Volume 9, Number 4 • July/August 2001 • Moving Forward

Technology Opportunity Showcasehighlights some unique technologies that NASA has developed and which we believe have strong potential for commercial application. While the descriptions provided here are brief, they should provide enough information to communicate the potential applications of the technology.or more detailed information, contact the person listed. Please mention that you read about it in Innovation

Method for Measuring Surface Shear Stress Magnitude and Direction Using Liquid Crystal Coatings

NASA Ames Research Center is seeking partners to license the Liquid Crystal Coating Method for Measuring Surface Shear Stress Patterns. This is a diagnostic technique that gives rapid visual information and measurements of surface shear stress magnitude and direction over an entire surface in a continuous, non-intrusive manner. In aerodynamics research, much valuable information can be gained from visualizing and measuring shear stress patterns on solid surfaces. Frictional forces generated by gases or liquids flowing over these surfaces can significantly influence the performance of aircraft, ships or surface-transport vehicles. Internal frictional forces, such as those caused by air compression through a jet engine or blood flow through an artificial heart chamber, also affect aerodynamic or mechanical performance. To date, measuring surface shear stress requires expensive mechanical balances or intrusive probes and sensors. This technique gives rapid visual information and measurements of surface shear stress magnitude and direction over an entire surface in a continuous, non-intrusive manner. A shear-sensitive liquid crystal coating is applied to the test surface, illuminated by a white light source, and the reflected color patterns are recorded using a color video camera.

Benefits of this technology include: non-intrusiveness, with no need to penetrate the surface or disturb the flow; ease of set-up, with optical access required only for illumination and video camera recording; inexpensiveness, with commercially available coatings costing less than $10/square foot of surface; immediate full-surface results revealing cause-and-effect relationships between changes in model configuration or test environment and the resulting surface shear field; compatibility with force and moment balances; one millisecond response to changing conditions; and accuracy equivalent to that of existing point-measurement sensors when properly calibrated.

Potential commercial uses of the technique include wind tunnel testing of aircraft and components, such as wings and control surfaces; wind tunnel testing of automotive designs; track testing of race cars; wind tunnel testing of missiles; and water tunnel testing of racing yachts. Molecules within a shear-sensitive liquid crystal coating scatter white light as a spectrum of colors, with each color having a different orientation relative to the surface. Under normal illumination, any surface point exposed to a shear vector directed away from the observer exhibits a color change, with the color shift being a function of shear magnitude and direction relative to that observer. Conversely, if the shear vector is directed toward the observer, the coating exhibits no color change and appears as a rust or brown color, independent of shear magnitude and direction. Based on these results, a full-surface shear stress visualization and measurement method, involving multiple oblique-view observations of the test surface, was formulated, successfully demonstrated and patented. Q

For more information, contact Cathy Pochel, Technology Commercialization Manager, NASA Ames Research Center, & 650/604-4595, 650/604-1592, ) cpochel@mail.arc.nasa.gov Please mention you read about it in Innovation.

New Technology for Smaller, Low-Cost Rotary Position Sensors

NASA Marshall Space Flight Center is seeking commercial companies to consider licensing or jointly developing a new technology for smaller, low-cost rotary position sensors. The technology can be used as a conventional resolver or integrated with signal-conditioning electronics in a single unit. Potential commercial applications include any rotational measurement application, such as: printers, photocopiers, fax machines; electric motors; robotics; medical scanners; antilock brake systems; and industrial manufacturing equipment.

Benefits of the new technology include: production of conventional resolver signals; production of high-quality sensor information; offer of a full 360-degree range; availability of a small package size at a low cost; low rotary inertia; multiple output capability possible, with internal signal-conditioning electronics; continuous, absolute output without discrete jumps (like with encoders); and electrical redundancy, which can be achieved with minimal volume or cost impact. The sensor unit also can incorporate signal conditioning electronics into the housing body to develop the desired output. The sensor measures absolute position over the full 360 degrees of rotation and can be miniaturized to fit into various applications. The design can be configured in slip-ring or brushless versions, and can easily provide electrically redundant signals. The technology is immune to permanent and alternating magnetic fields, which aids in accuracy. Q

For more information, contact Rhonda Thompson at Marshall Space Flight Center Technology Transfer Office, & 256/544-4329, ) Rhonda.c.Thompson@msfc.nasa.gov Please mention you read about it in Innovation.