels were forge-welded together, predominantly by hand, to form a composite material. Optical microscopy, energy dispersive spectroscopy, and Vickers hardness mechanical testing were conducted at different stages throughout the blade-making process to evaluate the microstructure and hardness evolution during formation. It was found that the pre-heat-treated blade microstructure was composed of ferrite and pearlite, and contained many nonmetallic inclusions. A final heat treatment was performed, which caused the average hardness of the blade edge to increase by more than a factor of two, indicating a martensitic transformation.

Optimization of pyrethroid and repellent on fabrics against Stegomyia albopicta (=Aedes albopictus) using a microencapsulation technique.

PubMed

Yao, T-T; Wang, L-K; Cheng, J-L; Hu, Y-Z; Zhao, J-H; Zhu, G-N

2015-03-01

A new approach employing a combination of pyrethroid and repellent is proposed to improve the protective efficacy of conventional pyrethroid-treated fabrics against mosquito vectors. In this context, the insecticidal and repellent efficacies of commonly used pyrethroids and repellents were evaluated by cone tests and arm-in-cage tests against Stegomyia albopicta (=Aedes albopictus) (Diptera: Culicidae). At concentrations of LD50 (estimated for pyrethroid) or ED50 (estimated for repellent), respectively, the knock-down effects of the pyrethroids or repellents were further compared. The results obtained indicated that deltamethrin and DEET were relatively more effective and thus these were selected for further study. Synergistic interaction was observed between deltamethrin and DEET at the ratios of 5 : 1, 2 : 1, 1 : 1 and 1 : 2 (but not 1 : 5). An optimal mixing ratio of 7 : 5 was then microencapsulated and adhered to fabrics using a fixing agent. Fabrics impregnated by microencapsulated mixtures gained extended washing durability compared with those treated with a conventional dipping method. Results indicated that this approach represents a promising method for the future impregnation of bednet, curtain and combat uniform materials. © 2014 The Royal Entomological Society.

Outcomes of Orbital Floor Reconstruction After Extensive Maxillectomy Using the Computer-Assisted Fabricated Individual Titanium Mesh Technique.

PubMed

Zhang, Wen-Bo; Mao, Chi; Liu, Xiao-Jing; Guo, Chuan-Bin; Yu, Guang-Yan; Peng, Xin

2015-10-01

Orbital floor defects after extensive maxillectomy can cause severe esthetic and functional deformities. Orbital floor reconstruction using the computer-assisted fabricated individual titanium mesh technique is a promising method. This study evaluated the application and clinical outcomes of this technique. This retrospective study included 10 patients with orbital floor defects after maxillectomy performed from 2012 through 2014. A 3-dimensional individual stereo model based on mirror images of the unaffected orbit was obtained to fabricate an anatomically adapted titanium mesh using computer-assisted design and manufacturing. The titanium mesh was inserted into the defect using computer navigation. The postoperative globe projection and orbital volume were measured and the incidence of postoperative complications was evaluated. The average postoperative globe projection was 15.91 ± 1.80 mm on the affected side and 16.24 ± 2.24 mm on the unaffected side (P = .505), and the average postoperative orbital volume was 26.01 ± 1.28 and 25.57 ± 1.89 mL, respectively (P = .312). The mean mesh depth was 25.11 ± 2.13 mm. The mean follow-up period was 23.4 ± 7.7 months (12 to 34 months). Of the 10 patients, 9 did not develop diplopia or a decrease in visual acuity and ocular motility. Titanium mesh exposure was not observed in any patient. All patients were satisfied with their postoperative facial symmetry. Orbital floor reconstruction after extensive maxillectomy with an individual titanium mesh fabricated using computer-assisted techniques can preserve globe projection and orbital volume, resulting in successful clinical outcomes. Copyright © 2015 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.

Fabrication of metal nanopatterns for organic field effect transistor electrodes by cracking and transfer printing

NASA Astrophysics Data System (ADS)

Wang, Xiaonan; Fu, Tingting; Wang, Zhe

2018-04-01

In this paper, we demonstrate a novel method for fabricating metal nanopatterns using cracking to address the limitations of traditional techniques. Parallel crack arrays were created in a polydimethylsiloxane (PDMS) mold using a combination of surface modification and control of strain fields. The elastic PDMS containing the crack arrays was subsequently used as a stamp to prepare nanoscale metal patterns on a substrate by transfer printing. To illustrate the functionality of this technique, we employed the metal patterns as the source and drain contacts of an organic field effect transistor. Using this approach, we fabricated transistors with channel lengths ranging from 70-600 nm. The performance of these devices when the channel length was reduced was studied. The drive current density increases as expected, indicating the creation of operational transistors with recognizable properties.

Spectral characterization of porous dielectric subwavelength THz fibers fabricated using a microstructured molding technique.

PubMed

Dupuis, Alexandre; Mazhorova, Anna; Désévédavy, Frédéric; Rozé, Mathieu; Skorobogatiy, Maksim

2010-06-21

We report two novel fabrication techniques, as well as THz spectral transmission and propagation loss measurements of subwavelength plastic wires with highly porous (up to 86%) and non-porous transverse geometries. The two fabrication techniques we describe are based on the microstructured molding approach. In one technique the mold is made completely from silica by stacking and fusing silica capillaries to the bottom of a silica ampoule. The melted material is then poured into the silica mold to cast the microstructured preform. Another approach uses a microstructured mold made of a sacrificial plastic which is co-drawn with a cast preform. Material from the sacrificial mold is then dissolved after fi ber drawing. We also describe a novel THz-TDS setup with an easily adjustable optical path length, designed to perform cutback measurements using THz fibers of up to 50 cm in length. We fi nd that while both porous and non-porous subwavelength fibers of the same outside diameter have low propagation losses (alpha

Fabrication of low-cost, cementless femoral stem 316L stainless steel using investment casting technique.

PubMed

Baharuddin, Mohd Yusof; Salleh, Sh-Hussain; Suhasril, Andril Arafat; Zulkifly, Ahmad Hafiz; Lee, Muhammad Hisyam; Omar, Mohd Afian; Abd Kader, Ab Saman; Mohd Noor, Alias; A Harris, Arief Ruhullah; Abdul Majid, Norazman

2014-07-01

Total hip arthroplasty is a flourishing orthopedic surgery, generating billions of dollars of revenue. The cost associated with the fabrication of implants has been increasing year by year, and this phenomenon has burdened the patient with extra charges. Consequently, this study will focus on designing an accurate implant via implementing the reverse engineering of three-dimensional morphological study based on a particular population. By using finite element analysis, this study will assist to predict the outcome and could become a useful tool for preclinical testing of newly designed implants. A prototype is then fabricated using 316L stainless steel by applying investment casting techniques that reduce manufacturing cost without jeopardizing implant quality. The finite element analysis showed that the maximum von Mises stress was 66.88 MPa proximally with a safety factor of 2.39 against endosteal fracture, and micromotion was 4.73 μm, which promotes osseointegration. This method offers a fabrication process of cementless femoral stems with lower cost, subsequently helping patients, particularly those from nondeveloped countries. Copyright © 2013 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

Yb-doped large-mode-area laser fiber fabricated by halide-gas-phase-doping technique

NASA Astrophysics Data System (ADS)

Peng, Kun; Wang, Yuying; Ni, Li; Wang, Zhen; Gao, Cong; Zhan, Huan; Wang, Jianjun; Jing, Feng; Lin, Aoxiang

2015-06-01

In this manuscript, we designed a rare-earth-halide gas-phase-doping setup to fabricate a large-mode-area fiber for high power laser applications. YbCl3 and AlCl3 halides are evaporated, carried respectively and finally mixed with usual host gas material SiCl4 at the hot zone of MCVD system. Owing to the all-gas-phasing reaction process and environment, the home-made Yb-doped fiber preform has a homogeneous large core and modulated refractive index profile to keep high beam quality. The drawn fiber core has a small numerical aperture of 0.07 and high Yb concentration of 9500 ppm. By using a master oscillator power amplifier system, nearly kW-level (951 W) laser output power was obtained with a slope efficiency of 83.3% at 1063.8 nm, indicating the competition and potential of the halide-gas-phase-doping technique for high power laser fiber fabrication.

Fabrication of balloon-expandable self-lock drug-eluting polycaprolactone stents using micro-injection molding and spray coating techniques.

PubMed

Liu, Shih-Jung; Chiang, Fu-Jun; Hsiao, Chao-Ying; Kau, Yi-Chuan; Liu, Kuo-Sheng

2010-10-01

The purpose of this report was to develop novel balloon-expandable self-lock drug-eluting poly(ε-caprolactone) stents. To fabricate the biodegradable stents, polycaprolactone (PCL) components were first fabricated by a lab-scale micro-injection molded machine. They were then assembled and hot-spot welded into mesh-like stents of 3 and 5 mm in diameters. A special geometry of the components was designed to self-lock the assembled stents and to resist the external pressure of the blood vessels after being expanded by balloons. Characterization of the biodegradable PCL stents was carried out. PCL stents exhibited comparable mechanical property to that of metallic stents. No significant collapse pressure reduction and weight loss of the stents were observed after being submerged in PBS for 12 weeks. In addition, the developed stent was coated with paclitaxel by a spray coating technique and the release characteristic of the drug was determined by an in vitro elution method. The high-performance liquid chromatography analysis showed that the biodegradable stents could release a high concentration of paclitaxel for more than 60 days. By adopting the novel techniques, we will be able to fabricate biodegradable drug-eluting PCL stents of different sizes for various cardiovascular applications.

Development of Ultraviolet (UV) Radiation Protective Fabric Using Combined Electrospinning and Electrospraying Technique

NASA Astrophysics Data System (ADS)

Sinha, Mukesh Kumar; Das, B. R.; Kumar, Kamal; Kishore, Brij; Prasad, N. Eswara

2017-06-01

The article reports a novel technique for functionization of nanoweb to develop ultraviolet (UV) radiation protective fabric. UV radiation protection effect is produced by combination of electrospinning and electrospraying technique. A nanofibrous web of polyvinylidene difluoride (PVDF) coated on polypropylene nonwoven fabric is produced by latest nanospider technology. Subsequently, web is functionalized by titanium dioxide (TiO2). The developed web is characterized for evaluation of surface morphology and other functional properties; mechanical, chemical, crystalline and thermal. An optimal (judicious) nanofibre spinning condition is achieved and established. The produced web is uniformly coated by defect free functional nanofibres in a continuous form of useable textile structural membrane for ultraviolet (UV) protective clothing. This research initiative succeeds in preparation and optimization of various nanowebs for UV protection. Field Emission Scanning Electron Microscope (FESEM) result reveals that PVDF webs photo-degradative behavior is non-accelerated, as compared to normal polymeric grade fibres. Functionalization with TiO2 has enhanced the photo-stability of webs. The ultraviolet protection factor of functionalized and non-functionalized nanowebs empirically evaluated to be 65 and 24 respectively. The developed coated layer could be exploited for developing various defence, para-military and civilian UV protective light weight clothing (tent, covers and shelter segments, combat suit, snow bound camouflaging nets). This research therefore, is conducted in an attempt to develop a scientific understanding of PVDF fibre coated webs for photo-degradation and applications for defence protective textiles. This technological research in laboratory scale could be translated into bulk productionization.

Fabrication

NASA Technical Reports Server (NTRS)

Angel, Roger; Helms, Richard; Bilbro, Jim; Brown, Norman; Eng, Sverre; Hinman, Steve; Hull-Allen, Greg; Jacobs, Stephen; Keim, Robert; Ulmer, Melville

1992-01-01

What aspects of optical fabrication technology need to be developed so as to facilitate existing planned missions, or enable new ones? Throughout the submillimeter to UV wavelengths, the common goal is to push technology to the limits to make the largest possible apertures that are diffraction limited. At any one wavelength, the accuracy of the surface must be better than lambda/30 (rms error). The wavelength range is huge, covering four orders of magnitude from 1 mm to 100 nm. At the longer wavelengths, diffraction limited surfaces can be shaped with relatively crude techniques. The challenge in their fabrication is to make as large as possible a reflector, given the weight and volume constraints of the launch vehicle. The limited cargo diameter of the shuttle has led in the past to emphasis on deployable or erectable concepts such as the Large Deployable Reflector (LDR), which was studied by NASA for a submillimeter astrophysics mission. Replication techniques that can be used to produce light, low-cost reflecting panels are of great interest for this class of mission. At shorter wavelengths, in the optical and ultraviolet, optical fabrication will tax to the limit the most refined polishing methods. Methods of mechanical and thermal stabilization of the substrate will be severely stressed. In the thermal infrared, the need for large aperture is tempered by the even stronger need to control the telescope's thermal emission by cooled or cryogenic operation. Thus, the SIRTF mirror at 1 meter is not large and does not require unusually high accuracy, but the fabrication process must produce a mirror that is the right shape at a temperature of 4 K. Future large cooled mirrors will present more severe problems, especially if they must also be accurate enough to work at optical wavelengths. At the very shortest wavelengths accessible to reflecting optics, in the x-ray domain, the very low count fluxes of high energy photons place a premium on the collecting area. It is

Fabrication

NASA Astrophysics Data System (ADS)

Angel, Roger; Helms, Richard; Bilbro, Jim; Brown, Norman; Eng, Sverre; Hinman, Steve; Hull-Allen, Greg; Jacobs, Stephen; Keim, Robert; Ulmer, Melville

1992-08-01

What aspects of optical fabrication technology need to be developed so as to facilitate existing planned missions, or enable new ones? Throughout the submillimeter to UV wavelengths, the common goal is to push technology to the limits to make the largest possible apertures that are diffraction limited. At any one wavelength, the accuracy of the surface must be better than lambda/30 (rms error). The wavelength range is huge, covering four orders of magnitude from 1 mm to 100 nm. At the longer wavelengths, diffraction limited surfaces can be shaped with relatively crude techniques. The challenge in their fabrication is to make as large as possible a reflector, given the weight and volume constraints of the launch vehicle. The limited cargo diameter of the shuttle has led in the past to emphasis on deployable or erectable concepts such as the Large Deployable Reflector (LDR), which was studied by NASA for a submillimeter astrophysics mission. Replication techniques that can be used to produce light, low-cost reflecting panels are of great interest for this class of mission. At shorter wavelengths, in the optical and ultraviolet, optical fabrication will tax to the limit the most refined polishing methods. Methods of mechanical and thermal stabilization of the substrate will be severely stressed. In the thermal infrared, the need for large aperture is tempered by the even stronger need to control the telescope's thermal emission by cooled or cryogenic operation. Thus, the SIRTF mirror at 1 meter is not large and does not require unusually high accuracy, but the fabrication process must produce a mirror that is the right shape at a temperature of 4 K. Future large cooled mirrors will present more severe problems, especially if they must also be accurate enough to work at optical wavelengths. At the very shortest wavelengths accessible to reflecting optics, in the x-ray domain, the very low count fluxes of high energy photons place a premium on the collecting area. It is

Fabrication of Multscale Fractal-Like Structures by Controlling Fluid Interface Instability

PubMed Central

Islam, Tanveer ul; Gandhi, Prasanna S.

2016-01-01

Nature, in quest for the best designs has shaped its vital systems into fractal geometries. Effectual way of spontaneous fabrication of scalable, ordered fractal-like structures by controlling Saffman-Taylor instability in a lifted Hele-Shaw cell is deployed here. In lifted Hele-Shaw cell uncontrolled penetration of low-viscosity fluid into its high-viscosity counterpart is known to develop irregular, non-repeatable, normally short-lived, branched patterns. We propose and characterize experimentally anisotropies in a form of spatially distributed pits on the cell plates to control initiation and further penetration of non-splitting fingers. The proposed control over shielding mechanism yields recipes for fabrication of families of ordered fractal-like patterns of multiple generations. As an example, we demonstrate and characterize fabrication of a Cayley tree fractal-like pattern. The patterns, in addition, are retained permanently by employing UV/thermally curable fluids. The proposed technique thus establishes solid foundation for bio-mimicking natural structures spanning multiple-scales for scientific and engineering use. PMID:27849003

Fabrication of Multscale Fractal-Like Structures by Controlling Fluid Interface Instability

NASA Astrophysics Data System (ADS)

Islam, Tanveer Ul; Gandhi, Prasanna S.

2016-11-01

Nature, in quest for the best designs has shaped its vital systems into fractal geometries. Effectual way of spontaneous fabrication of scalable, ordered fractal-like structures by controlling Saffman-Taylor instability in a lifted Hele-Shaw cell is deployed here. In lifted Hele-Shaw cell uncontrolled penetration of low-viscosity fluid into its high-viscosity counterpart is known to develop irregular, non-repeatable, normally short-lived, branched patterns. We propose and characterize experimentally anisotropies in a form of spatially distributed pits on the cell plates to control initiation and further penetration of non-splitting fingers. The proposed control over shielding mechanism yields recipes for fabrication of families of ordered fractal-like patterns of multiple generations. As an example, we demonstrate and characterize fabrication of a Cayley tree fractal-like pattern. The patterns, in addition, are retained permanently by employing UV/thermally curable fluids. The proposed technique thus establishes solid foundation for bio-mimicking natural structures spanning multiple-scales for scientific and engineering use.

Wire electric-discharge machining and other fabrication techniques

NASA Technical Reports Server (NTRS)

Morgan, W. H.

1983-01-01

Wire electric discharge machining and extrude honing were used to fabricate a two dimensional wing for cryogenic wind tunnel testing. Electric-discharge cutting is done with a moving wire electrode. The cut track is controlled by means of a punched-tape program and the cutting feed is regulated according to the progress of the work. Electric-discharge machining involves no contact with the work piece, and no mechanical force is exerted. Extrude hone is a process for honing finish-machined surfaces by the extrusion of an abrasive material (silly putty), which is forced through a restrictive fixture. The fabrication steps are described and production times are given.

Fabrication of assembled ZnO/TiO2 heterojunction thin film transistors using solution processing technique

NASA Astrophysics Data System (ADS)

Liau, Leo Chau-Kuang; Lin, Yun-Guo

2015-01-01

Ceramic-based metal-oxide-semiconductor (MOS) field-effect thin film transistors (TFTs), which were assembled by ZnO and TiO2 heterojunction films coated using solution processing technique, were fabricated and characterized. The fabrication of the device began with the preparation of ZnO and TiO2 films by spin coating. The ZnO and TiO2 films that were stacked together and annealed at 450 °C were characterized as a p-n junction diode. Two types of the devices, p-channel and n-channel TFTs, were produced using different assemblies of ZnO and TiO2 films. Results show that the p-channel TFTs (p-TFTs) and n-channel TFTs (n-TFTs) using the assemblies of ZnO and TiO2 films were demonstrated by source-drain current vs. drain voltage (IDS-VDS) measurements. Several electronic properties of the p- and n- TFTs, such as threshold voltage (Vth), on-off ratio, channel mobility, and subthreshold swing (SS), were determined by current-voltage (I-V) data analysis. The ZnO/TiO2-based TFTs can be produced using solution processing technique and an assembly approach.

Polymeric PLC-type thermo-optic optical attenuator fabricated by UV imprint technique

NASA Astrophysics Data System (ADS)

Kim, Jin Tae; Choi, Choon-Gi

2006-01-01

A planar lightwave circuit-type polymer thermo-optic optical attenuator was fabricated via a UV imprint technique. In order to reduce the step for filling of cores and minimize the detrimental residual slab waveguide, convex ridge-type micro cores for guidance of light were defined with an accuracy of ±0.5 μm on the under-clad by a single step of imprinting. The voltage-controlled polymer optical attenuator showed 30-dB attenuation with 80-mW electrical input power at a wavelength of 1.55 μm. The rise and fall times are less than 5 ms. It displays about 0.2- and 1-dB polarization dependence at 0- and 10-dB attenuations, respectively.

Comparison the Marginal and Internal Fit of Metal Copings Cast from Wax Patterns Fabricated by CAD/CAM and Conventional Wax up Techniques

PubMed Central

Vojdani, M; Torabi, K; Farjood, E; Khaledi, AAR

2013-01-01

Statement of Problem: Metal-ceramic crowns are most commonly used as the complete coverage restorations in clinical daily use. Disadvantages of conventional hand-made wax-patterns introduce some alternative ways by means of CAD/CAM technologies. Purpose: This study compares the marginal and internal fit of copings cast from CAD/CAM and conventional fabricated wax-patterns. Materials and Method: Twenty-four standardized brass dies were prepared and randomly divided into 2 groups according to the wax-patterns fabrication method (CAD/CAM technique and conventional method) (n=12). All the wax-patterns were fabricated in a standard fashion by means of contour, thickness and internal relief (M1-M12: representative of CAD/CAM group, C1-C12: representative of conventional group). CAD/CAM milling machine (Cori TEC 340i; imes-icore GmbH, Eiterfeld, Germany) was used to fabricate the CAD/CAM group wax-patterns. The copings cast from 24 wax-patterns were cemented to the corresponding dies. For all the coping-die assemblies cross-sectional technique was used to evaluate the marginal and internal fit at 15 points. The Student’s t- test was used for statistical analysis (α=0.05). Results: The overall mean (SD) for absolute marginal discrepancy (AMD) was 254.46 (25.10) um for CAD/CAM group and 88.08(10.67) um for conventional group (control). The overall mean of internal gap total (IGT) was 110.77(5.92) um for CAD/CAM group and 76.90 (10.17) um for conventional group. The Student’s t-test revealed significant differences between 2 groups. Marginal and internal gaps were found to be significantly higher at all measured areas in CAD/CAM group than conventional group (p< 0.001). Conclusion: Within limitations of this study, conventional method of wax-pattern fabrication produced copings with significantly better marginal and internal fit than CAD/CAM (machine-milled) technique. All the factors for 2 groups were standardized except wax pattern fabrication technique, therefore

Fabrication of cross-shaped Cu-nanowire resistive memory devices using a rapid, scalable, and designable inorganic-nanowire-digital-alignment technique (Conference Presentation)

NASA Astrophysics Data System (ADS)

Xu, Wentao; Lee, Yeongjun; Min, Sung-Yong; Park, Cheolmin; Lee, Tae-Woo

2016-09-01

Resistive random-access memory (RRAM) is a candidate next generation nonvolatile memory due to its high access speed, high density and ease of fabrication. Especially, cross-point-access allows cross-bar arrays that lead to high-density cells in a two-dimensional planar structure. Use of such designs could be compatible with the aggressive scaling down of memory devices, but existing methods such as optical or e-beam lithographic approaches are too complicated. One-dimensional inorganic nanowires (i-NWs) are regarded as ideal components of nanoelectronics to circumvent the limitations of conventional lithographic approaches. However, post-growth alignment of these i-NWs precisely on a large area with individual control is still a difficult challenge. Here, we report a simple, inexpensive, and rapid method to fabricate two-dimensional arrays of perpendicularly-aligned, individually-conductive Cu-NWs with a nanometer-scale CuxO layer sandwiched at each cross point, by using an inorganic-nanowire-digital-alignment technique (INDAT) and a one-step reduction process. In this approach, the oxide layer is self-formed and patterned, so conventional deposition and lithography are not necessary. INDAT eliminates the difficulties of alignment and scalable fabrication that are encountered when using currently-available techniques that use inorganic nanowires. This simple process facilitates fabrication of cross-point nonvolatile memristor arrays. Fabricated arrays had reproducible resistive switching behavior, high on/off current ratio (Ion/Ioff) 10 6 and extensive cycling endurance. This is the first report of memristors with the resistive switching oxide layer self-formed, self-patterned and self-positioned; we envision that the new features of the technique will provide great opportunities for future nano-electronic circuits.

One-Step Fabrication of Stretchable Copper Nanowire Conductors by a Fast Photonic Sintering Technique and Its Application in Wearable Devices.

PubMed

Ding, Su; Jiu, Jinting; Gao, Yue; Tian, Yanhong; Araki, Teppei; Sugahara, Tohru; Nagao, Shijo; Nogi, Masaya; Koga, Hirotaka; Suganuma, Katsuaki; Uchida, Hiroshi

2016-03-09

Copper nanowire (CuNW) conductors have been considered to have a promising perspective in the area of stretchable electronics due to the low price and high conductivity. However, the fabrication of CuNW conductors suffers from harsh conditions, such as high temperature, reducing atmosphere, and time-consuming transfer step. Here, a simple and rapid one-step photonic sintering technique was developed to fabricate stretchable CuNW conductors on polyurethane (PU) at room temperature in air environment. It was observed that CuNWs were instantaneously deoxidized, welded and simultaneously embedded into the soft surface of PU through the one-step photonic sintering technique, after which highly conductive network and strong adhesion between CuNWs and PU substrates were achieved. The CuNW/PU conductor with sheet resistance of 22.1 Ohm/sq and transmittance of 78% was achieved by the one-step photonic sintering technique within only 20 μs in air. Besides, the CuNW/PU conductor could remain a low sheet resistance even after 1000 cycles of stretching/releasing under 10% strain. Two flexible electronic devices, wearable sensor and glove-shaped heater, were fabricated using the stretchable CuNW/PU conductor, demonstrating that our CuNW/PU conductor could be integrated into various wearable electronic devices for applications in food, clothes, and medical supplies fields.

Engineering Non-Wetting Antimicrobial Fabrics

NASA Astrophysics Data System (ADS)

van den Berg, Desmond

This research presents novel techniques and a review of commercially available fabrics for their antimicrobial potential. Based on previous research into the advantages of superhydrophobic self-cleaning surfaces against bacterial contamination, insights into what can make a superhydrophobic fabric inherently antimicrobial were analyzed. Through comparing the characterization results of scanning electron microscopy (SEM) and optical profilometry to microbiology experiments, hypotheses into the relationship between the contact area of a bacterial solution and the extent of contamination is developed. Contact scenario experiments, involving the use of fluorescence microscopy and calculating colony forming units, proved that the contamination potential of any fabric is due to the wetting state exhibited by the fabric, as well as the extent of surface texturing. Transmission experiments, utilizing a novel technique of stamping a contaminated fabric, outlined the importance of retention of solutions or bacteria during interactions within the hospital environment on the extent of contamination.

Fabrication of Thermoelectric Devices Using Additive-Subtractive Manufacturing Techniques: Application to Waste-Heat Energy Harvesting

NASA Astrophysics Data System (ADS)

Tewolde, Mahder

Thermoelectric generators (TEGs) are solid-state devices that convert heat directly into electricity. They are well suited for waste-heat energy harvesting applications as opposed to primary energy generation. Commercially available thermoelectric modules are flat, inflexible and have limited sizes available. State-of-art manufacturing of TEG devices relies on assembling prefabricated parts with soldering, epoxy bonding, and mechanical clamping. Furthermore, efforts to incorporate them onto curved surfaces such as exhaust pipes, pump housings, steam lines, mixing containers, reaction chambers, etc. require custom-built heat exchangers. This is costly and labor-intensive, in addition to presenting challenges in terms of space, thermal coupling, added weight and long-term reliability. Additive manufacturing technologies are beginning to address many of these issues by reducing part count in complex designs and the elimination of sub-assembly requirements. This work investigates the feasibility of utilizing such novel manufacturing routes for improving the manufacturing process of thermoelectric devices. Much of the research in thermoelectricity is primarily focused on improving thermoelectric material properties by developing of novel materials or finding ways to improve existing ones. Secondary to material development is improving the manufacturing process of TEGs to provide significant cost benefits. To improve the device fabrication process, this work explores additive manufacturing technologies to provide an integrated and scalable approach for TE device manufacturing directly onto engineering component surfaces. Additive manufacturing techniques like thermal spray and ink-dispenser printing are developed with the aim of improving the manufacturing process of TEGs. Subtractive manufacturing techniques like laser micromachining are also studied in detail. This includes the laser processing parameters for cutting the thermal spray materials efficiently by

Elasto-Capillary Folding Using Stop-Programmable Hinges Fabricated by 3D Micro-Machining

PubMed Central

Legrain, Antoine; Berenschot, Erwin J. W.; Tas, Niels R.; Abelmann, Leon

2015-01-01

We show elasto-capillary folding of silicon nitride objects with accurate folding angles between flaps of (70.6 ± 0.1)° and demonstrate the feasibility of such accurate micro-assembly with a final folding angle of 90°. The folding angle is defined by stop-programmable hinges that are fabricated starting from silicon molds employing accurate three-dimensional corner lithography. This nano-patterning method exploits the conformal deposition and the subsequent timed isotropic etching of a thin film in a 3D shaped silicon template. The technique leaves a residue of the thin film in sharp concave corners which can be used as an inversion mask in subsequent steps. Hinges designed to stop the folding at 70.6° were fabricated batchwise by machining the V-grooves obtained by KOH etching in (110) silicon wafers; 90° stop-programmable hinges were obtained starting from silicon molds obtained by dry etching on (100) wafers. The presented technique has potential to achieve any folding angle and opens a new route towards creating structures with increased complexity, which will ultimately lead to a novel method for device fabrication. PMID:25992886

Fabrication of IrSi(3)/p-Si Schottky diodes by a molecular beam epitaxy technique

NASA Technical Reports Server (NTRS)

Lin, T. L.; Iannelli, J. M.

1990-01-01

IrSi(3)/p-Si Schottky diodes have been fabricated by a molecular beam epitaxy technique at 630 C. Good surface morphology was observed for IrSi(3) layers grown at temperatures below 680 C, and an increasing tendency to form islands is observed in samples grown at higher temperatures. Good diode current-voltage characteristics were observed and Schottky barrier heights of 0.14-0.18 eV were determined by activation energy analysis and spectral response measurement.

Electrochemical Fabrication of Metallic Quantum Wires

ERIC Educational Resources Information Center

Tao, Nongjian

2005-01-01

The fabrication of metallic quantum wires using simple electrochemical techniques is described. The conductance of the system can be readily measured that allows one to constantly monitor the conductance during fabrication and use conductance quantization as a signature to guide the fabrication.

The Fabrication Technique and Property Analysis of Racetrack-Type High Temperature Superconducting Magnet for High Power Motor

NASA Astrophysics Data System (ADS)

Xie, S. F.; Wang, Y.; Wang, D. Y.; Zhang, X. J.; Zhao, B.; Zhang, Y. Y.; Li, L.; Li, Y. N.; Chen, P. M.

2013-03-01

The superconducting motor is now the focus of the research on the application of high temperature superconducting (HTS) materials. In this manuscript, we mainly introduce the recent progress on the fabrication technique and property research of the superconducting motor magnet in Luoyang Ship Material Research Institute (LSMRI) in China, including the materials, the winding and impregnation technique, and property measurement of magnet. Several techniques and devices were developed to manufacture the magnet, including the technique of insulation and thermal conduction, the device for winding the racetrack-type magnet, etc. At last, the superconducting magnet used for the MW class motor were successfully developed, which is the largest superconducting motor magnet in china at present. The critical current of the superconducting magnet exceeds the design value (90 A at 30 K).

Large Area 2D and 3D Colloidal Photonic Crystals Fabricated by a Roll-to-Roll Langmuir-Blodgett Method.

PubMed

Parchine, Mikhail; McGrath, Joe; Bardosova, Maria; Pemble, Martyn E

2016-06-14

We present our results on the fabrication of large area colloidal photonic crystals on flexible poly(ethylene terephthalate) (PET) film using a roll-to-roll Langmuir-Blodgett technique. Two-dimensional (2D) and three-dimensional (3D) colloidal photonic crystals from silica nanospheres (250 and 550 nm diameter) with a total area of up to 340 cm(2) have been fabricated in a continuous manner compatible with high volume manufacturing. In addition, the antireflective properties and structural integrity of the films have been enhanced via the use of a second roll-to-roll process, employing a slot-die coating of an optical adhesive over the photonic crystal films. Scanning electron microscopy images, atomic force microscopy images, and UV-vis optical transmission and reflection spectra of the fabricated photonic crystals are analyzed. This analysis confirms the high quality of the 2D and 3D photonic crystals fabricated by the roll-to-roll LB technique. Potential device applications of the large area 2D and 3D colloidal photonic crystals on flexible PET film are briefly reviewed.

Thermocapillary Technique for Shaping and Fabricating Optical Ribbon Waveguides

NASA Astrophysics Data System (ADS)

Fiedler, Kevin; Troian, Sandra

The demand for ever increasing bandwidth and higher speed communication has ushered the next generation optoelectronic integrated circuits which directly incorporate polymer optical waveguide devices. Polymer melts are very versatile materials which have been successfully cast into planar single- and multimode waveguides using techniques such as embossing, photolithography and direct laser writing. In this talk, we describe a novel thermocapillary patterning method for fabricating waveguides in which the free surface of an ultrathin molten polymer film is exposed to a spatially inhomogeneous temperature field via thermal conduction from a nearby cooled mask pattern held in close proximity. The ensuring surface temperature distribution is purposely designed to pool liquid selectively into ribbon shapes suitable for optical waveguiding, but with rounded and not rectangular cross sectional areas due to capillary forces. The solidified waveguide patterns which result from this non-contact one step procedure exhibit ultrasmooth interfaces suitable for demanding optoelectronic applications. To complement these studies, we have also conducted finite element simulations for quantifying the influence of non-rectangular cross-sectional shapes on mode propagation and losses. Kf gratefully acknowledges support from a NASA Space Technology Research Fellowship.

Site-controlled quantum dots fabricated using an atomic-force microscope assisted technique

PubMed Central

Usuki, T; Ohshima, T; Sakuma, Y; Kawabe, M; Okada, Y; Takemoto, K; Miyazawa, T; Hirose, S; Nakata, Y; Takatsu, M; Yokoyama, N

2006-01-01

An atomic-force microscope assisted technique is developed to control the position and size of self-assembled semiconductor quantum dots (QDs). Presently, the site precision is as good as ± 1.5 nm and the size fluctuation is within ± 5% with the minimum controllable lateral diameter of 20 nm. With the ability of producing tightly packed and differently sized QDs, sophisticated QD arrays can be controllably fabricated for the application in quantum computing. The optical quality of such site-controlled QDs is found comparable to some conventionally self-assembled semiconductor QDs. The single dot photoluminescence of site-controlled InAs/InP QDs is studied in detail, presenting the prospect to utilize them in quantum communication as precisely controlled single photon emitters working at telecommunication bands.

Fabricating Structural Stiffeners By Superplastic Forming

NASA Technical Reports Server (NTRS)

Bales, Thomas T.; Shinn, Joseph M., Jr.; Hales, Stephen J.; James, William F.

1994-01-01

Superplastic forming (SPF) of aluminum alloys effective technique for making strong, lightweight structural components conforming to close dimensional tolerances. Technique applied in experimental fabrication of prototypes of stiffening ribs for cylindrical tanks. When making structural panel, stiffening ribs spot-welded to metal skin. Use of discrete eliminates machining waste, and use of SPF. Cost of fabrication reduced.

An integrated optical oxygen sensor fabricated using rapid-prototyping techniques.

PubMed

Chang-Yen, David A; Gale, Bruce K

2003-11-01

This paper details the design and fabrication of an integrated optical biochemical sensor using a select oxygen-sensitive fluorescent dye, tris(2,2'-bipyridyl) dichlororuthenium(ii) hexahydrate, combined with polymeric waveguides that are fabricated on a glass substrate. The sensor uses evanescent interaction of light confined within the waveguide with the dye that is immobilized on an SU-8 waveguide surface. Adhesion of the dye to the integrated waveguide surface is accomplished using a unique process of spin-coating/electrostatic layer-by-layer formation. The SU-8 waveguide was chemically modified to allow the deposition process. Exposure of the dye molecules to the analyte and subsequent chemical interaction is achieved by directly coupling the fluid channel to the integrated waveguide. The completed sensor was linear in the dissolved oxygen across a wide range of interest and had a sensitivity of 0.6 ppm. A unique fabrication aspect of this sensor is the inherent simplicity of the design, and the resulting rapidity of fabrication, while maintaining a high degree of functionality and flexibility.

Fabrication of ultra-fine grained aluminium tubes by RTES technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jafarzadeh, H., E-mail: h.jafarzadeh@ut.ac.ir; Abrinia, K.

Recently, repetitive tube expansion and shrinking have been exploited as a means for producing ultra-fine grained and nano-crystalline microstructures for magnesium alloy tubes. This method includes two different half-cycles and was based on pressing a tubular part through an angular channel die with two shear zones. Since the aluminium alloys are the most widely used materials in industries, in this study, repetitive tube expansion and shrinking as a new severe plastic deformation technique was applied to commercially pure aluminium for fabricating ultra-fine grained aluminium tubes for the first time and the ability of this process in significant grain refinement ismore » determined even after single cycle. Transmission electron microscopy and X-ray diffraction were used to evaluate the microstructure of the repetitive tube expansion and shrinking processed materials and the examinations showed ultra-fine grains with the average grain size of 320 nm after one cycle of repetitive tube expansion and shrinking. The yield strength, ultimate tensile strength increased notably by the factor of 2.17 and 1.27 respectively, after one cycle of repetitive tube expansion and shrinking, whereas the elongation to failure as well as the uniform elongation decreased. Furthermore, micro-hardness distribution through the part's section proposed the hardness increasing to ~ 55 HV from the initial value of ~ 28 HV after one cycle of repetitive tube expansion and shrinking. - Highlights: • RTES was introduced for fabricating the UFGed AA1050 tubes for the first time. • Nano-grained AA1050 tube was obtained by RTES process. • Grain size of ~ 320 nm was obtained after two half-cycles of RTES process. • Yield and ultimate strength increased by the factor of 2.17 and 1.27 respectively. • The microhardness increased to ~ 55 HV from the initial value of ~ 28 HV.« less

Highly conducting and crystalline doubly doped tin oxide films fabricated using a low-cost and simplified spray technique

NASA Astrophysics Data System (ADS)

Ravichandran, K.; Muruganantham, G.; Sakthivel, B.

2009-11-01

Doubly doped (simultaneous doping of antimony and fluorine) tin oxide films (SnO 2:Sb:F) have been fabricated by employing an inexpensive and simplified spray technique using perfume atomizer from aqueous solution of SnCl 2 precursor. The structural studies revealed that the films are highly crystalline in nature with preferential orientation along the (2 0 0) plane. It is found that the size of the crystallites of the doubly doped tin oxide films is larger (69 nm) than that (27 nm) of their undoped counterparts. The dislocation density of the doubly doped film is lesser (2.08×10 14 lines/m 2) when compared with that of the undoped film (13.2×10 14 lines/m 2), indicating the higher degree of crystallinity of the doubly doped films. The SEM images depict that the films are homogeneous and uniform. The optical transmittance in the visible range and the optical band gap of the doubly doped films are 71% and 3.56 eV respectively. The sheet resistance (4.13 Ω/□) attained for the doubly doped film in this study is lower than the values reported for spray deposited fluorine or antimony doped tin oxide films prepared from aqueous solution of SnCl 2 precursor (without using methanol or ethanol).

