The relationship between geometry and the distribution of stress within the struts of bioresorbable scaffolds

Coronary stents are tubular scaffold structures used to recover the lumen diameter of diseased coronary arteries that have narrowed. The recent development of bioresorbable stents has shown some promise in terms of clinical outcome. However, it is clear that the mechanical properties of these plastic devices need to be improved for their benefits to be fully exploited. Many studies to date have taken a 'macro' approach to design studies of coronary stents and hence seek to optimise design variables such as the 'number of connectors' or 'ring spacing'. To our knowledge no work to date considers the plastic strain exploited along the profile of the device in crimping and expansion and how this effects behaviour of the device. Whilst few studies document the detail of the parameterisation of the CAD models constructed it does not appear that any have been developed using the same method that was developed early in this utilising a Fourier series to describe the profile of the device. This project seeks to undertake a detailed analysis of the distribution of stress and strain around the profile of these scaffolds post crimping and expansion. This detailed analysis will aid our understanding of how and where plastic strain is exploited along the structure of the stent and in turn help to design scaffolds with improved mechanical properties. This knowledge can then potentially be applied to other biomedical scaffolds. A parametric model of the device will be created to allow for convenient changes to the geometry of the stent and seek to minimise the number of design variables whilst aintaining a flexible design. Structural FEA (finite element analysis) will be conducted on a range of stent geometries and then design optimisation via surrogate modelling will be carried out to obtain an optimised design.