Tech Briefs Magazine - May 2021 - 31

tion of measurement errors due to polarization effects in the fiber optic system. Additionally, because the technology can accurately track polarization
changes along a string of sensors, it may
prove to be useful in the application of
new sensor types such as pressure, twisting, and bending along the sensing fiber.

This approach separates the signal into
three 60-degree polarizations using a
commercial 3-axis polarization filtering
arrangement. The light returning from a
sensing fiber is split three equal ways and
each third of the return is linearly filtered
before being optoelectronically converted and amplified. The linear filters on
Light signal at 3
polarization angles

Composite polarization
ellipse

Composite representation of three polarized light signals from the same source. (Image: NASA)

the three splitter outputs are positioned
at 0°, 60°, and 120° with respect to the
cross-section of the fibers emerging from
the splitter. The information from the
three signals is processed to provide a
thorough understanding of birefringent
effects throughout the sensor length.
This technique offers the same benefits
as active polarization control with very little change to prior hardware found in traditional OFDR systems. The hardware
used to implement the new approach is
less expensive than an OFDR system implementing active polarization control
because less expensive, passive, non-polarized components achieve the same results.
NASA is actively seeking licensees to commercialize this technology. Please contact
NASA's Licensing Concierge at AgencyPatent-Licensing@mail.nasa.gov or call us
at 202-358-7432 to initiate licensing discussions. Follow this link for more information:
https://technology.nasa.gov/patent/LARTOPS-324.

Accelerometer and Gyroscope Designs Based on Carbon
Nanotube Tape
Carbon nanotubes (CNTs) in tape form enable new sensor components for consumer
electronics and other applications.
Marshall Space Flight Center, Alabama

N

ASA Marshall Space Flight Center
developed designs for two microelectromechanical systems (MEMS) motion and position sensors: a single-axis
accelerometer and a gyroscope. The
designs leverage a highly aligned multiwall carbon nanotube (MWCNT) tape
with a P(VDF-TrFE) matrix that is mechanically robust and has excellent piezoelectric properties as the sensing and
actuating element.
The use of CNT tape in a gyroscope is
made possible by recent improvements to
CNT processing that yield longer CNTs
that are more highly aligned. The use of
CNTs makes the accelerometer and gyroscopes stronger and more robust, without
increasing their size or weight. The chief
advantage, compared to silicone (Si) and
quartz sensors, is easier manufacturing
that requires no machining.
NASA's accelerometer was designed to
address the shortcomings of conventional piezoelectric-based accelerometers
that are made from ceramic materials
such as barium titanate (BaTiO3) or lead
titanate (PZT). These materials are inher-

The high-voltage probe, copper mesh grid, and
P(VDF-TrFE) sample (white) for corona poling.

ently brittle, have a tendency to be noisy,
have difficulty sensing low frequencies,
are subject to static charge buildup that
affects polarization, and are relatively
large and expensive. The unique feature
of the NASA innovation is the use of carbon nanotube/P(VDF-TrFE) tape as the
actuating and sensing element.

Tech Briefs, May 2021

www.techbriefs.com

Cov

ToC

The new accelerometer acts as a
spring-mass system. There is a moving
mass between fixed walls and attached to
two CNT tapes on both sides. The mass is
displaced along a single axis when an
applied force acts on the mass. This sensor uses one tape as an actuator to damp
motion of the moving mass, while the
other tape is used for sensing the mass
displacement.
The single-axis accelerometer can be
used alone or as the basis for a two-axis
gyroscope. The CNT tape is used as the
vibrating element in the gyroscope. The
NASA gyroscope design covers three configurations: CNT tape wrapped around
the conductive rotor of the gyroscope,
the same CNT tape layered with piezo
material to form a rotor shape, and piezosprayed CNT tape used as a rotor.
NASA is actively seeking licensees to commercialize this technology. Please contact
Sammy Nabors at sammy.nabors@nasa.gov
or 256-544-5226 to initiate licensing discussions. Follow this link for more information:
https://technology.nasa.gov/patent/MFSTOPS-55.
31


https://technology.nasa.gov/patent/LAR-TOPS-324 https://technology.nasa.gov/patent/MFS-TOPS-55 http://www.techbriefs.com http://www.abpi.net/ntbpdfclicks/l.php?202105TBNAV

Tech Briefs Magazine - May 2021

Table of Contents for the Digital Edition of Tech Briefs Magazine - May 2021

Tech Briefs Magazine - May 2021 - Intro
Tech Briefs Magazine - May 2021 - Sponsor
Tech Briefs Magazine - May 2021 - Cov1
Tech Briefs Magazine - May 2021 - Cov2
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