Controlling the alignment and degradation of 3D printed poly-L-lactic acid for redesigned coronary stents
type: CreativeWork
description: Cardiac stents are used for treating heart disease, widening the blocked artery to restore normal blood flow. However, most stents are permanent. This posits several problems, including the long-term risk of restenosis and thrombosis. Consequently, significant research is focused on creating biodegradable stents. The most commercially successful material for this is polylactic acid (PLA), although, numerous challenges remain before the stent’s wider implantation. As a material, PLA is widely used within fused filament fabrication (FFF) 3D printing. FFF could be a viable technique for manufacturing patient-specific cardiac stents. Furthermore, the ideal strut thicknesses, no greater than 100 µm, are readily achievable using FFF. However, achieving the required radial stiffness at this size remains a challenge within 3D printed PLA. This thesis explored methods to improve the polymer chain alignment and resultant Young’s modulus of 3D printed single-layer poly-L-lactic acid (PLLA). Results showed that polymer chain alignment can be increased by raising the bed temperature, lowering the nozzle temperature or increasing nozzle diameter, with birefringence increasing from 0.0007 ± 0.0001 to 0.0011 ± 0.0003. In addition, post-printing annealing and sample shearing were explored. By changing the annealing time and temperature, the crystallinity and crystal structure could be controlled. The resultant Young’s modulus increased from 2.00 ± 0.46 GPa to 2.77 ± 0.28 GPa. Sample shearing formed an oriented crystal structure and increased the Young’s modulus to 2.78 ± 0.17 GPa. In a small number of reported cases, implanted commercial PLA stents have suffered from uncontrolled degradation and increased risk of late-stage thrombosis. Internal differences in microstructure, arising from the manufacturing and implantation process, resulted in an asymmetric degradation profile. If, however, the effect of microstructure on degradation rate was better understood, a "safety stent" could…
abstract: Cardiac stents are used for treating heart disease, widening the blocked artery to restore normal blood flow. However, most stents are permanent. This posits several problems, including the long-term risk of restenosis and thrombosis. Consequently, significant research is focused on creating biodegradable stents. The most commercially successful material for this is polylactic acid (PLA), although, numerous challenges remain before the stent’s wider implantation. As a material, PLA is widely used within fused filament fabrication (FFF) 3D printing. FFF could be a viable technique for manufacturing patient-specific cardiac stents. Furthermore, the ideal strut thicknesses, no greater than 100 µm, are readily achievable using FFF. However, achieving the required radial stiffness at this size remains a challenge within 3D printed PLA. This thesis explored methods to improve the polymer chain alignment and resultant Young’s modulus of 3D printed single-layer poly-L-lactic acid (PLLA). Results showed that polymer chain alignment can be increased by raising the bed temperature, lowering the nozzle temperature or increasing nozzle diameter, with birefringence increasing from 0.0007 ± 0.0001 to 0.0011 ± 0.0003. In addition, post-printing annealing and sample shearing were explored. By changing the annealing time and temperature, the crystallinity and crystal structure could be controlled. The resultant Young’s modulus increased from 2.00 ± 0.46 GPa to 2.77 ± 0.28 GPa. Sample shearing formed an oriented crystal structure and increased the Young’s modulus to 2.78 ± 0.17 GPa. In a small number of reported cases, implanted commercial PLA stents have suffered from uncontrolled degradation and increased risk of late-stage thrombosis. Internal differences in microstructure, arising from the manufacturing and implantation process, resulted in an asymmetric degradation profile. If, however, the effect of microstructure on degradation rate was better understood, a "safety stent" could…
author: Malone, Luke
language: eng
keywords: 3D printing, Cardiac Stents, Degradation, Poly lactic acid (PLA)
license: https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/c7ff3f1d-3201-42d9-8f3f-34becbed2c63/download
license: http://purl.org/NET/rdflicense/allrightsreserved
date published: 2024-08-12
date modified: 2026-07-22T22:24:08Z
provider: Cambridge University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Cambridge

PropertyValue
property ID: DOI
value: 10.17863/CAM.116688