THE LASER USER
ISSUE 115 MARCH 2025 LASER WELDING
4. Deployment modelling Figure 2: (A) Surface finish and (B) metabolic activity of different surface conditions [2]
Modelling the different stages of the stent deployment procedure was crucial to assess the capability of the TNTZO stents for actual use. Two different strut widths of 200 μm (S200) and 80 μm (S80) were simulated while keeping the same strut thickness of 200 μm (see Figure 4). As plastic deformation is limited to 15% to avoid stent failure, S80 showed a 74% diameter reduction compared to only 40% for S200 due to the higher flexibility of the thinner struts. For both stents, localised plastic deformation happens at the corners of the zigzag structure, with a shorter spread in S80 struts compared to S200. Also, the crimping force needed for S80 is 86% lower compared to S200 which promotes it to be used in more complex and tight blood vessels. These values show superior performance compared to S316LVM stents that need almost double the crimping force for only 50% diameter reduction [5]. Overall, the stent showed impressive mechanical behaviour and biocompatibility properties that boost the potential for commercial use.
Conclusion
Figure 3: (A) LMM of open stent from L-PBFed tubes, (B) FE and experimental 3 Point Bending (3PB) testing [2].
3. Laser Micro Machining
Optimised LMM parameters were successfully used to cut the open stent design with 200 μm thick struts (see Figure 3A). The 4.5 mm overhanging structure marked in the figure is easily achievable using this hybrid manufacturing technique compared to the design limitations (or rules) of using L-PBF only, as stated by Finazzi et al. [4]. The machined struts had high geometrical dimensional stability along the stent with no evidence for internal or surface cracks. Few LMM residues were washed off afte the electropolishing process. The stent passed standard mechanical 3-Point bending testing (3PB) according to ASTM F2606-8, without yielding (see Figure 3B).
Figure 4: Stresses in S200 and S80 during deployment modelling [2].
Peter Ibrahim has recently completed his PhD research at AMPLab, University of Birmingham, focusing on laser processing of beta titanium alloys for medical applications.
SEE OBSERVATIONS P30 27
This study highlights the transformative potential of laser-based manufacturing techniques in the production of arterial stents. By combining the design flexibility of L-PBF with the precision of LMM, the proposed hybrid approach addresses the challenges of traditional stent manufacturing. The resulting TNTZO stents exhibited improved mechanical performance, biocompatibility, and customisation, making them a promising candidate for future biomedical applications.
References
[1] P. Ibrahim, et al. Materials Science and Engineering: A, p. 146617, Jul. 2024, doi: 10.1016/
j.msea.2024.146617.
[2] P. Ibrahim et al., Mater Des, vol. 247, Nov. 2024, doi: 10.1016/
j.matdes.2024.113420.
[3] M. Attallah, et al. “Method of manufacturing a medical device,” Patent WO 2021/181116 A1, Sep. 16, 2021
[4] V. Finazzi et al. Procedia Structural Integrity, Elsevier B.V., 2019, pp. 16–23. doi: 10.1016/j. prostr.2019.07.004.
[5] J. Bukala, et al. Int J Numer Method Biomed Eng, vol. 33, no. 12, Dec. 2017, doi: 10.1002/ cnm.2890.
Contact: Peter Ibrahim
P.ibrahim@bham.ac.uk www.birmingham.ac.uk
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