Development of biomimetic MEMS microphones inspired by Ormia Ochracea working in audio range

Student thesis: Doctoral Thesis

Abstract

The design, fabrication, characterization and analysis of two categories of novel Micro-electro-mechanical-system microphones inspired by the fly Ormia ochracea’s ears are presented in this thesis. The first category is the microphone composed of two coaxial single crystal silicon plates rotating along the same beam fixed to a certain thickness substrate that produces four resonance frequencies – two more resonance frequencies than previously published designs, which broadens the working frequency bands that having efficient directional response. Depending on the position of the torsional beam, the first can also be divided into two models: the symmetric dual-plate model and the asymmetric dual-plate model. Both models use the same fabrication process, and the mechanical vibrations of their diaphragms are sensed by deposited piezoelectric material. The symmetric dual-plate model offers sine dependence response at the two rocking modes and cosine dependence response at the bending modes. The asymmetric dual-plate is built to unify the directional response at four resonance frequencies. Its torsional beam is biased from the centre in order to create a mass difference between the diaphragm on the two sides of the torsional beam, which not only results in cosine dependence responses at all four resonance frequencies but also beyond the resonance. The second category is designed particularly for low-frequency hearing aids that enhances the acoustic response at low frequency band below 3 kHz. This microphone has two resonance frequencies of which one is down to 500 Hz, and it is also allocated both capacitive comb-finger sensing and piezoelectric sensing units. It has uniform bi-directional response below the frequency of interest.Chapter 1 gives the basic knowledge of the acoustic and microphones as well as the literature review of Omira ochracea and its previous inspired microphones. Chapter 2 and Chapter 3 relate to the dual-plate multi-band operational microphones, including their modal analysis, finite element simulation and electrical measurement. Chapter 4 presents the MEMS microphone operating at low-frequency range. The noise performance is improved along with the development process. Chapter 5 summaries the features of each categories and lists the future work of the research.
Date of Award31 Oct 2019
Original languageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsUniversity of Strathclyde
SupervisorJames Windmill (Supervisor) & Deepak Uttamchandani (Supervisor)

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