MEMS enabled miniaturisation of photoacoustic imaging and sensing systems

Student thesis: Doctoral Thesis

Abstract

This work presents multiple advances toward miniaturised photoacoustic imaging systems. Miniaturising the system is done in two steps. Firstly, by using novel custom arrays of piezoelectric miniaturised ultrasound transducers. The arrays were fabricated using a cost-efficient multi-user process. The achievable upper frequency limits were restricted by the design limitations of the multi-user process. The designs comprised of a single frequency and two frequency staggered arrays. They were characterised using laser Doppler velocimetry, pitch and catch technique as well as photoacoustic excitation. Additionally, the arrays were compared to commercial bulk ultrasound transducers. The custom-made PMUT arrays perform well compared to commercial transducer, despite their significantly smaller (two orders of magnitude) detection area. Secondly, an optical resolution photoacoustic microscope consisting consisting of MEMS based excitation - using a fast-scanning micro-mirror for Q-switching - and detection schemes is built and used to image synthetic targets and phantoms. Furthermore, a simulation model of the system is developed to evaluate influences of the miniaturised elements on the photoacoustic signal generation and received spectra and signal strength. Finally, a novel photoacoustic excitation scheme based on CW - laser excitation and a MEMS based fast-scanning micro-mirror is presented and its performance relative to pulsed excitation photoacoustic imaging is evaluated. Here, the photoacoustic excitation is not due to fast pulsed laser excitation, but caused by scanning a focused CW - beam over a sample.
Date of Award31 Aug 2021
Original languageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsUniversity of Strathclyde
SupervisorDeepak Uttamchandani (Supervisor) & Gordon Flockhart (Supervisor)

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