J. Eaton-Evans, Z. You, University of Oxford, Oxford, United Kingdom; A. Darbyshire, R. Bakhshi, A. Seifalian, University College London, London, United Kingdom
Reducing the insertion profile and improving the durability of endovascular devices represent major challenges for medical devices designers. This paper presents an innovative design for a self-expanding Abdominal Aortic Aneurysm (
AAA) stent graft that incorporates a Nitinol scaffold with a polyhedral oligomeric silsequioxane
- poly(carbonate-urea)urethane
nanocomposite polymer material, chosen for its excellent biocompatibility and superior cardiovascular properties. Origami folding theory is used to develop a folding pattern that can be moulded into the polymer material. A geometrical analysis is conducted to optimise the pattern to achieve a minimal device diameter. Finite element analysis is used to design a Nitinol wire scaffold that is compatible with the origami folding pattern. Numerical simulations are carried out to examine the radial strength of the Nitinol support and to investigate the stresses and mechanical behaviour of the structure during compression to its insertion diameter. Experimental work is conducted to evaluate the bond strength between Nitinol and the nanocomposite polymer, and the definition of the folding pattern in the polymer is discussed. The next stages in the development of the device are considered.
Summary: An innovative design for a self-expanding Abdominal Aortic Aneurysm (AAA) stent graft that incorporates a Nitinol scaffold with a polyhedral oligomeric silsequioxane- poly(carbonate-urea)urethane nanocomposite polymer material, is presented. A numerical analysis is conducted to optimise the mechanical properties of the Nitinol support scaffold. Origami folding theory is used to devise an optimal fold pattern for the device. The incorporation of this pattern with the Nitinol scaffold is discussed and investigations to examine the bonding of Nitinol scaffold to the polymer are presented.
