Fabrication and characterisation of novel ultrasound transducers

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Jiang, Yun (2013). Fabrication and characterisation of novel ultrasound transducers. University of Birmingham. Ph.D.

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Abstract

1-3 connectivity piezoceramic-polymer composites that can operate above 30 MHz are in demand to improve spatial resolution for biomedical ultrasound imaging applications. However, increasing the operational frequency of these materials is extremely challenging as ultrafine dimensions are required in conventional composite designs. An innovative randomised composite design has been previously reported to relax overall dimensional restrictions and to eliminate spurious resonance modes. However, realisation of such a design presents a significant challenge to conventional fabrication techniques.

In this work, a novel moulding approach based on a combination of gel casting and soft lithography techniques has been developed for producing random composites. A maximum green strength of 38 MPa has been obtained in the gel-cast green bodies. Irregular-shaped ceramic segments with feature sizes varying from 2 to 50 μm and aspect ratios up 70 have been achieved. Random piezocomposites with operational frequencies up to 100 MHz and thickness coupling factors over 0.5 have been fabricated and demonstrated. Two complete transducers working at 30 MHz and 70 MHz incorporating the random composites have been produced and characterised. Results from the transducers demonstrated their functional performance and showed the potential of the novel random piezocomposites for high frequency ultrasound applications.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

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