Iron-based biodegradable stents: impact of surface roughness on mechanical properties

Nowadays, coronary permanent stents are used to open clogged arteries. However, after 6 to 12 months, the artery recovered its mechanical properties, and the stent becomes useless. Moreover, risks of late complications, such as thrombosis or restenosis, are increased by the presence of permanent stents. Biodegradable stents aim at decreasing these risks. Such application requires good mechanical properties to support the expansion process, but also during the healing period (about 1 year) and an adapted degradation rate. Iron alloys are investigated since they exhibit good mechanical properties.However, their degradation rates are too slow for biodegradable stents. Therefore, a potential solution would be to increase the interface area by surface patterning. Roughness can have different origins in stent application. The two main ones come from machining process and plastic deformation. The present research aims at evaluating the impact of surface roughness on the mechanical properties of Fe-based biodegradable stents. Concerning roughness introduction, grinding steps were performed and associated roughness parameters were evaluated using white light interferometry. Another experiment characterised the evolution of roughness on a flat sample with respect to plastic deformation. A latter stage was the immersion tests of samples with different roughnesses to observe the degradation rate evolution