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Title: Layer guided acoustic wave sensors
Author: Evans, Carl Richard
ISNI:       0000 0001 3450 6809
Awarding Body: Nottingham Trent University
Current Institution: Nottingham Trent University
Date of Award: 2006
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This thesis reports an experimental investigation into the use of polymer layers deposited on acoustic wave sensors. Both quartz crystal microbalances (QCM) and acoustic plate mode (APM) devices exhibit a predominantly shear motion of the sensing surface and are therefore suitable for sensing in a liquid environment. Data is presented showing the effect of patterning layers of SU-8 photoresist on a quartz crystal microbalance (QCM) and subsequent chemical treatment to increase hydrophobicity. Patterns consisting of 5 pm diameter pillars separated by 10 pm have been fabricated with heights from 3 pm up to 20 pm in addition to equivalent flat layers. The change in resonant frequency of the QCM has been investigated as the surfaces were submerged in solutions of PEG and glycerol. It is shown that for 10 pm pillars the change in resonant frequency is significantly different to expected theory suggesting a resonant effect at this particular height. Shear horizontal acoustic plate mode (APM) sensors provide a mass sensitive surface. Layer guided APM have been previously reported for quartz, this thesis extends this work to investigate lithium tantalate. Wafers have been lapped and polished prior to the fabrication of interdigital transducers (IDT). The effect of building up successive polymer layers is reported for both the surface containing the IDT and the opposite face. The data demonstrates the ability of lithium tantalate to support layer guided acoustic plate modes (LG-APM). The sensitivity of the LGAPM have been investigated using a systematic deposition of gold layers. The sensitivity of the LG-APM is shown to be equivalent to a traditional APM operating at five to six times the frequency. A biosensor application of the LG-APM is presented that demonstrates the use for investigating major histocompatibility complexes (MHC) - peptide interactions, which play a vital role in the immune system. In this work we monitor the immobilisation of a class I heavy chain on the LG-APM surface, and the binding of the B2m and subsequent binding of a peptide.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available