The fabrication of ZnO nanowire field-effect transistors by roll-transfer printing

NASA Astrophysics Data System (ADS)

Chang, Yi-Kuei; Hong, Franklin Chau-Nan

2009-05-01

A method with the potential to fabricate large-area nanowire field-effect transistors (NW-FETs) was demonstrated in this study. Using a high-speed roller (20-80 cm min-1), transfer printing was successfully employed to transfer vertically aligned zinc oxide (ZnO) nanowires grown on a donor substrate to a polydimethylsiloxane (PDMS) stamp and then print the ordered ZnO nanowire arrays on the received substrate for the fabrication of NW-FETs. ZnO NW-FETs fabricated by this method exhibit high performances with a threshold voltage of around 0.25 V, a current on/off ratio as high as 105, a subthreshold slope of 360 mV/dec, and a field-effect mobility of around 90 cm2 V-1 s-1. The excellent device characteristics suggest that the roll-transfer printing technique, which is compatible with the roll-to-roll (R2R) process and operated in atmosphere, has a good potential for the high-speed fabrication of large-area nanowire transistors for flexible devices and flat panel displays.

The fabrication of ZnO nanowire field-effect transistors by roll-transfer printing.

PubMed

Chang, Yi-Kuei; Hong, Franklin Chau-Nan

2009-05-13

A method with the potential to fabricate large-area nanowire field-effect transistors (NW-FETs) was demonstrated in this study. Using a high-speed roller (20-80 cm min(-1)), transfer printing was successfully employed to transfer vertically aligned zinc oxide (ZnO) nanowires grown on a donor substrate to a polydimethylsiloxane (PDMS) stamp and then print the ordered ZnO nanowire arrays on the received substrate for the fabrication of NW-FETs. ZnO NW-FETs fabricated by this method exhibit high performances with a threshold voltage of around 0.25 V, a current on/off ratio as high as 10(5), a subthreshold slope of 360 mV/dec, and a field-effect mobility of around 90 cm(2) V(-1) s(-1). The excellent device characteristics suggest that the roll-transfer printing technique, which is compatible with the roll-to-roll (R2R) process and operated in atmosphere, has a good potential for the high-speed fabrication of large-area nanowire transistors for flexible devices and flat panel displays.

Fabrication of microchannels in polycrystalline diamond using pre-fabricated Si substrates

NASA Astrophysics Data System (ADS)

Chandran, Maneesh; Elfimchev, Sergey; Michaelson, Shaul; Akhvlediani, Rozalia; Ternyak, Orna; Hoffman, Alon

2017-10-01

In this paper, we report on a simple, feasible method to fabricate microchannels in diamond. Polycrystalline diamond microchannels were produced by fabricating trenches in a Si wafer and subsequently depositing a thin layer of diamond onto this substrate using the hot filament vapor deposition technique. Fabrication of trenches in the Si substrate at different depths was carried out by standard photolithography, and the subsequent deposition of the diamond layer was performed by the hot filament chemical vapor deposition technique. The growth mechanism of diamond that leads to the formation of closed diamond microchannels is discussed in detail based on the Knudsen number and growth chemistry of diamond. Variations in the crystallite size, crystalline quality, and thickness of the diamond layer along the trench depths were systematically analyzed using cross-sectional scanning electron microscopy and Raman spectroscopy. Defect density and formation of non-diamond forms of carbon in the diamond layer were found to increase with the trench depth, which sets a limit of 5-45 μm trench depth (or an aspect ratio of 1-9) for the fabrication of diamond microchannels using this method under the present conditions.

A novel open-tray impression technique for fabrication of a provisional prosthesis on immediate load implants in a completely edentulous arch.

PubMed

Kaneko, Takahiro; Yamagishi, Kiyoshi; Horie, Norio; Shimoyama, Tetsuo

2013-01-01

To evaluate the clinical outcome of a novel open-tray impression technique for fabrication of a provisional prosthesis supported by immediately loaded implants in a completely edentulous arch. An open-tray impression technique was evaluated in this retrospective study that included patients treated between March 2006 and October 2009. Preoperatively, a diagnostic prosthesis was delivered, and a novel open tray was fabricated based on this prosthesis. After implant placement, the impression and interocclusal record were taken simultaneously using the novel open tray. Laboratory-fabricated, screw-retained, all-acrylic resin provisional restorations were delivered on the same day of surgery. The prosthesis was assessed from the day of surgery until replacement with a definitive prosthesis. The study included 21 patients (mean age, 64.5 years) and a total of 125 implants. Of these, 104 implants were immediately loaded. In all patients, well-fitting provisional restorations supported by a minimum of four implants were delivered. Fracture of the first molar cusp was observed in one case after 30 days. However, there was no extensive fracture in the framework or functional disorder of the prosthesis. No implant failed during the follow-up after implant surgery. This protocol enabled fabrication of a well-fitting acrylic resin provisional prosthesis supported by immediately loaded implants because the impression was taken while in centric occlusion and an occlusion identical to the diagnostic prosthesis could be reconstructed.

Fit accuracy of metal partial removable dental prosthesis frameworks fabricated by traditional or light curing modeling material technique: An in vitro study

PubMed Central

Anan, Mohammad Tarek M.; Al-Saadi, Mohannad H.

2015-01-01

Objective The aim of this study was to compare the fit accuracies of metal partial removable dental prosthesis (PRDP) frameworks fabricated by the traditional technique (TT) or the light-curing modeling material technique (LCMT). Materials and methods A metal model of a Kennedy class III modification 1 mandibular dental arch with two edentulous spaces of different spans, short and long, was used for the study. Thirty identical working casts were used to produce 15 PRDP frameworks each by TT and by LCMT. Every framework was transferred to a metal master cast to measure the gap between the metal base of the framework and the crest of the alveolar ridge of the cast. Gaps were measured at three points on each side by a USB digital intraoral camera at ×16.5 magnification. Images were transferred to a graphics editing program. A single examiner performed all measurements. The two-tailed t-test was performed at the 5% significance level. Results The mean gap value was significantly smaller in the LCMT group compared to the TT group. The mean value of the short edentulous span was significantly smaller than that of the long edentulous span in the LCMT group, whereas the opposite result was obtained in the TT group. Conclusion Within the limitations of this study, it can be concluded that the fit of the LCMT-fabricated frameworks was better than the fit of the TT-fabricated frameworks. The framework fit can differ according to the span of the edentate ridge and the fabrication technique for the metal framework. PMID:26236129

An investigation of density measurement method for yarn-dyed woven fabrics based on dual-side fusion technique

NASA Astrophysics Data System (ADS)

Zhang, Rui; Xin, Binjie

2016-08-01

Yarn density is always considered as the fundamental structural parameter used for the quality evaluation of woven fabrics. The conventional yarn density measurement method is based on one-side analysis. In this paper, a novel density measurement method is developed for yarn-dyed woven fabrics based on a dual-side fusion technique. Firstly, a lab-used dual-side imaging system is established to acquire both face-side and back-side images of woven fabric and the affine transform is used for the alignment and fusion of the dual-side images. Then, the color images of the woven fabrics are transferred from the RGB to the CIE-Lab color space, and the intensity information of the image extracted from the L component is used for texture fusion and analysis. Subsequently, three image fusion methods are developed and utilized to merge the dual-side images: the weighted average method, wavelet transform method and Laplacian pyramid blending method. The fusion efficacy of each method is evaluated by three evaluation indicators and the best of them is selected to do the reconstruction of the complete fabric texture. Finally, the yarn density of the fused image is measured based on the fast Fourier transform, and the yarn alignment image could be reconstructed using the inverse fast Fourier transform. Our experimental results show that the accuracy of density measurement by using the proposed method is close to 99.44% compared with the traditional method and the robustness of this new proposed method is better than that of conventional analysis methods.

Piezoelectric Sol-Gel Composite Film Fabrication by Stencil Printing.

PubMed

Kaneko, Tsukasa; Iwata, Kazuki; Kobayashi, Makiko

2015-09-01

Piezoelectric films using sol-gel composites could be useful as ultrasonic transducers in various industrial fields. For sol-gel composite film fabrication, the spray coating technique has been used often because of its adaptability for various substrates. However, the spray technique requires multiple spray coating processes and heating processes and this is an issue of concern, especially for on-site fabrication in controlled areas. Stencil printing has been developed to solve this issue because this method can be used to fabricate thick sol-gel composite films with one coating process. In this study, PbTiO3 (PT)/Pb(Zr,Ti)O3 (PZT) films, PZT/PZT films, and Bi4Ti3O12 (BiT)/PZT films were fabricated by stencil printing, and PT/ PZT films were also fabricated using the spray technique. After fabrication, a thermal cycle test was performed for the samples to compare their ultrasonic performance. The sensitivity and signal-to-noise-ratio (SNR) of the ultrasonic response of PT/PZT fabricated by stencil printing were equivalent to those of PT/PZT fabricated by the spray technique, and better than those of other samples between room temperature and 300°C. Therefore, PT/PZT films fabricated by stencil printing could be a good candidate for nondestructive testing (NDT) ultrasonic transducers from room temperature to 300°C.

Fabrication of rectangular cross-sectional microchannels on PMMA with a CO2 laser and underwater fabricated copper mask

NASA Astrophysics Data System (ADS)

Prakash, Shashi; Kumar, Subrata

2017-09-01

CO2 lasers are commonly used for fabricating polymer based microfluidic devices. Despite several key advantages like low cost, time effectiveness, easy to operate and no requirement of clean room facility, CO2 lasers suffer from few disadvantages like thermal bulging, improper dimensional control, difficulty to produce microchannels of other than Gaussian cross sectional shapes and inclined surface walls. Many microfluidic devices require square or rectangular cross-sections which are difficult to produce using normal CO2 laser procedures. In this work, a thin copper sheet of 40 μm was used as a mask above the PMMA (Polymethyl-methacrylate) substrate while fabricating the microchannels utilizing the raster scanning feature of the CO2 lasers. Microchannels with different width dimensions were fabricated utilizing a CO2 laser in with mask and without-mask conditions. A comparison of both the fabricating process has been made. It was found that microchannels with U shape cross section and rectangular cross-section can efficiently be produced using the with mask technique. In addition to this, this technique can provide perfect dimensional control and better surface quality of the microchannel walls. Such a microchannel fabrication process do not require any post-processing. The fabrication of mask using a nanosecond fiber laser has been discussed in details. An underwater laser fabrication method was adopted to overcome heat related defects in mask preparation. Overall, the technique was found to be easy to adopt and significant improvements were observed in microchannel fabrication.

ZEP520A cold-development technique and tool for ultimate resolution to fabricate 1Xnm bit pattern EB master mold for nano-imprinting lithography for HDD/BPM development

NASA Astrophysics Data System (ADS)

Kobayashi, Hideo; Iyama, Hiromasa

2012-06-01

Poor solvent developers are effective for resolution enhancement on a polymer-type EB resist such as ZEP520A. Another way is to utilize "cold-development" technique which was accomplished by a dip-development technique usually. We then designed and successfully built a single-wafer spin-development tool for the cold-development down to -10degC in order to dissolve difficulties of the dip-development. The cold-development certainly helped improve ZEP520A resolution and hole CD size uniformity, and achieved 35nm pitch BPM patterns with the standard developer ZED-N50, but not 25nm pitch yet. By employing a poor solvent mixture of iso-Propyl Alcohol (IPA) and Fluoro-Carbon (FC), 25nm pitch BPM patterns were accomplished. However, the cold-development showed almost no improvement on the IPA/FC mixture developer solvent. This paper describes cold-development technique and a tool, as well as its results, for ZEP520A resolution enhancement to fabricate 1Xnm bits (holes) for EB master-mold for Nano-Imprinting Lithography for 1Tbit/inch2 and 25nm pitch Bit Patterned Media development.

Novel Engineering and Fabrication Techniques Tested in Low-Noise- Research Fan Blades

NASA Technical Reports Server (NTRS)

Cunningham, Cameron C.

2003-01-01

A major source of fan noise in commercial turbofan engines is the interaction of the wake from the fan blades with the stationary vanes (stators) directly behind them. The Trailing Edge Blowing (TEB) project team at the NASA Glenn Research Center designed and fabricated new fan blades to study the effects of fan trailing edge blowing as a potential noise-reduction concept. The intent is to fill the rotor wake by supplying air to the rotor blade trailing edge at the proper conditions to minimize the wake deficit, and thus generate less noise. The TEB hardware is designed for the Active Noise Control Fan (ANCF) test rig in Glenn's Aeroacoustic Propulsion Laboratory. For this test, the air is fed from an external supply through the shaft of the rig. It is distributed to the base of each blade through an impeller, where it is forced into a plenum at the core of each blade. In actual engine configuration, air would most likely be bled from the compressor, but only at times when noise is an issue, such as takeoffs and landings. Glenn researchers designed and manufactured the blades in-house, using new techniques and concepts. The skins, which were designed for maximum strength in the directions of highest stress, were molded from multiple layers of carbon fiber. Considerable use was made of rapid prototyping techniques, such as laser sintering. The core was sintered from a lightweight polymer, and the retainer was CNC-machined (computer numerical control machined) from aluminum. All the components were joined with a cold-cure aerospace adhesive. These techniques and processes reduced the overall cost and allowed the new concept to be studied much sooner than would be possible using traditional fabrication methods. Since this test rig did not support the use of blade-monitoring techniques such as strain gauges, extensive bench testing was required to qualify the design. The blades were examined using a variety of methods including holography, pull tests (cyclic and

Fabrication of SiC membrane HCG blue reflector using nanoimprint lithography

NASA Astrophysics Data System (ADS)

Lai, Ying-Yu; Matsutani, Akihiro; Lu, Tien-Chang; Wang, Shing-Chung; Koyama, Fumio

2015-02-01

We designed and fabricated a suspended SiC-based membrane high contrast grating (HCG) reflectors. The rigorous coupled-wave analysis (RCWA) was employed to verify the structural parameters including grating periods, grating height, filling factors and air-gap height. From the optimized simulation results, the designed SiC-based membrane HCG has a wide reflection stopband (reflectivity (R) <90%) of 135 nm for the TE polarization, which centered at 480 nm. The suspended SiC-based membrane HCG reflectors were fabricated by nanoimprint lithography and two-step etching technique. The corresponding reflectivity was measured by using a micro-reflectivity spectrometer. The experimental results show a high reflectivity (R<90%), which is in good agreement with simulation results. This achievement should have an impact on numerous III-N based photonic devices operating in the blue wavelength or even ultraviolet region.

Diagnostics of glass fiber reinforced polymers and comparative analysis of their fabrication techniques with the use of acoustic emission

NASA Astrophysics Data System (ADS)

Bashkov, O. V.; Bryansky, A. A.; Panin, S. V.; Zaikov, V. I.

2016-11-01

Strength properties of the glass fiber reinforced polymers (GFRP) fabricated by vacuum and vacuum autoclave molding techniques were analyzed. Measurements of porosity of the GFRP parts manufactured by various molding techniques were conducted with the help of optical microscopy. On the basis of experimental data obtained by means of acoustic emission hardware/software setup, the technique for running diagnostics and forecasting the bearing capacity of polymeric composite materials based on the result of three-point bending tests has been developed. The operation principle of the technique is underlined by the evaluation of the power function index change which takes place on the dependence of the total acoustic emission counts versus the loading stress.

Micro Machining Enhances Precision Fabrication

NASA Technical Reports Server (NTRS)

2007-01-01

Advanced thermal systems developed for the Space Station Freedom project are now in use on the International Space Station. These thermal systems employ evaporative ammonia as their coolant, and though they employ the same series of chemical reactions as terrestrial refrigerators, the space-bound coolers are significantly smaller. Two Small Business Innovation Research (SBIR) contracts between Creare Inc. of Hanover, NH and Johnson Space Center developed an ammonia evaporator for thermal management systems aboard Freedom. The principal investigator for Creare Inc., formed Mikros Technologies Inc. to commercialize the work. Mikros Technologies then developed an advanced form of micro-electrical discharge machining (micro-EDM) to make tiny holes in the ammonia evaporator. Mikros Technologies has had great success applying this method to the fabrication of micro-nozzle array systems for industrial ink jet printing systems. The company is currently the world leader in fabrication of stainless steel micro-nozzles for this market, and in 2001 the company was awarded two SBIR research contracts from Goddard Space Flight Center to advance micro-fabrication and high-performance thermal management technologies.

Prewarping techniques in imaging: applications in nanotechnology and biotechnology

NASA Astrophysics Data System (ADS)

Poonawala, Amyn; Milanfar, Peyman

2005-03-01

In all imaging systems, the underlying process introduces undesirable distortions that cause the output signal to be a warped version of the input. When the input to such systems can be controlled, pre-warping techniques can be employed which consist of systematically modifying the input such that it cancels out (or compensates for) the process losses. In this paper, we focus on the mask (reticle) design problem for 'optical micro-lithography', a process similar to photographic printing used for transferring binary circuit patterns onto silicon wafers. We use a pixel-based mask representation and model the above process as a cascade of convolution (aerial image formation) and thresholding (high-contrast recording) operations. The pre-distorted mask is obtained by minimizing the norm of the difference between the 'desired' output image and the 'reproduced' output image. We employ the regularization framework to ensure that the resulting masks are close-to-binary as well as simple and easy to fabricate. Finally, we provide insight into two additional applications of pre-warping techniques. First is 'e-beam lithography', used for fabricating nano-scale structures, and second is 'electronic visual prosthesis' which aims at providing limited vision to the blind by using a prosthetic retinally implanted chip capable of electrically stimulating the retinal neuron cells.

Characterization of complementary patterned metallic membranes produced simultaneously by a dual fabrication process

NASA Astrophysics Data System (ADS)

Hao, Qingzhen; Zeng, Yong; Wang, Xiande; Zhao, Yanhui; Wang, Bei; Chiang, I.-Kao; Werner, Douglas H.; Crespi, Vincent; Huang, Tony Jun

2010-11-01

An efficient technique is developed to fabricate optically thin metallic films with subwavelength patterns and their complements simultaneously. By comparing the spectra of the complementary films, we show that Babinet's principle nearly holds for these structures in the optical domain. Rigorous full-wave simulations are employed to verify the experimental observations. It is further demonstrated that a discrete-dipole approximation can qualitatively describe the spectral dependence of the metallic membranes on the geometry of the constituent particles as well as the illuminating polarization.

Laser-assisted advanced assembly for MEMS fabrication

NASA Astrophysics Data System (ADS)

Atanasov, Yuriy Andreev

Micro Electro-Mechanical Systems (MEMS) are currently fabricated using methods originally designed for manufacturing semiconductor devices, using minimum if any assembly at all. The inherited limitations of this approach narrow the materials that can be employed and reduce the design complexity, imposing limitations on MEMS functionality. The proposed Laser-Assisted Advanced Assembly (LA3) method solves these problems by first fabricating components followed by assembly of a MEMS device. Components are micro-machined using a laser or by photolithography followed by wet/dry etching out of any material available in a thin sheet form. A wide range of materials can be utilized, including biocompatible metals, ceramics, polymers, composites, semiconductors, and materials with special properties such as memory shape alloys, thermoelectric, ferromagnetic, piezoelectric, and more. The approach proposed allows enhancing the structural and mechanical properties of the starting materials through heat treatment, tribological coatings, surface modifications, bio-functionalization, and more, a limited, even unavailable possibility with existing methods. Components are transferred to the substrate for assembly using the thermo-mechanical Selective Laser Assisted Die Transfer (tmSLADT) mechanism for microchips assembly, already demonstrated by our team. Therefore, the mechanical and electronic part of the MEMS can be fabricated using the same equipment/method. The viability of the Laser-Assisted Advanced Assembly technique for MEMS is demonstrated by fabricating magnetic switches for embedding in a conductive carbon-fiber metamaterial for use in an Electromagnetic-Responsive Mobile Cyber-Physical System (E-RMCPS), which is expected to improve the wireless communication system efficiency within a battery-powered device.

Thermal Skin fabrication technology

NASA Technical Reports Server (NTRS)

Milam, T. B.

1972-01-01

Advanced fabrication techniques applicable to Thermal Skin structures were investigated, including: (1) chemical machining; (2) braze bonding; (3) diffusion bonding; and (4) electron beam welding. Materials investigated were nickel and nickel alloys. Sample Thermal Skin panels were manufactured using the advanced fabrication techniques studied and were structurally tested. Results of the program included: (1) development of improved chemical machining processes for nickel and several nickel alloys; (2) identification of design geometry limits; (3) identification of diffusion bonding requirements; (4) development of a unique diffusion bonding tool; (5) identification of electron beam welding limits; and (6) identification of structural properties of Thermal Skin material.

Low cost fabrication of ablative heat shields

NASA Technical Reports Server (NTRS)

Cecka, A. M.; Schofield, W. C.

1972-01-01

A material and process study was performed using subscale panels in an attempt to reduce the cost of fabricating ablative heat shield panels. Although no improvements were made in the material formulation, a significant improvement was obtained in the processing methods compared to those employed in the previous work. The principal feature of the new method is the press filling and curing of the ablation material in a single step with the bonding and curing of the face sheet. This method was chosen to replace the hand troweling and autoclave curing procedure used previously. Double-curvature panels of the same size as the flat panels were fabricated to investigate fabrication problems. It was determined that the same materials and processes used for flat panels can be used to produce the curved panels. A design with severe curvatures consisting of radii of 24 x 48 inches was employed for evaluation. Ten low-density and ten high-density panels were fabricated. With the exception of difficulties related to short run non-optimum tooling, excellent panel filling and density uniformity were obtained.

Magnetic fabric constraints of the emplacement of igneous intrusions

NASA Astrophysics Data System (ADS)

Maes, Stephanie M.

Fabric analysis is critical to evaluating the history, kinematics, and dynamics of geological deformation. This is particularly true of igneous intrusions, where the development of fabric is used to constrain magmatic flow and emplacement mechanisms. Fabric analysis was applied to three mafic intrusions, with different tectonic and petrogenetic histories, to study emplacement and magma flow: the Insizwa sill (Mesozoic Karoo Large Igneous Province, South Africa), Sonju Lake intrusion (Proterozoic Midcontinent Rift, Minnesota, USA), and Palisades sill (Mesozoic rift basin, New Jersey, USA). Multiple fabric analysis techniques were used to define the fabric in each intrusive body. Using digital image analysis techniques on multiple thin sections, the three-dimensional shape-preferred orientation (SPO) of populations of mineral phases were calculated. Low-field anisotropy of magnetic susceptibility (AMS) measurements were used as a proxy for the mineral fabric of the ferromagnetic phases (e.g., magnetite). In addition, a new technique---high-field AMS---was used to isolate the paramagnetic component of the fabric (e.g., silicate fabric). Each fabric analysis technique was then compared to observable field fabrics as a framework for interpretation. In the Insizwa sill, magnetic properties were used to corroborate vertical petrologic zonation and distinguish sub-units within lithologically defined units. Abrupt variation in magnetic properties provides evidence supporting the formation of the Insizwa sill by separate magma intrusions. Low-field AMS fabrics in the Sonju Lake intrusion exhibit consistent SW-plunging lineations and SW-dipping foliations. These fabric orientations provide evidence that the cumulate layers in the intrusion were deposited in a dynamic environment, and indicate magma flowed from southwest to northeast, parallel to the pre-existing rift structures. In the Palisades sill, the magnetite SPO and low-field AMS lineation have developed orthogonal to

Hemoglobin protein hollow shells fabricated through covalent layer-by-layer technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duan Li; He Qiang; Max Planck Institute of Colloids and Interfaces, Golm/Potsdam D-14476

2007-03-09

Hemoglobin (Hb) protein microcapsules held together by cross-linker, glutaraldehyde (GA), were successfully fabricated by covalent layer-by-layer (LbL) technique. The Schiff base reaction occurred on the colloid templates between the aldehyde groups of GA and free amino sites of Hb results in the formation of GA/Hb microcapsules after the removal of the templates. The structure of obtained monodisperse protein microcapsule was characterized by transmission electron microscopy (TEM) and confocal laser scanning microscopy (CLSM). The UV-Vis spectra measurements demonstrate the existence of Hb in the assembled capsules. Cyclic voltammetry (CV) and potential-controlled amperometric measurements (I-t curve) confirm that hemoglobin microcapsules after fabricationmore » remain their heme electroactivity. Moreover, direct electron transfer process from protein to electrode surface was performed to detect the heme electrochemistry without using any mediator or promoter. The experiments of fluorescence recovery after photobleaching (FRAP) by CLSM demonstrate that the hemoglobin protein microcapsules have an improved permeability comparing to the conventional polyelectrolyte microcapsules.« less

New Technique for Fabrication of Scanning Single-Electron Transistor Microscopy Tips

NASA Astrophysics Data System (ADS)

Goodwin, Eric; Tessmer, Stuart

Fabrication of glass tips for Scanning Single-Electron Transistor Microscopy (SSETM) can be expensive, time consuming, and inconsistent. Various techniques have been tried, with varying levels of success in regards to cost and reproducibility. The main requirement for SSETM tips is to have a sharp tip ending in a micron-scale flat face to allow for deposition of a quantum dot. Drawing inspiration from methods used to create tips from optical fibers for Near-Field Scanning Optical Microscopes, our group has come up with a quick and cost effective process for creating SSETM tips. By utilizing hydrofluoric acid to etch the tips and oleic acid to guide the etch profile, optical fiber tips with appropriate shaping can be rapidly prepared. Once etched, electric leads are thermally evaporated onto each side of the tip, while an aluminum quantum dot is evaporated onto the face. Preliminary results using various metals, oxide layers, and lead thicknesses have proven promising.

Material property for designing, analyzing, and fabricating space structures

NASA Technical Reports Server (NTRS)

Kolkailah, Faysal A.

1991-01-01

An analytical study was made of plasma assisted bullet projectile. The finite element analysis and the micro-macromechanic analysis was applied to an optimum design technique for the multilayered graphite-epoxy composite projectile that will achieve hypervelocity of 6 to 10 Km/s. The feasibility was determined of dialectics to monitor cure of graphite-epoxies. Several panels were fabricated, cured, and tested with encouraging results of monitoring the cure of graphite-epoxies. The optimum cure process for large structures was determined. Different orientation were used and three different curing cycles were employed. A uniaxial tensile test was performed on all specimens. The optimum orientation with the optimum cure cycle were concluded.

Developing High-Frequency Quantitative Ultrasound Techniques to Characterize Three-Dimensional Engineered Tissues

NASA Astrophysics Data System (ADS)

Mercado, Karla Patricia E.

Tissue engineering holds great promise for the repair or replacement of native tissues and organs. Further advancements in the fabrication of functional engineered tissues are partly dependent on developing new and improved technologies to monitor the properties of engineered tissues volumetrically, quantitatively, noninvasively, and nondestructively over time. Currently, engineered tissues are evaluated during fabrication using histology, biochemical assays, and direct mechanical tests. However, these techniques destroy tissue samples and, therefore, lack the capability for real-time, longitudinal monitoring. The research reported in this thesis developed nondestructive, noninvasive approaches to characterize the structural, biological, and mechanical properties of 3-D engineered tissues using high-frequency quantitative ultrasound and elastography technologies. A quantitative ultrasound technique, using a system-independent parameter known as the integrated backscatter coefficient (IBC), was employed to visualize and quantify structural properties of engineered tissues. Specifically, the IBC was demonstrated to estimate cell concentration and quantitatively detect differences in the microstructure of 3-D collagen hydrogels. Additionally, the feasibility of an ultrasound elastography technique called Single Tracking Location Acoustic Radiation Force Impulse (STL-ARFI) imaging was demonstrated for estimating the shear moduli of 3-D engineered tissues. High-frequency ultrasound techniques can be easily integrated into sterile environments necessary for tissue engineering. Furthermore, these high-frequency quantitative ultrasound techniques can enable noninvasive, volumetric characterization of the structural, biological, and mechanical properties of engineered tissues during fabrication and post-implantation.

Fabrication of sinterable silicon nitride by injection molding

NASA Technical Reports Server (NTRS)

Quackenbush, C. L.; French, K.; Neil, J. T.

1982-01-01

Transformation of structural ceramics from the laboratory to production requires development of near net shape fabrication techniques which minimize finish grinding. One potential technique for producing large quantities of complex-shaped parts at a low cost, and microstructure of sintered silicon nitride fabricated by injection molding is discussed and compared to data generated from isostatically dry-pressed material. Binder selection methodology, compounding of ceramic and binder components, injection molding techniques, and problems in binder removal are discussed. Strength, oxidation resistance, and microstructure of sintered silicon nitride fabricated by injection molding is discussed and compared to data generated from isostatically dry-pressed material.

Comparison of three-dimensional printing and vacuum freeze-dried techniques for fabricating composite scaffolds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Kai; Li, Ruixin; Jiang, Wenxue, E-mail: jiangortholivea@sina.cn

In this study, the performances of different preparation methods of the scaffolds were analyzed for chondrocyte tissue engineering. Silk fibroin/collagen (SF/C) was fabricated using a vacuum freeze-dried technique and by 3D printing. The porosity, water absorption expansion rates, mechanical properties, and pore sizes of the resulting materials were evaluated. The proliferation and metabolism of the cells was detected at different time points using an MTT assay. Cell morphologies and distributions were observed by histological analysis and scanning electron microscopy (SEM). The porosity, water absorption expansion rate, and Young’s modulus of the material obtained via 3D printing were significantly higher thanmore » those obtained by the freeze-dried method, while the pore size did not differ significantly between the two methods. MTT assay results showed that the metabolism of cells seeded on the 3D printed scaffolds was more viable than the metabolism on the freeze-dried material. H&E staining of the scaffolds revealed that the number of cells in the 3D printed scaffold was higher in comparison to a similar measurement on the freeze-dried material. Consequently, stem cells grew well inside the 3D printed scaffolds, as measured by SEM, while the internal structure of the freeze-dried scaffold was disordered. Compared with the freeze-dried technique, the 3D printed scaffold exhibited better overall performance and was more suitable for cartilage tissue engineering. - Highlights: • Silk fibroin/collagen was fabricated using 3D printing. • Physical characterization and Cell compatibility were compared. • 3D printed scaffold exhibited better overall performance.« less

Fabrication technique for a custom face mask for the treatment of obstructive sleep apnea.

PubMed

Prehn, Ronald S; Colquitt, Tom

2016-05-01

The development of the positive airway pressure custom mask (TAP-PAP CM) has changed the treatment of obstructive sleep apnea. The TAP-PAP CM is used in continuous positive airway pressure therapy (CPAP) and is fabricated from the impression of the face. This mask is then connected to a post screwed into the mechanism of the TAP3 (Thornton Anterior Positioner) oral appliance. This strapless CPAP face mask features an efficient and stable CPAP interface with mandibular stabilization (Hybrid Therapy). A technique with a 2-stage polyvinyl siloxane face impression is described that offers improvements over the established single-stage face impression. This 2-stage impression technique eliminates problems inherent in the single-stage face impression, including voids, compressed tissue, inadequate borders, and a rushed experience due to the setting time of the single stage. The result is a custom mask with an improved seal to the CPAP device. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

New alnico magnets fabricated from pre-alloyed gas-atomized powder through diverse consolidation techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, W.; Zhou, L.; Kassen, A. G.

2015-05-25

Fine Alnico 8 spherical powder produced by gas atomization was consolidated through hot pressing (HP), hot isostatic pressing (HIP), and compression molding and subsequent sintering (CMS) techniques. The effects of different fabrication techniques and processing parameters on microstructure and magnetic properties were analyzed and compared. The HP, HIP, and CMS magnets exhibited different features in microstructures and magnetic properties. Magnetically annealed at 840°C for 10 min and subsequently tempered at 650°C for 5h and 580°C for 15h, the HIP sample achieved the best coercivity (H cj =1845 Oe) due to spinodally decomposed (SD) phases with uniform and well-faceted mosaic morphology.more » As a result, the CMS sample had a lower Hcj than HIP and HP samples, but a higher remanence and thus the best energy product (6.5 MGOe) due to preferential grain alignment induced by abnormal grain growth.« less

Fabrication of semiconductor-polymer compound nonlinear photonic crystal slab with highly uniform infiltration based on nano-imprint lithography technique.

PubMed

Qin, Fei; Meng, Zi-Ming; Zhong, Xiao-Lan; Liu, Ye; Li, Zhi-Yuan

2012-06-04

We present a versatile technique based on nano-imprint lithography to fabricate high-quality semiconductor-polymer compound nonlinear photonic crystal (NPC) slabs. The approach allows one to infiltrate uniformly polystyrene materials that possess large Kerr nonlinearity and ultrafast nonlinear response into the cylindrical air holes with diameter of hundred nanometers that are perforated in silicon membranes. Both the structural characterization via the cross-sectional scanning electron microscopy images and the optical characterization via the transmission spectrum measurement undoubtedly show that the fabricated compound NPC samples have uniform and dense polymer infiltration and are of high quality in optical properties. The compound NPC samples exhibit sharp transmission band edges and nondegraded high quality factor of microcavities compared with those in the bare silicon PC. The versatile method can be expanded to make general semiconductor-polymer hybrid optical nanostructures, and thus it may pave the way for reliable and efficient fabrication of ultrafast and ultralow power all-optical tunable integrated photonic devices and circuits.

Rapid Model Fabrication and Testing for Aerospace Vehicles

NASA Technical Reports Server (NTRS)

Buck, Gregory M.

2000-01-01

Advanced methods for rapid fabrication and instrumentation of hypersonic wind tunnel models are being developed and evaluated at NASA Langley Research Center. Rapid aeroheating model fabrication and measurement techniques using investment casting of ceramic test models and thermographic phosphors are reviewed. More accurate model casting techniques for fabrication of benchmark metal and ceramic test models are being developed using a combination of rapid prototype patterns and investment casting. White light optical scanning is used for coordinate measurements to evaluate the fabrication process and verify model accuracy to +/- 0.002 inches. Higher-temperature (<210C) luminescent coatings are also being developed for simultaneous pressure and temperature mapping, providing global pressure as well as global aeroheating measurements. Together these techniques will provide a more rapid and complete experimental aerodynamic and aerothermodynamic database for future aerospace vehicles.

Electrohydrodynamic bubbling: an alternative route to fabricate porous structures of silk fibroin based materials.

PubMed

Ekemen, Zeynep; Ahmad, Zeeshan; Stride, Eleanor; Kaplan, David; Edirisinghe, Mohan

2013-05-13

Conventional fabrication techniques and structures employed in the design of silk fibroin (SF) based porous materials provide only limited control over pore size and require several processing stages. In this study, it is shown that, by utilizing electrohydrodynamic bubbling, not only can new hollow spherical structures of SF be formed in a single step by means of bubbles, but the resulting bubbles can serve as pore generators when dehydrated. The bubble characteristics can be controlled through simple adjustments to the processing parameters. Bubbles with diameters in the range of 240-1000 μm were fabricated in controlled fashion. FT-IR characterization confirmed that the rate of air infused during processing enhanced β-sheet packing in SF at higher flow rates. Dynamic mechanical analysis also demonstrated a correlation between air flow rate and film tensile strength. Results indicate that electrohydrodynamically generated SF and their composite bubbles can be employed as new tools to generate porous structures in a controlled manner with a range of potential applications in biocoatings and tissue engineering scaffolds.

Marginal fit of all-ceramic crowns fabricated using two extraoral CAD/CAM systems in comparison with the conventional technique

PubMed Central

Alqahtani, Fawaz

2017-01-01

Objective The purpose of this study was to determine the effect of two extraoral computer-aided design (CAD) and computer-aided manufacturing (CAM) systems, in comparison with conventional techniques, on the marginal fit of monolithic CAD/CAM lithium disilicate ceramic crowns. Study design This is an in vitro interventional study. Place and duration of study The study was carried out at the Department of Prosthodontics, School of Dentistry, Prince Sattam Bin Abdul-Aziz University, Saudi Arabia, from December 2015 to April 2016. Methodology A marginal gap of 60 lithium disilicate crowns was evaluated by scanning electron microscopy. In total, 20 pressable lithium disilicate (IPS e.max Press [Ivoclar Vivadent]) ceramic crowns were fabricated using the conventional lost-wax technique as a control group. The experimental all-ceramic crowns were produced based on a scan stone model and milled using two extraoral CAD/CAM systems: the Cerec group was fabricated using the Cerec CAD/CAM system, and the Trios group was fabricated using Trios CAD and milled using Wieland Zenotec CAM. One-way analysis of variance (ANOVA) and the Scheffe post hoc test were used for statistical comparison of the groups (α=0.05). Results The mean (±standard deviation) of the marginal gap of each group was as follows: the Control group was 91.15 (±15.35) µm, the Cerec group was 111.07 (±6.33) µm, and the Trios group was 60.17 (±11.09) µm. One-way ANOVA and the Scheffe post hoc test showed a statistically significant difference in the marginal gap between all groups. Conclusion It can be concluded from the current study that all-ceramic crowns, fabricated using the CAD/CAM system, show a marginal accuracy that is acceptable in clinical environments. The Trios CAD group displayed the smallest marginal gap. PMID:28352204

Marginal fit of all-ceramic crowns fabricated using two extraoral CAD/CAM systems in comparison with the conventional technique.

PubMed

Alqahtani, Fawaz

2017-01-01

The purpose of this study was to determine the effect of two extraoral computer-aided design (CAD) and computer-aided manufacturing (CAM) systems, in comparison with conventional techniques, on the marginal fit of monolithic CAD/CAM lithium disilicate ceramic crowns. This is an in vitro interventional study. The study was carried out at the Department of Prosthodontics, School of Dentistry, Prince Sattam Bin Abdul-Aziz University, Saudi Arabia, from December 2015 to April 2016. A marginal gap of 60 lithium disilicate crowns was evaluated by scanning electron microscopy. In total, 20 pressable lithium disilicate (IPS e.max Press [Ivoclar Vivadent]) ceramic crowns were fabricated using the conventional lost-wax technique as a control group. The experimental all-ceramic crowns were produced based on a scan stone model and milled using two extraoral CAD/CAM systems: the Cerec group was fabricated using the Cerec CAD/CAM system, and the Trios group was fabricated using Trios CAD and milled using Wieland Zenotec CAM. One-way analysis of variance (ANOVA) and the Scheffe post hoc test were used for statistical comparison of the groups (α=0.05). The mean (±standard deviation) of the marginal gap of each group was as follows: the Control group was 91.15 (±15.35) µm, the Cerec group was 111.07 (±6.33) µm, and the Trios group was 60.17 (±11.09) µm. One-way ANOVA and the Scheffe post hoc test showed a statistically significant difference in the marginal gap between all groups. It can be concluded from the current study that all-ceramic crowns, fabricated using the CAD/CAM system, show a marginal accuracy that is acceptable in clinical environments. The Trios CAD group displayed the smallest marginal gap.

