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Title: Novel ultrasonic transducers and array designs using self-similar fractal geometries
Author: Fang, Haoyu
ISNI:       0000 0004 7967 2394
Awarding Body: University of Strathclyde
Current Institution: University of Strathclyde
Date of Award: 2018
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Wider operational bandwidth is an important requirement of an ultrasound transducer across many applications. Naturally occurring resonating systems utilise structures containing a range of length scales to produce a broad operating bandwidth. In this work, a novel concept of designing a piezoelectric composite using a fractal geometry is proposed in order to explore the potential of enhancing the operational performance, particularly in terms of transducer bandwidth and sensitivity. Piezoelectric composite configurations were designed using four well-known fractal geometries: Sierpinski Gasket, Sierpinski Carpet, Cantor Set and Cantor Tartan. The fractal composite devices were realised as either 1-3 connectivity or 2-2 connectivity configurations and compared with their corresponding equivalent conventional composite counterpart. Finite element modelling was utilised to design and explore the behaviour of these four fractal composite designs. A single element ultrasound transducer with SG fractal geometry and an ultrasound array with CS fractal geometry were fabricated and importantly, their experimental performance correlated well with the FE predictions. In this study, fractal composites, with a nominal central operating frequency of 1MHz, have been designed and fabricated with improved bandwidth (and in some case, sensitivity also) when compared to equivalent conventional composite devices. Moreover, the enhanced bandwidth is shown to provide higher resolution imaging performance. Overall, the careful selection of different resonant frequencies within a composite structure has been shown to improve operational performance and it is anticipated that this transducer concept will become more prevalent as 3D piezoelectric fabrication processes mature.
Supervisor: O'Leary, Richard ; Gachagan, Anthony ; Mulholland, Anthony Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral