Manufacturing & Prototyping

Artificial Hair Cells for Sensing Flows

Small, robust sensors can be fabricated on a variety of substrates. The purpose of this article is to present additional information about the flow-velocity sensors described briefly in the immediately preceding article. As noted therein, these sensors can be characterized as artificial hair cells that implement an approximation of the sensory principle of flow-sensing cilia of fish: A cilium is bent by an amount proportional to the flow to which it is exposed. A nerve cell at the base of the cilium senses the flow by sensing the bending of the cilium. In an artificial hair cell, the artificial cilium is a microscopic cantilever beam, and the bending of an artificial cilium is measured by means of a strain gauge at its base (see Figure 1).

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Improved Oxygen-Beam Texturing of Glucose-Monitoring Optics

Textures can be more nearly optimized for greater utilization of light. An improved method has been devised for using directed, hyperthermal beams of oxygen atoms and ions to impart desired textures to the tips of polymethylmethacrylate [PMMA] optical fibers to be used in monitoring the glucose content of blood. The improved method incorporates, but goes beyond, the method described in “Texturing Blood- Glucose-Monitoring Optics Using Oxygen Beams” (LEW-17642- 1), NASA Tech Briefs, Vol. 29, No. 4 (April 2005), page 11a. The basic principle of operation of such a glucose-monitoring sensor is as follows: The textured surface of the optical fiber is coated with chemicals that interact with glucose in such a manner as to change the reflectance of the surface. Light is sent down the optical fiber and is reflected from, the textured surface. The resulting change in reflectance of the light is measured as an indication of the concentration of glucose.

Posted in: Manufacturing & Prototyping, Briefs, TSP

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Tool for Two Types of Friction Stir Welding

The same mechanism could be used for conventional or selfreacting FSW. A tool that would be useable in both conventional and self-reacting friction stir welding (FSW) has been proposed. The tool would embody both a prior tooling concept for self-reacting FSW and an auto-adjustable pin-tool (APT) capability developed previously as an augmentation for conventional FSW.

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Deforming Fibrous Insulating Tiles To Fit Curved Surfaces

Flat billets are heated and pressed gently against curved mold surfaces. A curved tile of refractory silica-fiber-based or alumina-fiber-based thermal-insulation material can be formed from an initially flat billet in a process that includes pressing against a curved mold surface during heating. The mold or tile curvature can be concave or convex. Curved tiles are needed for thermal protection of curved surfaces of spacecraft reentering the terrestrial atmosphere; curved thermal-protection tiles may also be useful on Earth in some industrial applications.

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Micromachining of a Mesoscale Vibratory Gyroscope

High-performance miniature gyroscopes would be fabricated by established micromachining techniques. A micromachining-based fabrication process has been proposed for low-volume production of copies of a mesoscale vibratory gyroscope. The process would include steps of photolithography, metallization, deep reactive-ion etching (RIE), Au/Au thermal-compression bonding, and anodic bonding. In the present state of the art, these process steps are well established and the process as a whole would be considered reproducible.

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Manufacturing Process Management for Test

Test is critical to the board manufacturing process. Effective test ensures quality and customer satisfaction both for the OEM (original equipment manufacturer) and the CEM (contract electronics manufacturer). By isolating defects before product shipment, test minimizes returns and related costs. But test takes time, and the cost can be prohibitive.

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Improved Process for Fabricating Carbon Nanotube Probes

An improved process has been developed for the efficient fabrication of carbon nanotube probes for use in atomic-force microscopes (AFMs) and nanomanipulators. Relative to prior nanotube tip production processes, this process offers advantages in alignment of the nanotube on the cantilever and stability of the nanotube's attachment. A procedure has also been developed at Ames that effectively sharpens the multiwalled nanotube, which improves the resolution of the multiwalled nanotube probes and, combined with the greater stability of multiwalled nanotube probes, increases the effective resolution of these probes, making them comparable in resolution to single-walled carbon nanotube probes. The robust attachment derived from this improved fabrication method and the natural strength and resiliency of the nanotube itself produces an AFM probe with an extremely long imaging lifetime. In a longevity test, a nanotube tip imaged a silicon nitride surface for 15 hours without measurable loss of resolution. In contrast, the resolution of conventional silicon probes noticeably begins to degrade within minutes. These carbon nanotube probes have many possible applications in the semiconductor industry, particularly as devices are approaching the nanometer scale and new atomic layer deposition techniques necessitate a higher resolution characterization technique. Previously at Ames, the use of nanotube probes has been demonstrated for imaging photoresist patterns with high aspect ratio. In addition, these tips have been used to analyze Mars simulant dust grains, extremophile protein crystals, and DNA structure. This NASA technology is being commercialized through Convergent Science and Technology Inc. ().

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