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Thus far, several potential application areas for ionomer transducers have emerged. Due to their unique
capabilities, the opportunities for devices based on ionomer transducers are limited only by imagination. Discover
Technologies is constantly seeking new concepts and partners with which to pursue them. If you have an idea for
our ionomer transducer technology, please do not hesitate to contact us.
Wall Shear Stress Sensors
Discover Technologies is currently developing wall shear stress sensors based on ionomer transducers under
contract from the Office of Naval Research. Friction shear stress accounts for most of the drag force on a
waterborne vessel, or any high-speed vehicle for that matter. Furthermore, turbulent flow leads to broadband
fluctuations in this stress. These fluctuations can have very small time scales and occur over very small spatial
dimensions. An understanding of this shear stress and its spatial and temporal distribution is critical for the
development of next generation high speed surface and submerged vessels. Additionally, this understanding will
lead to fundamental improvements in our comprehension of the physics of fluid / wall interactions and very high
Reynolds number turbulent flow.
Discover Technologies has fabricated and tested prototype wall shear stress sensors in collaboration with Dr.
Pavlos Vlachos in the Mechanical Engineering Department at Virginia Tech. These prototypes were characterized
using a custom oscillating plate apparatus designed to generate a Stokes layer. Based on the Stokes layer
assumption, the sensors were characterized over a range of shear stress of +/- 3 Pa and a range of frequency of
30 to 130 Hz. Over this range, the sensors exhibited a signal to noise ratio of 60 dB and a mean absolute error of
4.92%, with respect to the full scale range. Discover Technologies and Virginia Tech are currently developing
improved sensors and sensor characterization protocols based on this initial success.
plate at 78 Hz. The shear stress determined analytically using the
Stokes layer assumption is shown for reference.
aircraft. Prototype sensor arrays have already been demonstrated that could be used to locate lines of
separation on these vehicles. These wall shear sensors and sensor arrays will offer many advantages over other
currently available techniques, including:
- flush mounted sensor is minimally invasive to the host vessel
- low sensor profile minimizes influence on the flow field
- large dynamic range
- low cost
- able to operate in the presence of ambient vibration and over a wide range of temperature
- sensors measure wall shear stress directly
This last point is of critical importance. Many technologies for measuring wall shear stress are actually directly
measuring fluid velocity or heat transfer. Because Discover Technologies' sensors perform a direct measurement
of wall shear stress, they are capable of operating without a priori knowledge of the flow characteristics. They will
also be capable of evaluating the effectiveness of novel friction reducing treatments currently under development.
Electroactive Polymer Pumps
One potential application for Discover Technologies' ionomer actuators is in small pumps. These pumps could be
used for drug delivery, microfluidic devices, active flow control, and a multitude of consumer applications. The
most likely configuration for a pump based on ionomer actuators would be a dual diaphragm device. The
advantages that an ionomeric pump could offer would be low voltage (battery) operation, extremely low noise
signature, high system efficiency, and highly accurate control of flow rate.
Discover Technologies has performed initial studies to evaluate the feasibility of a pump operated by ionomer
actuators. Thus far a complete prototype has not been tested, but the concept has been demonstrated using a
single diaphragm.
operated by ionomer actuators.
fixture used to test the concept of an EAP pump.
The diameter of the actuator is 1 inch.
Another technology that can benefit from the unique properties of ionomeric actuators is optical membranes. Due
to their low modulus, the mechanical impedance of these actuators is well-matched to common optical membrane
materials. Also, a single ionomer actuator is capable of generating displacements that range from microns to
centimeters. For this reason, these materials can be used for static shape correction and jitter suppression.
These actuators could also be used to correct for optical aberrations due to atmospheric interference.
Membrane optics could also benefit from the scalability of ionomeric transducers. Although these devices are
currently manufactured on the centimeter scale, there is no fundamental limitation preventing the eventual
realization of meter scale devices. Additionally, ionomer actuators can be patterned to provide multiple individual
domains on an optical membrane that can be individually addressed. Finally, ionomeric transducers can act as
both the sensing and actuating elements in an optical system. Signals measured by one set of transducers can
be used to provide a control signal for another set. Alternatively, the individual regions of a patterned device
could be switched from actuation to sensing depending on the requirements of the situation.
Polymer Microphones
Another possible application for ionomeric polymer transducers is acoustics. Due to their sensitivity to vibration,
ionomer transducers could be used as polymer microphones. As with the wall shear sensors, it may be possible
to create novel arrays of microphones, thus allowing for the development of a sensing skin to be used to map
pressure fluctuations over the surface of an object. These microphones could also potentially be made in very
small sizes and because of their remarkable sensitivity may be useful as bone conduction pickups. The
development of successful microphones based on ionomeric sensors could lead to advances in electronic
eavesdropping, hydrophones, weather measurement instruments, and sonar. The advantages for ionomeric
polymer transducers in these applications would be their small size, light weight, high sensitivity, and simple
design.
