Montgomery Liljeroth, Ebba;
(2023)
Auxetic Structures in Cardiovascular Stent Design.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
Deformations of the great vessels during the cardiac cycle are characterised by simultaneous dilatation and elongation. Congenital conditions, vascular diseases or natural ageing often affect the great vessels, and stents and stent-graft devices are required to restore the proper cardiovascular function. However, these devices are generally highly stiff and not designed to replicate the physiological dynamics of healthy vessels. This PhD project aims at investigating the properties of auxetic structures to design stents that can mimic the great vessels’ physiological deformations. These structures differ from standard materials and provide unusual mechanical properties thanks to their negative Poisson’s ratios. The project focused on three different auxetic cellular configurations that are suitable for adaptation to tubular cellular structures and are reported to exhibit highly negative Poisson’s ratios: re-entrant hexagonal honeycomb, double-arrowhead shape and hexachiral shape. This has required the derivation and validation of new analytical models, filling the gaps in the current description. The effect of the possible changes in the characteristic geometric parameters defining each auxetic configuration over the mechanical response of the tubular structure to circumferential expansion, axial tension and twisting was analysed analytically and by finite element modelling. The different ranges of Poisson’s ratios, Young’s moduli and shear moduli for all three configurations are presented in a consistent unified nomenclature. This allows a direct comparison between the available options, simplifying the selection on the most suitable auxetic structure. Comparison to clinical data confirms that auxetic configurations can be leveraged to mimic the range of physiological dynamics of the great vessels. In the context of stents and stent-grafts, this may contribute to enhance their physiological behaviour and long-term outcomes, by restoring more natural vessel dynamics and reducing late complications.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Auxetic Structures in Cardiovascular Stent Design |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2023. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Population Health Sciences > Institute of Cardiovascular Science UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Population Health Sciences > Institute of Cardiovascular Science > Childrens Cardiovascular Disease |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10172325 |
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