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The replication of micron scale pillar arrays for medical ultrasound applications

Clipsham, Timothy Jack (2010)
Ph.D. thesis, University of Birmingham.

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1-3 Piezocomposites show significant improvements over conventional, monolithic transducers. However, a 10 MHz piezocomposite would require a pillar array structure with an aspect ratio of > 9 and a feature size of < 30 μm; which makes fabrication difficult and increasing the operating frequency challenging. Several processes have been developed to improve on the industry standard, dice and fill, but they remain laboratory based. Viscous polymer (VP) embossing has been demonstrated as a route to smaller feature sizes and higher aspect ratios, but the process is limited by the availability of suitable moulds, which must be replicated to make the process cost effective. This thesis reviews the micro replication and fabrication processes necessary to produce moulds for 1-3 piezocomposites, and characterises the replication process from hot embossing to a functioning 1-3 piezocomposite. It demonstrates that the Bosch process and electroforming can be combined to produce a master with a deeper array structure than has been previously demonstrated by these two processes. Piezocomposites have also been made which have pillar widths that are not possible by dice and fill, by filling hot embossed moulds that have aspect ratios of 14 and feature sizes of 30 μm.

Type of Work:Ph.D. thesis.
Supervisor(s):Button, T (Professor)
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:Department of Metallurgy and Materials
Subjects:TN Mining engineering. Metallurgy
Institution:University of Birmingham
ID Code:517
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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