One-step fabrication of submicrostructures by low one-photon absorption direct laser writing technique with local thermal effect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nguyen, Dam Thuy Trang; Tong, Quang Cong; Ledoux-Rak, Isabelle

In this work, local thermal effect induced by a continuous-wave laser has been investigated and exploited to optimize the low one-photon absorption (LOPA) direct laser writing (DLW) technique for fabrication of polymer-based microstructures. It was demonstrated that the temperature of excited SU8 photoresist at the focusing area increases to above 100 °C due to high excitation intensity and becomes stable at that temperature thanks to the use of a continuous-wave laser at 532 nm-wavelength. This optically induced thermal effect immediately completes the crosslinking process at the photopolymerized region, allowing obtain desired structures without using the conventional post-exposure bake (PEB) step, which ismore » usually realized after the exposure. Theoretical calculation of the temperature distribution induced by local optical excitation using finite element method confirmed the experimental results. LOPA-based DLW technique combined with optically induced thermal effect (local PEB) shows great advantages over the traditional PEB, such as simple, short fabrication time, high resolution. In particular, it allowed the overcoming of the accumulation effect inherently existed in optical lithography by one-photon absorption process, resulting in small and uniform structures with very short lattice constant.« less

One-step fabrication of submicrostructures by low one-photon absorption direct laser writing technique with local thermal effect

NASA Astrophysics Data System (ADS)

Nguyen, Dam Thuy Trang; Tong, Quang Cong; Ledoux-Rak, Isabelle; Lai, Ngoc Diep

2016-01-01

In this work, local thermal effect induced by a continuous-wave laser has been investigated and exploited to optimize the low one-photon absorption (LOPA) direct laser writing (DLW) technique for fabrication of polymer-based microstructures. It was demonstrated that the temperature of excited SU8 photoresist at the focusing area increases to above 100 °C due to high excitation intensity and becomes stable at that temperature thanks to the use of a continuous-wave laser at 532 nm-wavelength. This optically induced thermal effect immediately completes the crosslinking process at the photopolymerized region, allowing obtain desired structures without using the conventional post-exposure bake (PEB) step, which is usually realized after the exposure. Theoretical calculation of the temperature distribution induced by local optical excitation using finite element method confirmed the experimental results. LOPA-based DLW technique combined with optically induced thermal effect (local PEB) shows great advantages over the traditional PEB, such as simple, short fabrication time, high resolution. In particular, it allowed the overcoming of the accumulation effect inherently existed in optical lithography by one-photon absorption process, resulting in small and uniform structures with very short lattice constant.

A novel method combining additive manufacturing and alloy infiltration for NdFeB bonded magnet fabrication

DOE PAGES

Li, Ling; Tirado, Angelica; Conner, Benjamin S.; ...

2017-04-27

In this paper, binder jetting additive manufacturing technique is employed to fabricate NdFeB isotropic bonded magnets, followed by an infiltration process with low-melting point eutectic alloys [i.e., Nd 3Cu 0.25Co 0.75 (NdCuCo) and Pr 3Cu 0.25Co 0.75 (PrCuCo)]. Densification and mechanical strength improvement are achieved for the as-printed porous part. Meanwhile, the intrinsic coercivity H ci is enhanced from 732 to 1345 kA/m and 1233 kA/m after diffusion of NdCuCo and PrCuCo, respectively. This study presents a novel method for fabricating complex-shaped bonded magnets with promising mechanical and magnetic properties.

A novel method combining additive manufacturing and alloy infiltration for NdFeB bonded magnet fabrication

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Ling; Tirado, Angelica; Conner, Benjamin S.

In this paper, binder jetting additive manufacturing technique is employed to fabricate NdFeB isotropic bonded magnets, followed by an infiltration process with low-melting point eutectic alloys [i.e., Nd 3Cu 0.25Co 0.75 (NdCuCo) and Pr 3Cu 0.25Co 0.75 (PrCuCo)]. Densification and mechanical strength improvement are achieved for the as-printed porous part. Meanwhile, the intrinsic coercivity H ci is enhanced from 732 to 1345 kA/m and 1233 kA/m after diffusion of NdCuCo and PrCuCo, respectively. This study presents a novel method for fabricating complex-shaped bonded magnets with promising mechanical and magnetic properties.

Micro/nano-fabrication technologies for cell biology.

PubMed

Qian, Tongcheng; Wang, Yingxiao

2010-10-01

Micro/nano-fabrication techniques, such as soft lithography and electrospinning, have been well-developed and widely applied in many research fields in the past decade. Due to the low costs and simple procedures, these techniques have become important and popular for biological studies. In this review, we focus on the studies integrating micro/nano-fabrication work to elucidate the molecular mechanism of signaling transduction in cell biology. We first describe different micro/nano-fabrication technologies, including techniques generating three-dimensional scaffolds for tissue engineering. We then introduce the application of these technologies in manipulating the physical or chemical micro/nano-environment to regulate the cellular behavior and response, such as cell life and death, differentiation, proliferation, and cell migration. Recent advancement in integrating the micro/nano-technologies and live cell imaging are also discussed. Finally, potential schemes in cell biology involving micro/nano-fabrication technologies are proposed to provide perspectives on the future research activities.

Micro/nano-fabrication technologies for cell biology

PubMed Central

Qian, Tongcheng

2012-01-01

Micro/nano-fabrication techniques, such as soft lithography and electrospinning, have been well-developed and widely applied in many research fields in the past decade. Due to the low costs and simple procedures, these techniques have become important and popular for biological studies. In this review, we focus on the studies integrating micro/nano-fabrication work to elucidate the molecular mechanism of signaling transduction in cell biology. We first describe different micro/nano-fabrication technologies, including techniques generating three-dimensional scaffolds for tissue engineering. We then introduce the application of these technologies in manipulating the physical or chemical micro/nano-environment to regulate the cellular behavior and response, such as cell life and death, differentiation, proliferation, and cell migration. Recent advancement in integrating the micro/nano-technologies and live cell imaging are also discussed. Finally, potential schemes in cell biology involving micro/nano-fabrication technologies are proposed to provide perspectives on the future research activities. PMID:20490938

Fabrication of high-resolution nanostructures of complex geometry by the single-spot nanolithography method

PubMed Central

Anisimova, Margarita; Samardak, Aleksei; Ognev, Alexey

2015-01-01

Summary The paper presents a method for the high-resolution production of polymer nanopatterns with controllable geometrical parameters by means of a single-spot electron-beam lithography technique. The essence of the method entails the overexposure of a positive-tone resist, spin-coated onto a substrate where nanoscale spots are exposed to an electron beam with a dose greater than 0.1 pC per dot. A single-spot enables the fabrication of a nanoring, while a chain of spots placed at distance of 5–30 nm from each other allows the production of a polymer pattern of complex geometry of sub-10 nm resolution. We demonstrate that in addition to the naturally oxidized silicon substrates, gold-coated substrates can also successfully be used for the single-spot nanopattering technique. An explanation of the results related to the resist overexposure was demonstrated using Monte Carlo simulations. Our nanofabrication method significantly accelerates (up to 10 times) the fabrication rate as compared to conventional lithography on positive-tone resist. This technique can be potentially employed in the electronics industry for the production of nanoprinted lithography molds, etching masks, nanoelectronics, nanophotonics, NEMS and MEMS devices. PMID:25977869

Fabrication of microlens array and bifocal microlens using the methods of laser ablation and solvent reflow

NASA Astrophysics Data System (ADS)

Yu, Cheng-Chian; Ho, Jeng-Rong

2015-12-01

Based on the techniques of laser microdrilling and solvent reflow, this study reports on a straightforward approach for fabricating plastic microlens arrays (MLAs). First, we use the ArF excimer laser to drill microholes on a polymethylmethacrylate plate for defining the lens number, initial depth, and diameter. The propylene glycol monomethyl ether acetate solvent is then employed to regulate the surface profile that leads to a resulting negative (concave) MLA. The corresponding positive (convex), polydimethyl-siloxane MLA is obtained by the soft-replica-molding technique. Through varying the pattern size and period on the mask and the light intensity for laser drilling and regulating the solvent in the reflow process, we exhibit the feasibility of making MLAs with various sizes and shapes. By modifying the laser ablation step to drill two microholes with different diameters and depths at two levels, we fabricate a bifocal microlens. The obtained microlenses have excellent surface and optical properties: surface roughness down to several nanometers and focal lengths varying from hundreds to thousands of micrometers. This approach is flexible for constructing microlenses with various sizes and shapes and can fabricate MLAs with a high fill factor.

CVD Polymers for Devices and Device Fabrication.

PubMed

Wang, Minghui; Wang, Xiaoxue; Moni, Priya; Liu, Andong; Kim, Do Han; Jo, Won Jun; Sojoudi, Hossein; Gleason, Karen K

2017-03-01

Chemical vapor deposition (CVD) polymerization directly synthesizes organic thin films on a substrate from vapor phase reactants. Dielectric, semiconducting, electrically conducting, and ionically conducting CVD polymers have all been readily integrated into devices. The absence of solvent in the CVD process enables the growth of high-purity layers and avoids the potential of dewetting phenomena, which lead to pinhole defects. By limiting contaminants and defects, ultrathin (<10 nm) CVD polymeric device layers have been fabricated in multiple laboratories. The CVD method is particularly suitable for synthesizing insoluble conductive polymers, layers with high densities of organic functional groups, and robust crosslinked networks. Additionally, CVD polymers are prized for the ability to conformally cover rough surfaces, like those of paper and textile substrates, as well as the complex geometries of micro- and nanostructured devices. By employing low processing temperatures, CVD polymerization avoids damaging substrates and underlying device layers. This report discusses the mechanisms of the major CVD polymerization techniques and the recent progress of their applications in devices and device fabrication, with emphasis on initiated CVD (iCVD) and oxidative CVD (oCVD) polymerization. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Micromechanical Structures Fabrication

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rajic, S

2001-05-08

Work in materials other than silicon for MEMS applications has typically been restricted to metals and metal oxides instead of more ''exotic'' semiconductors. However, group III-V and II-VI semiconductors form a very important and versatile collection of material and electronic parameters available to the MEMS and MOEMS designer. With these materials, not only are the traditional mechanical material variables (thermal conductivity, thermal expansion, Young's modulus, etc.) available, but also chemical constituents can be varied in ternary and quaternary materials. This flexibility can be extremely important for both friction and chemical compatibility issues for MEMS. In addition, the ability to continuallymore » vary the bandgap energy can be particularly useful for many electronics and infrared detection applications. However, there are two major obstacles associated with alternate semiconductor material MEMS. The first issue is the actual fabrication of non-silicon micro-devices and the second impediment is communicating with these novel devices. We have implemented an essentially material independent fabrication method that is amenable to most group III-V and II-VI semiconductors. This technique uses a combination of non-traditional direct write precision fabrication processes such as diamond turning, ion milling, laser ablation, etc. This type of deterministic fabrication approach lends itself to an almost trivial assembly process. We also implemented a mechanical, electrical, and optical self-aligning hybridization technique for these alternate-material MEMS substrates.« less

Fabrication of ZnO Nanowires Arrays by Anodization and High-Vacuum Die Casting Technique, and Their Piezoelectric Properties

PubMed Central

Kuo, Chin-Guo; Chang, Ho; Wang, Jian-Hao

2016-01-01

In this investigation, anodic aluminum oxide (AAO) with arrayed and regularly arranged nanopores is used as a template in the high-vacuum die casting of molten zinc metal (Zn) into the nanopores. The proposed technique yields arrayed Zn nanowires with an aspect ratio of over 600. After annealing, arrayed zinc oxide (ZnO) nanowires are obtained. Varying the anodizing time yields AAO templates with thicknesses of approximately 50 μm, 60 μm, and 70 μm that can be used in the fabrication of nanowires of three lengths with high aspect ratios. Experimental results reveal that a longer nanowire generates a greater measured piezoelectric current. The ZnO nanowires that are fabricated using an alumina template are anodized for 7 h and produce higher piezoelectric current of up to 69 pA. PMID:27023546

Fabrication of ZnO Nanowires Arrays by Anodization and High-Vacuum Die Casting Technique, and Their Piezoelectric Properties.

PubMed

Kuo, Chin-Guo; Chang, Ho; Wang, Jian-Hao

2016-03-24

In this investigation, anodic aluminum oxide (AAO) with arrayed and regularly arranged nanopores is used as a template in the high-vacuum die casting of molten zinc metal (Zn) into the nanopores. The proposed technique yields arrayed Zn nanowires with an aspect ratio of over 600. After annealing, arrayed zinc oxide (ZnO) nanowires are obtained. Varying the anodizing time yields AAO templates with thicknesses of approximately 50 μm, 60 μm, and 70 μm that can be used in the fabrication of nanowires of three lengths with high aspect ratios. Experimental results reveal that a longer nanowire generates a greater measured piezoelectric current. The ZnO nanowires that are fabricated using an alumina template are anodized for 7 h and produce higher piezoelectric current of up to 69 pA.

Transmission and group-delay characterization of coupled resonator optical waveguides apodized through the longitudinal offset technique.

PubMed

Doménech, J D; Muñoz, P; Capmany, J

2011-01-15

In this Letter, the amplitude and group delay characteristics of coupled resonator optical waveguides apodized through the longitudinal offset technique are presented. The devices have been fabricated in silicon-on-insulator technology employing deep ultraviolet lithography. The structures analyzed consisted of three racetracks resonators uniform (nonapodized) and apodized with the aforementioned technique, showing a delay of 5 ± 3 ps and 4 ± 0.5 ps over 1.6 and 1.4 nm bandwidths, respectively.

Fabrication of Orientation-Controlled 3D Tissues Using a Layer-by-Layer Technique and 3D Printed a Thermoresponsive Gel Frame.

PubMed

Tsukamoto, Yoshinari; Akagi, Takami; Shima, Fumiaki; Akashi, Mitsuru

2017-06-01

Herein, we report the fabrication of orientation-controlled tissues similar to heart and nerve tissues using a cell accumulation and three-dimensional (3D) printing technique. We first evaluated the 3D shaping ability of hydroxybutyl chitosan (HBC), a thermoresponsive polymer, by using a robotic dispensing 3D printer. HBC polymer could be laminated to a height of 1124 ± 14 μm. Based on this result, we fabricated 3D gel frames of various shapes, such as square, triangular, rectangular, and circular, for shape control of 3D tissue and then normal human cardiac fibroblasts (NHCFs) coated with extracellular matrix nanofilms were seeded in the frames. Observation of shape-controlled tissues after 1 day of cultivation showed that the orientation of fibroblasts was in one direction when a short-sided, thin, rectangular-shaped frame was used. Next, we tried to fabricate orientation-controlled tissue with a vascular network by coculturing NHCF and normal human cardiac microvascular endothelial cells. As a consequence of cultivation for 4 days, observation of cocultured tissue confirmed aligned cells and blood capillaries in orientation-controlled tissue. Our results clearly demonstrated that it would be possible to control the cell orientation by controlling the shape of the tissues by combining a cell accumulation technique and a 3D printing system. The results of this study suggest promising strategies for the fabrication of oriented 3D tissues in vitro. These tissues, mimicking native organ structures, such as muscle and nerve tissue with a cell alignment structure, would be useful for tissue engineering, regenerative medicine, and pharmaceutical applications.

Review article: Fabrication of nanofluidic devices

PubMed Central

Duan, Chuanhua; Wang, Wei; Xie, Quan

2013-01-01

Thanks to its unique features at the nanoscale, nanofluidics, the study and application of fluid flow in nanochannels/nanopores with at least one characteristic size smaller than 100 nm, has enabled the occurrence of many interesting transport phenomena and has shown great potential in both bio- and energy-related fields. The unprecedented growth of this research field is apparently attributed to the rapid development of micro/nanofabrication techniques. In this review, we summarize recent activities and achievements of nanofabrication for nanofluidic devices, especially those reported in the past four years. Three major nanofabrication strategies, including nanolithography, microelectromechanical system based techniques, and methods using various nanomaterials, are introduced with specific fabrication approaches. Other unconventional fabrication attempts which utilize special polymer properties, various microfabrication failure mechanisms, and macro/microscale machining techniques are also presented. Based on these fabrication techniques, an inclusive guideline for materials and processes selection in the preparation of nanofluidic devices is provided. Finally, technical challenges along with possible opportunities in the present nanofabrication for nanofluidic study are discussed. PMID:23573176

Hollow Core Bragg Waveguide Design and Fabrication for Enhanced Raman Spectroscopy

NASA Astrophysics Data System (ADS)

Ramanan, Janahan

Raman spectroscopy is a widely used technique to unambiguously ascertain the chemical composition of a sample. The caveat with this technique is its extremely weak optical cross-section, making it difficult to measure Raman signal with standard optical setups. In this thesis, a novel hollow core Bragg Reflection Waveguide was designed to simultaneously increase the generation and collection of Raman scattered photons. A robust fabrication process of this waveguide was developed employing flip-chip bonding methods to securely seal the hollow core channel. The waveguide air-core propagation loss was experimentally measured to be 0.17 dB/cm, and the Raman sensitivity limit was measured to be 3 mmol/L for glycerol solution. The waveguide was also shown to enhance Raman modes of standard household aerosols that could not be seen with other devices.

High-performance and high-reliability SOT-6 packaged diplexer based on advanced IPD fabrication techniques

NASA Astrophysics Data System (ADS)

Qiang, Tian; Wang, Cong; Kim, Nam-Young

2017-08-01

A diplexer offering the advantages of compact size, high performance, and high reliability is proposed on the basis of advanced integrated passive device (IPD) fabrication techniques. The proposed diplexer is developed by combining a third-order low-pass filter (LPF) and a third-order high-pass filter (HPF), which are designed on the basis of the elliptic function prototype low-pass filter. Primary components, such as inductors and capacitors, are designed and fabricated with high Q-factor and appropriate values, and they are subsequently used to construct a compact diplexer having a chip area of 900 μm × 1100 μm (0.009 λ0 × 0.011 λ0, where λ0 is the guided wavelength). In addition, a small-outline transistor (SOT-6) packaging method is adopted, and reliability tests (including temperature, humidity, vibration, and pressure) are conducted to guarantee long-term stability and commercial success. The packaged measurement results indicate excellent RF performance with insertion losses of 1.39 dB and 0.75 dB at operation bands of 0.9 GHz and 1.8 GHz, respectively. The return loss is lower than 10 dB from 0.5 GHz to 4.0 GHz, while the isolation is higher than 15 dB from 0.5 GHz to 3.0 GHz. Thus, it can be concluded that the proposed SOT-6 packaged diplexer is a promising candidate for GSM/CDMA applications. Synthetic solution of diplexer design, RF performance optimization, fabrication process, packaging, RF response measurement, and reliability test is particularly explained and analyzed in this work.

Fabrication of glass gas cells for the HALOE and MAPS satellite experiments

NASA Technical Reports Server (NTRS)

Sullivan, E. M.; Walthall, H. G.

1984-01-01

The Halogen Occultation Experiment (HALOE) and the Measurement of Air Pollution from Satellites (MAPS) experiment are satellite-borne experiments which measure trace constituents in the Earth's atmosphere. The instruments which obtain the data for these experiments are based on the gas filter correlation radiometer measurement technique. In this technique, small samples of the gases of interest are encapsulated in glass cylinders, called gas cells, which act as very selective optical filters. This report describes the techniques employed in the fabrication of the gas cells for the HALOE and MAPS instruments. Details of the method used to fuse the sapphire windows (required for IR transmission) to the glass cell bodies are presented along with detailed descriptions of the jigs and fixtures used during the assembly process. The techniques and equipment used for window inspection and for pairing the HALOE windows are discussed. Cell body materials and the steps involved in preparing the cell bodies for the glass-to-sapphire fusion process are given.

Replacement of a hopeless maxillary central incisor: a technique for the fabrication of an immediate implant-supported interim restoration.

PubMed

Graiff, Lorenzo; Vigolo, Paolo

2012-04-01

Placement of a dental implant and an interim restoration in the esthetic zone immediately following tooth extraction is now a common procedure. However, in such clinical situations, the fabrication of an appropriate interim restoration may be challenging. The aim of this article is to present a technique for modifying the extracted tooth so it can be used as an implant-supported interim restoration.

An electrochemical and structural study of highly uniform tin oxide nanowires fabricated by a novel, scalable solvoplasma technique as anode material for sodium ion batteries

NASA Astrophysics Data System (ADS)

Mukherjee, Santanu; Schuppert, Nicholas; Bates, Alex; Jasinski, Jacek; Hong, Jong-Eun; Choi, Moon Jong; Park, Sam

2017-04-01

A novel solvoplasma based technique was used to fabricate highly uniform SnO2 nanowires (NWs) for application as an anode in sodium-ion batteries (SIBs). This technique is scalable, rapid, and utilizes a rigorous cleaning process to produce very pure SnO2 NWs with enhanced porosity; which improves sodium-ion hosting and reaction kinetics. The batch of NWs obtained from the plasma process were named the "as-made" sample and after cleaning the "pure" sample. Structural characterization showed that the as-made sample has a K+ ion impurity which is absent in the pure samples. The pure samples have a higher maximum specific capacity, 400.71 mAhg-1, and Coulombic efficiency, 85%, compared to the as-made samples which have a maximum specific capacity of 174.69 mAhg-1 and Coulombic efficiency of 74% upon cycling. A study of the electrochemical impedance spectra showed that the as-made samples have a higher interfacial and diffusion resistance than the pure samples and resistances increased after 50 cycles of cell operation for both samples due to progressive electrode degradation. Specific energy vs specific power plots were employed to analyze the performance of the system with respect to the working conditions.

Investigation of radiation hardened SOI wafer fabricated by ion-cut technique

NASA Astrophysics Data System (ADS)

Chang, Yongwei; Wei, Xing; Zhu, Lei; Su, Xin; Gao, Nan; Dong, Yemin

2018-07-01

Total ionizing dose (TID) effect on Silicon-on-Insulator (SOI) wafers due to inherent buried oxide (BOX) is a significant concern as it leads to the degradation of electrical properties of SOI-based devices and circuits, even failures of the systems associated with them. This paper reports the radiation hardening implementation of SOI wafer fabricated by ion-cut technique integrated with low-energy Si+ implantation. The electrical properties and radiation response of pseudo-MOS transistors are analyzed. The results demonstrate that the hardening process can significantly improve the TID tolerance of SOI wafers by generating Si nanocrystals (Si-NCs) within the BOX. The presence of Si-NCs created through Si+ implantation is evidenced by high-resolution transmission electron microscopy (HR-TEM). Under the pass gate (PG) irradiation bias, the anti-radiation properties of H-gate SOI nMOSFETs suggest that the radiation hardened SOI wafers with optimized Si implantation dose can perform effectively in a radiation environment. The radiation hardening process provides an excellent way to reinforce the TID tolerance of SOI wafers.

The fabrication of well-interconnected polycaprolactone/hydroxyapatite composite scaffolds, enhancing the exposure of hydroxyapatite using the wire-network molding technique.

PubMed

Cho, Yong Sang; Hong, Myoung Wha; Jeong, Hoon-Jin; Lee, Seung-Jae; Kim, Young Yul; Cho, Young-Sam

2017-11-01

In this study, the fabrication method was proposed for the well-interconnected polycaprolactone/hydroxyapatite composite scaffold with exposed hydroxyapatite using modified WNM technique. To characterize well-interconnected scaffolds in terms of hydroxyapatite exposure, several assessments were performed as follows: morphology, mechanical property, wettability, calcium ion release, and cell response assessments. The results of these assessments were compared with those of control scaffolds which were fabricated by precision extruding deposition (PED) apparatus. The control PED scaffolds have interconnected pores with nonexposed hydroxyapatite. Consequently, cell attachment of proposed WNM scaffold was improved by increased hydrophilicity and surface roughness of scaffold surface resulting from the exposure of hydroxyapatite particles and fabrication process using powders. Moreover, cell proliferation and differentiation of WNM scaffold were increased, because the exposure of hydroxyapatite particles may enhance cell adhesion and calcium ion release. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2315-2325, 2017. © 2016 Wiley Periodicals, Inc.

Applications of Semiconductor Fabrication Methods to Nanomedicine: A Review of Recent Inventions and Techniques

PubMed Central

Rajasekhar, Achanta; Gimi, Barjor; Hu, Walter

2013-01-01

We live in a world of convergence where scientific techniques from a variety of seemingly disparate fields are being applied cohesively to the study and solution of biomedical problems. For instance, the semiconductor processing field has been primarily developed to cater to the needs of the ever decreasing transistor size and cost while increasing functionality of electronic circuits. In recent years, pioneers in this field have equipped themselves with a powerful understanding of how the same techniques can be applied in the biomedical field to develop new and efficient systems for the diagnosis, analysis and treatment of various conditions in the human body. In this paper, we review the major inventions and experimental methods which have been developed for nano/micro fluidic channels, nanoparticles fabricated by top-down methods, and in-vivo nanoporous microcages for effective drug delivery. This paper focuses on the information contained in patents as well as the corresponding technical publications. The goal of the paper is to help emerging scientists understand and improvise over these inventions. PMID:24312161

Fabrication of multi-well chips for spheroid cultures and implantable constructs through rapid prototyping techniques.

PubMed

Lopa, Silvia; Piraino, Francesco; Kemp, Raymond J; Di Caro, Clelia; Lovati, Arianna B; Di Giancamillo, Alessia; Moroni, Lorenzo; Peretti, Giuseppe M; Rasponi, Marco; Moretti, Matteo

2015-07-01

Three-dimensional (3D) culture models are widely used in basic and translational research. In this study, to generate and culture multiple 3D cell spheroids, we exploited laser ablation and replica molding for the fabrication of polydimethylsiloxane (PDMS) multi-well chips, which were validated using articular chondrocytes (ACs). Multi-well ACs spheroids were comparable or superior to standard spheroids, as revealed by glycosaminoglycan and type-II collagen deposition. Moreover, the use of our multi-well chips significantly reduced the operation time for cell seeding and medium refresh. Exploiting a similar approach, we used clinical-grade fibrin to generate implantable multi-well constructs allowing for the precise distribution of multiple cell types. Multi-well fibrin constructs were seeded with ACs generating high cell density regions, as shown by histology and cell fluorescent staining. Multi-well constructs were compared to standard constructs with homogeneously distributed ACs. After 7 days in vitro, expression of SOX9, ACAN, COL2A1, and COMP was increased in both constructs, with multi-well constructs expressing significantly higher levels of chondrogenic genes than standard constructs. After 5 weeks in vivo, we found that despite a dramatic size reduction, the cell distribution pattern was maintained and glycosaminoglycan content per wet weight was significantly increased respect to pre-implantation samples. In conclusion, multi-well chips for the generation and culture of multiple cell spheroids can be fabricated by low-cost rapid prototyping techniques. Furthermore, these techniques can be used to generate implantable constructs with defined architecture and controlled cell distribution, allowing for in vitro and in vivo investigation of cell interactions in a 3D environment. © 2015 Wiley Periodicals, Inc.

Methods for Fabricating Gradient Alloy Articles with Multi-Functional Properties

NASA Technical Reports Server (NTRS)

Hofmann, Douglas C. (Inventor); Suh, Eric J. (Inventor); Borgonia, John Paul C. (Inventor); Dillon, Robert P. (Inventor); Mulder, Jerry L. (Inventor); Gardner, Paul B. (Inventor)

2015-01-01

Systems and methods for fabricating multi-functional articles comprised of additively formed gradient materials are provided. The fabrication of multi-functional articles using the additive deposition of gradient alloys represents a paradigm shift from the traditional way that metal alloys and metal/metal alloy parts are fabricated. Since a gradient alloy that transitions from one metal to a different metal cannot be fabricated through any conventional metallurgy techniques, the technique presents many applications. Moreover, the embodiments described identify a broad range of properties and applications.

Toughness characterization by small specimen test technique for HIPed joints of F82H steel aiming at first wall fabrication in fusion

NASA Astrophysics Data System (ADS)

Kishimoto, H.; Ono, T.; Sakasegawa, H.; Tanigawa, H.; Kohno, Y.; Kohyama, A.

2013-09-01

Reduced activation ferritic/martensitic steels (RAFMs), such as F82H steels, have been developed as candidates of structural materials for fusion. In the design of a fusion reactor, cooling channels are built in the first wall of the blanket. One large issue is to determine how to join rectangular tubes to thin panels to fabricate the first wall. Hot Isostatic Pressing (HIPing) is a solution to solve the issue. Because of the thin HIPed walls of the channels, the specimen size for inspection of HIPed interface is limited. In the present research, Small Specimen Test Techniques (SSTT) are screened for the destructive toughness investigation technique of HIPed F82H joints. 1/3 size Charpy V-notch impact (1/3 CVN) and small punch (SP) tests are employed for the present research. The toughness of the HIPed joints is strongly affected by various surface finishing of specimens treated previous to the HIPing. In the present research, several kinds of HIPed joints were surface finished by different methods and investigated by 1/3 CVN impact test. The HIPed F82H joints had different toughness ranging from 20% to 70% of the toughness of the F82H base metal. The SP test is also available for the investigation of toughness change by the HIPing. The sensitivity of 1/3 CVN impact test against toughness change was better than the SP test, it revealed that the SP test has some limitations.

Fabrication And Characterization Of Photonic Crystal Slow Light Waveguides And Cavities

PubMed Central

Reardon, Christopher Paul; Rey, Isabella H.; Welna, Karl; O'Faolain, Liam; Krauss, Thomas F.

2012-01-01

Slow light has been one of the hot topics in the photonics community in the past decade, generating great interest both from a fundamental point of view and for its considerable potential for practical applications. Slow light photonic crystal waveguides, in particular, have played a major part and have been successfully employed for delaying optical signals1-4 and the enhancement of both linear5-7 and nonlinear devices.8-11 Photonic crystal cavities achieve similar effects to that of slow light waveguides, but over a reduced band-width. These cavities offer high Q-factor/volume ratio, for the realization of optically12 and electrically13 pumped ultra-low threshold lasers and the enhancement of nonlinear effects.14-16 Furthermore, passive filters17 and modulators18-19 have been demonstrated, exhibiting ultra-narrow line-width, high free-spectral range and record values of low energy consumption. To attain these exciting results, a robust repeatable fabrication protocol must be developed. In this paper we take an in-depth look at our fabrication protocol which employs electron-beam lithography for the definition of photonic crystal patterns and uses wet and dry etching techniques. Our optimised fabrication recipe results in photonic crystals that do not suffer from vertical asymmetry and exhibit very good edge-wall roughness. We discuss the results of varying the etching parameters and the detrimental effects that they can have on a device, leading to a diagnostic route that can be taken to identify and eliminate similar issues. The key to evaluating slow light waveguides is the passive characterization of transmission and group index spectra. Various methods have been reported, most notably resolving the Fabry-Perot fringes of the transmission spectrum20-21 and interferometric techniques.22-25 Here, we describe a direct, broadband measurement technique combining spectral interferometry with Fourier transform analysis.26 Our method stands out for its simplicity and

Electron Beam Lithography Double Step Exposure Technique for Fabrication of Mushroom-Like Profile in Bilayer Resist System

NASA Astrophysics Data System (ADS)

Kornelia, Indykiewicz; Bogdan, Paszkiewicz; Tomasz, Szymański; Regina, Paszkiewicz

2015-01-01

The Hi/Lo bilayer resist system exposure in e-beam lithography (EBL) process, intended for mushroom-like profile fabrication, was studied. Different exposure parameters and theirs influence on the resist layers were simulated in CASINO software and the obtained results were compared with the experimental data. The AFM technique was used for the estimation of the e-beam penetration depth in the resist stack. Performed numerical and experimental results allow us to establish the useful ranges of the exposure parameters.

Fabrication of a novel biosensor for macromolecules detection through molecular imprinting technique

NASA Astrophysics Data System (ADS)

Yu, Yingjie

There is an increasing need for precise molecular detection as a diagnostic tool for early identification of diseases, pathogens, and abnormal protein levels in the body. Typical chemical analytical methods are generally costly, unstable, and time-consuming. Molecular imprinting (MI) technique, based on the "lock and key model", could be a simple method to overcome those shortcomings. In this study, a self-assembled monolayer (SAM) was employed as a platform to fabricate MI biosensor for detection of macromolecules. I demonstrated that, when the monolayer was formed on a rough surface, this method was in fact templating molecules in three dimensions, and hence was not limited by the height of the monolayer, but rather by the height of the roughness. This hypothesis was tested on biomolecules of multiple length scales. The SAM is assembled on the walls of the niche, forming a 3D pattern of the analyte uniquely molded to its contour. The surfaces with multi-scale roughness were prepared by evaporation of gold onto electropolished (smooth) and unpolished (rough) Si wafers, where the native roughness was found to have a normal distribution centered around 5 and 90 nm respectively. Our studies, using molecules, such as proteins, i.e., hemoglobin, ranging from a few nanometers, to viruses (i.e. polio, adenovirus), ranging from several tens of nanometers, and protein complexes ranging from several hundred nanometers, showed that when the size of the analyte matched the roughness of the gold surface, this method was very effective and could detect even small changes in the configuration, such as those induced by changes in the pH of the system. The detection method was further quantified by applying it to the detection of CEA in pancreatic cyst fluid obtained from 18 patients under IRB 95867-6. The results of the MI biosensor were directly compared with those obtained using ELISA in the hospital pathology laboratory with excellent agreement, except that the MI biosensor

Marginal and internal fit of cobalt-chromium copings fabricated using the conventional and the direct metal laser sintering techniques: A comparative in vitro study.

PubMed

Ullattuthodi, Sujana; Cherian, Kandathil Phillip; Anandkumar, R; Nambiar, M Sreedevi

2017-01-01

This in vitro study seeks to evaluate and compare the marginal and internal fit of cobalt-chromium copings fabricated using the conventional and direct metal laser sintering (DMLS) techniques. A master model of a prepared molar tooth was made using cobalt-chromium alloy. Silicone impression of the master model was made and thirty standardized working models were then produced; twenty working models for conventional lost-wax technique and ten working models for DMLS technique. A total of twenty metal copings were fabricated using two different production techniques: conventional lost-wax method and DMLS; ten samples in each group. The conventional and DMLS copings were cemented to the working models using glass ionomer cement. Marginal gap of the copings were measured at predetermined four points. The die with the cemented copings are standardized-sectioned with a heavy duty lathe. Then, each sectioned samples were analyzed for the internal gap between the die and the metal coping using a metallurgical microscope. Digital photographs were taken at ×50 magnification and analyzed using measurement software. Statistical analysis was done by unpaired t -test and analysis of variance (ANOVA). The results of this study reveal that no significant difference was present in the marginal gap of conventional and DMLS copings ( P > 0.05) by means of ANOVA. The mean values of internal gap of DMLS copings were significantly greater than that of conventional copings ( P < 0.05). Within the limitations of this in vitro study, it was concluded that the internal fit of conventional copings was superior to that of the DMLS copings. Marginal fit of the copings fabricated by two different techniques had no significant difference.

An exploration of the reflow technique for the fabrication of an in vitro microvascular system to study occlusive clots.

PubMed

Li, Yang; Pan, Chuer; Li, Yunfeng; Kumacheva, Eugenia; Ramachandran, Arun

2017-09-08

Embolic ischemia and pulmonary embolism are health emergencies that arise when a particle such as a blood clot occludes a smaller blood vessel in the brain or the lungs, and restricts flow of blood downstream of the vessel. In this work, the reflow technique (Wang et al. Biomed. Microdevices 2007, 9, 657) was adapted to produce a microchannel network that mimics the occlusion process. The technique was first revisited and a simple geometrical model was developed to quantitatively explain the shapes of the resulting microchannels for different reflow parameters. A critical modification was introduced to the reflow protocol to fabricate nearly circular microchannels of different diameters from the same master, which is not possible with the traditional reflow technique. To simulate the phenomenon of occlusion by clots, a microchannel network with three generations of branches with different diameters and branching angles was fabricated, into which fibrin clots were introduced. At low constant pressure drop (ΔP), a clot blocked a branch entrance only partially, while at higher ΔP, the branch was completely blocked. Instances of simultaneous blocking of multiple channels by clots, and the consequent changes in the flow rates in the unblocked branches of the network, were also monitored. This work provides the framework for a systematic study of the distribution of clots in a network, and the rate of dissolution of embolic clots upon the introduction of a thrombolytic drug into the network.

Processing Techniques Developed to Fabricate Lanthanum Titanate Piezoceramic Material for High-Temperature Smart Structures

NASA Technical Reports Server (NTRS)

Goldsby, Jon C.; Farmer, Serene C.; Sayir, Ali

2004-01-01

Piezoelectric ceramic materials are potential candidates for use as actuators and sensors in intelligent gas turbine engines. For piezoceramics to be applied in gas turbine engines, they will have to be able to function in temperatures ranging from 1000 to 2500 F. However, the maximum use temperature for state-of-the-art piezoceramic materials is on the order of 300 to 400 F. Research activities have been initiated to develop high-temperature piezoceramic materials for gas turbine engine applications. Lanthanum titanate has been shown to have high-temperature piezoelectric properties with Curie temperatures of T(sub c) = 1500 C and use temperatures greater than 1000 C. However, the fabrication of lanthanum titanate poses serious challenges because of the very high sintering temperatures required for densification. Two different techniques have been developed at the NASA Glenn Research Center to fabricate dense lanthanum titanate piezoceramic material. In one approach, lower sintering temperatures were achieved by adding yttrium oxide to commercially available lanthanum titanate powder. Addition of only 0.1 mol% yttrium oxide lowered the sintering temperature by as much as 300 C, to just 1100 C, and dense lanthanum titanate was produced by pressure-assisted sintering. The second approach utilized the same commercially available powders but used an innovative sintering approach called differential sintering, which did not require any additive.

Quantum Dot Solar Cell Fabrication Protocols

DOE PAGES

Chernomordik, Boris D.; Marshall, Ashley R.; Pach, Gregory F.; ...

2016-09-26

Colloidally synthesized quantum-confined semiconducting spherical nanocrystals, often referred to as quantum dots (QDs), offer a high degree of chemical, optical, and electronic tunability. As a result, there is an increasing interest in employing colloidal QDs for electronic and optical applications that is reflected in a growing number of publications. In this protocol we provide detailed procedures for the fabrication of QD solar cells specifically employing PbSe and PbS QDs. Here we include details that are learned through experience, beyond those in typical methodology sections, and include example pictures and videos to aid in fabricating QD solar cells. Although successful solarmore » cell fabrication is ultimately learned through experience, this protocol is intended to accelerate that process. The protocol developed here is intended to be a general starting point for developing PbS and PbSe QD test bed solar cells. We include steps for forming conductive QD films via dip coating as well as spin coating. Finally, we provide protocols that detail the synthesis of PbS and PbSe QDs through a unique cation exchange reaction and discuss how different QD synthetic routes could impact the resulting solar cell performance.« less

Quantum Dot Solar Cell Fabrication Protocols

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chernomordik, Boris D.; Marshall, Ashley R.; Pach, Gregory F.

Colloidally synthesized quantum-confined semiconducting spherical nanocrystals, often referred to as quantum dots (QDs), offer a high degree of chemical, optical, and electronic tunability. As a result, there is an increasing interest in employing colloidal QDs for electronic and optical applications that is reflected in a growing number of publications. In this protocol we provide detailed procedures for the fabrication of QD solar cells specifically employing PbSe and PbS QDs. Here we include details that are learned through experience, beyond those in typical methodology sections, and include example pictures and videos to aid in fabricating QD solar cells. Although successful solarmore » cell fabrication is ultimately learned through experience, this protocol is intended to accelerate that process. The protocol developed here is intended to be a general starting point for developing PbS and PbSe QD test bed solar cells. We include steps for forming conductive QD films via dip coating as well as spin coating. Finally, we provide protocols that detail the synthesis of PbS and PbSe QDs through a unique cation exchange reaction and discuss how different QD synthetic routes could impact the resulting solar cell performance.« less

Biased Target Ion Beam Deposition and Nanoskiving for Fabricating NiTi Alloy Nanowires

NASA Astrophysics Data System (ADS)

Hou, Huilong; Horn, Mark W.; Hamilton, Reginald F.

