Material selection and manufacture for a polymer heart valve application

This thesis reports on the material selection, manufacture and testing of a polymer heart valve made entirely from block copolymer. Selection based on Ashby diagrams pointed towards styrene-based and polyurethane-based block copolymers as candidate materials for study. Styrene-based block copolymers had been well studied in their fatigue behaviour, but more insight was required into their biostability. On the other hand, polyurethane-based block copolymers are reputable for their resistance to in vivo degradation, but further study was required to understand their performance in the application. To form a holistic comparison between these materials, both their biostability and fatigue were studied. All materials were characterised for their structural, thermal and mechanical properties before and after accelerated ageing by oxidation and hydrolysis. Thermal ageing in air was also studied. Collection of this qualitative and quantitative information builds a useful database of results from which to develop an understanding of the nature of degradation in these polymers. Variations in results for ageing in different environments sheds light on the importance of selecting suitable ageing environments to simulate in vivo degradation in polymers. Studies in this thesis present the unique potential of polyisobutylene-based polyurethane for the polymer heart valve application, with excellent performance in biostability experiments and fatigue. As part of these studies, a compression moulding technique was developed to make the first prototype heart valves from this polymer. Performance testing on rapid-failure rigid post heart valve prototypes made from polyisobutylene-based polyurethane, along with a styrene-based block copolymer and Elast-Eon, a well-known commercial biomaterial, have shed light on its outstanding durability, placing it as a top contender in this material selection study. Following these findings, experimental fatigue data was applied alongside a finite element model of a polyisobutylene-based polyurethane heart valve to create a lifetime prediction curve for rigid post heart valve prototypes. With the clinical need for a prosthetic heart valve that is both effectively durable and biocompatible, the performance of BCPs reported in this thesis illuminate the path towards a polymer-based solution, highlighting the promise of polyurethane-based block copolymers and identifying factors influencing polymer degradation to provide a framework for the assessment of new candidate materials to be developed.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2023

Author dc:creator

• Patel, Ruhi

Advisors dc:contributor.advisor

• Moggridge, Geoffrey
• Busfield, James

• Polymer heart valve

Licence

• https://www.repository.cam.ac.uk/bitstreams/ce4b9fbb-d2f4-48d9-996d-f95da5bf21f6/download
• https://www.rioxx.net/licenses/all-rights-reserved/

Language dc:language

eng

DOI dc:identifier.doi

https://doi.org/10.17863/CAM.110585

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/371388