| dc.contributor |
Nash, Geoff |
|
| dc.contributor |
Petrov, Peter |
|
| dc.creator |
Brown, J |
|
| dc.date |
2022-10-31T08:27:35Z |
|
| dc.date |
2022-10-31 |
|
| dc.date |
2022-10-28T10:45:00Z |
|
| dc.date |
2022-10-31T08:27:35Z |
|
| dc.date.accessioned |
2023-02-23T12:17:52Z |
|
| dc.date.available |
2023-02-23T12:17:52Z |
|
| dc.identifier |
ORCID: 0000-0002-2264-0194 (Brown, Jessica) |
|
| dc.identifier |
http://hdl.handle.net/10871/131499 |
|
| dc.identifier.uri |
http://localhost:8080/xmlui/handle/CUHPOERS/258692 |
|
| dc.description |
This thesis investigates the sensitivity of phononic metamaterials to the presence
of materials and changes in their environment.
The behaviour of surface acoustic waves (SAWs) in periodic arrays of holes
was investigated with finite element modelling and experimentally. SAW bandstructures
and bandgap attenuation were obtained from simulations of arrays
of cylindrical and annular holes which were filled with materials with different
SAW velocities. Each type of hole array exhibited two distinct scattering
regimes (Mie and Bragg scattering). The dependence of the bandgap frequency
on the velocity was found to be stronger for annular holes than for cylindrical
holes, suggesting that annular holes are potentially a better route to create tuneable
phononic metamaterials. Annular holes also displayed a higher bandgap
attenuation than cylindrical holes, meaning that annular hole arrays might be
exploited for greater sensitivity in applications such as mass loading sensing.
SAW attenuation due to mass loading of air was calculated by measuring SAW
amplitude on a SAW device using an oscilloscope system and by laser Doppler
vibrometry (LDV). An extraordinary increase of 2 to 3 orders of magnitude
in mass loading attenuation was observed at the bandgap frequency when a
phononic metamaterial was present, with only 4 resonator elements needed to
produce this result. The measurements obtained by both experimental systems
displayed similar frequency dependencies of mass loading attenuation coefficients.
Some mass loading effects were also reproduced using finite element
modelling. These approaches show great promise for improving the sensitivity
of SAW pressure sensors.
Finally, bandstructures were obtained from finite element simulations for an
array of annular holes filled with a small sphere comprised of materials with
different SAW velocities. The array exhibited similar scattering regimes as before,
with an overlapping region. The dependence of the bandgap frequency
on the velocity was found to be stronger when the annular holes contained the
sphere than when they are fully-filled, suggesting that annular holes are potentially
a good candidate for probing biological cells. Higher bandgap attenuation
by up to a factor of 2 was exhibited by the single spherical inclusion compared to
fully-filled holes. Since annular holes have more degrees of geometrical freedom
than conventional phononic crystals, devices with greater sensitivity might be
realised for applications such as biological sensing and lab-on-a-chip diagnostics. |
|
| dc.description |
Engineering and Physical Sciences Research Council (EPSRC) |
|
| dc.publisher |
University of Exeter |
|
| dc.publisher |
Centre for Metamaterial Research and Innovation |
|
| dc.rights |
http://www.rioxx.net/licenses/all-rights-reserved |
|
| dc.title |
Phononic Metamaterials for Surface Acoustic Wave Sensing |
|
| dc.type |
Thesis or dissertation |
|
| dc.type |
PhD in Physics |
|
| dc.type |
Doctoral |
|
| dc.type |
Doctoral Thesis |
|