2016-12-01

Nanoskiving is a novel nanofabrication technique to produce shape memory alloy nanowires. Our previous work was the first to successfully fabricate NiTi alloy nanowires using the top-down approach, which leverages thin film technology and ultramicrotomy for ultra-thin sectioning. For this work, we utilized biased target ion beam deposition technology to fabricate nanoscale (i.e., sub-micrometer) NiTi alloy thin films. In contrast to our previous work, rapid thermal annealing was employed for heat treatment, and the B2 austenite to R-phase martensitic transformation was confirmed using stress-temperature and diffraction measurements. The ultramicrotome was programmable and facilitated sectioning the films to produce nanowires with thickness-to-width ratios ranging from 4:1 to 16:1. Energy dispersive X-ray spectroscopy analysis confirmed the elemental Ni and Ti make-up of the wires. The findings exposed the nanowires exhibited a natural ribbon-like curvature, which depended on the thickness-to-width ratio. The results demonstrate nanoskiving is a potential nanofabrication technique for producing NiTi alloy nanowires that are continuous with an unprecedented length on the order of hundreds of micrometers.

A review on fabricating tissue scaffolds using vat photopolymerization.

PubMed

Chartrain, Nicholas A; Williams, Christopher B; Whittington, Abby R

2018-05-09

Vat Photopolymerization (stereolithography, SLA), an Additive Manufacturing (AM) or 3D printing technology, holds particular promise for the fabrication of tissue scaffolds for use in regenerative medicine. Unlike traditional tissue scaffold fabrication techniques, SLA is capable of fabricating designed scaffolds through the selective photopolymerization of a photopolymer resin on the micron scale. SLA offers unprecedented control over scaffold porosity and permeability, as well as pore size, shape, and interconnectivity. Perhaps even more significantly, SLA can be used to fabricate vascular networks that may encourage angio and vasculogenesis. Fulfilling this potential requires the development of new photopolymers, the incorporation of biochemical factors into printed scaffolds, and an understanding of the effects scaffold geometry have on cell viability, proliferation, and differentiation. This review compares SLA to other scaffold fabrication techniques, highlights significant advances in the field, and offers a perspective on the field's challenges and future directions. Engineering de novo tissues continues to be challenging due, in part, to our inability to fabricate complex tissue scaffolds that can support cell proliferation and encourage the formation of developed tissue. The goal of this review is to first introduce the reader to traditional and Additive Manufacturing scaffold fabrication techniques. The bulk of this review will then focus on apprising the reader of current research and provide a perspective on the promising use of vat photopolymerization (stereolithography, SLA) for the fabrication of complex tissue scaffolds. Copyright © 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Monoamine oxidase B layer-by-layer film fabrication and characterization toward dopamine detection.

PubMed

Miyazaki, Celina Massumi; Pereira, Tamyris Paschoal; Mascagni, Daniela Branco Tavares; de Moraes, Marli Leite; Ferreira, Marystela

2016-01-01

In this work nanostructured film composites of the monoamine oxidase B (MAO-B) enzyme, free or encapsulated in liposomes, were fabricated by the layer-by-layer (LbL) self-assembly technique, employing polyethylene imine (PEI) as polycation. Initially, the MAO-B enzyme was incorporated into liposomes in order to preserve its enzymatic structure ensuring their activity and catalytic stability. The LbL film growth was monitored by surface plasmon resonance (SPR) by gold resonance angle shift analysis after each bilayer deposition. Subsequently, the films were applied as amperometric biosensors for dopamine detection using Prussian Blue (PB) as the electron mediator. The biosensor fabricated by MAO-B incorporated into liposomes composed of DPPG:POPG in the ratio (1:4) (w/w) showed the best performance with a sensitivity of 0.86 (μA cm(-2))/(mmol L(-1)) and a detection limit of 0.33 mmol L(-1).

Preparation of well-defined erythromycin imprinted non-woven fabrics via radiation-induced RAFT-mediated grafting

NASA Astrophysics Data System (ADS)

Söylemez, Meshude Akbulut; Barsbay, Murat; Güven, Olgun

2018-01-01

Radiation-induced RAFT polymerization technique was applied to synthesize well-defined molecularly imprinted polymers (MIPs) of erythromycin (ERY). Methacrylic acid (MAA) was grafted onto porous polyethylene (PE)/polypropylene (PP) nonwoven fabrics, under γ-irradiation by employing 2-pheny-2-propyl benzodithioate as the RAFT agent and ethylene glycol dimethacrylate (EGDMA) as the crosslinker. MAA/erythromycin ratios of 2/1, 4/1, 6/1 were tested to optimize the synthesis of MIPs. The highest binding capacity was encountered at a MAA/ERY ratio of 4/1. Non-imprinted polymers (NIPs) were also synthesized in the absence of ERY. The MIPs synthesized by RAFT method presented a better binding capacity compared to those prepared by conventional method where no RAFT agent was employed.

Fabrication and Characterization of High Temperature Resin/Carbon Nanofiber Composites

NASA Technical Reports Server (NTRS)

Ghose, Sayata; Watson, Kent A.; Working, Dennis C.; Criss, Jim M.; Siochi, Emilie J.; Conell, John W.

2005-01-01

As part of ongoing efforts to develop multifunctional advanced composites, blends of PETI-330 and carbon nanofibers (CNF) were prepared and characterized. Dry mixing techniques were employed and the effect of CNF loading level on melt viscosity was determined. The resulting powders were characterized for degree of mixing, thermal and rheological properties. Based on the characterization results, samples containing 30 and 40 wt% CNF were scaled up to approx.300 g and used to fabricate moldings 10.2 cm x 15.2 cm x 0.32 cm thick. The moldings were fabricated by injecting the mixtures at 260-280 C into a stainless steel tool followed by curing for 1 h at 371 C. The tool was designed to impart high shear during the injection process in an attempt to achieve some alignment of CNFs in the flow direction. Moldings were obtained that were subsequently characterized for thermal, mechanical and electrical properties. The degree of dispersion and alignment of CNFs were investigated using high-resolution scanning electron microscopy. The preparation and preliminary characterization of PETI-330/CNF composites will be discussed.

Buried structure for increasing fabrication performance of micromaterial by electromigration

NASA Astrophysics Data System (ADS)

Kimura, Yasuhiro; Saka, Masumi

2016-06-01

The electromigration (EM) technique is a physical synthetic growth method for micro/nanomaterials. EM causes atomic diffusion in a metal line by high-density electron flows. The intentional control of accumulation and relaxation of atoms by EM can lead to the fabrication of a micro/nanomaterial. TiN passivation has been utilized as a component of sample in the EM technique. Although TiN passivation can simplify the cumbersome processes for preparing the sample, the leakage of current naturally occurs because of the conductivity of TiN as a side effect and decreases the performance of micro/nanomaterial fabrication. In the present work, we propose a buried structure, which contributes to significantly decreasing the current for fabricating an Al micromaterial by confining the current flow in the EM technique. The fabrication performance was evaluated based on the threshold current for fabricating an Al micromaterial using the buried structure and the previous structure with the leakage of current.

Film Fabrication Technologies at NREL

NASA Technical Reports Server (NTRS)

Mcconnell, Robert D.

1993-01-01

The National Renewable Energy Laboratory (NREL) has extensive capabilities for fabricating a variety of high-technology films. Much of the in-house work in NREL's large photovoltaics (PV) program involves the fabrication of multiple thin-film semiconducting layers constituting a thin-film PV device. NREL's smaller program in superconductivity focuses on the fabrication of superconducting films on long, flexible tape substrates. This paper focuses on four of NREL's in-house research groups and their film fabrication techniques, developed for a variety of elements, alloys, and compounds to be deposited on a variety of substrates. As is the case for many national laboratories, NREL's technology transfer efforts are focusing on Cooperative Research and Development Agreements (CRADA's) between NREL researchers and private industry researchers.

Nanocrystal thin film fabrication methods and apparatus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kagan, Cherie R.; Kim, David K.; Choi, Ji-Hyuk

Nanocrystal thin film devices and methods for fabricating nanocrystal thin film devices are disclosed. The nanocrystal thin films are diffused with a dopant such as Indium, Potassium, Tin, etc. to reduce surface states. The thin film devices may be exposed to air during a portion of the fabrication. This enables fabrication of nanocrystal-based devices using a wider range of techniques such as photolithography and photolithographic patterning in an air environment.

Assessing the Effectiveness of Statistical Classification Techniques in Predicting Future Employment of Participants in the Temporary Assistance for Needy Families Program

ERIC Educational Resources Information Center

Montoya, Isaac D.

2008-01-01

Three classification techniques (Chi-square Automatic Interaction Detection [CHAID], Classification and Regression Tree [CART], and discriminant analysis) were tested to determine their accuracy in predicting Temporary Assistance for Needy Families program recipients' future employment. Technique evaluation was based on proportion of correctly…

The effect of core material, veneering porcelain, and fabrication technique on the biaxial flexural strength and weibull analysis of selected dental ceramics.

PubMed

Lin, Wei-Shao; Ercoli, Carlo; Feng, Changyong; Morton, Dean

2012-07-01

The objective of this study was to compare the effect of veneering porcelain (monolithic or bilayer specimens) and core fabrication technique (heat-pressed or CAD/CAM) on the biaxial flexural strength and Weibull modulus of leucite-reinforced and lithium-disilicate glass ceramics. In addition, the effect of veneering technique (heat-pressed or powder/liquid layering) for zirconia ceramics on the biaxial flexural strength and Weibull modulus was studied. Five ceramic core materials (IPS Empress Esthetic, IPS Empress CAD, IPS e.max Press, IPS e.max CAD, IPS e.max ZirCAD) and three corresponding veneering porcelains (IPS Empress Esthetic Veneer, IPS e.max Ceram, IPS e.max ZirPress) were selected for this study. Each core material group contained three subgroups based on the core material thickness and the presence of corresponding veneering porcelain as follows: 1.5 mm core material only (subgroup 1.5C), 0.8 mm core material only (subgroup 0.8C), and 1.5 mm core/veneer group: 0.8 mm core with 0.7 mm corresponding veneering porcelain with a powder/liquid layering technique (subgroup 0.8C-0.7VL). The ZirCAD group had one additional 1.5 mm core/veneer subgroup with 0.7 mm heat-pressed veneering porcelain (subgroup 0.8C-0.7VP). The biaxial flexural strengths were compared for each subgroup (n = 10) according to ISO standard 6872:2008 with ANOVA and Tukey's post hoc multiple comparison test (p≤ 0.05). The reliability of strength was analyzed with the Weibull distribution. For all core materials, the 1.5 mm core/veneer subgroups (0.8C-0.7VL, 0.8C-0.7VP) had significantly lower mean biaxial flexural strengths (p < 0.0001) than the other two subgroups (subgroups 1.5C and 0.8C). For the ZirCAD group, the 0.8C-0.7VL subgroup had significantly lower flexural strength (p= 0.004) than subgroup 0.8C-0.7VP. Nonetheless, both veneered ZirCAD groups showed greater flexural strength than the monolithic Empress and e.max groups, regardless of core thickness and fabrication techniques

Evaluation of the marginal fit of metal copings fabricated on three different marginal designs using conventional and accelerated casting techniques: an in vitro study.

PubMed

Vaidya, Sharad; Parkash, Hari; Bhargava, Akshay; Gupta, Sharad

2014-01-01

Abundant resources and techniques have been used for complete coverage crown fabrication. Conventional investing and casting procedures for phosphate-bonded investments require a 2- to 4-h procedure before completion. Accelerated casting techniques have been used, but may not result in castings with matching marginal accuracy. The study measured the marginal gap and determined the clinical acceptability of single cast copings invested in a phosphate-bonded investment with the use of conventional and accelerated methods. One hundred and twenty cast coping samples were fabricated using conventional and accelerated methods, with three finish lines: Chamfer, shoulder and shoulder with bevel. Sixty copings were prepared with each technique. Each coping was examined with a stereomicroscope at four predetermined sites and measurements of marginal gaps were documented for each. A master chart was prepared for all the data and was analyzed using Statistical Package for the Social Sciences version. Evidence of marginal gap was then evaluated by t-test. Analysis of variance and Post-hoc analysis were used to compare two groups as well as to make comparisons between three subgroups . Measurements recorded showed no statistically significant difference between conventional and accelerated groups. Among the three marginal designs studied, shoulder with bevel showed the best marginal fit with conventional as well as accelerated casting techniques. Accelerated casting technique could be a vital alternative to the time-consuming conventional casting technique. The marginal fit between the two casting techniques showed no statistical difference.

Electrowetting Lens Employing Hemispherical Cavity Formed by Hydrofluoric Acid, Nitric Acid, and Acetic Acid Etching of Silicon

NASA Astrophysics Data System (ADS)

Lee, June Kyoo; Choi, Ju Chan; Jang, Won Ick; Kim, Hak-Rin; Kong, Seong Ho

2012-06-01

We demonstrate the design of an electrowetting lens employing a high-aspect-ratio hemispherical lens cavity and its micro-electro-mechanical-system (MEMS) fabrication process in this study. Our preliminary simulation results showed that the physical and electrical durability of the lens can be improved by the mitigation of stresses on the insulator at the hemispherical cavity. High-aspect-ratio hemispherical cavities with various diameters and very smooth sidewall surfaces were uniformly fabricated on a silicon wafer by a sophisticated isotropic wet etching technique. Moreover, we experimentally investigated the optical properties of the MEMS-based electrowetting lens with the proposed cavity. Two immiscible liquids in the proposed lens cavity were electrostatically controlled with negligible optical distortion and low focal-length hysteresis due to the fully axis-symmetrical geometry and smooth sidewall of the cavity.

Epoxy bond and stop etch fabrication method

DOEpatents

Simmons, Jerry A.; Weckwerth, Mark V.; Baca, Wes E.

2000-01-01

A class of epoxy bond and stop etch (EBASE) microelectronic fabrication techniques is disclosed. The essence of such techniques is to grow circuit components on top of a stop etch layer grown on a first substrate. The first substrate and a host substrate are then bonded together so that the circuit components are attached to the host substrate by the bonding agent. The first substrate is then removed, e.g., by a chemical or physical etching process to which the stop etch layer is resistant. EBASE fabrication methods allow access to regions of a device structure which are usually blocked by the presence of a substrate, and are of particular utility in the fabrication of ultrafast electronic and optoelectronic devices and circuits.

Flow characterization of electroconvective micromixer with a nanoporous polymer membrane in-situ fabricated using a laser polymerization technique

PubMed Central

Hwang, Sangbeom; Song, Simon

2015-01-01

Electroconvection is known to cause strong convective mixing in a microchannel near a nanoporous membrane or a nanochannel in contact with an electrolyte solution due to the external electric field. This study addresses micromixer behavior subject to electroconvection occurring near a nanoporous membrane in-situ fabricated by a laser polymerization technique on a microfluidic chip. We found that the micromixer behavior can be categorized into three regimes. Briefly, the weak electroconvection regime is characterized by weak mixing performance at a low applied voltage and KCl concentration, whereas the strong electroconvection regime has a high mixing performance when the applied voltage and KCl concentration are moderately high. Finally, the incomplete electroconvection regime has an incomplete electric double-layer overlap in the nanopores of the membrane when the electrolyte concentration is very high. The mixing index reached 0.92 in the strong electroconvection regime. The detailed fabrication methods for the micromixer and characterization results are discussed in this paper. PMID:26064195

Flow characterization of electroconvective micromixer with a nanoporous polymer membrane in-situ fabricated using a laser polymerization technique.

PubMed

Hwang, Sangbeom; Song, Simon

2015-05-01

Electroconvection is known to cause strong convective mixing in a microchannel near a nanoporous membrane or a nanochannel in contact with an electrolyte solution due to the external electric field. This study addresses micromixer behavior subject to electroconvection occurring near a nanoporous membrane in-situ fabricated by a laser polymerization technique on a microfluidic chip. We found that the micromixer behavior can be categorized into three regimes. Briefly, the weak electroconvection regime is characterized by weak mixing performance at a low applied voltage and KCl concentration, whereas the strong electroconvection regime has a high mixing performance when the applied voltage and KCl concentration are moderately high. Finally, the incomplete electroconvection regime has an incomplete electric double-layer overlap in the nanopores of the membrane when the electrolyte concentration is very high. The mixing index reached 0.92 in the strong electroconvection regime. The detailed fabrication methods for the micromixer and characterization results are discussed in this paper.

Fabrication of three-dimensional polymer quadratic nonlinear grating structures by layer-by-layer direct laser writing technique

NASA Astrophysics Data System (ADS)

Bich Do, Danh; Lin, Jian Hung; Diep Lai, Ngoc; Kan, Hung-Chih; Hsu, Chia Chen

2011-08-01

We demonstrate the fabrication of a three-dimensional (3D) polymer quadratic nonlinear (χ(2)) grating structure. By performing layer-by-layer direct laser writing (DLW) and spin-coating approaches, desired photobleached grating patterns were embedded in the guest--host dispersed-red-1/poly(methylmethacrylate) (DR1/PMMA) active layers of an active-passive alternative multilayer structure through photobleaching of DR1 molecules. Polyvinyl-alcohol and SU8 thin films were deposited between DR1/PMMA layers serving as a passive layer to separate DR1/PMMA active layers. After applying the corona electric field poling to the multilayer structure, nonbleached DR1 molecules in the active layers formed polar distribution, and a 3D χ(2) grating structure was obtained. The χ(2) grating structures at different DR1/PMMA nonlinear layers were mapped by laser scanning second harmonic (SH) microscopy, and no cross talk was observed between SH images obtained from neighboring nonlinear layers. The layer-by-layer DLW technique is favorable to fabricating hierarchical 3D polymer nonlinear structures for optoelectronic applications with flexible structural design.

Fabrication of three-dimensional polymer quadratic nonlinear grating structures by layer-by-layer direct laser writing technique.

PubMed

Do, Danh Bich; Lin, Jian Hung; Lai, Ngoc Diep; Kan, Hung-Chih; Hsu, Chia Chen

2011-08-10

We demonstrate the fabrication of a three-dimensional (3D) polymer quadratic nonlinear (χ(2)) grating structure. By performing layer-by-layer direct laser writing (DLW) and spin-coating approaches, desired photobleached grating patterns were embedded in the guest-host dispersed-red-1/poly(methylmethacrylate) (DR1/PMMA) active layers of an active-passive alternative multilayer structure through photobleaching of DR1 molecules. Polyvinyl-alcohol and SU8 thin films were deposited between DR1/PMMA layers serving as a passive layer to separate DR1/PMMA active layers. After applying the corona electric field poling to the multilayer structure, nonbleached DR1 molecules in the active layers formed polar distribution, and a 3D χ(2) grating structure was obtained. The χ(2) grating structures at different DR1/PMMA nonlinear layers were mapped by laser scanning second harmonic (SH) microscopy, and no cross talk was observed between SH images obtained from neighboring nonlinear layers. The layer-by-layer DLW technique is favorable to fabricating hierarchical 3D polymer nonlinear structures for optoelectronic applications with flexible structural design.

Fabrication and evaluation of evanescent wave absorption based polyaniline-cladding modified fiber optic urea biosensor

NASA Astrophysics Data System (ADS)

Botewad, S. N.; Pahurkar, V. G.; Muley, G. G.

2018-01-01

The fabrication and study of cladding modified intrinsic fiber optic urea biosensor has been reported in the present investigation. A simple cladding modification technique was used to construct the sensor by uncladding the small portion from optical fiber. Further bare core was decorated by supportive porous, chemically and optically sensitive matrix material polyaniline (PANI) as an active cladding for enzyme residency. Enzyme-urease (Urs) was cross-linked on the active cladding region via glutaraldehyde solution. Confirmation of the prepared PANI in proper form determined by ultraviolet-visible and Fourier transform infrared spectroscopic techniques. X-ray diffraction technique was employed for nature and compatibility examination of PANI. Sensor parameters such as sensitivity, selectivity, stability and lower detection limit have been analyzed by absorption variation study in evanescent wave field. The response of prepared sensor was studied towards urea in the wide concentration range 100 nM-100 mM and confirmed its lowest detection limit as 100 nM. The stability of sensor was found 28 days with little variation in response. The fabricated sensor has not shown any response towards interference species like glucose, ascorbic acid, L-alanine, L-arginine and their combination with urea solution and hence found selective for urea solution only.

Mass production compatible fabrication techniques of single-crystalline silver metamaterials and plasmonics devices

NASA Astrophysics Data System (ADS)

Rodionov, Ilya A.; Baburin, Alexander S.; Zverev, Alexander V.; Philippov, Ivan A.; Gabidulin, Aidar R.; Dobronosova, Alina A.; Ryzhova, Elena V.; Vinogradov, Alexey P.; Ivanov, Anton I.; Maklakov, Sergey S.; Baryshev, Alexander V.; Trofimov, Igor V.; Merzlikin, Alexander M.; Orlikovsky, Nikolay A.; Rizhikov, Ilya A.

2017-08-01

During last 20 years, great results in metamaterials and plasmonic nanostructures fabrication were obtained. However, large ohmic losses in metals and mass production compatibility still represent the most serious challenge that obstruct progress in the fields of metamaterials and plasmonics. Many recent research are primarily focused on developing low-loss alternative materials, such as nitrides, II-VI semiconductor oxides, high-doped semiconductors, or two-dimensional materials. In this work, we demonstrate that our perfectly fabricated silver films can be an effective low-loss material system, as theoretically well-known. We present a fabrication technology of plasmonic and metamaterial nanodevices on transparent (quartz, mica) and non-transparent (silicon) substrates by means of e-beam lithography and ICP dry etch instead of a commonly-used focused ion beam (FIB) technology. We eliminate negative influence of litho-etch steps on silver films quality and fabricate square millimeter area devices with different topologies and perfect sub-100 nm dimensions reproducibility. Our silver non-damage fabrication scheme is tested on trial manufacture of spasers, plasmonic sensors and waveguides, metasurfaces, etc. These results can be used as a flexible device manufacture platform for a broad range of practical applications in optoelectronics, communications, photovoltaics and biotechnology.

A new fabrication method for precision antenna reflectors for space flight and ground test

NASA Technical Reports Server (NTRS)

Sharp, G. Richard; Wanhainen, Joyce S.; Ketelsen, Dean A.

1991-01-01

Communications satellites are using increasingly higher frequencies that require increasingly precise antenna reflectors for use in space. Traditional industry fabrication methods for space antenna reflectors employ successive modeling techniques using high- and low-temperature molds for reflector face sheets and then a final fit-up of the completed honeycomb sandwich panel antenna reflector to a master pattern. However, as new missions are planned at much higher frequencies, greater accuracies will be necessary than are achievable using these present methods. A new approach for the fabrication of ground-test solid-surface antenna reflectors is to build a rigid support structure with an easy-to-machine surface. This surface is subsequently machined to the desired reflector contour and coated with a radio-frequency-reflective surface. This method was used to fabricate a 2.7-m-diameter ground-test antenna reflector to an accuracy of better than 0.013 mm (0.0005 in.) rms. A similar reflector for use on spacecraft would be constructed in a similar manner but with space-qualified materials. The design, analysis, and fabrication of the 2.7-m-diameter precision antenna reflector for antenna ground tests and the extension of this technology to precision, space-based antenna reflectors are described.

Research on subsurface defects of potassium dihydrogen phosphate crystals fabricated by single point diamond turning technique

NASA Astrophysics Data System (ADS)

Tie, Guipeng; Dai, Yifan; Guan, Chaoliang; Chen, Shaoshan; Song, Bing

2013-03-01

Potassium dihydrogen phosphate (KDP) crystals, which are widely used in high-power laser systems, are required to be free of defects on fabricated subsurfaces. The depth of subsurface defects (SSD) of KDP crystals is significantly influenced by the parameters used in the single point diamond turning technique. In this paper, based on the deliquescent magnetorheological finishing technique, the SSD of KDP crystals is observed and the depths under various cutting parameters are detected and discussed. The results indicate that no SSD is generated under small parameters and with the increase of cutting parameters, SSD appears and the depth rises almost linearly. Although the ascending trends of SSD depths caused by cutting depth and feed rate are much alike, the two parameters make different contributions. Taking the same material removal efficiency as a criterion, a large cutting depth generates shallower SSD depth than a large feed rate. Based on the experiment results, an optimized cutting procedure is obtained to generate defect-free surfaces.

A Review of Statistical Disclosure Control Techniques Employed by Web-Based Data Query Systems.

PubMed

Matthews, Gregory J; Harel, Ofer; Aseltine, Robert H

We systematically reviewed the statistical disclosure control techniques employed for releasing aggregate data in Web-based data query systems listed in the National Association for Public Health Statistics and Information Systems (NAPHSIS). Each Web-based data query system was examined to see whether (1) it employed any type of cell suppression, (2) it used secondary cell suppression, and (3) suppressed cell counts could be calculated. No more than 30 minutes was spent on each system. Of the 35 systems reviewed, no suppression was observed in more than half (n = 18); observed counts below the threshold were observed in 2 sites; and suppressed values were recoverable in 9 sites. Six sites effectively suppressed small counts. This inquiry has revealed substantial weaknesses in the protective measures used in data query systems containing sensitive public health data. Many systems utilized no disclosure control whatsoever, and the vast majority of those that did deployed it inconsistently or inadequately.

PREFACE: Atomically controlled fabrication technology: new physics and functional device realization Atomically controlled fabrication technology: new physics and functional device realization

NASA Astrophysics Data System (ADS)

Kuwahara, Yuji; Kasai, Hideaki

2011-10-01

To realize next generation functional devices, atomic level controllability of the application and fabrication techniques is necessary. The conventional route to advance solid state devices, which involves improvement of 'instrumental accuracy', is now facing a major paradigm shift towards 'phenomenal accuracy'. Therefore, to keep up with this critical turn in the development of devices, pioneering research (both theoretical and experimental) on relevant materials, focusing on new physics at the atomic scale, is inevitable. This special section contains articles on the advancements in fabrication of functional devices with an emphasis on the exploration, clarification and understanding of atomistic phenomena. Research articles reporting theoretical and experimental findings on various materials such as semiconductors, metals, magnetic and organic systems, collectively present and 'capture' the appropriate processes and mechanisms of this rapidly developing field. The theoretical investigations employ first-principles quantum-mechanical simulations to clarify and bring about design principles and guidelines, or to develop more reliable computational methods. Experimental studies, on the other hand, introduce novel capabilities to build, view and manipulate materials at the atomic scale by employing pioneering techniques. Thus, the section pays significant attention to novel structures and properties and the accompanying fabrication techniques and design arising from the understanding of properties and structures at the atomic scale. We hope that researchers in the area of physics, materials science and engineering, interested in the development of functional devices via atomic level control, will find valuable information in this collaborative work. We are grateful to all of the authors for their contributions. Atomically controlled fabrication contents On the mechanism of carbon nanotube formation: the role of the catalyst G N Ayre, T Uchino, B Mazumder, A L Hector

Fabrication and characterization of active nanostructures

NASA Astrophysics Data System (ADS)

Opondo, Noah F.

Three different nanostructure active devices have been designed, fabricated and characterized. Junctionless transistors based on highly-doped silicon nanowires fabricated using a bottom-up fabrication approach are first discussed. The fabrication avoids the ion implantation step since silicon nanowires are doped in-situ during growth. Germanium junctionless transistors fabricated with a top down approach starting from a germanium on insulator substrate and using a gate stack of high-k dielectrics and GeO2 are also presented. The levels and origin of low-frequency noise in junctionless transistor devices fabricated from silicon nanowires and also from GeOI devices are reported. Low-frequency noise is an indicator of the quality of the material, hence its characterization can reveal the quality and perhaps reliability of fabricated transistors. A novel method based on low-frequency noise measurement to envisage trap density in the semiconductor bandgap near the semiconductor/oxide interface of nanoscale silicon junctionless transistors (JLTs) is presented. Low-frequency noise characterization of JLTs biased in saturation is conducted at different gate biases. The noise spectrum indicates either a Lorentzian or 1/f. A simple analysis of the low-frequency noise data leads to the density of traps and their energy within the semiconductor bandgap. The level of noise in silicon JLT devices is lower than reported values on transistors fabricated using a top-down approach. This noise level can be significantly improved by improving the quality of dielectric and the channel interface. A micro-vacuum electron device based on silicon field emitters for cold cathode emission is also presented. The presented work utilizes vertical Si nanowires fabricated by means of self-assembly, standard lithography and etching techniques as field emitters in this dissertation. To obtain a high nanowire density, hence a high current density, a simple and inexpensive Langmuir Blodgett technique

Design and fabrication of a 1-DOF drive mode and 2-DOF sense mode micro-gyroscope using SU-8 based UV-LIGA process

NASA Astrophysics Data System (ADS)

Verma, Payal; Juneja, Sucheta; Savelyev, Dmitry A.; Khonina, Svetlana N.; Gopal, Ram

2016-04-01

This paper presents design and fabrication of a 1-DOF (degree-of-freedom) drive mode and 2-DOF sense mode micro-gyroscope. It is an inherently robust structure and offers a high sense frequency bandwidth. The proposed design utilizes resonance of the1-DOF drive mode oscillator and employs dynamic amplification concept in sense modes to increase the sensitivity while maintaining robustness. The 2-DOF in the sense direction renders the device immune to process imperfections and environmental effects. The design is simulated using FEA software (CoventorWare®). The device is designed considering process compatibility with SU-8 based UV-LIGA process, which is an economical fabrication technique. The complete fabrication process is presented along with SEM images of the fabricated device. The device has 9 µm thick Nickel as the key structural layer with an overall reduced key structure size of 2.2 mm by 2.1 mm.

Productive Nanosystems: The Physics of Molecular Fabrication

ERIC Educational Resources Information Center

Drexler, K. Eric

2005-01-01

Fabrication techniques are the foundation of physical technology, and are thus of fundamental interest. Physical principles indicate that nanoscale systems will be able to fabricate a wide range of structures, operating with high productivity and precise molecular control. Advanced systems of this kind will require intermediate generations of…

Fabrication de structures tridimensionnelles de nanocomposites polymeres charges de nanotubes de carbone a simple paroi

NASA Astrophysics Data System (ADS)

Laberge Lebel, Louis

There is currently a worldwide effort for advances in micro and nanotechnologies due to their high potential for technological applications in fields such as microelectromechanical systems (MEMS), organic electronics and structural microstructures for aerospace. In these applications, carbon nanotube/polymer nanocomposites represent interesting material options compared to conventional resins for their enhanced mechanical and electrical properties. However, several significant scientific and technological challenges must first be overcome in order to rapidly and cost-effectively fabricate nanocomposite-based microdevices. Fabrication techniques have emerged for fabricating one- of two-dimensional (1D/2D) nanocomposite structures but few techniques are available for three-dimensional (3D) nanocomposite structures. The overall objective of this thesis is the development of a manufacturing technique allowing the fabrication of 3D structures of single-walled carbon nanotube (C-SWNT)/polymer nanocomposite. This thesis reports the development of a direct-write fabrication technique that greatly extends the fabrication space for 3D carbon nanotube/polymer nanocomposite structures. The UV-assisted direct-write (UV-DW) technique employs the robotically-controlled micro-extrusion of a nanocomposite filament combined with a UV exposure that follows the extrusion point. Upon curing, the increased rigidity of the extruded filament enables the creation of multi-directional shapes along the trajectory of the extrusion point. The C-SWNT material is produced by laser ablation of a graphite target and purified using a nitric acid reflux. The as-grown and purified material is characterized under transmission electron microscopy and Raman spectroscopy. The purification procedure successfully graphed carboxylic groups on the surface of the C-SWNTs, shown by X-ray photoelectron spectroscopies. An incorporation procedure in the polymer is developed involving a non

Fabrication of Pop-up Detector Arrays on Si Wafers

NASA Technical Reports Server (NTRS)

Li, Mary J.; Allen, Christine A.; Gordon, Scott A.; Kuhn, Jonathan L.; Mott, David B.; Stahle, Caroline K.; Wang, Liqin L.

1999-01-01

High sensitivity is a basic requirement for a new generation of thermal detectors. To meet the requirement, close-packed, two-dimensional silicon detector arrays have been developed in NASA Goddard Space Flight Center. The goal of the task is to fabricate detector arrays configured with thermal detectors such as infrared bolometers and x-ray calorimeters to use in space fliGht missions. This paper focuses on the fabrication and the mechanical testing of detector arrays in a 0.2 mm pixel size, the smallest pop-up detectors being developed so far. These array structures, nicknamed "PUDS" for "Pop-Up Detectors", are fabricated on I pm thick, single-crystal, silicon membranes. Their designs have been refined so we can utilize the flexibility of thin silicon films by actually folding the silicon membranes to 90 degrees in order to obtain close-packed two-dimensional arrays. The PUD elements consist of a detector platform and two legs for mechanical support while also serving as electrical and thermal paths. Torsion bars and cantilevers connecting the detector platform to the legs provide additional flexures for strain relief. Using micro-electromechanical structure (MEMS) fabrication techniques, including photolithography, anisotropic chemical etching, reactive-ion etching, and laser dicing, we have fabricated PLTD detector arrays of fourteen designs with a variation of four parameters including cantilever length, torsion bar length and width, and leg length. Folding tests were conducted to test mechanical stress distribution for the array structures. We obtained folding yields and selected optimum design parameters to reach minimal stress levels. Computer simulation was also employed to verify mechanical behaviors of PUDs in the folding process. In addition, scanning electron microscopy was utilized to examine the flatness of detectors and the alignment of detector pixels in arrays. The fabrication of thermistors and heaters on the pop-up detectors is under way

Marginal discrepancy dimensions of single unit metal crowns fabricated by using CAD-CAM-milled acrylate resin polymer blocks or a conventional waxing technique.

PubMed

Lalande, David; Hodd, Jeffrey A; Brousseau, John S; Ramos, Van; Dunham, Daniel; Rueggeberg, Frederick

2017-10-14

Because crowns with open margins are a well-known problem and can lead to complications, it is important to assess the accuracy of margins resulting from the use of a new technique. Currently, data regarding the marginal fit of computer-aided design and computer-aided manufacturing (CAD-CAM) technology to fabricate a complete gold crown (CGC) from a castable acrylate resin polymer block are lacking. The purpose of this in vitro study was to compare marginal discrepancy widths of CGCs fabricated by using either conventional hand waxing or acrylate resin polymer blocks generated by using CAD-CAM technology. A plastic model of a first mandibular molar was prepared by using a 1-mm, rounded chamfer margin on the entire circumference of the tooth. The master die was duplicated 30 times, and 15 wax patterns were fabricated by using a manual waxing technique, and 15 were fabricated by using CAD-CAM technology. All patterns were invested and cast, and resulting CGCs were cemented on their respective die by using resin-modified glass ionomer cement. The specimens were then embedded in acrylic resin and sectioned buccolingually. The buccal and lingual marginal discrepancies of each sectioned portion were measured by using microscopy at ×50 magnification. Data were subjected to repeated measures 2-way ANOVA, by using the Tukey post hoc pairwise comparison test (α=.05). The factor of "technique" had no significant influence on marginal discrepancy measurement (P=.431), but a significant effect of "margin location" (P=.019) was noted. The confounding combination of factors was found to be significantly lower marginal discrepancy dimensions of the lingual margin discrepancy than on the buccal side by using CAD-CAM technology. The marginal discrepancy of CAD-CAM acrylate resin crowns was not significantly different from those made with a conventional manual method; however, lingual margin discrepancies present from CAD-CAM-prepared crowns were significantly less than those

Two-step fabrication technique of gold tips for use in point-contact spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Narasiwodeyar, S.; Dwyer, M.; Liu, M.

For a successful point-contact spectroscopy (PCS) measurement, metallic tips of proper shape and smoothness are essential to ensure the ballistic nature of a point-contact junction. Until recently, the fabrication of Au tips suitable for use in point-contact spectroscopy has remained more of an art involving a trial and error method rather than an automated scientific process. To address these issues, we have developed a technique with which one can prepare high quality Au tips reproducibly and systematically. It involves an electronic control of the driving voltages used for an electrochemical etching of a gold wire in a HCl-glycerol mixture ormore » a HCl solution. We find that a stopping current, below which the circuit is set to shut off, is a single very important parameter to produce an Au tip of desired shape. We present detailed descriptions for a two-step etching process for Au tips and also test results from PCS measurements using them.« less

Meniscus-force-mediated layer transfer technique using single-crystalline silicon films with midair cavity: Application to fabrication of CMOS transistors on plastic substrates

NASA Astrophysics Data System (ADS)

Sakaike, Kohei; Akazawa, Muneki; Nakagawa, Akitoshi; Higashi, Seiichiro

2015-04-01

A novel low-temperature technique for transferring a silicon-on-insulator (SOI) layer with a midair cavity (supported by narrow SiO2 columns) by meniscus force has been proposed, and a single-crystalline Si (c-Si) film with a midair cavity formed in dog-bone shape was successfully transferred to a poly(ethylene terephthalate) (PET) substrate at its heatproof temperature or lower. By applying this proposed transfer technique, high-performance c-Si-based complementary metal-oxide-semiconductor (CMOS) transistors were successfully fabricated on the PET substrate. The key processes are the thermal oxidation and subsequent hydrogen annealing of the SOI layer on the midair cavity. These processes ensure a good MOS interface, and the SiO2 layer works as a “blocking” layer that blocks contamination from PET. The fabricated n- and p-channel c-Si thin-film transistors (TFTs) on the PET substrate showed field-effect mobilities of 568 and 103 cm2 V-1 s-1, respectively.

Nuclear Fabrication Consortium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Levesque, Stephen

2013-04-05

This report summarizes the activities undertaken by EWI while under contract from the Department of Energy (DOE) Office of Nuclear Energy (NE) for the management and operation of the Nuclear Fabrication Consortium (NFC). The NFC was established by EWI to independently develop, evaluate, and deploy fabrication approaches and data that support the re-establishment of the U.S. nuclear industry: ensuring that the supply chain will be competitive on a global stage, enabling more cost-effective and reliable nuclear power in a carbon constrained environment. The NFC provided a forum for member original equipment manufactures (OEM), fabricators, manufacturers, and materials suppliers to effectivelymore » engage with each other and rebuild the capacity of this supply chain by : Identifying and removing impediments to the implementation of new construction and fabrication techniques and approaches for nuclear equipment, including system components and nuclear plants. Providing and facilitating detailed scientific-based studies on new approaches and technologies that will have positive impacts on the cost of building of nuclear plants. Analyzing and disseminating information about future nuclear fabrication technologies and how they could impact the North American and the International Nuclear Marketplace. Facilitating dialog and initiate alignment among fabricators, owners, trade associations, and government agencies. Supporting industry in helping to create a larger qualified nuclear supplier network. Acting as an unbiased technology resource to evaluate, develop, and demonstrate new manufacturing technologies. Creating welder and inspector training programs to help enable the necessary workforce for the upcoming construction work. Serving as a focal point for technology, policy, and politically interested parties to share ideas and concepts associated with fabrication across the nuclear industry. The report the objectives and summaries of the Nuclear Fabrication

A Simplified Technique for Fabrication of Orbital Prosthesis

PubMed Central

Thakral, G.K.; Mohapatra, Abhilash; Seth, Jyotsna; Vashisht, Pallavi

2014-01-01

Eye is a vital organ not only for vision, but also an important component of facial expression, and over-all personality of a person. Loss of eye, apart from leading to impaired vision has a crippling effect on the psychology of the patient. Prosthodontic rehabilitation of such cases includes fabrication of prosthesis by acrylic resin, silicone and implants. However, not all patients are willing to use implants for maxillofacial rehabilitation. Therefore, a custom made orbital prosthesis serves as an affordable and satisfactory alternative. PMID:25121068

Silk as a biocohesive sacrificial binder in the fabrication of hydroxyapatite load bearing scaffolds.

