Multi-Objective Design of a Biodegradable Coronary Artery Stent - Cardiovascular and Cardiac Therapeutic Devices - page 19

Fig. 14 Response surface model for non-dimensional tissue drug concentration. See caption for

Fig. 12

and an example is available in [ 37 ] along with a discussion that helps to explain
the noise in the data. In essence, when the links deform under load, they can come
into self-contact, and this distorts the moment-curvature profile used to extract the
flexibility metric. Despite this problem, flexibility is shown to be primarily
dependent on the outer abscissa parameter that defines the link amplitude, as
evidenced by the fact that individual tiles change far more significantly in Fig. 15
from left to right than they do from bottom to top. Furthermore, a flexibility
improvement of 14 %, relative to the baseline design, was demonstrated in [ 25 ]
without a decrease in the other objectives.

5 A Real Design Case

Based on the knowledge gained in earlier studies [ 21 , 25 ], a DSO project was
undertaken to design a biodegradable polymer stent which was to become the first
prototype of the Arterius Biodegradable Scaffold (ABS), Arterius Ltd. This design
cycle needed to be completed within 6 months. Starting from an initial concept, a
parametric CAD model was constructed and developed during preliminary design.
The process of setting up and developing the CAD model occupied most of the
time of problem setup. In contrast, since a range of simulation models were
available from other studies of metallic stents [ 21 , 25 ], relatively modest effort was