Manufacturing & Prototyping

Fabrication of Gate-Electrode Integrated Carbon-Nanotube Bundle Field Emitters

Emission tips and a gate electrode are integrated into a monolithic device. Figure 1. A Gate Electrode Overhangs a recess containing an array of bundles of carbon nanotubes (see part a). In part (b) are scanning electron micrograph (SEM) images of fabricated field-emitter devices.A continuing effort to develop carbon- nanotube-based field emitters (cold cathodes) as high-current-density electron sources has yielded an optimized device design and a fabrication scheme to implement the design. One major element of the device design is to use a planar array of bundles of carbon nanotubes as the field-emission tips and to optimize the critical dimensions of the array (principally, heights of bundles and distances between them) to obtain high area-averaged current density and high reliability over a long operational lifetime — a concept that was discussed in more detail in “Arrays of Bundles of Carbon Nanotubes as Field Emitters” (NPO-40817), NASA Tech Briefs, Vol. 31, No. 2 (February 2007), page 58. Another major element of the design is to configure the gate electrodes (anodes used to extract, accelerate, and/or focus electrons) as a ring that overhangs a recess wherein the bundles of nanotubes are located [see Figure 1(a)], such that by virtue of the proximity between the ring and the bundles, a relatively low applied potential suffices to generate the large electric field needed for emission of electrons.

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Ski Binding Prototype Designed and Tested with FEA Software

Weight and strength of plastic and metal components were optimized with finite-element analysis. G3 Genuine Guide Gear (G3) of North Vancouver, British Columbia, Canada, is a specialized manufacturer of backcountry ski and safety equipment — including telemark bindings and accessories, climbing skins, and shovels and saws — designed for guides and avalanche professionals.

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Vacuum Packaging of MEMS With Multiple Internal Seal Rings

Each internal seal ring would be part of an electrical feed-through. A proposed method of design and fabrication of vacuum-packaged microelectromechanical systems (MEMS) and of individual microelectromechanical devices involves the use of multiple internal seal rings (MISRs) in conjunction with vias (through holes plated with metal for electrical contacts). The proposed method is compatible with mass production in a wafer-level fabrication process, in which the dozens of MEMS or individual microelectromechanical devices on a typical wafer are simultaneously vacuum packaged by bonding a capping wafer before the devices are singulated (cut apart by use of a dicing saw). In addition to being compatible with mass production, the proposed method would eliminate the need for some complex and expensive production steps and would yield more reliable vacuum seals.

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Gimballed Shoulders for Friction Stir Welding

Digging of edges of shoulders into workpieces would be reduced or eliminated. In a proposed improvement of tooling for friction stir welding, gimballed shoulders would supplant shoulders that, heretofore, have been fixedly aligned with pins. The proposal is especially relevant to self-reacting friction stir welding.

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Patterning of Indium Tin Oxide Films

The patterns are formed by laser printing directly onto the films. A relatively rapid, economical process has been devised for patterning a thin film of indium tin oxide (ITO) that has been deposited on a polyester film. ITO is a transparent, electrically conductive substance made from a mixture of indium oxide and tin oxide that is commonly used in touch panels, liquid-crystal and plasma display devices, gas sensors, and solar photovoltaic panels. In a typical application, the ITO film must be patterned to form electrodes, current collectors, and the like. Heretofore it has been common practice to pattern an ITO film by means of either a laser ablation process or a photolithography/etching process. The laser ablation process includes the use of expensive equipment to precisely position and focus a laser. The photolithography/etching process is time-consuming.

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Dog-Bone Horns for Piezoelectric Ultrasonic/Sonic Actuators

Relative to other shapes, the dog-bone shape offers better performance. A shape reminiscent of a dog bone has been found to be superior to other shapes for mechanical-amplification horns that are components of piezoelectrically driven actuators used in a series of related devices denoted generally as ultrasonic/sonic drill/corers (USDCs). The first of these devices was reported in “Ultrasonic/Sonic Drill/Corers With Integrated Sensors” (NPO-20856), NASA Tech Briefs, Vol. 25, No. 1 (January 2001), page 38. The dog-bone shape was conceived especially for use in a more recent device in the series, denoted an ultrasonic/ sonic gopher, that was described in “Ultrasonic/Sonic Mechanisms for Drilling and Coring” (NPO-30291), NASA Tech Briefs, Vol. 27, No. 9 (September 2003), page 65. The figure shows an example of a dog-bone-shaped horn and other components of an ultrasonic gopher.

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Creep Forming of Carbon-Reinforced Ceramic-Matrix Composites

A set of lecture slides describes an investigation of creep forming as a means of imparting desired curvatures to initially flat stock plates of carbon-reinforced ceramic-matrix composite (C-CMC) materials. The investigation is apparently part of a continuing effort to develop improved means of applying small CCMC repair patches to reinforced carbon- carbon leading edges of aerospace vehicles (e.g., space shuttles) prior to reentry into the atmosphere of the Earth.

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