PubMed

McNamara, Stephanie L; Rnjak-Kovacina, Jelena; Schmidt, Daniel F; Lo, Tim J; Kaplan, David L

2014-08-01

Limitations of current clinical methods for bone repair continue to fuel the demand for a high strength, bioactive bone replacement material. Recent attempts to produce porous scaffolds for bone regeneration have been limited by the intrinsic weakness associated with high porosity materials. In this study, ceramic scaffold fabrication techniques for potential use in load-bearing bone repairs have been developed using naturally derived silk from Bombyx mori. Silk was first employed for ceramic grain consolidation during green body formation, and later as a sacrificial polymer to impart porosity during sintering. These techniques allowed preparation of hydroxyapatite (HA) scaffolds that exhibited a wide range of mechanical and porosity profiles, with some displaying unusually high compressive strength up to 152.4 ± 9.1 MPa. Results showed that the scaffolds exhibited a wide range of compressive strengths and moduli (8.7 ± 2.7 MPa to 152.4 ± 9.1 MPa and 0.3 ± 0.1 GPa to 8.6 ± 0.3 GPa) with total porosities of up to 62.9 ± 2.7% depending on the parameters used for fabrication. Moreover, HA-silk scaffolds could be molded into large, complex shapes, and further machined post-sinter to generate specific three-dimensional geometries. Scaffolds supported bone marrow-derived mesenchymal stem cell attachment and proliferation, with no signs of cytotoxicity. Therefore, silk-fabricated HA scaffolds show promise for load bearing bone repair and regeneration needs. Copyright © 2014 Elsevier Ltd. All rights reserved.

Silk as a biocohesive sacrificial binder in the fabrication of hydroxyapatite load bearing scaffolds

PubMed Central

McNamara, Stephanie L.; Rnjak-Kovacina, Jelena; Schmidt, Daniel; Lo, Tim J.; Kaplan, David L.

2014-01-01

Limitations of current clinical methods for bone repair continue to fuel the demand for a high strength, bioactive bone replacement material. Recent attempts to produce porous scaffolds for bone regeneration have been limited by the intrinsic weakness associated with high porosity materials. In this study, ceramic scaffold fabrication techniques for potential use in load-bearing bone repairs have been developed using naturally derived silk from Bombyx mori. Silk was first employed for ceramic grain consolidation during green body formation, and later as a sacrificial polymer to impart porosity during sintering. These techniques allowed preparation of hydroxyapatite (HA) scaffolds that exhibited a wide range of mechanical and porosity profiles, with some displaying unusually high compressive strength up to 152.4 ± 9.1 MPa. Results showed that the scaffolds exhibited a wide range of compressive strengths and moduli (8.7 ± 2.7 MPa to 152.4 ± 9.1 MPa and 0.3 ± 0.1 GPa to 8.6 ± 0.3 GPa) with total porosities of up to 62.9 ± 2.7% depending on the parameters used for fabrication. Moreover, HA-silk scaffolds could be molded into large, complex shapes, and further machined post-sinter to generate specific three-dimensional geometries. Scaffolds supported bone marrow-derived mesenchymal stem cell attachment and proliferation, with no signs of cytotoxicity. Therefore, silk-fabricated HA scaffolds show promise for load bearing bone repair and regeneration needs. PMID:24881027

Gel Fabrication of Molybdenum “Beads”

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lowden, Richard Andrew; Armstrong, Beth L.; Cooley, Kevin M.

2016-11-01

Spherical molybdenum particles or “beads” of various diameters are of interest as feedstock materials for the additive manufacture of targets and assemblies used in the production of 99Mo medical isotopes using accelerator technology. Small metallic beads or ball bearings are typically fabricated from wire; however, small molybdenum spheres cannot readily be produced in this manner. Sol-gel processes are often employed to produce small dense microspheres of metal oxides across a broad diameter range that in the case of molybdenum could be reduced and sintered to produce metallic spheres. These Sol-gel type processes were examined for forming molybdenum oxide beads; however,more » the molybdenum trioxide was chemically incompatible with commonly used gelation materials. As an alternative, an aqueous alginate process being assessed for the fabrication of oxide spheres for catalyst applications was employed to form molybdenum trioxide beads that were successfully reduced and sintered to produce small molybdenum spheres.« less

Digital fabrication of textiles: an analysis of electrical networks in 3D knitted functional fabrics

NASA Astrophysics Data System (ADS)

Vallett, Richard; Knittel, Chelsea; Christe, Daniel; Castaneda, Nestor; Kara, Christina D.; Mazur, Krzysztof; Liu, Dani; Kontsos, Antonios; Kim, Youngmoo; Dion, Genevieve

2017-05-01

Digital fabrication methods are reshaping design and manufacturing processes through the adoption of pre-production visualization and analysis tools, which help minimize waste of materials and time. Despite the increasingly widespread use of digital fabrication techniques, comparatively few of these advances have benefited the design and fabrication of textiles. The development of functional fabrics such as knitted touch sensors, antennas, capacitors, and other electronic textiles could benefit from the same advances in electrical network modeling that revolutionized the design of integrated circuits. In this paper, the efficacy of using current state-of-the-art digital fabrication tools over the more common trialand- error methods currently used in textile design is demonstrated. Gaps are then identified in the current state-of-the-art tools that must be resolved to further develop and streamline the rapidly growing field of smart textiles and devices, bringing textile production into the realm of 21st century manufacturing.

Fabrication of Cantilever-Bump Type Si Probe Card

NASA Astrophysics Data System (ADS)

Park, Jeong-Yong; Lee, Dong-Seok; Kim, Dong-Kwon; Lee, Jong-Hyun

2000-12-01

Probe card is most important part in the test system which selects the good or bad chip of integrated circuit (IC) chips. Silicon vertical probe card is able to test multiple semiconductor chips simultaneously. We presented cantilever-bump type vertical probe card. It was fabricated by dry etching using RIE(reactive ion etching) technique and porous silicon micromachining using silicon direct bonded (SDB) wafer. Cantilevers and bumps were fabricated by isotropic etching using RIE@. 3-dimensional structures were formed by porous silicon micromachining technique using SDB wafer. Contact resistance of fabricated probe card was less than 2 Ω and its life time was more than 200,000 turns. The process used in this work is very simple and reproducible, which has good controllability in the tip dimension and spacing. It is expected that the fabricated probe card can reduce testing time, can promote productivity and enables burn-in test.

Employ Simulation Techniques. Second Edition. Module C-5 of Category C--Instructional Execution. Professional Teacher Education Module Series.

ERIC Educational Resources Information Center

Ohio State Univ., Columbus. National Center for Research in Vocational Education.

One of a series of performance-based teacher education learning packages focusing upon specific professional competencies of vocational teachers, this learning module deals with employing simulation techniques. It consists of an introduction and four learning experiences. Covered in the first learning experience are various types of simulation…

Three-Dimensional Printing of Multifunctional Nanocomposites: Manufacturing Techniques and Applications.

PubMed

Farahani, Rouhollah D; Dubé, Martine; Therriault, Daniel

2016-07-01

The integration of nanotechnology into three-dimensional printing (3DP) offers huge potential and opportunities for the manufacturing of 3D engineered materials exhibiting optimized properties and multifunctionality. The literature relating to different 3DP techniques used to fabricate 3D structures at the macro- and microscale made of nanocomposite materials is reviewed here. The current state-of-the-art fabrication methods, their main characteristics (e.g., resolutions, advantages, limitations), the process parameters, and materials requirements are discussed. A comprehensive review is carried out on the use of metal- and carbon-based nanomaterials incorporated into polymers or hydrogels for the manufacturing of 3D structures, mostly at the microscale, using different 3D-printing techniques. Several methods, including but not limited to micro-stereolithography, extrusion-based direct-write technologies, inkjet-printing techniques, and popular powder-bed technology, are discussed. Various examples of 3D nanocomposite macro- and microstructures manufactured using different 3D-printing technologies for a wide range of domains such as microelectromechanical systems (MEMS), lab-on-a-chip, microfluidics, engineered materials and composites, microelectronics, tissue engineering, and biosystems are reviewed. Parallel advances on materials and techniques are still required in order to employ the full potential of 3D printing of multifunctional nanocomposites. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Organic Lasers: Recent Developments on Materials, Device Geometries, and Fabrication Techniques.

PubMed

Kuehne, Alexander J C; Gather, Malte C

2016-11-09

Organic dyes have been used as gain medium for lasers since the 1960s, long before the advent of today's organic electronic devices. Organic gain materials are highly attractive for lasing due to their chemical tunability and large stimulated emission cross section. While the traditional dye laser has been largely replaced by solid-state lasers, a number of new and miniaturized organic lasers have emerged that hold great potential for lab-on-chip applications, biointegration, low-cost sensing and related areas, which benefit from the unique properties of organic gain materials. On the fundamental level, these include high exciton binding energy, low refractive index (compared to inorganic semiconductors), and ease of spectral and chemical tuning. On a technological level, mechanical flexibility and compatibility with simple processing techniques such as printing, roll-to-roll, self-assembly, and soft-lithography are most relevant. Here, the authors provide a comprehensive review of the developments in the field over the past decade, discussing recent advances in organic gain materials, which are today often based on solid-state organic semiconductors, as well as optical feedback structures, and device fabrication. Recent efforts toward continuous wave operation and electrical pumping of solid-state organic lasers are reviewed, and new device concepts and emerging applications are summarized.

Fabrication process of superconducting integrated circuits with submicron Nb/AlOx/Nb junctions using electron-beam direct writing technique

NASA Astrophysics Data System (ADS)

Aoyagi, Masahiro; Nakagawa, Hiroshi

1997-07-01

For enhancing operating speed of a superconducting integrated circuit (IC), the device size must be reduced into the submicron level. For this purpose, we have introduced electron beam (EB) direct writing technique into the fabrication process of a Nb/AlOx/Nb Josephson IC. A two-layer (PMMA/(alpha) M-CMS) resist method called the portable conformable mask (PCM) method was utilized for having a high aspect ratio. The electron cyclotron resonance (ECR) plasma etching technique was utilized. We have fabricated micron or submicron-size Nb/AlOx/Nb Josephson junctions, where the size of the junction was varied from 2 micrometer to 0.5 micrometer at 0.1 micrometer intervals. These junctions were designed for evaluating the spread of the junction critical current. We achieved minimum-to-maximum Ic spread of plus or minus 13% for 0.81-micrometer-square (plus or minus 16% for 0.67-micrometer-square) 100 junctions spreading in 130- micrometer-square area. The size deviation of 0.05 micrometer was estimated from the spread values. We have successfully demonstrated a small-scale logic IC with 0.9-micrometer-square junctions having a 50 4JL OR-gate chain, where 4JL means four junctions logic family. The circuit was designed for measuring the gate delay. We obtained a preliminary result of the OR- gate logic delay, where the minimum delay was 8.6 ps/gate.

Fabrication of zein nanostructure

NASA Astrophysics Data System (ADS)

Luecha, Jarupat

The concerns on the increase of polluting plastic wastes as well as the U.S. dependence on imported petrochemical products have driven an attention towards alternative biodegradable polymers from renewable resources. Zein protein, a co-product from ethanol production from corn, is a good candidate. This research project aims to increase zein value by adopting nanotechnology for fabricating advanced zein packaging films and zein microfluidic devices. Two nanotechnology approaches were focused: the polymer nanoclay nanocomposite technique where the nanocomposite structures were created in the zein matrix, and the soft lithography and the microfluidic devices where the micro and nanopatterns were created on the zein film surfaces. The polymer nanoclay nanocomposite technique was adopted in the commonly used zein film fabrication processes which were solvent casting and extrusion blowing methods. The two methods resulted in partially exfoliated nanocomposite structures. The impact of nanoclays on the physical properties of zein films strongly depended on the film preparation techniques. The impact of nanoclay concentration was more pronounced in the films made by extrusion blowing technique than by the solvent casting technique. As the processability limitation for the extrusion blowing technique of the zein sample containing hight nanoclay content, the effect of the nanoclay content on the rheological properties of zein hybrid resins at linear and nonlinear viscoelastic regions were further investigated. A pristine zein resin exhibited soft solid like behavior. On the other hand, the zein hybrid with nanoclay content greater than 5 wt.% showed more liquid like behavior, suggesting that the nanoclays interrupted the entangled zein network. There was good correspondence between the experimental data and the predictions of the Wagner model for the pristine zein resins. However, the model failed to predict the steady shear properties of the zein nanoclay nanocomposite

Robust Polypropylene Fabrics Super-Repelling Various Liquids: A Simple, Rapid and Scalable Fabrication Method by Solvent Swelling.

PubMed

Zhu, Tang; Cai, Chao; Duan, Chunting; Zhai, Shuai; Liang, Songmiao; Jin, Yan; Zhao, Ning; Xu, Jian

2015-07-01

A simple, rapid (10 s) and scalable method to fabricate superhydrophobic polypropylene (PP) fabrics is developed by swelling the fabrics in cyclohexane/heptane mixture at 80 °C. The recrystallization of the swollen macromolecules on the fiber surface contributes to the formation of submicron protuberances, which increase the surface roughness dramatically and result in superhydrophobic behavior. The superhydrophobic PP fabrics possess excellent repellency to blood, urine, milk, coffee, and other common liquids, and show good durability and robustness, such as remarkable resistances to water penetration, abrasion, acidic/alkaline solution, and boiling water. The excellent comprehensive performance of the superhydrophobic PP fabrics indicates their potential applications as oil/water separation materials, protective garments, diaper pads, or other medical and health supplies. This simple, fast and low cost method operating at a relatively low temperature is superior to other reported techniques for fabricating superhydrophobic PP materials as far as large scale manufacturing is considered. Moreover, the proposed method is applicable for preparing superhydrophobic PP films and sheets as well.

Design, fabrication and characterization of an arrayable all-polymer microfluidic valve employing highly magnetic rare-earth composite polymer

NASA Astrophysics Data System (ADS)

Rahbar, Mona; Shannon, Lesley; Gray, Bonnie L.

2016-05-01

We present a new magnetically actuated microfluidic valve that employs a highly magnetic composite polymer (M-CP) containing rare-earth hard-magnetic powder for its actuating element and for its valve seat. The M-CP offers much higher magnetization compared to the soft-magnetic, ferrite-based composite polymers typically used in microfluidic applications. Each valve consists of a permanently magnetized M-CP flap and valve seat mounted on a microfluidic channel system fabricated in poly(dimethylsiloxane) (PDMS). Each valve is actuated under a relatively small external magnetic field of 80 mT provided by a small permanent magnet mounted on a miniature linear actuator. The performance of the valve with different flap thicknesses is characterized. In addition, the effect of the magnetic valve seat on the valve’s performance is also characterized. It is experimentally shown that a valve with a 2.3 mm flap thickness, actuated under an 80 mT magnetic field, is capable of completely blocking liquid flow at a flow rate of 1 ml min-1 for pressures up to 9.65 kPa in microfluidic channels 200 μm wide and 200 μm deep. The valve can also be fabricated into an array for flow switching between multiple microfluidic channels under continuous flow conditions. The performance of arrays of valves for flow routing is demonstrated for flow rates up to 5 ml min-1 with larger microfluidic channels of up to 1 mm wide and 500 μm deep. The design of the valves is compatible with other commonly used polymeric microfluidic components, as well as other components that use the same novel permanently magnetic composite polymer, such as our previously reported cilia-based mixing devices.

Fabricate Optical Microfiber by Using Flame Brushing Technique and Coated with Polymer Polyaniline for Sensing Application

NASA Astrophysics Data System (ADS)

Razak, N. A.; Hamida, B. A.; Irawati, N.; Habaebi, M. H.

2017-06-01

Adiabaticity is one of the essential criteria in producing good fabricated tapered fibers. Good tapered fibers can be use in sensor application such as humidity sensor, temperature sensor and refractive index sensor. In this paper, good tapering silica fiber is produced by using flame brushing technique and then, the microfiber is coated with polymer Polyaniline (PAni) to sense different type of alcohols with different concentrations. The outcome of this experiment gives excellent repeatability in the detection of alcohol sensing with a sensitivity of 0.1332 μW/% and a resolution of 3.764%. In conclusion, conducting polymer coated optical microfiber sensor for alcohol detection with low cost, effective and simple set-up was successfully achieved in this study.

Seasonal changes in the techniques employed by wild chimpanzees in the Mahale Mountains, Tanzania, to feed on termites (Pseudacanthotermes spiniger).

PubMed

Uehara, S

1982-01-01

During a short period, wild chimpanzees of group K in the Mahale Mountains employ a set of several techniques, including tool use, to feed on one species of termite (Pseudacanthotermes spiniger). They appear to use each technique appropriately according to phenological changes in the prey insect's activities. The chimpanzees also ingest small pieces of soil from the tower of P. spiniger's mound throughout the year. Geophagy presumably makes them visually and tactually aware of the phenological changes of the termite's reproductive cycle. Analyses of fecal samples from the chimpanzees indicate interannual fluctuations in the amount of termites ingested. On the other hand, the chimpanzees of group B, ranging to the north of group K, utilize a fishing technique to obtain another type of termite (Macrotermes?herus) on a large scale during the first half of the wet season. Fecal analysis data show that chimpanzees of group B consume far more termites than those of group K. The probability that the same or similar tool-using techniques as fishing may be employed in feeding on different types of insects by chimpanzees of different unit groups according to subtle local differences in the insect fauna of their home ranges is discussed.

Fabrication and characterization of high impact hybrid matrix composites from thermoset resin and dyneema-glass fabric reinforcement

NASA Astrophysics Data System (ADS)

Patel, R. H.; Sharma, S.; Pansuriya, T.; Malgani, E. V.; Sevkani, V.

2018-05-01

Hybrid composites have been fabricated by hand lay-up technique with epoxy resin and diethylene tri amine as a hardener for high impact energy absorption with sandwich stacking of different reinforcements of dyneema and glass fabric. High impact grade composites are nowadays gaining a lot of importance in the field of high mechanical load bearing applications, ballistics and bulletproofing. The present work emphases on the fabrication and mechanical properties of the hybrid composites of cut resistant dyneema fabric along with glass fabric reinforced in the thermosetting resin. i.e. epoxy. The prime importance while fabricating such materials have been given to the processing along with selection of the raw materials. High impact resistive materials with low density and henceforth low weight have been manufactured and characterized by IZOD impact tester, UTM, Archimedes density meter and SEM. Throughout the work, satisfactory results have been obtained. Impact resistance was observed to be boosted three times as that of the reference sample of glass fabric and epoxy. The density of the hybrid composite is observed to be 25% as that of the reference sample.

Vapor-phase deposition of polymers as a simple and versatile technique to generate paper-based microfluidic platforms for bioassay applications.

PubMed

Demirel, Gokhan; Babur, Esra

2014-05-21

Given their simplicity and functionality, paper-based microfluidic systems are considered to be ideal and promising bioassay platforms for use in less developed countries or in point-of-care services. Although a series of innovative techniques have recently been demonstrated for the fabrication of such platforms, development of simple, inexpensive and versatile new strategies are still needed in order to reach their full potential. In this communication, we describe a simple yet facile approach to fabricate paper-based sensor platforms with a desired design through a vapor-phase polymer deposition technique. We also show that the fabricated platforms could be readily employed for the detection of various biological target molecules including glucose, protein, ALP, ALT, and uric acid. The limit of detection for each target molecule was calculated to be 25 mg dL(-1) for glucose, 1.04 g L(-1) for protein, 7.81 unit per L for ALP, 1.6 nmol L(-1) for ALT, and 0.13 mmol L(-1) for uric acid.

Fabrication of nanostructure by physical vapor deposition with glancing angle deposition technique and its applications

NASA Astrophysics Data System (ADS)

Horprathum, M.; Eiamchai, P.; Kaewkhao, J.; Chananonnawathorn, C.; Patthanasettakul, V.; Limwichean, S.; Nuntawong, N.; Chindaudom, P.

2014-09-01

A nanostructural thin film is one of the highly exploiting research areas particularly in applications in sensor, photocatalytic, and solar-cell technologies. In the past two decades, the integration of glancing-angle deposition (GLAD) technique to physical vapor deposition (PVD) process has gained significant attention for well-controlled multidimensional nanomorphologies because of fast, simple, cost-effective, and mass-production capability. The performance and functional properties of the coated thin films generally depend upon their nanostructural compositions, i.e., large aspect ratio, controllable porosity, and shape. Such structural platforms make the fabricated thin films very practical for several realistic applications. We therefore present morphological and nanostructural properties of various deposited materials, which included metals, i.e., silver (Ag), and oxide compounds, i.e., tungsten oxide (WO3), titanium dioxide (TiO2), and indium tin oxide (ITO). Different PVD techniques based on DC magnetron sputtering and electron-beam evaporation, both with the integrated GLAD component, were discussed. We further explore engineered nanostructures which enable controls of optical, electrical, and mechanical properties. These improvements led to several practical applications in surface-enhanced Raman, smart windows, gas sensors, self-cleaning materials and transparent conductive oxides (TCO).

Apparatus and method for fabricating a microbattery

DOEpatents

Shul, Randy J.; Kravitz, Stanley H.; Christenson, Todd R.; Zipperian, Thomas E.; Ingersoll, David

2002-01-01

An apparatus and method for fabricating a microbattery that uses silicon as the structural component, packaging component, and semiconductor to reduce the weight, size, and cost of thin film battery technology is described. When combined with advanced semiconductor packaging techniques, such a silicon-based microbattery enables the fabrication of autonomous, highly functional, integrated microsystems having broad applicability.

Technique for fabrication of ultrathin foils in cylindrical geometry for liner-plasma implosion experiments with sub-megaampere currents

NASA Astrophysics Data System (ADS)

Yager-Elorriaga, D. A.; Steiner, A. M.; Patel, S. G.; Jordan, N. M.; Lau, Y. Y.; Gilgenbach, R. M.

2015-11-01

In this work, we describe a technique for fabricating ultrathin foils in cylindrical geometry for liner-plasma implosion experiments using sub-MA currents. Liners are formed by wrapping a 400 nm, rectangular strip of aluminum foil around a dumbbell-shaped support structure with a non-conducting center rod, so that the liner dimensions are 1 cm in height, 6.55 mm in diameter, and 400 nm in thickness. The liner-plasmas are imploded by discharging ˜600 kA with ˜200 ns rise time using a 1 MA linear transformer driver, and the resulting implosions are imaged four times per shot using laser-shadowgraphy at 532 nm. This technique enables the study of plasma implosion physics, including the magneto Rayleigh-Taylor, sausage, and kink instabilities on initially solid, imploding metallic liners with university-scale pulsed power machines.

Fabrication and characterization of anode catalyst layers with structural variations for DMFC

NASA Astrophysics Data System (ADS)

Wang, Dazhi; Shi, Peng; Zhou, Peng; Mao, Qing; Liang, Junsheng; Wang, Suli; Li, Yang; Ren, Tongqun; Sun, Gongquan

2018-04-01

In this work, the electrohydrodynamic jet (E-Jet) Layer-by-Layer (LbL) deposition technique was employed to produce anode catalyst layer (CL) structure for direct methanol fuel cells (DMFC). The CLs with different thickness and porosity were fabricated with the control of the E-Jet deposition parameters. Then, the deposited anode CLs with structural variations were assembled to membrane electrode assemblies (MEAs). The results showed that the anode CL with higher porosity contributed higher dispersed catalyst, which further induced greater electrochemical active surface area (ESA) and higher performance. At optimized working condition the anode CL with high-dispersed catalyst of was produced using the E-Jet LbL deposition technique. It was observed that the peak power density is 72.8 mW cm‑2 for the cell having a porosity of 0.63, which has an increase of about 33% after modification of the CL structure.

A multilayer membrane amperometric glucose sensor fabricated using planar techniques for large-scale production.

PubMed

Matsumoto, T; Saito, S; Ikeda, S

2006-03-23

This paper reports on a multilayer membrane amperometric glucose sensor fabricated using planar techniques. It is characterized by good reproducibility and suitable for large-scale production. The glucose sensor has 82 electrode sets formed on a single glass substrate, each with a platinum working electrode (WE), a platinum counter electrode (CE) and an Ag/AgCl reference electrode (RE). The electrode sets are coated with a membrane consisting of five layers: gamma-aminopropyltriethoxysilane (gamma-APTES), Nafion, glucose oxidase (GOX), gamma-APTES and perfluorocarbon polymer (PFCP), in that order. Tests have shown that the sensor has acceptably low dispersion (relative standard deviation, R.S.D.=42.9%, n=82), a wide measurement range (1.11-111 mM) and measurement stability over a 27-day period. Measurements of the glucose concentration in a control human urine sample demonstrated that the sensor has very low dispersion (R.S.D.=2.49%, n=10).

A simple method using two-step hot embossing technique with shrinking for fabrication of cross microchannels on PMMA substrate and its application to electrophoretic separation of amino acids in functional drinks.

PubMed

Wiriyakun, Natta; Nacapricha, Duangjai; Chantiwas, Rattikan

2016-12-01

This work presents a simple hot embossing method with a shrinking procedure to produce cross-shape microchannels on poly(methyl methacrylate) (PMMA) substrate for the fabrication of an electrophoresis chip. The proposed method employed a simple two-step hot embossing technique, carried out consecutively on the same piece of substrate to make the crossing channels. Studies of embossing conditions, i.e. temperature, pressure and time, were carried out to investigate their effects on the dimension of the microchannels. Applying a simple shrinking procedure reduced the size of the channels from 700±20µm wide×150±5µm deep to 250±10µm wide×30±2µm deep, i.e. 80% and 64% reduction in the depth and width, respectively. Thermal fusion was employed to bond the PMMA substrate with a PMMA cover plate to produce the microfluidic device. Replication of microchip was achieved by precise control of conditions in the fabrication process (pressure, temperature and time), resulting in lower than 7% RSD of channel dimension, width and depth (n =10 devices). The method was simple and robust without the use of expensive equipment to construct the microstructure on a thermoplastic substrate. The PMMA microchip was used for demonstration of amine functionalization on the PMMA surface, measurement of electroosmotic flow and for electrophoretic separation of amino acids in functional drink samples. The precision of migration time and peak area of the amino acids, Lys, Ile and Phe at 125μM to 500μM, were in the range 3.2-4.2% RSD (n=9 devices) and 4.5-5.3% RSD (n=9 devices), respectively. Copyright © 2016 Elsevier B.V. All rights reserved.

Design and fabrication of planar structures with graded electromagnetic properties

NASA Astrophysics Data System (ADS)

Good, Brandon Lowell

Successfully integrating electromagnetic properties in planar structures offers numerous benefits to the microwave and optical communities. This work aims at formulating new analytic and optimized design methods, creating new fabrication techniques for achieving those methods, and matching appropriate implementation of methods to fabrication techniques. The analytic method consists of modifying an approach that realizes perfect antireflective properties from graded profiles. This method is shown for all-dielectric and magneto-dielectric grading profiles. The optimized design methods are applied to transformer (discrete) or taper (continuous) designs. From these methods, a subtractive and an additive manufacturing technique were established and are described. The additive method, dry powder dot deposition, enables three dimensional varying electromagnetic properties in a structural composite. Combining the methods and fabrication is shown in two applied methodologies. The first uses dry powder dot deposition to design one dimensionally graded electromagnetic profiles in a planar fiberglass composite. The second method simultaneously applies antireflective properties and adjusts directivity through a slab through the use of subwavelength structures to achieve a flat antireflective lens. The end result of this work is a complete set of methods, formulations, and fabrication techniques to achieve integrated electromagnetic properties in planar structures.

Material engineering to fabricate rare earth erbium thin films for exploring nuclear energy sources

NASA Astrophysics Data System (ADS)

Banerjee, A.; Abhilash, S. R.; Umapathy, G. R.; Kabiraj, D.; Ojha, S.; Mandal, S.

2018-04-01

High vacuum evaporation and cold-rolling techniques to fabricate thin films of the rare earth lanthanide-erbium have been discussed in this communication. Cold rolling has been used for the first time to successfully fabricate films of enriched and highly expensive erbium metal with areal density in the range of 0.5-1.0 mg/cm2. The fabricated films were used as target materials in an advanced nuclear physics experiment. The experiment was designed to investigate isomeric states in the heavy nuclei mass region for exploring physics related to nuclear energy sources. The films fabricated using different techniques varied in thickness as well as purity. Methods to fabricate films with thickness of the order of 0.9 mg/cm2 were different than those of 0.4 mg/cm2 areal density. All the thin films were characterized using multiple advanced techniques to accurately ascertain levels of contamination as well as to determine their exact surface density. Detailed fabrication methods as well as characterization techniques have been discussed.

Reflectance spectra characteristics from an SPR grating fabricated by nano-imprint lithography technique for biochemical nanosensor applications

NASA Astrophysics Data System (ADS)

Setiya Pradana, Jalu; Hidayat, Rahmat

2018-04-01

In this paper, we report our research work on developing a Surface Plasmon Resonance (SPR) element with sub-micron (hundreds of nanometers) periodicity grating structure. This grating structure was fabricated by using a simple nano-imprint lithography technique from an organically siloxane polymers, which was then covered by nanometer thin gold layer. The formed grating structure was a very well defined square-shaped periodic structure. The measured reflectance spectra indicate the SPR wave excitation on this grating structure. For comparison, the simulations of reflectance spectra have been also carried out by using Rigorous Coupled-Wave Analysis (RCWA) method. The experimental results are in very good agreement with the simulation results.

Electrophoretic fabrication of chitosan-zirconium-oxide nanobiocomposite platform for nucleic acid detection.

PubMed

Das, Maumita; Dhand, Chetna; Sumana, Gajjala; Srivastava, A K; Nagarajan, R; Nain, Lata; Iwamoto, M; Manaka, Takaaki; Malhotra, B D

2011-03-14

The present work describes electrophoretic fabrication of nanostructured chitosan-zirconium-oxide composite (CHIT-NanoZrO(2)) film (180 nm) onto indium-tin-oxide (ITO)-coated glass plate. This nanobiocomposite film has been explored as immobilization platform for probe DNA specific to M. Tuberculosis as model biomolecule to investigate its sensing characteristics. It is revealed that pH-responsive behavior of CHIT and its cationic skeleton is responsible for the movement of CHIT-NanoZrO(2) colloids toward cathode during electrophoretic deposition. The FT-IR, SEM, TEM, and EDX techniques have been employed for the structural, morphological, and composition analysis of the fabricated electrodes. The morphological studies clearly reveal uniform inter-linking and dispersion of hexagonal nanograins of ZrO(2) (30-50 nm) into the chitosan matrix, resulting in homogeneous nanobiocomposite formation. Electrochemical response measurements of DNA/CHIT-NanoZrO(2)/ITO bioelectrode, carried out using cyclic voltammetry and differential pulse voltammetry, reveal that this bioelectrode can specifically detect complementary target DNA up to 0.00078 μM with sensitivity of 6.38 × 10(-6) AμM(-1).

Microfluidic channel fabrication method

DOEpatents

Arnold, Don W.; Schoeniger, Joseph S.; Cardinale, Gregory F.

2001-01-01

A new channel structure for microfluidic systems and process for fabricating this structure. In contrast to the conventional practice of fabricating fluid channels as trenches or grooves in a substrate, fluid channels are fabricated as thin walled raised structures on a substrate. Microfluidic devices produced in accordance with the invention are a hybrid assembly generally consisting of three layers: 1) a substrate that can or cannot be an electrical insulator; 2) a middle layer, that is an electrically conducting material and preferably silicon, forms the channel walls whose height defines the channel height, joined to and extending from the substrate; and 3) a top layer, joined to the top of the channels, that forms a cover for the channels. The channels can be defined by photolithographic techniques and are produced by etching away the material around the channel walls.

Fabrication of Graded Porous and Skin-Core Structure RDX-Based Propellants via Supercritical CO2 Concentration Profile

NASA Astrophysics Data System (ADS)

Yang, Weitao; Li, Yuxiang; Ying, Sanjiu

2015-04-01

A fabrication process to produce graded porous and skin-core structure propellants via supercritical CO2 concentration profile is reported in this article. It utilizes a partial gas saturation technique to obtain nonequilibrium gas concentration profiles in propellants. Once foamed, the propellant obtains a graded porous or skin-pore structure. This fabrication method was studied with RDX(Hexogen)-based propellant under an SC-CO2 saturation condition. The principle was analyzed and the one-dimensional diffusion model was employed to estimate the gas diffusion coefficient and to predict the gas concentration profiles inside the propellant. Scanning electron microscopy images were used to analyze the effects of partial saturation on the inner structure. The results also suggested that the sorption time and desorption time played an important role in gas profile generation and controlled the inner structure of propellants.

Indirect fabrication of multiple post-and-core patterns with a vinyl polysiloxane matrix.

PubMed

Sabbak, Sahar Asaad

2002-11-01

In the described technique, a vinyl polysiloxane material is used as a matrix for the indirect fabrication of multiple custom-cast posts and cores. The matrix technique enables the clinician to fabricate multiple posts and cores in a short period of time. The form, harmony, and common axis of preparation for all cores are well controlled before the definitive crown/fixed partial denture restorations are fabricated. Oral tissues are not exposed to the heat of polymerization or the excess monomer of the resin material when this technique is used.

Employing X-ray absorption technique for better detector resolution and measurement of low cross-section events

NASA Astrophysics Data System (ADS)

Sharma, Gaurav; Puri, Nitin K.; Kumar, Pravin; Nandi, T.

2018-03-01

The versatility of X-ray absorption technique is experimentally employed for enhancing the detector resolution and to rejuvenate the low probable transitions obscured in the pile-up region, during a beam-foil spectroscopy experiment. The multiple aluminum absorber layers (10 μm each) are used to suppress the pile-up contribution drastically and to restore a weak transition which is about 1.38 × 104 times weaker than a one-electron-one-photon transitions viz. Kα and Khα. The weak line is possibly originating from a two-electron-one-photon transition in He-like Ti. Further, the transitions, which were obscured in the spectra due to high intensity ratio, are revived by dissimilar line intensity attenuation using this technique. The measured lifetimes of Kα line with and without intensity attenuation match well within error bar. The present technique finds potential implications in understanding the structure of multiple-core-vacant ions and other low cross section processes in ion-solid collisions.

Static tool influence function for fabrication simulation of hexagonal mirror segments for extremely large telescopes.

PubMed

Kim, Dae Wook; Kim, Sug-Whan

2005-02-07

We present a novel simulation technique that offers efficient mass fabrication strategies for 2m class hexagonal mirror segments of extremely large telescopes. As the first of two studies in series, we establish the theoretical basis of the tool influence function (TIF) for precessing tool polishing simulation for non-rotating workpieces. These theoretical TIFs were then used to confirm the reproducibility of the material removal foot-prints (measured TIFs) of the bulged precessing tooling reported elsewhere. This is followed by the reverse-computation technique that traces, employing the simplex search method, the real polishing pressure from the empirical TIF. The technical details, together with the results and implications described here, provide the theoretical tool for material removal essential to the successful polishing simulation which will be reported in the second study.

Fabrication of silk fibroin film using centrifugal casting technique for corneal tissue engineering.

PubMed

Lee, Min Chae; Kim, Dong-Kyu; Lee, Ok Joo; Kim, Jung-Ho; Ju, Hyung Woo; Lee, Jung Min; Moon, Bo Mi; Park, Hyun Jung; Kim, Dong Wook; Kim, Su Hyeon; Park, Chan Hum

2016-04-01

Films prepared from silk fibroin have shown potential as biomaterials in tissue engineering applications for the eye. Here, we present a novel process for fabrication of silk fibroin films for corneal application. In this work, fabrication of silk fibroin films was simply achieved by centrifugal force. In contrast to the conventional dry casting method, we carried out the new process in a centrifuge with a rotating speed of 4000 rpm, where centrifugal force was imposed on an aluminum tube containing silk fibroin solution. In the present study, we also compared the surface roughness, mechanical properties, transparency, and cell proliferation between centrifugal and dry casting method. In terms of surface morphology, films fabricated by the centrifugal casting have less surface roughness than those by the dry casting. For elasticity and transparency, silk fibroin films obtained from the centrifugal casting had favorable results compared with those prepared by dry casting. Furthermore, primary human corneal keratocytes grew better in films prepared by the centrifugal casting. Therefore, our results suggest that this new fabrication process for silk fibroin films offers important potential benefits for corneal tissue regeneration. © 2015 Wiley Periodicals, Inc.

In vitro and in vivo performance of bioactive Ti6Al4V/TiC/HA implants fabricated by a rapid microwave sintering technique.

PubMed

Choy, Man Tik; Tang, Chak Yin; Chen, Ling; Wong, Chi Tak; Tsui, Chi Pong

2014-09-01

Failure of the bone-implant interface in a joint prosthesis is a main cause of implant loosening. The introduction of a bioactive substance, hydroxyapatite (HA), to a metallic bone-implant may enhance its fixation on human bone by encouraging direct bone bonding. Ti6Al4V/TiC/HA composites with a reproducible porous structure (porosity of 27% and pore size of 6-89 μm) were successfully fabricated by a rapid microwave sintering technique. This method allows the biocomposites to be fabricated in a short period of time under ambient conditions. Ti6Al4V/TiC/HA composites exhibited a compressive strength of 93 MPa, compressive modulus of 2.9 GPa and microhardness of 556 HV which are close to those of the human cortical bone. The in vitro preosteoblast MC3T3-E1 cells cultured on the Ti6Al4V/TiC/HA composite showed that the composite surface could provide a biocompatible environment for cell adhesion, proliferation and differentiation without any cytotoxic effects. This is among the first attempts to study the in vivo performance of load-bearing Ti6Al4V/TiC and Ti6Al4V/TiC/HA composites in a live rabbit. The results indicated that the Ti6Al4V/TiC/HA composite had a better bone-implant interface compared with the Ti6Al4V/TiC implant. Based on the microstructural features, the mechanical properties, and the in vitro and in vivo test results from this study, the Ti6Al4V/TiC/HA composites have the potential to be employed in load-bearing orthopedic applications. Copyright © 2014 Elsevier B.V. All rights reserved.

An automated flow injection system for metal determination by flame atomic absorption spectrometry involving on-line fabric disk sorptive extraction technique.

PubMed

Anthemidis, A; Kazantzi, V; Samanidou, V; Kabir, A; Furton, K G

2016-08-15

A novel flow injection-fabric disk sorptive extraction (FI-FDSE) system was developed for automated determination of trace metals. The platform was based on a minicolumn packed with sol-gel coated fabric media in the form of disks, incorporated into an on-line solid-phase extraction system, coupled with flame atomic absorption spectrometry (FAAS). This configuration provides minor backpressure, resulting in high loading flow rates and shorter analytical cycles. The potentials of this technique were demonstrated for trace lead and cadmium determination in environmental water samples. The applicability of different sol-gel coated FPSE media was investigated. The on-line formed complex of metal with ammonium pyrrolidine dithiocarbamate (APDC) was retained onto the fabric surface and methyl isobutyl ketone (MIBK) was used to elute the analytes prior to atomization. For 90s preconcentration time, enrichment factors of 140 and 38 and detection limits (3σ) of 1.8 and 0.4μgL(-1) were achieved for lead and cadmium determination, respectively, with a sampling frequency of 30h(-1). The accuracy of the proposed method was estimated by analyzing standard reference materials and spiked water samples. Copyright © 2016 Elsevier B.V. All rights reserved.

