Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.600286
Title: Development of a Lorentz force drive system for a torsional paddle microresonator using Focused Ion Beam machining
Author: Chitsaz Charandabi, Sahand
ISNI:       0000 0004 5350 6304
Awarding Body: University of Birmingham
Current Institution: University of Birmingham
Date of Award: 2014
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Abstract:
This thesis focuses on the concept, design, fabrication and characterisation of a torsional micro paddle resonator. The ultimate intention is to use the device for rapid detection of anthrax bacteria. A comprehensive research was carried out to review the state of the art in MEMS based mass sensing. Various driving and detection strategies were investigated and discussed. Based on evidence from literature, a novel approach was adopted to realise a device with improved functionality and overcome currently existing drawbacks. The working principle of the proposed device is based on electromagnetic actuation and monitoring of the shift in resonance frequency of a micro paddle. The design of the paddle was optimised using theoretical and finite element methods. Dual beam Focused Ion Beam (FIB) machining techniques were used to fabricate the prototype devices. The chosen substrate is a LPCVD 200 nm thick silicon nitride membrane. Prior to milling the substrate, the sputtering rate of silicon nitride was validated experimentally to ensure machining stability. Different actuating pattern designs were fabricated to generate torque including micro spiral coil, micro dual loop, and single conductive track on the micro paddle. The geometry was finalised for a defined working condition of 1 MHz resonance frequency. Important fabrication parameters were discussed and damage prevention issues were investigated. The sensitivity to the added mass was experimentally characterised and found to be 2.35 fg/Hz. To characterise the asymmetrical paddle resonator, piezoelectric excitation was applied to the device and a laser Doppler vibrometer was used to record the resonant frequency. Resonant frequencies of 0.841 and 0.818 MHz were detected by testing the device in an air medium and a quality factor of about 300 was calculated by applying a Lorentzian curve fit to collected data.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.600286  DOI: Not available
Keywords: TJ Mechanical engineering and machinery
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