Fused Filament Fabrication of Bioresorbable Stent on a Rotating Mandrel

Abstract

Bioresorbable stents have the potential to restore patency to blood vessels while minimising the risk of long-term complications. Bioresorbable stents can dissolve after restoring flow to a blocked artery, leaving behind a blood vessel with restored vascular tone. This can provide increased lumen gain, long-term vascular rehabilitation, and long-term healing. Additive manufacturing (AM) could offer new design freedom and patient-specific solutions; however, AM fabrication of bioresorbable stents, especially for specific patients, is challenging. In recent times, AM-based Fused Filament Fabrication (FFF) has gained popularity for printing stents by employing a rotating mandrel as a printing bed. However, using standard slicing methodology is challenging when generating extrusion profiles with strut dimensions at this size scale. By eliminating the requirement for a CAD model and instead slicing based on direct extrusion path generation from parametric curves, a method has been proposed for the FFF printing of bioresorbable stents on rotating mandrels. A Grasshopper (plugin in Rhinoceros) -based visual programming method was adopted for the generation of the required shapes of curves for the stent. The extrusion profile (gCode) was generated by Grasshopper for 3D printing on an FFF multi-axis machine. Poly (l-lactic) acid (PLLA) polymer material was chosen along with a standard zigzag stent shape for testing the proposed methodology. The extrusion temperature, nozzle speed, and extrusion values were varied as per the design of the experiment (Taguchi L9) approach to study their effect on the stent strut width and flexural strength. The optimisation was carried out to obtain a feasible relationship between parameters to print minimum strut width and maximum flexural strength. The proposed methodology successfully demonstrates printing complex stent shapes without a CAD model and slicing.