Characterization of surface modified polyester fabric.

PubMed

Joseph, Roy; Shelma, R; Rajeev, A; Muraleedharan, C V

2009-12-01

Woven polyethylene terephthalate (PET) fabric has been used in the construction of vascular grafts and sewing ring of prosthetic heart valves. In an effort to improve haemocompatibility and tissue response to PET fabric, a fluoropolymer, polyvinylidine fluoride (PVDF), was coated on PET fabric by dip coating technique. The coating was found to be uniform and no significant changes occurred on physical properties such as water permeability and burst strength. Cell culture cytotoxicity studies showed that coated PET was non-cytotoxic to L929 fibroblast cell lines. In vitro studies revealed that coating improved haemocompatibility of PET fabric material. Coating reduced platelet consumption of PET fabric by 50%. Upon surface modification leukocyte consumption of PET was reduced by 24%. About 60% reduction in partial thromboplastin time (PTT) observed when PET was coated with PVDF. Results of endothelial cell proliferation studies showed that surface coating did not have any substantial impact on cell proliferation. Overall results indicate that coating has potential to improve haemocompatibility of PET fabric without affecting its mechanical performance.

Fabrication of large diffractive optical elements in thick film on a concave lens surface.

PubMed

Xie, Yongjun; Lu, Zhenwu; Li, Fengyou

2003-05-05

We demonstrate experimentally the technique of fabricating large diffractive optical elements (DOEs) in thick film on a concave lens surface (mirrors) with precise alignment by using the strategy of double exposure. We adopt the method of double exposure to overcome the difficulty of processing thick photoresist on a large curved substrate. A uniform thick film with arbitrary thickness on a concave lens can be obtained with this technique. We fabricate a large concentric circular grating with a 10-ìm period on a concave lens surface in film with a thickness of 2.0 ìm after development. It is believed that this technique can also be used to fabricate larger DOEs in thicker film on the concave or convex lens surface with precise alignment. There are other potential applications of this technique, such as fabrication of micro-optoelectromechanical systems (MOEMS) or microelectromechanical systems (MEMS) and fabrication of microlens arrays on a large concave lens surface or convex lens surface with precise alignment.

Unidirectional Fabric Drape Testing Method

PubMed Central

Mei, Zaihuan; Yang, Jingzhi; Zhou, Ting; Zhou, Hua

2015-01-01

In most cases, fabrics such as curtains, skirts, suit pants and so on are draped under their own gravity parallel to fabric plane while the gravity is perpendicular to fabric plane in traditional drape testing method. As a result, it does not conform to actual situation and the test data is not convincing enough. To overcome this problem, this paper presents a novel method which simulates the real mechanical conditions and ensures the gravity is parallel to the fabric plane. This method applied a low-cost Kinect Sensor device to capture the 3-dimensional (3D) drape profile, thus we obtained the drape degree parameters and aesthetic parameters by 3D reconstruction and image processing and analysis techniques. The experiment was conducted on our self-devised drape-testing instrument by choosing different kinds of weave structure fabrics as our testing samples and the results were compared with those of traditional method and subjective evaluation. Through regression and correlation analysis we found that this novel testing method was significantly correlated with the traditional and subjective evaluation method. We achieved a new, non-contact 3D measurement method for drape testing, namely unidirectional fabric drape testing method. This method is more suitable for evaluating drape behavior because it is more in line with actual mechanical conditions of draped fabrics and has a well consistency with the requirements of visual and aesthetic style of fabrics. PMID:26600387

Adaptation and micro-structure of Co-Cr alloy maxillary complete denture base plates fabricated by selective laser melting technique.

PubMed

Ye, Ye; Jiao, Ting; Zhu, Jiarui; Sun, Jian

2018-01-24

The purpose of the study was to evaluate the adaptation and micro-structure of Co-Cr alloy maxillary complete denture base plates fabricated by the selective laser melting (SLM) technique. Twenty pairs of edentulous casts were randomly and evenly divided into two groups, and manufacturing of the Co-Cr alloy maxillary complete denture base was conducted either by the SLM technique or by the conventional method. The base-cast sets were transversally sectioned into three sections at the distal canines, mesial of the first molars and the posterior palatal zone. The gap between the metal base and cast was measured in these three sections with a stereoscopic microscope, and the data were analysed using t tests. A total of five specimens of 5 mm diameter were fabricated with the Co-Cr alloy by SLM and the traditional casting technology. A scanning electron microscope (SEM) was used to evaluate the differences in microstructure between these specimens. There was no statistical difference between the three sections in all four groups (P > 0.05). At the region of the canines, the clearance value for the SLM Co-Cr alloy group was larger than that of the conventional method group (P < 0.05). At the mesial of the first molar region and the posterior palatal zone, there was no statistical difference between the gaps observed in the two groups (P > 0.05). The SLM Co-Cr alloy has a denser microstructure behaviour and less casting defect than the cast Co-Cr alloy. The SLM technique showed initial feasibility for the manufacture of dental bases of complete dentures, but large sample studies are needed to prove its reliability in clinical applications. The mechanical properties and microstructure of the denture frameworks prepared by selective laser melting indicate that these dentures are appropriate for clinical use.

Fabrication of strain gauge based sensors for tactile skins

NASA Astrophysics Data System (ADS)

Baptist, Joshua R.; Zhang, Ruoshi; Wei, Danming; Saadatzi, Mohammad Nasser; Popa, Dan O.

2017-05-01

Fabricating cost effective, reliable and functional sensors for electronic skins has been a challenging undertaking for the last several decades. Application of such skins include haptic interfaces, robotic manipulation, and physical human-robot interaction. Much of our recent work has focused on producing compliant sensors that can be easily formed around objects to sense normal, tension, or shear forces. Our past designs have involved the use of flexible sensors and interconnects fabricated on Kapton substrates, and piezoresistive inks that are 3D printed using Electro Hydro Dynamic (EHD) jetting onto interdigitated electrode (IDE) structures. However, EHD print heads require a specialized nozzle and the application of a high-voltage electric field; for which, tuning process parameters can be difficult based on the choice of inks and substrates. Therefore, in this paper we explore sensor fabrication techniques using a novel wet lift-off photolithographic technique for patterning the base polymer piezoresistive material, specifically Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) or PEDOT:PSS. Fabricated sensors are electrically and thermally characterized, and temperaturecompensated designs are proposed and validated. Packaging techniques for sensors in polymer encapsulants are proposed and demonstrated to produce a tactile interface device for a robot.

Development of flame retardant cotton fabric based on ionic liquids via sol-gel technique.

NASA Astrophysics Data System (ADS)

Bentis, A.; Boukhriss, A.; Boyer, D.; Gmouh, S.

2017-10-01

In this study, flame retardant cotton fabrics were developed by the sol-gel method, in order to enhance their flame retardant proprieties. For this aim, seven sols were prepared using tetraethylorthosilicate (TEOS) and different ionic liquids (ILs) consist on pyridinium and Methylimidazolium cations with different anions such as: PF6-, CH3COO-, and Br-. Those sols were applied separately to the cotton fabrics by a pad-dry-cure process. The flame retardant properties of functionalized cotton fabrics before and after washing were determined by the vertical flame tests according to ISO6940:2004(F) standard. The effects of anions have been thoroughly investigated, aiming at the optimization of the targeted properties. Thermogravimetric and mechanical according to NF EN ISO 13934-1:2013standard, analyses have been also investigated. The results showed that flame retardancy, thermal stability and mechanical properties of treated fabrics were enhanced by using ionic liquids.

Low-cost and large-scale flexible SERS-cotton fabric as a wipe substrate for surface trace analysis

NASA Astrophysics Data System (ADS)

Chen, Yanmin; Ge, Fengyan; Guang, Shanyi; Cai, Zaisheng

2018-04-01

The large-scale surface enhanced Raman scattering (SERS) cotton fabrics were fabricated based on traditional woven ones using a dyeing-like method of vat dyes, where silver nanoparticles (Ag NPs) were in-situ synthesized by 'dipping-reducing-drying' process. By controlling the concentration of AgNO3 solution, the optimal SERS cotton fabric was obtained, which had a homogeneous close packing of Ag NPs. The SERS cotton fabric was employed to detect p-Aminothiophenol (PATP). It was found that the new fabric possessed excellent reproducibility (about 20%), long-term stability (about 57 days) and high SERS sensitivity with a detected concentration as low as 10-12 M. Furthermore, owing to the excellent mechanical flexibility and good absorption ability, the SERS cotton fabric was employed to detect carbaryl on the surface of an apple by simply swabbing, which showed great potential in fast trace analysis. More importantly, this study may realize large-scale production with low cost by a traditional cotton fabric.

Technique for fabrication of ultrathin foils in cylindrical geometry for liner-plasma implosion experiments with sub-megaampere currents

DOE PAGES

Yager-Elorriaga, D. A.; Steiner, A. M.; Patel, S. G.; ...

2015-11-19

In this study, we describe a technique for fabricating ultrathin foils in cylindrical geometry for liner-plasma implosion experiments using sub-MA currents. Liners are formed by wrapping a 400 nm, rectangular strip of aluminum foil around a dumbbell-shaped support structure with a non-conducting center rod, so that the liner dimensions are 1 cm in height, 6.55 mm in diameter, and 400 nm in thickness. The liner-plasmas are imploded by discharging ~600 kA with ~200 ns rise time using a 1 MA linear transformer driver, and the resulting implosions are imaged four times per shot using laser-shadowgraphy at 532 nm. As amore » result, this technique enables the study of plasma implosion physics, including the magneto Rayleigh-Taylor, sausage, and kink instabilities on initially solid, imploding metallic liners with university-scale pulsed power machines.« less

Technique for fabrication of ultrathin foils in cylindrical geometry for liner-plasma implosion experiments with sub-megaampere currents

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yager-Elorriaga, D. A.; Steiner, A. M.; Patel, S. G.

In this study, we describe a technique for fabricating ultrathin foils in cylindrical geometry for liner-plasma implosion experiments using sub-MA currents. Liners are formed by wrapping a 400 nm, rectangular strip of aluminum foil around a dumbbell-shaped support structure with a non-conducting center rod, so that the liner dimensions are 1 cm in height, 6.55 mm in diameter, and 400 nm in thickness. The liner-plasmas are imploded by discharging ~600 kA with ~200 ns rise time using a 1 MA linear transformer driver, and the resulting implosions are imaged four times per shot using laser-shadowgraphy at 532 nm. As amore » result, this technique enables the study of plasma implosion physics, including the magneto Rayleigh-Taylor, sausage, and kink instabilities on initially solid, imploding metallic liners with university-scale pulsed power machines.« less

A review: fabrication of porous polyurethane scaffolds.

PubMed

Janik, H; Marzec, M

2015-03-01

The aim of tissue engineering is the fabrication of three-dimensional scaffolds that can be used for the reconstruction and regeneration of damaged or deformed tissues and organs. A wide variety of techniques have been developed to create either fibrous or porous scaffolds from polymers, metals, composite materials and ceramics. However, the most promising materials are biodegradable polymers due to their comprehensive mechanical properties, ability to control the rate of degradation and similarities to natural tissue structures. Polyurethanes (PUs) are attractive candidates for scaffold fabrication, since they are biocompatible, and have excellent mechanical properties and mechanical flexibility. PU can be applied to various methods of porous scaffold fabrication, among which are solvent casting/particulate leaching, thermally induced phase separation, gas foaming, emulsion freeze-drying and melt moulding. Scaffold properties obtained by these techniques, including pore size, interconnectivity and total porosity, all depend on the thermal processing parameters, and the porogen agent and solvents used. In this review, various polyurethane systems for scaffolds are discussed, as well as methods of fabrication, including the latest developments, and their advantages and disadvantages. Copyright © 2014. Published by Elsevier B.V.

Deformation and Fabric in Compacted Clay Soils

NASA Astrophysics Data System (ADS)

Wensrich, C. M.; Pineda, J.; Luzin, V.; Suwal, L.; Kisi, E. H.; Allameh-Haery, H.

2018-05-01

Hydromechanical anisotropy of clay soils in response to deformation or deposition history is related to the micromechanics of platelike clay particles and their orientations. In this article, we examine the relationship between microstructure, deformation, and moisture content in kaolin clay using a technique based on neutron scattering. This technique allows for the direct characterization of microstructure within representative samples using traditional measures such as orientation density and soil fabric tensor. From this information, evidence for a simple relationship between components of the deviatoric strain tensor and the deviatoric fabric tensor emerge. This relationship may provide a physical basis for future anisotropic constitutive models based on the micromechanics of these materials.

Novel fabrication technique of hybrid structure lens array for 3D images

NASA Astrophysics Data System (ADS)

Lee, Junsik; Kim, Junoh; Kim, Cheoljoong; Shin, Dooseub; Koo, Gyohyun; Won, Yong Hyub

2016-03-01

Tunable liquid lens arrays can produce three dimensional images by using electrowetting principle that alters surface tensions by applying voltage. This method has advantages of fast response time and low power consumption. However, it is challenging to fabricate a high fill factor liquid lens array and operate three dimensional images which demand high diopter. This study describes a hybrid structure lens array which has not only a liquid lens array but a solid lens array. A concave-shape lens array is unavoidable when using only the liquid lens array and some voltages are needed to make the lens flat. By placing the solid lens array on the liquid lens array, initial diopter can be positive. To fabricate the hybrid structure lens array, a conventional lithographic process in semiconductor manufacturing is needed. A negative photoresist SU-8 was used as chamber master molds. PDMS and UV adhesive replica molding are done sequentially. Two immiscible liquids, DI water and dodecane, are injected in the fabricated chamber, followed by sealing. The fabricated structure has a 20 by 20 pattern of cylindrical shaped circle array and the aperture size of each lens is 1mm. The thickness of the overall hybrid structure is about 2.8mm. Hybrid structure lens array has many advantages. Solid lens array has almost 100% fill factor and allow high efficiency. Diopter can be increased by more than 200 and negative diopter can be shifted to the positive region. This experiment showed several properties of the hybrid structure and demonstrated its superiority.

Fabrication of cooled radial turbine rotor

NASA Technical Reports Server (NTRS)

Hammer, A. N.; Aigret, G. G.; Psichogios, T. P.; Rodgers, C.

1986-01-01

A design and fabrication program was conducted to evaluate a unique concept for constructing a cooled, high temperature radial turbine rotor. This concept, called split blade fabrication was developed as an alternative to internal ceramic coring. In this technique, the internal cooling cavity is created without flow dividers or any other detail by a solid (and therefore stronger) ceramic plate which can be more firmly anchored within the casting shell mold than can conventional detailed ceramic cores. Casting is conducted in the conventional manner, except that the finished product, instead of having finished internal cooling passages, is now a split blade. The internal details of the blade are created separately together with a carrier sheet. The inserts are superalloy. Both are produced by essentially the same software such that they are a net fit. The carrier assemblies are loaded into the split blade and the edges sealed by welding. The entire wheel is Hot Isostatic Pressed (HIPed), braze bonding the internal details to the inside of the blades. During this program, two wheels were successfully produced by the split blade fabrication technique.

A wideband CMOS single-ended low noise amplifier employing negative resistance technique

NASA Astrophysics Data System (ADS)

Guo, Benqing; Chen, Hongpeng; Wang, Xuebing; Chen, Jun; Li, Yueyue; Jin, Haiyan; Yang, Yongjun

2018-02-01

A wideband common-gate CMOS low noise amplifier with negative resistance technique is proposed. A novel single-ended negative resistance structure is employed to improve gain and noise of the LNA. The inductor resonating is adopted at the input stage and load stage to meet wideband matching and compensate gain roll-off at higher frequencies. Implemented in a 0.18 μm CMOS technology, the proposed LNA demonstrates in simulations a maximal gain of 16.4 dB across the 3 dB bandwidth of 0.2-3 GHz. The in-band noise figure of 3.4-4.7 dB is obtained while the IIP3 of 5.3-6.8 dBm and IIP2 of 12.5-17.2 dBm are post-simulated in the designed frequency band. The LNA core consumes a power dissipation of 3.8 mW under a 1.5 V power supply.

Fabrication of High Temperature Cermet Materials for Nuclear Thermal Propulsion

NASA Technical Reports Server (NTRS)

Hickman, Robert; Panda, Binayak; Shah, Sandeep

2005-01-01

Processing techniques are being developed to fabricate refractory metal and ceramic cermet materials for Nuclear Thermal Propulsion (NTP). Significant advances have been made in the area of high-temperature cermet fuel processing since RoverNERVA. Cermet materials offer several advantages such as retention of fission products and fuels, thermal shock resistance, hydrogen compatibility, high conductivity, and high strength. Recent NASA h d e d research has demonstrated the net shape fabrication of W-Re-HfC and other refractory metal and ceramic components that are similar to UN/W-Re cermet fuels. This effort is focused on basic research and characterization to identify the most promising compositions and processing techniques. A particular emphasis is being placed on low cost processes to fabricate near net shape parts of practical size. Several processing methods including Vacuum Plasma Spray (VPS) and conventional PM processes are being evaluated to fabricate material property samples and components. Surrogate W-Re/ZrN cermet fuel materials are being used to develop processing techniques for both coated and uncoated ceramic particles. After process optimization, depleted uranium-based cermets will be fabricated and tested to evaluate mechanical, thermal, and hot H2 erosion properties. This paper provides details on the current results of the project.

Effect of immobilization technique on performance ZnO nanorods based enzymatic electrochemical glucose biosensor

NASA Astrophysics Data System (ADS)

Shukla, Mayoorika; Pramila; Palani, I. A.; Singh, Vipul

2017-11-01

In this paper, ZnO Nanorods (ZNR) have been synthesized over Platinum (Pt) coated glass substrate with in-situ addition KMnO4 during hydrothermal growth process. Significant variation in ZnO nanostructures was observed by KMnO4 addition during the growth. Glucose oxidase was later immobilized over ZNRs. The as-prepared ZNRs were further utilized for glucose detection by employing amperometric electrochemical transduction method. In order to optimize the performance of the prepared biosensor two different immobilization techniques i.e. physical adsorption and cross linking have been employed and compared. Further investigations suggest that immobilization via cross linking method resulted in the improvement of the biosensor performance, thereby significantly affecting the sensitivity and linear range of the fabricated biosensor. Among the two types of biosensors fabricated using ZNR, the best performance was shown by cross linked electrodes. The sensitivity for the same was found to be 17.7 mA-cm-2-M-1, along with a wide linear range of 0.5-8.5 mM.

Vapour phase techniques for deposition of CZTS thin films: A review

NASA Astrophysics Data System (ADS)

Kaur, Ramanpreet; Kumar, Sandeep; Singh, Sukhpal

2018-05-01

With the surge of thin film photovoltaic technologies in recent years, for cost reduction and increased production there is a need for earth abundant and non-toxic raw materials. Existing thin film solar cells comprising CuInS2 (CIS), CuInGaSe2 (CIGS) and CdTe contain elements that are rare in earth's crust and in case of CdTe toxic. Cu2ZnSnS4 (CZTS), having Kesterite structure, a direct band gap of 1.4 - 1.5 eV and an absorption coefficient of 104 cm-1 makes a promising candidate for absorber layer in thin film solar cells. So far many physical and chemical techniques have been employed for deposition of CZTS thin films. This review focuses on various vapour phase techniques used for fabrication of films, recent advances in these techniques and their future outlook.

Fabrication of an X-Ray Imaging Detector

NASA Technical Reports Server (NTRS)

Alcorn, G. E.; Burgess, A. S.

1986-01-01

X-ray detector array yields mosaic image of object emitting 1- to 30-keV range fabricated from n-doped silicon wafer. In proposed fabrication technique, thin walls of diffused n+ dopant divide wafer into pixels of rectangular cross section, each containing central electrode of thermally migrated p-type metal. This pnn+ arrangement reduces leakage current by preventing transistor action caused by pnp structure of earlier version.

Fabrication of Polymer Optical Fibre (POF) Gratings

PubMed Central

Luo, Yanhua; Yan, Binbin; Zhang, Qijin; Peng, Gang-Ding; Wen, Jianxiang; Zhang, Jianzhong

2017-01-01

Gratings inscribed in polymer optical fibre (POF) have attracted remarkable interest for many potential applications due to their distinctive properties. This paper overviews the current state of fabrication of POF gratings since their first demonstration in 1999. In particular we summarize and discuss POF materials, POF photosensitivity, techniques and issues of fabricating POF gratings, as well as various types of POF gratings. PMID:28273844

Fabrication of novel plasmonics-active substrates

NASA Astrophysics Data System (ADS)

Dhawan, Anuj; Gerhold, Michael; Du, Yan; Misra, Veena; Vo-Dinh, Tuan

2009-02-01

This paper describes methodologies for fabricating of highly efficient plasmonics-active SERS substrates - having metallic nanowire structures with pointed geometries and sub-5 nm gap between the metallic nanowires enabling concentration of high EM fields in these regions - on a wafer-scale by a reproducible process that is compatible with large-scale development of these substrates. Excitation of surface plasmons in these nanowire structures leads to substantial enhancement in the Raman scattering signal obtained from molecules lying in the vicinity of the nanostructure surface. The methodologies employed included metallic coating of silicon nanowires fabricated by employing deep UV lithography as well as controlled growth of silicon germanium on silicon nanostructures to form diamond-shaped nanowire structures followed by metallic coating. These SERS substrates were employed for detecting chemical and biological molecules of interest. In order to characterize the SERS substrates developed in this work, we obtained SERS signals from molecules such as p-mercaptobenzoic acid (pMBA) and cresyl fast violet (CFV) attached to or adsorbed on the metal-coated SERS substrates. It was observed that both gold-coated triangular shaped nanowire substrates as well as gold-coated diamond shaped nanowire substrates provided very high SERS signals for the nanowires having sub-15 nm gaps and that the SERS signal depends on the closest spacing between the metal-coated silicon and silicon germanium nanowires. SERS substrates developed by the different processes were also employed for detection of biological molecules such as DPA (Dipicolinic Acid), an excellent marker for spores of bacteria such as Anthrax.

Carbon nanotube collimator fabrication and application

DOEpatents

Chow, Lee; Chai, Guangyu; Schenkel, Thomas

2010-07-06

Apparatus, methods, systems and devices for fabricating individual CNT collimators. Micron size fiber coated CNT samples are synthesized with chemical vapor deposition method and then the individual CNT collimators are fabricated with focused ion beam technique. Unfocused electron beams are successfully propagated through the CNT collimators. The CNT nano-collimators are used for applications including single ion implantation and in high-energy physics, and allow rapid, reliable testing of the transmission of CNT arrays for transport of molecules.

Fabrication of a Mo based high temperature TZM alloy by non-consumable arc melting technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chakraborty, S.P.; Krishnamurthy, N., E-mail: spc@barc.gov.in

High temperature structural materials are in great demand for power, chemical and nuclear industries which can perform beyond 1000 °C as super alloys usually fail. In this regard, Mo based TZM alloy is capable of retaining strength up to 1500 °C with excellent corrosion compatibility against molten alkali metals. Hence, currently this alloy is considered an important candidate material for high temperature compact nuclear and fusion reactors. Due to reactive nature of Mo and having high melting point, manufacturing this alloy by conventional process is unsuitable. Powder metallurgy technique has limited success due to restriction in quantity and purity. Thismore » paper deals with fabrication of TZM alloy by nonconsumable tungsten arc melting technique. Initially a ternary master alloy of Mo-Ti-Zr was prepared which subsequently by dilution method, was converted into TZM alloy gradually by external addition of Mo and C in various proportions. A number of melting trials were conducted to optimize the process parameters like current, voltage and time to achieve desired alloy composition. The alloy was characterized with respect to composition, elemental distribution profile, microstructure, hardness profile and phase analysis. Well consolidated alloy button was obtained having desired composition, negligible material loss and having microstructure as comparable to standard TZM alloy. (author)« less

Controllable Fabrication of Non-Close-Packed Colloidal Nanoparticle Arrays by Ion Beam Etching

NASA Astrophysics Data System (ADS)

Yang, Jie; Zhang, Mingling; Lan, Xu; Weng, Xiaokang; Shu, Qijiang; Wang, Rongfei; Qiu, Feng; Wang, Chong; Yang, Yu

2018-06-01

Polystyrene (PS) nanoparticle films with non-close-packed arrays were prepared by using ion beam etching technology. The effects of etching time, beam current, and voltage on the size reduction of PS particles were well investigated. A slow etching rate, about 9.2 nm/min, is obtained for the nanospheres with the diameter of 100 nm. The rate does not maintain constant with increasing the etching time. This may result from the thermal energy accumulated gradually in a long-time bombardment of ion beam. The etching rate increases nonlinearly with the increase of beam current, while it increases firstly then reach its saturation with the increase of beam voltage. The diameter of PS nanoparticles can be controlled in the range from 34 to 88 nm. Based on the non-close-packed arrays of PS nanoparticles, the ordered silicon (Si) nanopillars with their average diameter of 54 nm are fabricated by employing metal-assisted chemical etching technique. Our results pave an effective way to fabricate the ordered nanostructures with the size less than 100 nm.

Electrical Investigation of Nanostructured Fe2O3/p-Si Heterojunction Diode Fabricated Using the Sol-Gel Technique

NASA Astrophysics Data System (ADS)

Mansour, Shehab A.; Ibrahim, Mervat M.

2017-11-01

Iron oxide (α-Fe2O3) nanocrystals have been synthesized via the sol-gel technique. The structural and morphological features of these nanocrystals were studied using x-ray diffraction, Fourier transform-infrared spectroscopy and transmission electron microscopy. Colloidal solution of synthesized α-Fe2O3 (hematite) was spin-coated onto a single-crystal p-type silicon (p-Si) wafer to fabricate a heterojunction diode with Mansourconfiguration Ag/Fe2O3/p-Si/Al. This diode was electrically characterized at room temperature using current-voltage (I-V) characteristics in the voltage range from -9 V to +9 V. The fabricated diode showed a good rectification behavior with a rectification factor 1.115 × 102 at 6 V. The junction parameters such as ideality factor, barrier height, series resistance and shunt resistance are determined using conventional I-V characteristics. For low forward voltage, the conduction mechanism is dominated by the defect-assisted tunneling process with conventional electron-hole recombination. However, at higher voltage, I-V ohmic and space charge-limited current conduction was became less effective with the contribution of the trapped-charge-limited current at the highest voltage range.

Soft liquid phase adsorption for fabrication of organic semiconductor films on wettability patterned surfaces.

PubMed

Watanabe, Satoshi; Akiyoshi, Yuri; Matsumoto, Mutsuyoshi

2014-01-01

We report a soft liquid-phase adsorption (SLPA) technique for the fabrication of organic semiconductor films on wettability-patterned substrates using toluene/water emulsions. Wettability-patterned substrates were obtained by the UV-ozone treatment of self-assembled monolayers of silane coupling agents on glass plates using a metal mask. Organic semiconductor polymer films were formed selectively on the hydrophobic part of the wettability-patterned substrates. The thickness of the films fabricated by the SLPA technique is significantly larger than that of the films fabricated by dip-coating and spin-coating techniques. The film thickness can be controlled by adjusting the volume ratio of toluene to water, immersion angle, immersion temperature, and immersion time. The SLPA technique allows for the direct production of organic semiconductor films on wettability-patterned substrates with minimized material consumption and reduced number of fabrication steps.

Design and fabrication of microstrip antenna arrays

NASA Technical Reports Server (NTRS)

1978-01-01

A microstrip array project was conducted to demonstrate the feasibility of designing and fabricating simple, low cost, low sidelobe phased arrays with circular disk microstrip radiating elements. Design data were presented for microstrip elements and arrays including the effects of the protective covers, the mutual interaction between elements, and stripline feed network design. Low cost multilayer laminate fabrication techniques were also investigated. Utilizing this design data two C-band low sidelobe arrays were fabricated and tested: an eight-element linear and a sixty-four element planar array. These arrays incorporated stripline Butler matrix feed networks to produce a low sidelobe broadside beam.

A new approach to characterize the effect of fabric deformation on thermal protective performance

NASA Astrophysics Data System (ADS)

Li, Jun; Li, Xiaohui; Lu, Yehu; Wang, Yunyi

2012-04-01

It is very important to evaluate thermal protective performance (TPP) in laboratory-simulated fire scenes as accurately as possible. For this paper, to thoroughly understand the effect of fabric deformation on basic physical properties and TPP of flame-retardant fabrics exposed to flash fire, a new modified TPP testing apparatus was developed. Different extensions were employed to simulate the various extensions displayed during different body motions. The tests were also carried out with different air gaps. The results showed a significant decrease in air permeability after deformation. However, the change of thickness was slight. The fabric deformation had a complicated effect on thermal protection with different air gaps. The change of TPP depended on the balance between the surface contact area and the thermal insulation. The newly developed testing apparatus could be well employed to evaluate the effect of deformation on TPP of flame-resistant fabrics.

Multi-Step Deep Reactive Ion Etching Fabrication Process for Silicon-Based Terahertz Components

NASA Technical Reports Server (NTRS)

Reck, Theodore (Inventor); Perez, Jose Vicente Siles (Inventor); Lee, Choonsup (Inventor); Cooper, Ken B. (Inventor); Jung-Kubiak, Cecile (Inventor); Mehdi, Imran (Inventor); Chattopadhyay, Goutam (Inventor); Lin, Robert H. (Inventor); Peralta, Alejandro (Inventor)

2016-01-01

A multi-step silicon etching process has been developed to fabricate silicon-based terahertz (THz) waveguide components. This technique provides precise dimensional control across multiple etch depths with batch processing capabilities. Nonlinear and passive components such as mixers and multipliers waveguides, hybrids, OMTs and twists have been fabricated and integrated into a small silicon package. This fabrication technique enables a wafer-stacking architecture to provide ultra-compact multi-pixel receiver front-ends in the THz range.

Fabricating waveguide Bragg gratings (WBGs) in bulk materials using ultrashort laser pulses

NASA Astrophysics Data System (ADS)

Ams, Martin; Dekker, Peter; Gross, Simon; Withford, Michael J.

2017-01-01

Optical waveguide Bragg gratings (WBGs) can be created in transparent materials using femtosecond laser pulses. The technique is conducted without the need for lithography, ion-beam fabrication methods, or clean room facilities. This paper reviews the field of ultrafast laser-inscribed WBGs since its inception, with a particular focus on fabrication techniques, WBG characteristics, WBG types, and WBG applications.

Solid Free-form Fabrication Technology and Its Application to Bone Tissue Engineering

PubMed Central

Lee, Jin Woo; Kim, Jong Young; Cho, Dong-Woo

2010-01-01

The development of scaffolds for use in cell-based therapies to repair damaged bone tissue has become a critical component in the field of bone tissue engineering. However, design of scaffolds using conventional fabrication techniques has limited further advancement, due to a lack of the required precision and reproducibility. To overcome these constraints, bone tissue engineers have focused on solid free-form fabrication (SFF) techniques to generate porous, fully interconnected scaffolds for bone tissue engineering applications. This paper reviews the potential application of SFF fabrication technologies for bone tissue engineering with respect to scaffold fabrication. In the near future, bone scaffolds made using SFF apparatus should become effective therapies for bone defects. PMID:24855546

Ion-beam assisted laser fabrication of sensing plasmonic nanostructures

PubMed Central

Kuchmizhak, Aleksandr; Gurbatov, Stanislav; Vitrik, Oleg; Kulchin, Yuri; Milichko, Valentin; Makarov, Sergey; Kudryashov, Sergey

2016-01-01

Simple high-performance, two-stage hybrid technique was developed for fabrication of different plasmonic nanostructures, including nanorods, nanorings, as well as more complex structures on glass substrates. In this technique, a thin noble-metal film on a dielectric substrate is irradiated by a single tightly focused nanosecond laser pulse and then the modified region is slowly polished by an accelerated argon ion (Ar+) beam. As a result, each nanosecond laser pulse locally modifies the initial metal film through initiation of fast melting and subsequent hydrodynamic processes, while the following Ar+-ion polishing removes the rest of the film, revealing the hidden topography features and fabricating separate plasmonic structures on the glass substrate. We demonstrate that the shape and lateral size of the resulting functional plasmonic nanostructures depend on the laser pulse energy and metal film thickness, while subsequent Ar+-ion polishing enables to vary height of the resulting nanostructures. Plasmonic properties of the fabricated nanostructures were characterized by dark-field micro-spectroscopy, Raman and photoluminescence measurements performed on single nanofeatures, as well as by supporting numerical calculations of the related electromagnetic near-fields and Purcell factors. The developed simple two-stage technique represents a new step towards direct large-scale laser-induced fabrication of highly ordered arrays of complex plasmonic nanostructures. PMID:26776569

Nanorobotic end-effectors: Design, fabrication, and in situ characterization

NASA Astrophysics Data System (ADS)

Fan, Zheng

Nano-robotic end-effectors have promising applications for nano-fabrication, nano-manufacturing, nano-optics, nano-medical, and nano-sensing; however, low performances of the conventional end-effectors have prevented the widespread utilization of them in various fields. There are two major difficulties in developing the end-effectors: their nano-fabrication and their advanced characterization in the nanoscale. Here we introduce six types of end-effectors: the nanotube fountain pen (NFP), the super-fine nanoprobe, the metal-filled carbon nanotube (m CNT)-based sphere-on-pillar (SOP) nanoantennas, the tunneling nanosensor, and the nanowire-based memristor. The investigations on the NFP are focused on nano-fluidics and nano-fabrications. The NFP could direct write metallic "inks" and fabricating complex metal nanostructures from 0D to 3D with a position servo control, which is critically important to future large-scale, high-throughput nanodevice production. With the help of NFP, we could fabricate the end-effectors such as super-fine nanoprobe and m CNT-based SOP nanoantennas. Those end-effectors are able to detect local flaws or characterize the electrical/mechanical properties of the nanostructure. Moreover, using electron-energy-loss-spectroscopy (EELS) technique during the operation of the SOP optical antenna opens a new basis for the application of nano-robotic end-effectors. The technique allows advanced characterization of the physical changes, such as carrier diffusion, that are directly responsible for the device's properties. As the device was coupled with characterization techniques of scanning-trasmission-electron-microscopy (STEM), the development of tunneling nanosensor advances this field of science into quantum world. Furthermore, the combined STEM-EELS technique plays an important role in our understanding of the memristive switching performance in the nanowire-based memristor. The developments of those nano-robotic end-effectors expend the study

Data Fabrication and Falsification and Empiricist Philosophy of Science

PubMed Central

Resnik, David B.

2014-01-01

Scientists have rules pertaining to data fabrication and falsification that are enforced with significant punishments, such as loss of funding, termination of employment, or imprisonment. These rules pertain to data that describe observable and unobservable entities. In this commentary I argue that scientists would not adopt rules that impose harsh penalties on researchers for data fabrication or falsification unless they believed that an aim of scientific research is to develop true theories and hypotheses about entities that exist, including unobservable ones. This argument presents a challenge for constructive empiricists, such as van Fraassen. Constructive empiricists need to be able to explain why rules pertaining to data fabrication and falsification do not threaten their philosophy of science. PMID:23982326

Data fabrication and falsification and empiricist philosophy of science.

PubMed

Resnik, David B

2014-06-01

Scientists have rules pertaining to data fabrication and falsification that are enforced with significant punishments, such as loss of funding, termination of employment, or imprisonment. These rules pertain to data that describe observable and unobservable entities. In this commentary I argue that scientists would not adopt rules that impose harsh penalties on researchers for data fabrication or falsification unless they believed that an aim of scientific research is to develop true theories and hypotheses about entities that exist, including unobservable ones. This argument presents a challenge for constructive empiricists, such as van Fraassen. Constructive empiricists need to be able to explain why rules pertaining to data fabrication and falsification do not threaten their philosophy of science.

The fit of cobalt-chromium three-unit fixed dental prostheses fabricated with four different techniques: a comparative in vitro study.

PubMed

Örtorp, Anders; Jönsson, David; Mouhsen, Alaa; Vult von Steyern, Per

2011-04-01

This study sought to evaluate and compare the marginal and internal fit in vitro of three-unit FDPs in Co-Cr made using four fabrication techniques, and to conclude in which area the largest misfit is present. An epoxy resin master model was produced. The impression was first made with silicone, and master and working models were then produced. A total of 32 three-unit Co-Cr FDPs were fabricated with four different production techniques: conventional lost-wax method (LW), milled wax with lost-wax method (MW), milled Co-Cr (MC), and direct laser metal sintering (DLMS). Each of the four groups consisted of eight FDPs (test groups). The FDPs were cemented on their cast and standardised-sectioned. The cement film thickness of the marginal and internal gaps was measured in a stereomicroscope, digital photos were taken at 12× magnification and then analyzed using measurement software. Statistical analyses were performed with one-way ANOVA and Tukey's test. Best fit based on the means (SDs) in μm for all measurement points was in the DLMS group 84 (60) followed by MW 117 (89), LW 133 (89) and MC 166 (135). Significant differences were present between MC and DLMS (p<0.05). The regression analyses presented differences within the parameters: production technique, tooth size, position and measurement point (p < 0.05). Best fit was found in the DLMS group followed by MW, LW and MC. In all four groups, best fit in both abutments was along the axial walls and in the deepest part of the chamfer preparation. The greatest misfit was present occlusally in all specimens. Copyright © 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Solid Freeform Fabrication: An Enabling Technology for Future Space Missions

NASA Technical Reports Server (NTRS)

Taminger, Karen M. B.; Hafley, Robert A.; Dicus, Dennis L.

2002-01-01

The emerging class of direct manufacturing processes known as Solid Freeform Fabrication (SFF) employs a focused energy beam and metal feedstock to build structural parts directly from computer aided design (CAD) data. Some variations on existing SFF techniques have potential for application in space for a variety of different missions. This paper will focus on three different applications ranging from near to far term to demonstrate the widespread potential of this technology for space-based applications. One application is the on-orbit construction of large space structures, on the order of tens of meters to a kilometer in size. Such structures are too large to launch intact even in a deployable design; their extreme size necessitates assembly or erection of such structures in space. A low-earth orbiting satellite with a SFF system employing a high-energy beam for high deposition rates could be employed to construct large space structures using feedstock launched from Earth. A second potential application is a small, multifunctional system that could be used by astronauts on long-duration human exploration missions to manufacture spare parts. Supportability of human exploration missions is essential, and a SFF system would provide flexibility in the ability to repair or fabricate any part that may be damaged or broken during the mission. The system envisioned would also have machining and welding capabilities to increase its utility on a mission where mass and volume are extremely limited. A third example of an SFF application in space is a miniaturized automated system for structural health monitoring and repair. If damage is detected using a low power beam scan, the beam power can be increased to perform repairs within the spacecraft or satellite structure without the requirement of human interaction or commands. Due to low gravity environment for all of these applications, wire feedstock is preferred to powder from a containment, handling, and safety

A Solder Based Self Assembly Project in an Introductory IC Fabrication Course

ERIC Educational Resources Information Center

Rao, Madhav; Lusth, John C.; Burkett, Susan L.

