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Description
Introduction
One of the main issues limiting the wide-spread application artificial vascular grafts is a high risk of thrombosis due to elasticity mismatch and kinking hazard1. One of possible solutions to these problems is incorporating 3D printed reinforcement to the design of implant2.
The aim of this study is to inspect the possibility of 3D printing with elastic medical grade materials on rotating mandrel. End goal being able to incorporate reinforcements in design of artificial grafts.
Methods
3D printer used allows for deposition of thermoplastic filament onto the rotating mandrel. This approach allows for production of cylindrical geometries without the need of supports3. Printhead with 0.4mm nozzle used during the study was standard commercially available filament printhead (FFF) produced by BioCloner Health.
Filament was extruded from medical grade polyurethane ChronoFlex with variable hardness from 75D to 75A. All materials were extruded using FilaBot NX2 filament extruder.
Printability assessment was carried out while controlling the printhead’s nozzle temperature and filament intake flowrate.
Mechanical test where carried out using Instron 2519 with standard 5kN load cell for longitude tensile stress test. For measurements of radial force custom „hook” system was used.
Results
All considered polyurethanes where suitable for filament fabrications. The value of Young modulus of filaments was similar among most of inspected samples. The filament made from the hardest source material (75D) stood out with young modulus value being around x30÷40 times greater than the rest of investigated materials.
It was observed that softness of the filament negatively impacts the maximal federate, due to the risk of bulking.
Discussion
Main observed obstacle for reliable 3D printing of elastic filaments is the high risk of clogging the nozzle or buckling of the material, as reported in the literature4. Those setbacks could be overcome with specially designed printhead or by increasing the diameter of the nozzle, however doing so would negatively impact the resolution of the print.
Frequent peeling off of the model after rapid change in the direction of the movement the mandrel it was concluded that the best practice is to maintain constant spin direction.
This study demonstrates that it is possible to print complex cylindrical structures made of medical grade materials is possible.
Acknowledgements
Rotating mandrel 3D printer and filament extruder were kindly provided by BioCloner Health
References
1. Das, K. K., Tiwari, R. M., Shankar, O., Maiti, P. & Dubey, A. K. Tissue‐engineered vascular grafts for cardiovascular disease management: Current strategies, challenges, and future perspectives. MedComm – Biomater. Appl. 3, (2024).
2. Shen, Y. et al. Development of 3D printed electrospun vascular graft loaded with tetramethylpyrazine for reducing thrombosis and restraining aneurysmal dilatation. Burn. Trauma 12, 1–17 (2024).
3. Reeser, K. & Doiron, A. L. Three-Dimensional Printing on a Rotating Cylindrical Mandrel: A Review of Additive-Lathe 3D Printing Technology. 3D Print. Addit. Manuf. 6, 293–307 (2019).
4. Zhou, L. Y., Fu, J. & He, Y. A Review of 3D Printing Technologies for Soft Polymer Materials. Adv. Funct. Mater. 30, 1–38 (2020).
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