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Surface Acoustic Wave (SAW) Sensor Arrays

Passive sensor networks for difficult measurement applications

How can variables be measured in environments that are too hot, too cold, or moving too fast for traditional circuit-based sensors?

A new technology for obtaining multiple, real-time measurements under extreme environmental conditions is being developed under Phase 1 and 2 funding contracts from NASA's Kennedy Space Center’s Small Business Technology Transfer (STTR) program. Opportunities for early deployment licensing and Phase 3 STTR contracts are now being accepted.

Passive, remote measuring systems can be created using new Orthogonal Frequency Code (OFC) multiplexing techniques and specially developed, next-generation SAW sensors. As a result, very cost effective applications such as spaceflight sensing (for instance, temperature, pressure, or acceleration monitoring), remote cryogenic fluid level sensing, or an almost limitless number of other rigorous monitoring applications are possible.

The STTR Phase 1 proof-of-feasibility demonstration is complete, and Phase 2 (enhancement and technology demonstration) is in progress. SAW sensor array development is being led by Don Malocha, PhD with the Consortium for Applied Acoustoelectronic Technology (CAAT) at the University of Central Florida (UCF). The members of UCF’s CAAT team have been recognized for 25 years as experts in the area of SAW analysis, design, mask generation, and device fabrication. CAAT’s industry partner, Mnemonics, Inc., also is a long-time, proven expert in the field of radio frequency systems for aerospace and defense. Mnemonics is assisting CAAT with development of the radio systems required to implement the new OFC algorithms and interrogate the remote sensors.

For more information about this licensing/development opportunity, please contact:

Technology Transfer Office
NASA's Kennedy Space Center
http://technology.ksc.nasa.gov/


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Benefits

  • Passive: Reflects measurement signals by using piezoelectric materials and requires no batteries, unlike traditional sensors that rely on active electronic components
  • Small, thin footprint: Offers a size smaller than the width and thickness of a quarter that can be attached to moving or obscure surfaces, as opposed to large and bulky traditional sensors
  • Wireless: Transmits over distances from several meters (MHz frequencies) to 50 meters (GHz frequencies) because of the use of spread spectrum OFC techniques; by building meshed networks, even further distances and coverage are possible
  • Large temperature ranges: Operates from -200°C to +1,000°C by the use of different piezoelectric materials
  • Environmentally tough: Works well in high radiation environments

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Applications

  • Cryogenic fluid level monitoring
  • Spacecraft surfaces that experience extreme temperatures
  • Turbine blade real-time stress and strain detection
  • Vehicle acceleration force monitoring
  • Rotational and directional sensing
  • Critical pressure loss detection
  • Toxic safety monitoring
  • Process safety monitoring (such as gas and oil industrial refining)
  • Variable measurement within sealed containers or in difficult-to-reach locations
 

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Technology Details

SAW technology has been available for many years. The nearly four billion traditional SAW devices produced annually are used primarily as electronic filters in cellular phones, televisions, and military applications (such as radar, electronics systems, and radio-frequency identification). SAW devices are solid state and convert electrical energy into a mechanical wave using a piezoelectric, crystalline substrate.


How it works

Two primary components are used in passive measurement systems, multiple passive SAW sensors and a single, active management station called an interrogator. During operation, the interrogator station generates a unique set of OFC codes, overlaid onto a spread spectrum, wide-band radio frequency (RF) signal.

A SAW device receives this coded signal via a localized antenna. The radio signal then propagates across the device as a surface acoustical wave and generates a unique, reflected wave that contains the encoded desired, local variable measurement. This reflected wave then emanates from the local antenna and is received back by the interrogator. The interrogator identifies which SAW sensor generated the signal and decodes the measurement. The resulting data point is handed off to an application specific program; then the process is repeated.


Why it is better

The new SAW sensors have the significant advantage over traditional sensors of operating passively and requiring no local, active electronic circuits. Using active electronic circuits in a sensor limits the environmental conditions in which they can be deployed. Traditional sensors cannot tolerate wide temperature ranges, and they are susceptible to failure in high radiation environments. Active circuits increase cost, increase complexity, and can decrease reliability.

The new SAW sensors are relatively inexpensive to manufacture. Because they have no moving parts and are essentially an all crystalline device, they can be vary compact and rugged. This allows their use in new applications that were not previously possible. With their low profile, no need for batteries, and wireless operation, they can even monitor every blade in a turbine engine rotating at 50,000 rpm.

Another major benefit sets this innovation apart. The SAW sensors array can monitor not only one but also many variables at the same time, within the same network. Array deployment is possible with many types of sensors, some measuring pressure, some measuring temperature, and others measuring stress or strain. Because each sensor has its own signature, and because the novel OFC techniques created by Dr. Malocha and CAAT support multiplexing multiple data streams, the limitation of deploying only individual sensors can be eliminated.


Patents

The work done by Dr. Malocha (link opens new browser window) and his team at UCF’s Consortium for Applied Acoustoelectronic Technology (CAAT) (link opens new browser window) has resulted in a growing portfolio of intellectual property. Most notable are the following:

  • Multi-transducer/antenna surface acoustic wave device sensor and tag (U.S. patent 7,623,037 (link opens new browser window) issued 24 November 2009)
  • Weighted SAW Reflector Gratings for Orthogonal Frequency Coded SAW ID Tags and Sensors (filed)
  • Orthogonal Frequency Coding for Communications, Tagging and Sensors (allowed)
  • Delayed Offset Multi-track OFC Sensors and Tags (filed)
  • Surface Acoustic Wave Device Coding for Multi-Device ID Tags and Sensors (filed)
  • In addition, Dr. Malocha has contributed to and/or authored many other patents and publications during his two-decade career.
  • For more information on work by Dr. Malocha and his CAAT team, or other UCF research and commercialization opportunities, please contact:

Andrea Adkins
University of Central Florida
Office of Research and Commercialization (link opens new browser window)
12201 Research Parkway, Suite 202, Orlando, FL 32826-3246
Phone: (407) 823-0138
Fax: (407) 882-9010
E-mail: aadkins@mail.ucf.edu

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Publications and Presentations

Publications

Presentations

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Commercial Opportunity

This technology is part of NASA’s Innovative Partnerships Program, which seeks to transfer technology into and out of NASA to benefit the space program and U.S. industry. NASA invites companies to inquire about the licensing possibilities for the Surface Acoustic Wave Sensor Arrays (KSC-13238-1) for commercial applications or sponsoring STTR Phase 3 development.

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For More Information

For more information about this licensing/development opportunity, please contact:

Technology Transfer Office
NASA's Kennedy Space Center
http://technology.ksc.nasa.gov/

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This technology is owned by NASA's Kennedy Space Center
KSC-13238 (KS-0024)