2015-01-01

Integrated circuit (IC) fabrication principles is an elective course in a senior undergraduate and early graduate student's curriculum. Over the years, the semiconductor industry relies heavily on students with developed expertise in the area of fabrication techniques, learned in an IC fabrication theory and laboratory course. The theory course…

Fabrication of three-dimensional scaffolds using precision extrusion deposition with an assisted cooling device.

PubMed

Hamid, Q; Snyder, J; Wang, C; Timmer, M; Hammer, J; Guceri, S; Sun, W

2011-09-01

In the field of biofabrication, tissue engineering and regenerative medicine, there are many methodologies to fabricate a building block (scaffold) which is unique to the target tissue or organ that facilitates cell growth, attachment, proliferation and/or differentiation. Currently, there are many techniques that fabricate three-dimensional scaffolds; however, there are advantages, limitations and specific tissue focuses of each fabrication technique. The focus of this initiative is to utilize an existing technique and expand the library of biomaterials which can be utilized to fabricate three-dimensional scaffolds rather than focusing on a new fabrication technique. An expanded library of biomaterials will enable the precision extrusion deposition (PED) device to construct three-dimensional scaffolds with enhanced biological, chemical and mechanical cues that will benefit tissue generation. Computer-aided motion and extrusion drive the PED to precisely fabricate micro-scaled scaffolds with biologically inspired, porosity, interconnectivity and internal and external architectures. The high printing resolution, precision and controllability of the PED allow for closer mimicry of tissues and organs. The PED expands its library of biopolymers by introducing an assisting cooling (AC) device which increases the working extrusion temperature from 120 to 250 °C. This paper investigates the PED with the integrated AC's capabilities to fabricate three-dimensional scaffolds that support cell growth, attachment and proliferation. Studies carried out in this paper utilized a biopolymer whose melting point is established to be 200 °C. This polymer was selected to illustrate the newly developed device's ability to fabricate three-dimensional scaffolds from a new library of biopolymers. Three-dimensional scaffolds fabricated with the integrated AC device should illustrate structural integrity and ability to support cell attachment and proliferation.

Fabrication of a Dipole-assisted Solid Phase Extraction Microchip for Trace Metal Analysis in Water Samples

PubMed Central

Chen, Ping-Hung; Chen, Shun-Niang; Tseng, Sheng-Hao; Deng, Ming-Jay; Lin, Yang-Wei; Sun, Yuh-Chang

2016-01-01

This paper describes a fabrication protocol for a dipole-assisted solid phase extraction (SPE) microchip available for trace metal analysis in water samples. A brief overview of the evolution of chip-based SPE techniques is provided. This is followed by an introduction to specific polymeric materials and their role in SPE. To develop an innovative dipole-assisted SPE technique, a chlorine (Cl)-containing SPE functionality was implanted into a poly(methyl methacrylate) (PMMA) microchip. Herein, diverse analytical techniques including contact angle analysis, Raman spectroscopic analysis, and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) analysis were employed to validate the utility of the implantation protocol of the C-Cl moieties on the PMMA. The analytical results of the X-ray absorption near-edge structure (XANES) analysis also demonstrated the feasibility of the Cl-containing PMMA used as an extraction medium by virtue of the dipole-ion interactions between the highly electronegative C-Cl moieties and the positively charged metal ions. PMID:27584954

A Novel Hybrid Axial-Radial Atmospheric Plasma Spraying Technique for the Fabrication of Solid Oxide Fuel Cell Anodes Containing Cu, Co, Ni, and Samaria-Doped Ceria

NASA Astrophysics Data System (ADS)

Cuglietta, Mark; Kuhn, Joel; Kesler, Olivera

2013-06-01

Composite coatings containing Cu, Co, Ni, and samaria-doped ceria (SDC) have been fabricated using a novel hybrid atmospheric plasma spraying technique, in which a multi-component aqueous suspension of CuO, Co3O4, and NiO was injected axially simultaneously with SDC injected radially in a dry powder form. Coatings were characterized for their microstructure, permeability, porosity, and composition over a range of plasma spray conditions. Deposition efficiency of the metal oxides and SDC was also estimated. Depending on the conditions, coatings displayed either layering or high levels of mixing between the SDC and metal phases. The deposition efficiencies of both feedstock types were strongly dependent on the nozzle diameter. Plasma-sprayed metal-supported solid oxide fuel cells utilizing anodes fabricated with this technique demonstrated power densities at 0.7 V as high as 366 and 113 mW/cm2 in humidified hydrogen and methane, respectively, at 800 °C.

Fabrication and characterization of the organic rectifying junctions by electrolysis

NASA Astrophysics Data System (ADS)

Karimov, Khasan; Ahmad, Zubair; Ali, Rashid; Noor, Adnan; Akmal, M.; Najeeb, M. A.; Shakoor, R. A.

2017-08-01

Unlike the conventional solution processable deposition techniques, in this study, we propose a novel and economical method for the fabrication of organic rectifying junctions. The solutions of the orange dye, copper phthalocyanine and NaCl were deposited on the surface-type interdigitated silver electrodes using electrolysis technique. Using the current-voltage (I-V) characteristics, the presence of rectifying behavior in the samples has been confirmed. This phenomenon, in principle, can be used for fabrication of the diodes, transistors and memory devices.

Application of multi-tone mask technology in photolithographic fabrication of color filter components in LCD

NASA Astrophysics Data System (ADS)

Takada, Yoshihiro; Fukui, Matoko; Sai, Tsunehiro

2008-11-01

Recent progresses in the photoresists and photolithography for LCD industry applications have been primarily driven by the following two factors: advancement in the material performances (high resolution, high contrast ratio, low dielectric constant) for higher display quality, and cost reduction in the fabrication process. Along with crucial demand for cost competitiveness by improving production efficiency, environmental consciousness has been a major priority at fabrication process design to minimize the amount of waste produced. Having said the above, integration of two or more fabrication processes into a single process by using multi-tone mask technology has been the interest of research, due to its obvious advantage of reducing fabrication processes and cost. For example, multi-tone mask technology application has been widely employed on the TFT side to reduce the different types of photomasks being used. Similar trend has been employed on the CF side as well, where application of multi-tone mask technology is being investigated to integrate fabrication of multiple CF micro-components into a single process. In this presentation, we demonstrate a new approach of fabricating photospacer and peripheral CF components (MVA protrusion, sub-photospacers) in a single integrated process through multi-tone mask technology.

Characterization techniques to predict mechanical behaviour of green ceramic bodies fabricated by ceramic microstereolithography

NASA Astrophysics Data System (ADS)

Adake, Chandrashekhar V.; Bhargava, Parag; Gandhi, Prasanna

2018-02-01

Ceramic microstereolithography (CMSL) has emerged as solid free form (SFF) fabrication technology in which complex ceramic parts are fabricated from ceramic suspensions which are formulated by dispersing ceramic particles in UV curable resins. Ceramic parts are fabricated by exposing ceramic suspension to computer controlled UV light which polymerizes resin to polymer and this polymer forms rigid network around ceramic particles. A 3-dimensional part is created by piling cured layers one over the other. These ceramic parts are used to build microelectromechanical (MEMS) devices after thermal treatment. In many cases green ceramic parts can be directly utilized to build MEMS devices. Hence characterization of these parts is essential in terms of their mechanical behaviour prior to their use in MEMS devices. Mechanical behaviour of these green ceramic parts depends on cross link density which in turn depends on chemical structure of monomer, concentrations of photoinitiator and UV energy dose. Mechanical behaviour can be determined with the aid of nanoindentation. And extent of crosslinking can be verified with the aid of DSC. FTIR characterization is used to analyse (-C=C-) double bond conversion. This paper explains characterization tools to predict the mechanical behaviour of green ceramic bodies fabricated in CMSL

Fabrication of p-type CuO thin films using chemical bath deposition technique and their solar cell applications with Si nanowires

NASA Astrophysics Data System (ADS)

Akgul, Funda Aksoy; Akgul, Guvenc

2017-02-01

Recently, CuO has attracted much interest owing to its suitable material properties, inexpensive fabrication cost and potential applications for optoelectronic devices. In this study, CuO thin films were deposited on glass substrates using chemical bath deposition technique and post-deposition annealing effect on the properties of the prepared samples were investigated. p-n heterojunction solar cells were then constructed by coating of p-type CuO films onto the vertically well-aligned n-type Si nanowires synthesized through MACE method. Photovoltaic performance of the fabricated devices were determined with current-voltage (I-V) measurements under AM 1.5 G illumination. The optimal short-circuit current density, open-circuit voltage, fill factor and power conversion efficiency were found to be 3.2 mA/cm-2, 337 mV, 37.9 and 0.45%, respectively. The observed performance clearly indicates that the investigated device structure could be a promising candidate for high-performance low-cost new-generation photovoltaic diodes.

Laser fabrication of perfect absorbers

NASA Astrophysics Data System (ADS)

Mizeikis, V.; Faniayeu, I.

2018-01-01

We describe design and characterization of electromagnetic metasurfaces consisting of sub-wavelength layers of artificially structured 3D metallic elements arranged into two-dimensional arrays. Such metasurfaces allow novel ways to control propagation, absorption, emission, and polarization state of electromagnetic waves, but their practical realization using traditional planar micro-/nano-fabrication techniques is extremely difficult at infra- red frequencies, where unit cell size must be reduced to few micrometers. We have addressed this challenge by using femtosecond direct laser write (DLW) technique as a high-resolution patterning tool for the fabrication of dielectric templates, followed by a simple metallization process. Functional metasurfaces consisting of metallic helices and vertical split-ring resonators that can be used as perfect absorbers and polarization converters at infra- red frequencies were obtained and characterized experimentally and theoretically. In the future they may find applications in narrow-band infra-red detectors and emitters, spectral filters, and combined into multi-functional, multi-layered structures.

Comparison of Fit of Dentures Fabricated by Traditional Techniques Versus CAD/CAM Technology.

PubMed

McLaughlin, J Bryan; Ramos, Van; Dickinson, Douglas P

2017-11-14

To compare the shrinkage of denture bases fabricated by three methods: CAD/CAM, compression molding, and injection molding. The effect of arch form and palate depth was also tested. Nine titanium casts, representing combinations of tapered, ovoid, and square arch forms and shallow, medium, and deep palate depths, were fabricated using electron beam melting (EBM) technology. For each base fabrication method, three poly(vinyl siloxane) impressions were made from each cast, 27 dentures for each method. Compression-molded dentures were fabricated using Lucitone 199 poly methyl methacrylate (PMMA), and injection molded dentures with Ivobase's Hybrid Pink PMMA. For CAD/CAM, denture bases were designed and milled by Avadent using their Light PMMA. To quantify the space between the denture and the master cast, silicone duplicating material was placed in the intaglio of the dentures, the titanium master cast was seated under pressure, and the silicone was then trimmed and recovered. Three silicone measurements per denture were recorded, for a total of 243 measurements. Each silicone measurement was weighed and adjusted to the surface area of the respective arch, giving an average and standard deviation for each denture. Comparison of manufacturing methods showed a statistically significant difference (p = 0.0001). Using a ratio of the means, compression molding had on average 41% to 47% more space than injection molding and CAD/CAM. Comparison of arch/palate forms showed a statistically significant difference (p = 0.023), with shallow palate forms having more space with compression molding. The ovoid shallow form showed CAD/CAM and compression molding had more space than injection molding. Overall, injection molding and CAD/CAM fabrication methods produced equally well-fitting dentures, with both having a better fit than compression molding. Shallow palates appear to be more affected by shrinkage than medium or deep palates. Shallow ovoid arch forms appear to benefit from

Fabrication and characterization of an egg-shaped hollow fiber microbubble

NASA Astrophysics Data System (ADS)

Wang, Guanjun; Ruan, Yinlan; Jia, Pinggang; Gui, Zhiguo; Zhang, Pengcheng; Wang, Chao; Liu, Shen; Liao, Changrui; Yin, Guolu; Wang, Yiping

2017-04-01

In this paper, an egg-shaped microbubble is proposed and analyzed firstly, which is fabricated by the pressure-assisted arc discharge technique. By tailoring the arc parameters and the position of glass tube during the fabrication process, the thinnest wall of the fabricated microbubble could reach to the level of 873nm. Then, the fiber Fabry-Perot interference technique is used to analyze the deformation of microbubble that under different filling pressures. It is found that the endface of micro-bubble occurs compression when the inner pressure increasing from 4Kpa to 1400KPa. And the pressure sensitivity of such egg-shaped microbubble sample is14.3pm/Kpa. Results of this study could be good reference for developing new pressure sensors, etc.

TECHNIQUES FOR THE FABRICATION OF GEOMEMBRANE FILLED SEAMS

EPA Science Inventory

Geomembranes employed to overlay the excavation for landfills must be seamed together on-site at the landfill. To ensure the integrity of the containment system of the landfill, these sheets or blankets must be carefully seamed. Present methods in common use are: extrusion fil...

Mechanical and Tear Properties of Fabric/Film Laminates

NASA Technical Reports Server (NTRS)

Said, Magdi A.

1998-01-01

Films reinforced with woven fabrics are being considered for the development of a material suitable for long duration scientific balloons under a program managed by the National Aeronautics and Space Administration (NASA). Recently developed woven fabrics provide a relatively high strength to weight ratio compared to standard homogenous films. Woven fabrics also have better crack propagation resistance and rip stop capabilities when compared to homogenous lightweight, high strength polymeric films such as polyester and nylon. If joining is required, such as in the case of scientific balloons, woven fabrics have the advantage over polymeric thin films to utilize traditional textile methods as well as other techniques including hot sealing, adhesion, and ultrasonic means. Woven fabrics, however, lack the barrier properties required for helium filled scientific balloons, therefore lamination with homogenous films is required to provide the gas barrier capabilities required in these applications.

Hyperbranched polymer functional cotton fabric for its in situ deposition of silver nanoparticles

NASA Astrophysics Data System (ADS)

Zhang, Desuo; Jiao, Chenlu; Xiong, Jiaqing; Lin, Hong; Chen, Yuyue

2015-06-01

This paper describes a strategy of fabricating silver nanoparticles (Ag NPs) finished cotton fabric through in situ synthesis method. In order to endow the cotton fabric with the capability of in situ synthesis of Ag NPs without any other reagents, an amino-terminated hyperbranched polymer (HBP-NH2) was employed to functionalize the cotton fabric. To this end, cotton fabric was oxidized to generate aldehyde groups and then HBP-NH2 was grafted on the oxidized cotton fabric based on the reaction between amino groups and aldehyde groups. Due to numerous imino and amino groups in the polymer and its special three-dimensional structure, the functional cotton fabric could take initiative to capture and reduce silver ions, control the formation of Ag NPs and fix them on the cotton fabric. The sizes of Ag NPs in situ synthesized on cotton fibers range from 4 to 10 nm. The prepared Ag NPs finished cotton fabric has excellent laundering durability.

Heat sealable, flame and abrasion resistant coated fabric

NASA Technical Reports Server (NTRS)

Tschirch, R. P.; Sidman, K. R. (Inventor)

1983-01-01

Flame retardant, abrasion resistant elastomeric compositions are disclosed which are comprised of thermoplastic polyurethane polymer and flame retarding amounts of a filler selected from decabromodiphenyloxide and antimony oxide in a 3:1 weight ratio, and decabromodiphenyloxide, antimony oxide, and ammonium polyphosphate in a 3:1:3 weight ratio respectively. Heat sealable coated fabrics employing such elastomeric compositions as coating film are produced by dissolving the elastomeric composition to form a solution, casting the solution onto a release paper and drying it to form an elastomeric film. The film is then bonded to a woven, knitted, or felted fabric.

Fabrication and Compressive Properties of Low to Medium Porosity Closed-Cell Porous Aluminum Using PMMA Space Holder Technique

PubMed Central

Jamal, Nur Ayuni; Tan, Ai Wen; Yusof, Farazila; Katsuyoshi, Kondoh; Hisashi, Imai; Singh, S.; Anuar, Hazleen

2016-01-01

In recent years, closed-cell porous Aluminum (Al) has drawn increasing attention, particularly in the applications requiring reduced weight and energy absorption capability such as in the automotive and aerospace industries. In the present work, porous Al with closed-cell structure was successfully fabricated by powder metallurgy technique using PMMA as a space holder. The effects of the amount of PMMA powder on the porosity, density, microstructure and compressive behaviors of the porous specimens were systematically evaluated. The results showed that closed-cell porous Al having different porosities (12%–32%) and densities (1.6478 g/cm3, 1.5125 g/cm3 and 1.305 g/cm3) could be produced by varying the amount of PMMA (20–30 wt %). Meanwhile, the compressive behavior results demonstrated that the plateau stress decreased and the energy absorption capacity increased with increasing amount of PMMA. However, the maximum energy absorption capacity was achieved in the closed-cell porous Al with the addition of 25 wt % PMMA. Therefore, fabrication of closed-cell porous Al using 25 wt % PMMA is considered as the optimal condition in the present study since the resultant closed-cell porous Al possessed good combinations of porosity, density and plateau stress, as well as energy absorption capacity. PMID:28773377

Fabrication and performance of Li4Ti5O12/C Li-ion battery electrodes using combined double flame spray pyrolysis and pressure-based lamination technique

NASA Astrophysics Data System (ADS)

Gockeln, Michael; Pokhrel, Suman; Meierhofer, Florian; Glenneberg, Jens; Schowalter, Marco; Rosenauer, Andreas; Fritsching, Udo; Busse, Matthias; Mädler, Lutz; Kun, Robert

2018-01-01

Reduction of lithium-ion battery (LIB) production costs is inevitable to make the use of LIB technology more viable for applications such as electric vehicles or stationary storage. To meet the requirements in today's LIB cost efficiency, our current research focuses on an alternative electrode fabrication method, characterized by a combination of double flame spray pyrolysis and lamination technique (DFSP/lamination). In-situ carbon coated nano-Li4Ti5O12 (LTO/C) was synthesized using versatile DFSP. The as-prepared composite powder was then directly laminated onto a conductive substrate avoiding the use of any solvent or binder for electrode preparation. The influence of lamination pressures on the microstructure and electrochemical performance of the electrodes was also investigated. Enhancements in intrinsic electrical conductivity were found for higher lamination pressures. Capacity retention of highest pressurized DFSP/lamination-prepared electrode was 87.4% after 200 dis-/charge cycles at 1C (vs. Li). In addition, LTO/C material prepared from the double flame spray pyrolysis was also used for fabricating electrodes via doctor blading technique. Laminated electrodes obtained higher specific discharge capacities compared to calendered and non-calendered blade-casted electrodes due to superior microstructural properties. Such a fast and industrially compelling integrative DFSP/lamination tool could be a prosperous, next generation technology for low-cost LIB electrode fabrication.

Biocompatible cephalosporin-hydroxyapatite-poly(lactic-co-glycolic acid)-coatings fabricated by MAPLE technique for the prevention of bone implant associated infections

NASA Astrophysics Data System (ADS)

Rădulescu, Dragoş; Grumezescu, Valentina; Andronescu, Ecaterina; Holban, Alina Maria; Grumezescu, Alexandru Mihai; Socol, Gabriel; Oprea, Alexandra Elena; Rădulescu, Marius; Surdu, Adrian; Trusca, Roxana; Rădulescu, Radu; Chifiriuc, Mariana Carmen; Stan, Miruna S.; Constanda, Sabrina; Dinischiotu, Anca

2016-06-01

In this study we aimed to obtain functionalized thin films based on hydroxyapatite/poly(lactic-co-glycolic acid) (HAp/PLGA) containing ceftriaxone/cefuroxime antibiotics (ATBs) deposited by Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique. The prepared thin films were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-Ray diffraction (XRD), selected area electron diffraction (SAED), and infra red (IR) analysis. HAp/PLGA/ATBs thin films sustained the growth of human osteoblasts, proving their good biocompatibility. The microscopic evaluation and the culture-based quantitative assay of the E. coli biofilm development showed that the thin films inhibited the initial step of microbial attachment as well as the subsequent colonization and biofilm development on the respective surfaces. This study demonstrates that MAPLE technique could represent an appealing technique for the fabrication of antibiotics-containing polymeric implant coatings. The bioevaluation results recommend this type of surfaces for the prevention of bone implant microbial contamination and for the enhanced stimulation of the implant osseointegration process.

Nanoporous Metallic Networks: Fabrication, Optical Properties, and Applications.

PubMed

Ron, Racheli; Haleva, Emir; Salomon, Adi

2018-05-17

Nanoporous metallic networks are a group of porous materials made of solid metals with suboptical wavelength sizes of both particles and voids. They are characterized by unique optical properties, as well as high surface area and permeability of guest materials. As such, they attract a great focus as novel materials for photonics, catalysis, sensing, and renewable energy. Their properties together with the ability for scaling-up evoke an increased interest also in the industrial field. Here, fabrication techniques of large-scale metallic networks are discussed, and their interesting optical properties as well as their applications are considered. In particular, the focus is on disordered systems, which may facilitate the fabrication technique, yet, endow the three-dimensional (3D) network with distinct optical properties. These metallic networks bridge the nanoworld into the macroscopic world, and therefore pave the way to the fabrication of innovative materials with unique optoelectronic properties. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Investigate the electrical and thermal properties of the low temperature resistant silver nanowire fabricated by two-beam laser technique

NASA Astrophysics Data System (ADS)

He, Gui-Cang; Dong, Xian-Zi; Liu, Jie; Lu, Heng; Zhao, Zhen-Sheng

2018-05-01

A two-beam laser fabrication technique is introduced to fabricate the single silver nanowire (AgNW) on polyethylene terephthalate (PET) substrate. The resistivity of the AgNW is (1.31 ± 0.05) × 10-7 Ω·m, which is about 8 times of the bulk silver resistivity (1.65 × 10-8 Ω·m). The AgNW electrical resistance is measured in temperature range of 10-300 K and fitted with the Bloch-Grüneisen formula. The fitting results show that the residue resistance is 153 Ω, the Debye temperature is 210 K and the electron-phonon coupling constant is (5.72 ± 0.24) × 10-8 Ω·m. Due to the surface scattering, the Debye temperature and the electron-phonon coupling constant are lower than those of bulk silver, and the residue resistance is bigger than that of bulk silver. Thermal conductivity of the single AgNW is calculated in the corresponding temperature range, which is the biggest at the temperature approaching the Debye temperature. The AgNW on PET substrate is the low temperature resistance material and is able to be operated stably at such a low temperature of 10 K.

Modified fabrication techniques lead to improved centrifugal blood pump performance.

PubMed

Pacella, J J; Goldstein, A H; Magovern, G J; Clark, R F

1994-01-01

The authors are developing an implantable centrifugal blood pump for short- and medium-term (1-6 months) left ventricular assist. They hypothesized that the application of result dependent modifications to this pump would lead to overall improved performance in long-term implantation studies. Essential requirements for pump operation, such as durability and resistance to clot formation, have been achieved through specialized fabrication techniques. The antithrombogenic character of the pump has been improved through coating at the cannula-housing interfaces and the baffle seal, and through changing the impeller blade material from polysulfone to pyrolytic carbon. The electronic components of the pump have been sealed for implantable use through specialized processes of dipping and potting, and the surfaces of the internal pump components have been treated to increase durability. The device has demonstrated efficacy in five chronic sheep implantation studies of 14, 10, 28, 35, and 154 day duration. Post mortem findings from the 14 day experiment showed stable fibrin entangled around the impeller shaft and blades. After pump modification, autopsy findings of the 10 day study showed no evidence of clot. Additionally, the results of the 28 day experiment showed only a small (2.0 mm) ring of fibrin at the shaft-seal interface. In the 35 and 154 day experiments, redesign of the stators have resulted in improved motor corrosion resistance. The 35 day study showed a small, 0.5 mm wide fibrin deposit at the lip seal, but no motor failure. In the 154 day experiment, the motor failed because of stator fluid corrosion, while the explanted pump was devoid of thrombus. Based on these findings, the authors believe that these pump refinements have contributed significantly to improvements in durability and resistance to clot formation.

Thermoelectric Device Fabrication Using Thermal Spray and Laser Micromachining

NASA Astrophysics Data System (ADS)

Tewolde, Mahder; Fu, Gaosheng; Hwang, David J.; Zuo, Lei; Sampath, Sanjay; Longtin, Jon P.

2016-02-01

Thermoelectric generators (TEGs) are solid-state devices that convert heat directly into electricity. They are used in many engineering applications such as vehicle and industrial waste-heat recovery systems to provide electrical power, improve operating efficiency and reduce costs. State-of-art TEG manufacturing is based on prefabricated materials and a labor-intensive process involving soldering, epoxy bonding, and mechanical clamping for assembly. This reduces their durability and raises costs. Additive manufacturing technologies, such as thermal spray, present opportunities to overcome these challenges. In this work, TEGs have been fabricated for the first time using thermal spray technology and laser micromachining. The TEGs are fabricated directly onto engineering component surfaces. First, current fabrication techniques of TEGs are presented. Next, the steps required to fabricate a thermal spray-based TEG module, including the formation of the metallic interconnect layers and the thermoelectric legs are presented. A technique for bridging the air gap between two adjacent thermoelectric elements for the top layer using a sacrificial filler material is also demonstrated. A flat 50.8 mm × 50.8 mm TEG module is fabricated using this method and its performance is experimentally characterized and found to be in agreement with expected values of open-circuit voltage based on the materials used.

Direct ink write fabrication of transparent ceramic gain media

NASA Astrophysics Data System (ADS)

Jones, Ivy Krystal; Seeley, Zachary M.; Cherepy, Nerine J.; Duoss, Eric B.; Payne, Stephen A.

2018-01-01

Solid-state laser gain media based on the garnet structure with two spatially distinct but optically contiguous regions have been fabricated. Transparent gain media comprised of a central core of Y2.97Nd0.03Al5.00O12.00 (Nd:YAG) and an undoped cladding region of Y3Al5O12 (YAG) were fabricated by direct ink write and transparent ceramic processing. Direct ink write (DIW) was employed to form the green body, offering a general route to preparing functionally structured solid-state laser gain media. Fully-dense transparent optical ceramics in a "top hat" geometry with YAG/Nd:YAG have been fabricated by DIW methods with optical scatter at 1064 nm of <3%/cm.

Direct ink write fabrication of transparent ceramic gain media

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jones, Ivy Krystal; Seeley, Zachary M.; Cherepy, Nerine J.

Solid-state laser gain media based on the garnet structure with two spatially distinct but optically contiguous regions have been fabricated. Transparent gain media comprised of a central core of Y 2.97Nd 0.03Al 5.00O 12.00 (Nd:YAG) and an undoped cladding region of Y 3Al 5O 12 (YAG) were fabricated by direct ink write and transparent ceramic processing. Direct ink write (DIW) was employed to form the green body, offering a general route to preparing functionally structured solid-state laser gain media. Lastly, fully-dense transparent optical ceramics in a “top hat” geometry with YAG/Nd:YAG have been fabricated by DIW methods with optical scattermore » at 1064 nm of <3%/cm.« less

Direct ink write fabrication of transparent ceramic gain media

DOE PAGES

Jones, Ivy Krystal; Seeley, Zachary M.; Cherepy, Nerine J.; ...

2018-11-06

Solid-state laser gain media based on the garnet structure with two spatially distinct but optically contiguous regions have been fabricated. Transparent gain media comprised of a central core of Y 2.97Nd 0.03Al 5.00O 12.00 (Nd:YAG) and an undoped cladding region of Y 3Al 5O 12 (YAG) were fabricated by direct ink write and transparent ceramic processing. Direct ink write (DIW) was employed to form the green body, offering a general route to preparing functionally structured solid-state laser gain media. Lastly, fully-dense transparent optical ceramics in a “top hat” geometry with YAG/Nd:YAG have been fabricated by DIW methods with optical scattermore » at 1064 nm of <3%/cm.« less

Fabrication and characterization of ordered arrays of nanostructures

NASA Astrophysics Data System (ADS)

Larson, Preston

2005-11-01

Nanostructures are currently of great interest because of their unique properties and potential applications in a wide range of areas such as opto-electronic and biomedical devices. Current research in nanotechnology involves fabrication and characterization of these structures, as well as theoretical and experimental studies to explore their unique and novel properties. Not only do nanostructures have the potential to be both evolutionary (state-of-the-art ICs have more and more features on the nanoscale) but revolutionary (quantum computing) as well. In this thesis, a combination of bottom-up and top-down approaches is explored to fabricate ordered arrays of nanostrucutures. The bottom-up approach involves the growth of self-organized porous anodic aluminum oxide (AAO) films. AAO films consist of a well ordered hexagonal array of close-packed pores with diameters and spacings ranging from around 5 to 500 nm. Via a top-down approach, these AAO films are then used as masks or templates to fabricate ordered arrays of nanostructures (i.e. dots, holes, meshes, pillars, rings, etc.) of various materials using conventional deposition and/or etching techniques. Using AAO films as masks allows a simple and economical method to fabricate arrays of structures with nano-scale dimensions. Furthermore, they allow the fabrication of large areas (many millimeters on a side) of highly uniform and well-ordered arrays of nanostructures, a crucial requirement for most characterization techniques and applications. Characterization of these nanostructures using various techniques (electron microscopy, atomic force microscopy, UV-Vis absorption spectroscopy, photoluminescence, capacitance-voltage measurements, magnetization hysteresis curves, etc.) will be presented. Finally, these structures provide a unique opportunity to determine the single and collective properties of nanostructure arrays and will have various future applications including but not limited to: data storage, light

Supersoft lithography: Candy-based fabrication of soft silicone microstructures

PubMed Central

Moraes, Christopher; Labuz, Joseph M.; Shao, Yue; Fu, Jianping; Takayama, Shuichi

2015-01-01

We designed a fabrication technique able to replicate microstructures in soft silicone materials (E < 1 kPa). Sugar-based ‘hard candy’ recipes from the confectionery industry were modified to be compatible with silicone processing conditions, and used as templates for replica molding. Microstructures fabricated in soft silicones can then be easily released by dissolving the template in water. We anticipate that this technique will be of particular importance in replicating physiologically soft, microstructured environments for cell culture, and demonstrate a first application in which intrinsically soft microstructures are used to measure forces generated by fibroblast-laden contractile tissues. PMID:26245893

Supersoft lithography: candy-based fabrication of soft silicone microstructures.

PubMed

Moraes, Christopher; Labuz, Joseph M; Shao, Yue; Fu, Jianping; Takayama, Shuichi

2015-01-01

We designed a fabrication technique able to replicate microstructures in soft silicone materials (E < 1 kPa). Sugar-based 'hard candy' recipes from the confectionery industry were modified to be compatible with silicone processing conditions, and used as templates for replica molding. Microstructures fabricated in soft silicones can then be easily released by dissolving the template in water. We anticipate that this technique will be of particular importance in replicating physiologically soft, microstructured environments for cell culture, and demonstrate a first application in which intrinsically soft microstructures are used to measure forces generated by fibroblast-laden contractile tissues.

Net shape fabrication of Alpha Silicon Carbide turbine components

NASA Technical Reports Server (NTRS)

Storm, R. S.

1982-01-01

Development of Alpha Silicon Carbide components by net shape fabrication techniques has continued in conjunction with several turbine engine programs. Progress in injection molding of simple parts has been extended to much larger components. Turbine rotors fabricated by a one piece molding have been successfully spin tested above design speeds. Static components weighing up to 4.5 kg and 33 cc in diameter have also been produced using this technique. Use of sintering fixtures significantly improves dimensional control. A new Si-SiC composite material has also been developed with average strengths up to 1000 MPa (150 ksi) at 1200 C.

Proceedings of the twelfth target fabrication specialists` meeting

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1999-04-01

Research in fabrication for inertial confinement fusion (ICF) comprises at least three broad categories: targets for high energy density physics on existing drivers, ignition capsule fabrication, and cryogenic fuel layer formation. The latter two are being pursued primarily for the National Ignition Facility (NIF). Scientists from over 14 laboratories, universities, and businesses contributed over 100 papers on all aspects of ICF target fabrication. The NIF is well along in construction and photos of poured concrete and exposed steel added to the technical excitement. It was clear from the meeting that there has been significant progress toward the fabrication of anmore » ignition target for NIF and that new techniques are resulting in higher quality targets for high energy density research.« less

Comparison of the Effect of Dentin Bonding, Dentin Sealing Agents on the Microleakage of Provisional Crowns Fabricated with Direct and Indirect Technique-An Invitro Study

PubMed Central

Muthukumar, B; Kumar, M Vasantha

2015-01-01

Background Postoperative sensitivity after temporization is a common complaint in Fixed Partial Denture patients. It is caused by weak and ill fitting temporary restorations which results in microleakage. This can be controlled by providing good temporary restorations and by coating the exposed dentinal tubules of the prepared tooth with dentin bonding agent or dental varnish. Aim The purpose of the study was to determine the effect of dentin-bonding, dentin sealing agents on the microleakage of temporary crowns made by tooth colored auto polymerizing resin fabricated with direct and indirect technique. Materials and Methods Thirty premolar and molar human teeth were collected which were extracted recently was used for the study. The teeth were marked and divided into 3 groups each containing 10 nos. They were individually mounted with self-cure acrylic resin. It was then mounted on a milling machine and crown preparations done. Temporary crowns were fabricated by direct and indirect method with two types of materials. In group A (Control group), the temporary crowns fabricated with both direct and indirect method were cemented directly with temporary luting cement. In group B dentine-bonding agent (solobond M) was applied once to the prepared surface of each tooth specimen before the cementation of temporary crowns where as in case of group C a single layer of dental varnish is applied prior to crown cementation. The entire specimens were immersed in 1% methylene blue and allowed to undergo thermal treatment. It was then sectioned in a hard tissue microtome. Each section was evaluated for dye penetration into the dentin tubules by comparing it with a visual scale. Statistical Analysis SPSS Version 13 software was used for non-parametric data analysis by a qualified statistician. P-values less than 0.05 (p-value<0.05) were considered to be statistically significant. Results Group B (Dentin Bonding Agent) specimens cemented with crowns fabricated in direct technique

Fiber Bragg grating fabrication for the implementation of sensors in the electronics and optoelectronics laboratory at BUAP

NASA Astrophysics Data System (ADS)

Bracamontes Rodríguez, Y. E.; Beltrán Pérez, G.; Castillo Mixcóatl, J.; Muñoz Aguirre, S.

2011-09-01

Fiber Bragg gratings (FBG) are important optical devices since they have been quite successful not only in the field of communications but also in sensor systems and optical fiber lasers. In the sensors area they are generally used as detection elements for different physical parameters such as temperature, strain, flow, etc. In the electronics and optoelectronics laboratory at Benemérita Universidad Autónoma de Puebla (LEyO-BUAP), there are already experimental setups of sensors as well as laser systems, where FBGs are fundamental elements for their adequate performance. However, these FBGs are commercial devices and they present limited characteristics in their transmission profiles, bandwidth and reflectivity. On the other hand, in some occasions, the delivery time from the fabricant to the customer is quite long. Therefore, it is important for LEyO to implement a system to fabricate this kind of devices, which would mean LEyO independence in the technological development. In this work, results of FBGs fabrication based on the phase mask technique are presented. Such mask is optimized for UV and it has a period of 1060 nm. A Nd:YAG pulsed laser with a 5 ns pulse length and an energy of 40 mJ was used as the UV source employing the 4th harmonic generation to obtain a 266 nm wavelength. Ge-doped fiber was used to fabricate the devices.

Technique for enhancing the power output of an electrostatic generator employing parametric resonance

DOEpatents

Post, Richard F.

2016-02-23

A circuit-based technique enhances the power output of electrostatic generators employing an array of axially oriented rods or tubes or azimuthal corrugated metal surfaces for their electrodes. During generator operation, the peak voltage across the electrodes occurs at an azimuthal position that is intermediate between the position of minimum gap and maximum gap. If this position is also close to the azimuthal angle where the rate of change of capacity is a maximum, then the highest rf power output possible for a given maximum allowable voltage at the minimum gap can be attained. This rf power output is then coupled to the generator load through a coupling condenser that prevents suppression of the dc charging potential by conduction through the load. Optimized circuit values produce phase shifts in the rf output voltage that allow higher power output to occur at the same voltage limit at the minimum gap position.

Note: Progress on the use of MgB2 superconducting joint technique for the development of MgB2 magnets for magnetic resonance imaging (MRI).

PubMed

Kim, Y G; Song, J B; Kim, J C; Kim, J M; Yoo, B H; Yun, S B; Hwang, D Y; Lee, H G

2017-08-01

This note presents a superconducting joint technique for the development of MgB 2 magnetic resonance imaging (MRI) magnets. The MgB 2 superconducting joint was fabricated by a powder processing method using Mg and B powders to establish a wire-bulk-wire connection. The joint resistance measured using a field-decay method was <10 -14 Ω, demonstrating that the proposed joint technique could be employed for developing "next-generation" MgB 2 MRI magnets operating in the persistent current mode.

Rapid Fabricating Technique for Multi-Layered Human Hepatic Cell Sheets by Forceful Contraction of the Fibroblast Monolayer

PubMed Central

Sakai, Yusuke; Koike, Makiko; Hasegawa, Hideko; Yamanouchi, Kosho; Soyama, Akihiko; Takatsuki, Mitsuhisa; Kuroki, Tamotsu; Ohashi, Kazuo; Okano, Teruo; Eguchi, Susumu

2013-01-01

Cell sheet engineering is attracting attention from investigators in various fields, from basic research scientists to clinicians focused on regenerative medicine. However, hepatocytes have a limited proliferation potential in vitro, and it generally takes a several days to form a sheet morphology and multi-layered sheets. We herein report our rapid and efficient technique for generating multi-layered human hepatic cell (HepaRG® cell) sheets using pre-cultured fibroblast monolayers derived from human skin (TIG-118 cells) as a feeder layer on a temperature-responsive culture dish. Multi-layered TIG-118/HepaRG cell sheets with a thick morphology were harvested on day 4 of culturing HepaRG cells by forceful contraction of the TIG-118 cells, and the resulting sheet could be easily handled. In addition, the human albumin and alpha 1-antitrypsin synthesis activities of TIG-118/HepaRG cells were approximately 1.2 and 1.3 times higher than those of HepaRG cells, respectively. Therefore, this technique is considered to be a promising modality for rapidly fabricating multi-layered human hepatocyte sheets from cells with limited proliferation potential, and the engineered cell sheet could be used for cell transplantation with highly specific functions. PMID:23923035

Rapid fabricating technique for multi-layered human hepatic cell sheets by forceful contraction of the fibroblast monolayer.

PubMed

Sakai, Yusuke; Koike, Makiko; Hasegawa, Hideko; Yamanouchi, Kosho; Soyama, Akihiko; Takatsuki, Mitsuhisa; Kuroki, Tamotsu; Ohashi, Kazuo; Okano, Teruo; Eguchi, Susumu

2013-01-01

Cell sheet engineering is attracting attention from investigators in various fields, from basic research scientists to clinicians focused on regenerative medicine. However, hepatocytes have a limited proliferation potential in vitro, and it generally takes a several days to form a sheet morphology and multi-layered sheets. We herein report our rapid and efficient technique for generating multi-layered human hepatic cell (HepaRG® cell) sheets using pre-cultured fibroblast monolayers derived from human skin (TIG-118 cells) as a feeder layer on a temperature-responsive culture dish. Multi-layered TIG-118/HepaRG cell sheets with a thick morphology were harvested on day 4 of culturing HepaRG cells by forceful contraction of the TIG-118 cells, and the resulting sheet could be easily handled. In addition, the human albumin and alpha 1-antitrypsin synthesis activities of TIG-118/HepaRG cells were approximately 1.2 and 1.3 times higher than those of HepaRG cells, respectively. Therefore, this technique is considered to be a promising modality for rapidly fabricating multi-layered human hepatocyte sheets from cells with limited proliferation potential, and the engineered cell sheet could be used for cell transplantation with highly specific functions.

