Design of a Shape Memory Alloy Self-Expanding Stent via Open Source Optimization Methods

The self-expanding stent remains the most common application of shape memory alloys in the biomedical field, and thus methods for improving the analysis and design optimization capabilities associated with these devices are of significant interest. A number of optimization approaches, many of them based on commercial software solutions, are being employed by engineers and researchers seeking the best design solutions (material responses, geometric configurations, etc.) for complex devices. However, the lack of adaptability and high cost of commercial optimization software can be restrictive to comprehensive engineering development in some cases. An alternative open source multi-disciplinary analysis and optimization framework known as OpenMDAO has been developed by NASA and offers an attractive alternative for stent design optimization. In this work we consider the constrained optimization problem of designing a self-expanding stent with a maximized radial restoring force that does not experience unreasonably high stresses during crimping nor fatigue-inducing strains during pulsatile loading. An innovative parameterization of a self-expanding stent is developed and employed. The design problem is addressed using multiple optimization algorithm options within the OpenMDAO framework and the effectiveness of the algorithms is compared.