Cochlear Properties and Micromachined Hair-like Shear Sensors.
Liu, Shuangqin.
2012
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Abstract: Orthotropic material properties of the gerbil basilar membrane are
determined using a geometrically nonlinear finite element composite orthotropic plate
model. This model extracts material properties based on point stiffness and space constant
reported from two sets of experimental data. Two boundary conditions are investigated. The
material properties are quantified at different loc... read moreations along the length of basilar
membrane for both boundary conditions. The orthotropy of gerbil basilar membrane varies
along the length of the gerbil basilar membrane from a maximum of 65 close to the base to a
minimum of 10 in the upper middle turn. A sixteen fold scaled-up guinea pig cochlea model
is designed and fabricated. The physical model geometry and fluid properties were chosen in
a way to satisfy scaling law which is derived from dimensionless analysis with Buckingham
Pi theorem to ensure the motion of the enlarged cochlear model resembles that of the guinea
pig cochlea. The frequency responses of the cochlear basilar membrane were recorded and
compared with a mathematical model based on WKB method. The test results show the
experiment characteristic frequencies are about 100-300Hz different from those computed
using WKB and the magnitudes of the ratio of cochlear membrane to drive velocity are about
15-25dB lower than those calculated from WKB method. The phases for WKB and experimental
results are very close. A novel hair-like sensor using capacitive sensing scheme for direct
shear measurement is designed, fabricated and tested. The capacitive sensor base is
fabricated using PolyMUMPsTM foundry process and hair posts sitting on the sensor base are
post fabricated at Tufts cleanroom facility. The sensors were successfully fabricated,
released and packaged. The sensors are tested in a flow cell with laminar air flow at
different flow rates using both LCR meter and a commercial differential capacitance
measurement sensor MS3110. The test results are compared with benchmark sensors which have
no hair posts. LCR meter tests showed a bulged sensor membrane under flow due to flow
pressure. Differential capacitance measurements using MS3110, which eliminate pressure
effect on sensor, showed higher sensitivities for the hair sensors than sensors without
hairs. The measured single hair sensor sensitivity is , about half of the predicted
sensitivity . The RMS resolution of the sensors in a 1Hz band for 32 sensors in parallel is
5.1Pa and the RMS resolution is 0.33Pa with 120 seconds of averaging.
Thesis (Ph.D.)--Tufts University, 2012.
Submitted to the Dept. of Mechanical Engineering.
Advisor: Robert White.
Committee: Jason Rife, Barry Trimmer, David Mountain, and Judith Gallman.
Keyword: Mechanical engineering.read less - ID:
- sj139c82q
- Component ID:
- tufts:20908
- To Cite:
- DCA Citation Guide EndNote