Fabrication of Josephson Junction without shadow evaporation

NASA Astrophysics Data System (ADS)

Wu, Xian; Ku, Hsiangsheng; Long, Junling; Pappas, David

We developed a new method of fabricating Josephson Junction (Al/AlOX/Al) without shadow evaporation. Statistics from room temperature junction resistance and measurement of qubits are presented. Unlike the traditional ``Dolan Bridge'' technique, this method requires two individual lithographies and straight evaporations of Al. Argon RF plasma is used to remove native AlOX after the first evaporation, followed by oxidation and second Al evaporation. Junction resistance measured at room temperature shows linear dependence on Pox (oxidation pressure), √{tox} (oxidation time), and inverse proportional to junction area. We have seen 100% yield of qubits made with this method. This method is promising because it eliminates angle dependence during Junction fabrication, facilitates large scale qubits fabrication.

One-dimensional, two-dimensional, and three-dimensional photonic crystals fabricated with interferometric techniques on ultrafine-grain silver halide emulsions

NASA Astrophysics Data System (ADS)

Ulibarrena, Manuel; Carretero, Luis; Acebal, Pablo; Madrigal, Roque; Blaya, Salvador; Fimia, Antonio

2004-09-01

Holographic techniques have been used for manufacturing multiple band one-dimensional, two-dimensional, and three-dimensional photonic crystals with different configurations, by multiplexing reflection and transmission setups on a single layer of holographic material. The recording material used for storage is an ultra fine grain silver halide emulsion, with an average grain size around 20 nm. The results are a set of photonic crystals with the one-dimensional, two-dimensional, and three-dimensional index modulation structure consisting of silver halide particles embedded in the gelatin layer of the emulsion. The characterisation of the fabricated photonic crystals by measuring their transmission band structures has been done and compared with theoretical calculations.

Fabrication of thermal-resistant gratings for high-temperature measurements using geometric phase analysis.

PubMed

Zhang, Q; Liu, Z; Xie, H; Ma, K; Wu, L

2016-12-01

Grating fabrication techniques are crucial to the success of grating-based deformation measurement methods because the quality of the grating will directly affect the measurement results. Deformation measurements at high temperatures entail heating and, perhaps, oxidize the grating. The contrast of the grating lines may change during the heating process. Thus, the thermal-resistant capability of the grating becomes a point of great concern before taking measurements. This study proposes a method that combines a laser-engraving technique with the processes of particle spraying and sintering for fabricating thermal-resistant gratings. The grating fabrication technique is introduced and discussed in detail. A numerical simulation with a geometric phase analysis (GPA) is performed for a homogeneous deformation case. Then, the selection scheme of the grating pitch is suggested. The validity of the proposed technique is verified by fabricating a thermal-resistant grating on a ZrO 2 specimen and measuring its thermal strain at high temperatures (up to 1300 °C). Images of the grating before and after deformation are used to obtain the thermal-strain field by GPA and to compare the results with well-established reference data. The experimental results indicate that this proposed technique is feasible and will offer good prospects for further applications.

[A new method of fabricating photoelastic model by rapid prototyping].

PubMed

Fan, Li; Huang, Qing-feng; Zhang, Fu-qiang; Xia, Yin-pei

2011-10-01

To explore a novel method of fabricating the photoelastic model using rapid prototyping technique. A mandible model was made by rapid prototyping with computerized three-dimensional reconstruction, then the photoelastic model with teeth was fabricated by traditional impression duplicating and mould casting. The photoelastic model of mandible with teeth, which was fabricated indirectly by rapid prototyping, was very similar to the prototype in geometry and physical parameters. The model was of high optical sensibility and met the experimental requirements. Photoelastic model of mandible with teeth indirectly fabricated by rapid prototyping meets the photoelastic experimental requirements well.

Silicon carbide semiconductor device fabrication and characterization

NASA Technical Reports Server (NTRS)

Davis, R. F.; Das, K.

1990-01-01

A number of basic building blocks i.e., rectifying and ohmic contacts, implanted junctions, MOS capacitors, pnpn diodes and devices, such as, MESFETs on both alpha and beta SiC films were fabricated and characterized. Gold forms a rectifying contact on beta SiC. Since Au contacts degrade at high temperatures, these are not considered to be suitable for high temperature device applications. However, it was possible to utilize Au contact diodes for electrically characterizing SiC films. Preliminary work indicates that sputtered Pt or Pt/Si contacts on beta SiC films are someways superior to Au contacts. Sputtered Pt layers on alpha SiC films form excellent rectifying contacts, whereas Ni layers following anneal at approximately 1050 C provide an ohmic contact. It has demonstrated that ion implantation of Al in substrates held at 550 C can be successfully employed for the fabrication of rectifying junction diodes. Feasibility of fabricating pnpn diodes and platinum gated MESFETs on alpha SiC films was also demonstrated.

Simplified Fabrication of Helical Copper Antennas

NASA Technical Reports Server (NTRS)

Petro, Andrew

2006-01-01

A simplified technique has been devised for fabricating helical antennas for use in experiments on radio-frequency generation and acceleration of plasmas. These antennas are typically made of copper (for electrical conductivity) and must have a specific helical shape and precise diameter.

Local electrophoretic deposition using a nanopipette for micropillar fabrication

NASA Astrophysics Data System (ADS)

Iwata, Futoshi; Metoki, Junya

2017-12-01

A novel and simple technique was developed for the fabrication of micropillars using a nanopipette that is a tapered glass capillary with a micrometer-sized aperture at the tip. The nanopipette was filled with a colloidal solution that included metal nanoparticles. Its tip was put in contact with a substrate, and the substrate was moved downward for continuous deposition of the metal colloidal solution to form micropillars. To improve fabrication reproducibility, the amount of Au colloidal solution deposited was controlled by a feedback loop that maintained a predefined constant current during electrophoretic deposition. The stiffness of the fabricated micropillars was evaluated by applying a loading force using a microcantilever under scanning electron microscopy. The Young’s modulus of the fabricated pillars was measured to be in the range of 7.7-14.8 GPa, depending on the fabrication parameters of the predefined current and fabrication speed.

Design of fabric preforms for double diaphragm forming

NASA Technical Reports Server (NTRS)

Luby, Steven; Bernardon, Edward

1992-01-01

Resin Transfer Molding (RTM) has the potential of becoming one of the most cost effective ways of producing composite structures since the raw materials used, resin and dry fabric, are less costly than prepregs. Unfortunately these low material costs are offset by the high labor costs incurred to layup the dry fabric into 3D shapes. To reduce the layup costs, double diaphragm forming is being investigated as a potential technique for creating a complex 3D preform from a simple flat layup. As part of our effort to develop double diaphragm forming into a production capable process, we have undertaken a series of experiments to investigate the interactions between process parameters, mold geometry, fabric weave, tow size, and the quality of the formed part. The results of these tests will be used to determine the forming geometry limitations of double diaphragm forming and to characterize the formability of fabric configurations. An important part of this work was the development of methods to measure and analyze fiber orientations, deformation angles, tow spreading, and shape conformation of the formed parts. This paper will describe the methods used to mark plies, the double diaphragm forming process, the techniques used to measure the formed parts, and the calculation of the parameters of interest. The results can be displayed as 3D contour plots. These experimental results have also been used to verify and improve a computer model which simulates the draping of fabrics over 3D mold shapes.

Design, fabrication and testing of hierarchical micro-optical structures and systems

NASA Astrophysics Data System (ADS)

Cannistra, Aaron Thomas

Micro-optical systems are becoming essential components in imaging, sensing, communications, computing, and other applications. Optically based designs are replacing electronic, chemical and mechanical systems for a variety of reasons, including low power consumption, reduced maintenance, and faster operation. However, as the number and variety of applications increases, micro-optical system designs are becoming smaller, more integrated, and more complicated. Micro and nano-optical systems found in nature, such as the imaging systems found in many insects and crustaceans, can have highly integrated optical structures that vary in size by orders of magnitude. These systems incorporate components such as compound lenses, anti-reflective lens surface structuring, spectral filters, and polarization selective elements. For animals, these hybrid optical systems capable of many optical functions in a compact package have been repeatedly selected during the evolutionary process. Understanding the advantages of these designs gives motivation for synthetic optical systems with comparable functionality. However, alternative fabrication methods that deviate from conventional processes are needed to create such systems. Further complicating the issue, the resulting device geometry may not be readily compatible with existing measurement techniques. This dissertation explores several nontraditional fabrication techniques for optical components with hierarchical geometries and measurement techniques to evaluate performance of such components. A micro-transfer molding process is found to produce high-fidelity micro-optical structures and is used to fabricate a spectral filter on a curved surface. By using a custom measurement setup we demonstrate that the spectral filter retains functionality despite the nontraditional geometry. A compound lens is fabricated using similar fabrication techniques and the imaging performance is analyzed. A spray coating technique for photoresist

Design and fabrication of zeolite macro- and micromembranes

NASA Astrophysics Data System (ADS)

Chau, Lik Hang Joseph

2001-07-01

The chemical nature of the support surface influences zeolite nucleation, crystal growth and elm adhesion. It had been demonstrated that chemical modification of support surface can significantly alter the zeolite film and has a good potential for large-scale applications for zeolite membrane production. The incorporation of titanium and vanadium metal ions into the structural framework of MFI zeolite imparts the material with catalytic properties. The effects of silica and metal (i.e., Ti and V) content, template concentration and temperature on the zeolite membrane growth and morphology were investigated. Single-gas permeation experiments were conducted for noble gases (He and Ar), inorganic gases (H2, N2, SF6) and hydrocarbons (methane, n-C4, i-C4) to determine the separation performance of these membranes. Using a new fabrication method based on microelectronic fabrication and zeolite thin film technologies, complex microchannel geometry and network (<5 mum), as well as zeolite arrays (<10 mum) were successfully fabricated onto highly orientated supported zeolite films. The zeolite micropatterns were stable even after repeated thermal cycling between 303 K and 873 K for prolonged periods of time. This work also demonstrates that zeolites (i.e., Sil-1, ZSM-5 and TS-1) can be employed as catalyst, membrane or structural materials in miniature chemical devices. Traditional semiconductor fabrication technology was employed in micromachining the device architecture. Four strategies for the manufacture of zeolite catalytic microreactors were discussed: zeolite powder coating, uniform zeolite film growth, localized zeolite growth, and etching of zeolite-silicon composite film growth inhibitors. Silicalite-1 was also prepared as free-standing membrane for zeolite membrane microseparators.

Off-plane x-ray reflection grating fabrication

NASA Astrophysics Data System (ADS)

Peterson, Thomas J.; DeRoo, Casey T.; Marlowe, Hannah; McEntaffer, Randall L.; Miles, Drew M.; Tutt, James H.; Schultz, Ted B.

2015-09-01

Off-plane X-ray diffraction gratings with precision groove profiles at the submicron scale will be used in next generation X-ray spectrometers. Such gratings will be used on a current NASA suborbital rocket mission, the Off-plane Grating Rocket Experiment (OGRE), and have application for future grating missions. The fabrication of these gratings does not come without challenges. High performance off-plane gratings must be fabricated with precise radial grating patterns, optically at surfaces, and specific facet angles. Such gratings can be made using a series of common micro-fabrication techniques. The resulting process is highly customizable, making it useful for a variety of different mission architectures. In this paper, we detail the fabrication method used to produce high performance off-plane gratings and report the results of a preliminary qualification test of a grating fabricated in this manner. The grating was tested in the off-plane `Littrow' configuration, for which the grating is most efficient for a given diffraction order, and found to achieve 42% relative efficiency in the blaze order with respect to all diffracted light.

Fabrication of 20 nm embedded longitudinal nanochannels transferred from metal nanowire patterns

NASA Technical Reports Server (NTRS)

Choi, D.; Yang, E. H.

2003-01-01

bstract we describe a technique for fabricating nanometer-scale channels embedded by dielectric materials. Longitudinal 'embedded ' nanochannels with an opening size 20 nm x 80 nm have been successfully fabricated on silicon wafer by transferring sacrificial nanowire structures.

Economic fabrication of a novel hybrid planar Grating/Fresnel lens for miniature spectrometers.

PubMed

Zhou, Qian; Li, Xinghui; Geng, Menglin; Hu, Haifei; Ni, Kai; Zhong, Lunchao; Yan, Peng; Wang, Xiaohao

2018-03-05

We propose a new technique to fabricate a highly specialized optical element, a hybrid planar Grating/Fresnel lens (G-Fresnel), which is particularly useful to improve or enable more-affordable miniature/portable spectrometers. Both the Fresnel and the grating surface are fabricated simultaneously by sandwiching soft PDMS between a hard grating and a pre-replicated negative Fresnel surface. Several adhesion reduction techniques are also investigated that help improve both fabrication and cost efficiency (by reducing the solidification time) as well as the lifetime of the mold. Alignment errors are systematically analyzed, and their effects on the G-Fresnel lens evaluated. A compact fabrication platform was built, which is smaller than a volume of 160☓140☓106 mm 3 to fit into a conventional vacuum drying oven, for the fabrication of a G-Fresnel lens with a diameter of 25.4 mm, an equivalent focal length of 25 mm, and a blazed grating pattern with 600 lines/mm spacing. The solidification time was reduced to 2 hours thanks to the improved adhesion reduction technique that permits a PDMS drying-temperature as high as 65 °C. The fabricated G-Fresnel lens was evaluated with regard to both geometrical fabrication precision and optical performance. The measured results, using a step gauge and atomic force microscopy, confirm that this replication technique produces high-quality replicates of the master surface-profile. Furthermore, a prototype spectrometer that uses a G-Fresnel lens was built and evaluated. The spectrometer fits within a volume of about 100 mm☓50 mm☓30 mm, and it operates across a wide wavelength spectrum (450 nm to 650 nm). Both the calculation based on the optical software ZEMAX and the experimental measurements are consistent and confirm that the spectrometer with the G-Fresnel lens can provide a spectral resolution of better than 1.2nm.

Fabrication of ceramic substrate-reinforced and free forms

NASA Technical Reports Server (NTRS)

Quentmeyer, R. J.; Mcdonald, G.; Hendricks, R. C.

1985-01-01

Components fabricated of, or coated with, ceramics have lower parasitic cooling requirements. Techniques are discussed for fabricating thin-shell ceramic components and ceramic coatings for applications in rocket or jet engine environments. Thin ceramic shells with complex geometric forms involving convolutions and reentrant surfaces were fabricated by mandrel removal. Mandrel removal was combined with electroplating or plasma spraying and isostatic pressing to form a metal support for the ceramic. Rocket engine thrust chambers coated with 0.08 mm (3 mil) of ZrO2-8Y2O3 had no failures and a tenfold increase in engine life. Some measured mechanical properties of the plasma-sprayed ceramic are presented.

High Contrast Internal and External Coronagraph Masks Produced by Various Techniques

NASA Technical Reports Server (NTRS)

Balasubramanian, Kunjithapatha; Wilson, Daniel; White, Victor; Muller, Richard; Dickie, Matthew; Yee, Karl; Ruiz, Ronald; Shaklan, Stuart; Cady, Eric; Kern, Brian;

Fabrication and Characterization of High Temperature Resin/Carbon Nanofiber Composites

NASA Technical Reports Server (NTRS)

Ghose, Sayata; Watson, Kent A.; Working, Dennis C.; Criss, Jim M.; Siochi, Emilie J.; Connell, John W.

2005-01-01

Multifunctional composites present a route to structural weight reduction. Nanoparticles such as carbon nanofibers (CNF) provide a compromise as a lower cost nanosize reinforcement that yields a desirable combination of properties. Blends of PETI-330 and CNFs were prepared and characterized to investigate the potential of CNF composites as a high performance structural medium. Dry mixing techniques were employed and the effect of CNF loading level on melt viscosity was determined. The resulting powders were characterized for degree of mixing, thermal and rheological properties. Based on the characterization results, samples containing 30 and 40 wt% CNF were scaled up to approx.300 g and used to fabricate moldings 10.2 cm x 15.2 cm x 0.32 cm thick. The moldings were fabricated by injecting the mixtures at 260-280 C into a stainless steel tool followed by curing for 1 h at 371 C. The tool was designed to impart high shear during the process in an attempt to achieve some alignment of CNFs in the flow direction. Moldings were obtained that were subsequently characterized for thermal, mechanical and electrical properties. The degree of dispersion and alignment of CNFs were investigated using high-resolution scanning electron microscopy. The preparation and preliminary characterization of PETI-330/CNF composites are discussed. Keywords: resins, carbon nanofibers, scanning electron microscopy, electrical properties, thermal conductivity,injection

Direct electrochemistry of Shewanella loihica PV-4 on gold nanoparticles-modified boron-doped diamond electrodes fabricated by layer-by-layer technique.

PubMed

Wu, Wenguo; Xie, Ronggang; Bai, Linling; Tang, Zuming; Gu, Zhongze

2012-05-01

Microbial Fuel Cells (MFCs) are robust devices capable of taping biological energy, converting pollutants into electricity through renewable biomass. The fabrication of nanostructured electrodes with good bio- and electrochemical activity, play a profound role in promoting power generation of MFCs. Au nanoparticles (AuNPs)-modified Boron-Doped Diamond (BDD) electrodes are fabricated by layer-by-layer (LBL) self-assembly technique and used for the direct electrochemistry of Shewanella loihica PV-4 in an electrochemical cell. Experimental results show that the peak current densities generated on the Au/PAH multilayer-modified BDD electrodes increased from 1.25 to 2.93 microA/cm(-2) as the layer increased from 0 to 6. Different cell morphologies of S. loihica PV-4 were also observed on the electrodes and the highest density of cells was attached on the (Au/PAH)6/BDD electrode with well-formed three-dimensional nanostructure. The electrochemistry of S. loihica PV-4 was enhanced on the (Au/PAH)4/BDD electrode due to the appropriate amount of AuNPsand thickness of PAH layer.

Fabrication of aluminum-carbon composites

NASA Technical Reports Server (NTRS)

Novak, R. C.

1973-01-01

A screening, optimization, and evaluation program is reported of unidirectional carbon-aluminum composites. During the screening phase both large diameter monofilament and small diameter multifilament reinforcements were utilized to determine optimum precursor tape making and consolidation techniques. Difficulty was encountered in impregnating and consolidating the multifiber reinforcements. Large diameter monofilament reinforcement was found easier to fabricate into composites and was selected to carry into the optimization phase in which the hot pressing parameters were refined and the size of the fabricated panels was scaled up. After process optimization the mechanical properties of the carbon-aluminum composites were characterized in tension, stress-rupture and creep, mechanical fatigue, thermal fatigue, thermal aging, thermal expansion, and impact.

FabricS: A user-friendly, complete and robust software for particle shape-fabric analysis

NASA Astrophysics Data System (ADS)

Moreno Chávez, G.; Castillo Rivera, F.; Sarocchi, D.; Borselli, L.; Rodríguez-Sedano, L. A.

2018-06-01

Shape-fabric is a textural parameter related to the spatial arrangement of elongated particles in geological samples. Its usefulness spans a range from sedimentary petrology to igneous and metamorphic petrology. Independently of the process being studied, when a material flows, the elongated particles are oriented with the major axis in the direction of flow. In sedimentary petrology this information has been used for studies of paleo-flow direction of turbidites, the origin of quartz sediments, and locating ignimbrite vents, among others. In addition to flow direction and its polarity, the method enables flow rheology to be inferred. The use of shape-fabric has been limited due to the difficulties of automatically measuring particles and analyzing them with reliable circular statistics programs. This has dampened interest in the method for a long time. Shape-fabric measurement has increased in popularity since the 1980s thanks to the development of new image analysis techniques and circular statistics software. However, the programs currently available are unreliable, old and are incompatible with newer operating systems, or require programming skills. The goal of our work is to develop a user-friendly program, in the MATLAB environment, with a graphical user interface, that can process images and includes editing functions, and thresholds (elongation and size) for selecting a particle population and analyzing it with reliable circular statistics algorithms. Moreover, the method also has to produce rose diagrams, orientation vectors, and a complete series of statistical parameters. All these requirements are met by our new software. In this paper, we briefly explain the methodology from collection of oriented samples in the field to the minimum number of particles needed to obtain reliable fabric data. We obtained the data using specific statistical tests and taking into account the degree of iso-orientation of the samples and the required degree of reliability

Fabrication of nanostructured electrodes and interfaces using combustion CVD

NASA Astrophysics Data System (ADS)

Liu, Ying

Reducing fabrication and operation costs while maintaining high performance is a major consideration for the design of a new generation of solid-state ionic devices such as fuel cells, batteries, and sensors. The objective of this research is to fabricate nanostructured materials for energy storage and conversion, particularly porous electrodes with nanostructured features for solid oxide fuel cells (SOFCs) and high surface area films for gas sensing using a combustion CVD process. This research started with the evaluation of the most important deposition parameters: deposition temperature, deposition time, precursor concentration, and substrate. With the optimum deposition parameters, highly porous and nanostructured electrodes for low-temperature SOFCs have been then fabricated. Further, nanostructured and functionally graded La0.8Sr0.2MnO2-La 0.8SrCoO3-Gd0.1Ce0.9O2 composite cathodes were fabricated on YSZ electrolyte supports. Extremely low interfacial polarization resistances (i.e. 0.43 Ocm2 at 700°C) and high power densities (i.e. 481 mW/cm2 at 800°C) were generated at operating temperature range of 600°C--850°C. The original combustion CVD process is modified to directly employ solid ceramic powder instead of clear solution for fabrication of porous electrodes for solid oxide fuel cells. Solid particles of SOFC electrode materials suspended in an organic solvent were burned in a combustion flame, depositing a porous cathode on an anode supported electrolyte. Combustion CVD was also employed to fabricate highly porous and nanostructured SnO2 thin film gas sensors with Pt interdigitated electrodes. The as-prepared SnO2 gas sensors were tested for ethanol vapor sensing behavior in the temperature range of 200--500°C and showed excellent sensitivity, selectivity, and speed of response. Moreover, several novel nanostructures were synthesized using a combustion CVD process, including SnO2 nanotubes with square-shaped or rectangular cross sections, well

Design and fabrication of self-assembled thin films

NASA Astrophysics Data System (ADS)

Topasna, Daniela M.; Topasna, Gregory A.

2015-10-01

Students experience the entire process of designing, fabricating and testing thin films during their capstone course. The films are fabricated by the ionic-self assembled monolayer (ISAM) technique, which is suited to a short class and is relatively rapid, inexpensive and environmentally friendly. The materials used are polymers, nanoparticles, and small organic molecules that, in various combinations, can create films with nanometer thickness and with specific properties. These films have various potential applications such as pH optical sensors or antibacterial coatings. This type of project offers students an opportunity to go beyond the standard lecture and labs and to experience firsthand the design and fabrication processes. They learn new techniques and procedures, as well as familiarize themselves with new instruments and optical equipment. For example, students learn how to characterize the films by using UV-Vis-NIR spectrophotometry and in the process learn how the instruments operate. This work compliments a previous exercise that we introduced where students use MATHCAD to numerically model the transmission and reflection of light from thin films.

Fabrication of a Highly Aligned Neural Scaffold via a Table Top Stereolithography 3D Printing and Electrospinning^.

PubMed

Lee, Se-Jun; Nowicki, Margaret; Harris, Brent; Zhang, Lijie Grace

2017-06-01

Three-dimensional (3D) bioprinting is a rapidly emerging technique in the field of tissue engineering to fabricate extremely intricate and complex biomimetic scaffolds in the range of micrometers. Such customized 3D printed constructs can be used for the regeneration of complex tissues such as cartilage, vessels, and nerves. However, the 3D printing techniques often offer limited control over the resolution and compromised mechanical properties due to short selection of printable inks. To address these limitations, we combined stereolithography and electrospinning techniques to fabricate a novel 3D biomimetic neural scaffold with a tunable porous structure and embedded aligned fibers. By employing two different types of biofabrication methods, we successfully utilized both synthetic and natural materials with varying chemical composition as bioink to enhance biocompatibilities and mechanical properties of the scaffold. The resulting microfibers composed of polycaprolactone (PCL) polymer and PCL mixed with gelatin were embedded in 3D printed hydrogel scaffold. Our results showed that 3D printed scaffolds with electrospun fibers significantly improve neural stem cell adhesion when compared to those without the fibers. Furthermore, 3D scaffolds embedded with aligned fibers showed an enhancement in cell proliferation relative to bare control scaffolds. More importantly, confocal microscopy images illustrated that the scaffold with PCL/gelatin fibers greatly increased the average neurite length and directed neurite extension of primary cortical neurons along the fiber. The results of this study demonstrate the potential to create unique 3D neural tissue constructs by combining 3D bioprinting and electrospinning techniques.

Remote sensing of atmospheric NO2 by employing the continuous-wave differential absorption lidar technique.

PubMed

Mei, Liang; Guan, Peng; Kong, Zheng

2017-10-02

Differential absorption lidar (DIAL) technique employed for remote sensing has been so far based on the sophisticated narrow-band pulsed laser sources, which require intensive maintenance during operation. In this work, a continuous-wave (CW) NO 2 DIAL system based on the Scheimpflug principle has been developed by employing a compact high-power CW multimode 450 nm laser diode as the light source. Laser emissions at the on-line and off-line wavelengths of the NO 2 absorption spectrum are implemented by tuning the injection current of the laser diode. Lidar signals are detected by a 45° tilted area CCD image sensor satisfying the Scheimpflug principle. Range-resolved NO 2 concentrations on a near-horizontal path are obtained by the NO 2 DIAL system in the range of 0.3-3 km and show good agreement with those measured by a conventional air pollution monitoring station. A detection sensitivity of ± 0.9 ppbv at 95% confidence level in the region of 0.3-1 km is achieved with 15-minute averaging and 700 m range resolution during hours of darkness, which allows accurate concentration measurement of ambient NO 2 . The low-cost and robust DIAL system demonstrated in this work opens up many possibilities for field NO 2 remote sensing applications.

Thermoelectric microdevice fabricated by a MEMS-like electrochemical process

NASA Technical Reports Server (NTRS)

Snyder, G. Jeffrey; Lim, James R.; Huang, Chen-Kuo; Fleurial, Jean-Pierre

2003-01-01

Microelectromechanical systems (MEMS) are the basis of many rapidly growing technologies, because they combine miniature sensors and actuators with communications and electronics at low cost. Commercial MEMS fabrication processes are limited to silicon-based materials or two-dimensional structures. Here we show an inexpensive, electrochemical technique to build MEMS-like structures that contain several different metals and semiconductors with three-dimensional bridging structures. We demonstrate this technique by building a working microthermoelectric device. Using repeated exposure and development of multiple photoresist layers, several different metals and thermoelectric materials are fabricated in a three-dimensional structure. A device containing 126 n-type and p-type (Bi, Sb)2Te3 thermoelectric elements, 20 microm tall and 60 microm in diameter with bridging metal interconnects, was fabricated and cooling demonstrated. Such a device should be of technological importance for precise thermal control when operating as a cooler, and for portable power when operating as a micro power generator.

Theoretical modeling and experiments on a DBR waveguide laser fabricated by the femtosecond laser direct-write technique.

PubMed

Duan, Yuwen; McKay, Aaron; Jovanovic, Nemanja; Ams, Martin; Marshall, Graham D; Steel, M J; Withford, Michael J

2013-07-29

We present a model for a Yb-doped distributed Bragg reflector (DBR) waveguide laser fabricated in phosphate glass using the femtosecond laser direct-write technique. The model gives emphasis to transverse integrals to investigate the energy distribution in a homogenously doped glass, which is an important feature of femtosecond laser inscribed waveguide lasers (WGLs). The model was validated with experiments comparing a DBR WGL and a fiber laser, and then used to study the influence of distributed rare earth dopants on the performance of such lasers. Approximately 15% of the pump power was absorbed by the doped "cladding" in the femtosecond laser inscribed Yb doped WGL case with the length of 9.8 mm. Finally, we used the model to determine the parameters that optimize the laser output such as the waveguide length, output coupler reflectivity and refractive index contrast.

Textile for heart valve prostheses: fabric long-term durability testing.

PubMed

Heim, Frederic; Durand, Bernard; Chakfe, Nabil

2010-01-01

The rapid developments and success in percutaneous vascular surgery over the last two decades with the now common stent grafts implantation, make the noninvasive surgery technique today attractive even for heart valve replacement. Less traumatic for the patient and also less time consuming, percutaneous heart valve replacement is however at its beginning and restricted to end of life patients. The noninvasive procedure expects from the heart valve prosthesis material to be resistant and adapted to folding requirements of the implantation process (catheter). Polyester fabric could be a suited material for heart valve implanted percutaneously. Highly flexible and resistant, polyester fabric proved to be well adapted to the dynamic behavior of a valve and polyester (Dacron) is also widely used for vascular grafts implantation and shows good biocompatibility and durability. However, today there's no data available on long-term durability of fabric used as heart valve material. The purpose of this work is to study the long term behavior of a microdenier polyester fabric construction under combined in vitro flexure and tension fatigue stress. In the novel in vitro testing technique presented, a fabric specimen was subjected to combined flexural and tensile fatigue generated by fluid flow under physiological pressure conditions. The results obtained show how flexural properties change with fatigue time, which reflects directly on the suitability of a fabric in such devices. It was also observed that these fabric structural changes directly influence the in vitro behavior of the textile heart valve prosthesis. (c) 2009 Wiley Periodicals, Inc.

Fabrication of Semi-Transparent Photovoltaic Cell by a Cost-Effective Technique

NASA Astrophysics Data System (ADS)

Nithyayini, K. N.; Ramasesha, Sheela K.

2015-09-01

Semi-transparent inorganic thin film PV cells have been fabricated using n-type (CdS) and p-type (CdTe) semiconductors. Large area devices which can be used as windows and skylights in buildings can be fabricated using cost effective solution processes. The device structure is Glass/TCO/CdTe/CdS/TCO. Chemically stable CdS and CdTe layers are deposited at temperatures 353 K to 373 K (80 °C to 100 °C) under controlled pH. The CdCl2 activation is carried out followed by air annealing. The p-n junction is formed by sintering the device at 673 K to 723 K (400 °C to 450 °C). The characterization of cells is carried out using XRD, SEM, AFM, and UV-Visible spectroscopy. The thickness of the cell is ~600 nm. The band gap values are 2.40 eV for CdS and 1.36 eV for CdTe with transmittance of about 70 pct in the visible region. Under 1.5 AM solar spectrum, V oc, and I sc of the initial device are 3.56e-01 V and 6.20e-04 A, respectively.

Fabrication and testing of a prototype longwall face alignment system

NASA Technical Reports Server (NTRS)

1981-01-01

Fabrication and testing of a laser system for instantaneous location of a longwall shearer are summarized. Calculations and measurements for the design of a laser based system for monitoring and controlling the trajectory of the shearing machine as it progresses along the longwall face are reported. An early version was fabricated by employing simple mechanical contrivances and a standard miners lamp. It is concluded that the advantages of the early version is the ability to test the longwall face without approval from the Mine Safety and Health Administration.

Consolidation and fabrication techniques for vanadium-20 w/o titanium /TV-20/

NASA Technical Reports Server (NTRS)

Burt, W. R.; Karasek, F. J.; Kramer, W. C.; Mayfield, R. M.; Mc Gowan, R. D.

1968-01-01

Tests of the mechanical properties, fuel compatibility, sodium corrosion and irradiation behavior were made for vanadium and vanadium alloy. Improved methods for consolidation and fabrication of bar, rod, sheet, and high-quality, small diameter, thin-wall tubing of vanadium-20 without titanium are reported.

Design and fabrication of a hybrid maglev model employing PML and SML

NASA Astrophysics Data System (ADS)

Sun, R. X.; Zheng, J.; Zhan, L. J.; Huang, S. Y.; Li, H. T.; Deng, Z. G.

2017-10-01

A hybrid maglev model combining permanent magnet levitation (PML) and superconducting magnetic levitation (SML) was designed and fabricated to explore a heavy-load levitation system advancing in passive stability and simple structure. In this system, the PML was designed to levitate the load, and the SML was introduced to guarantee the stability. In order to realize different working gaps of the two maglev components, linear bearings were applied to connect the PML layer (for load) and the SML layer (for stability) of the hybrid maglev model. Experimental results indicate that the hybrid maglev model possesses excellent advantages of heavy-load ability and passive stability at the same time. This work presents a possible way to realize a heavy-load passive maglev concept.

The research on surface characteristics of optical lens by 3D printing technique and precise diamond turning technique

NASA Astrophysics Data System (ADS)

Huang, Chien-Yao; Chang, Chun-Ming; Ho, Cheng-Fong; Lee, Tai-Wen; Lin, Ping-Hung; Hsu, Wei-Yao

2017-06-01

The advantage of 3D printing technique is flexible in design and fabrication. Using 3D printing technique, the traditional manufacturing limitations are not considered. The optical lens is the key component in an optical system. The traditional process to manufacture optical plastic lens is injection molding. However injection molding is only suitable for plastics lens, it cannot fabricate optical and mechanical components at same time. The assembly error of optical system can be reduced effectively with fabricating optical and mechanical components at same time. The process of printing optical and mechanical components simultaneously is proposed in previous papers, but the optical surface of printing components is not transparent. If we increase the transmittance of the optical surface, the printing components which fabricated by 3D printing process could be high transmission. Therefore, precise diamond turning technique has been used to turning the surface of 3D printing optical lens in this paper. The precise diamond turning techniques could process surfaces of components to meet the requirements of optical system. A 3D printing machine, Stratasys Connex 500, and a precise diamond turning machine, Precitech Freeform705XG, have been used in this paper, respectively. The dimension, roughness, transmission and printing types of 3D printing components have been discussed in this paper. After turning and polishing process, the roughness of 3D printing component is below 0.05 μm and the transmittance increase above 80 %. This optical module can be used in hand-held telescope and other system which need lens and special mechanical structure fabricated simultaneously.

Development and fabrication of an advanced liquid cooling garment

NASA Technical Reports Server (NTRS)

Hixon, C. W.

1978-01-01

A tube/fin concept liquid cooling garment head cooler was developed, fabricated and delivered to NASA-ARC. The head cooler was fabricated from polyurethane film which sandwiches the transport fluid tubing and a thermally conductive fin material. The head cooler garment is sewn to form a skull cap and covered with a comfort liner. In addition, two Neonate heating garments were fabricated and supplied to NASA for further finishing and use in medical tests. The resulting garment is flexible, elastic and conforms to the head comfortably. Tests on a tube/fin element of identical construction as the head cooler demonstrated good thermal effectiveness. Use of commercially available materials and development of relatively simple fabrication techniques give the potential for a low garment cost.

Fabric-based active electrode design and fabrication for health monitoring clothing.

PubMed

Merritt, Carey R; Nagle, H Troy; Grant, Edward

2009-03-01

In this paper, two versions of fabric-based active electrodes are presented to provide a wearable solution for ECG monitoring clothing. The first version of active electrode involved direct attachment of surface-mountable components to a textile screen-printed circuit using polymer thick film techniques. The second version involved attaching a much smaller, thinner, and less obtrusive interposer containing the active electrode circuitry to a simplified textile circuit. These designs explored techniques for electronic textile interconnection, chip attachment to textiles, and packaging of circuits on textiles for durability. The results from ECG tests indicate that the performance of each active electrode is comparable to commercial Ag/AgCl electrodes. The interposer-based active electrodes survived a five-cycle washing test while maintaining good signal integrity.

Low-cost fabrication of optical waveguides, interconnects and sensing structures on all-polymer-based thin foils

NASA Astrophysics Data System (ADS)

Rezem, Maher; Kelb, Christian; Günther, Axel; Rahlves, Maik; Reithmeier, Eduard; Roth, Bernhard

2016-03-01

Micro-optical sensors based on optical waveguides are widely used to measure temperature, force and strain but also to detect biological and chemical substances such as explosives or toxins. While optical micro-sensors based on silicon technology require complex and expensive process technologies, a new generation of sensors based completely on polymers offer advantages especially in terms of low-cost and fast production techniques. We have developed a process to integrate micro-optical components such as embedded waveguides and optical interconnects into polymer foils with a thickness well below one millimeter. To enable high throughput production, we employ hot embossing technology, which is capable of reel-to-reel fabrication with a surface roughness in the optical range. For the waveguide fabrication, we used the thermoplastic polymethylmethacrylate (PMMA) as cladding and several optical adhesives as core materials. The waveguides are characterized with respect to refractive indices and propagation losses. We achieved propagation losses are as low as 0.3 dB/cm. Furthermore, we demonstrate coupling structures and their fabrication especially suited to integrate various light sources such as vertical-cavity surface-emitting lasers (VCSEL) and organic light emitting diodes (OLED) into thin polymer foils. Also, we present a concept of an all-polymer and waveguide based deformation sensor based on intensity modulation, which can be fabricated by utilizing our process. For future application, we aim at a low-cost and high-throughput reel-to-reel production process enabling the fabrication of large sensor arrays or disposable single-use sensing structures, which will open optical sensing to a large variety of application fields ranging from medical diagnosis to automotive sensing.

Three-dimensional plotter technology for fabricating polymeric scaffolds with micro-grooved surfaces.

PubMed

Son, JoonGon; Kim, GeunHyung

2009-01-01

Various mechanical techniques have been used to fabricate biomedical scaffolds, including rapid prototyping (RP) devices that operate from CAD files of the target feature information. The three-dimensional (3-D) bio-plotter is one RP system that can produce design-based scaffolds with good mechanical properties for mimicking cartilage and bones. However, the scaffolds fabricated by RP have very smooth surfaces, which tend to discourage initial cell attachment. Initial cell attachment, migration, differentiation and proliferation are strongly dependent on the chemical and physical characteristics of the scaffold surface. In this study, we propose a new 3-D plotting method supplemented with a piezoelectric system for fabricating surface-modified scaffolds. The effects of the physically-modified surface on the mechanical and hydrophilic properties were investigated, and the results of cell culturing of chondrocytes indicate that this technique is a feasible new method for fabricating high-quality 3-D polymeric scaffolds.

Hidden explosives detector employing pulsed neutron and x-ray interrogation

DOEpatents

Schultz, F.J.; Caldwell, J.T.

1993-04-06

Methods and systems for the detection of small amounts of modern, highly-explosive nitrogen-based explosives, such as plastic explosives, hidden in airline baggage. Several techniques are employed either individually or combined in a hybrid system. One technique employed in combination is X-ray imaging. Another technique is interrogation with a pulsed neutron source in a two-phase mode of operation to image both nitrogen and oxygen densities. Another technique employed in combination is neutron interrogation to form a hydrogen density image or three-dimensional map. In addition, deliberately-placed neutron-absorbing materials can be detected.