Thermo-Mechanical Characterization of 4D-Printed Biodegradable Shape-Memory Scaffolds Using Four-Axis 3D-Printing System

• Published in: Materials Vol. 16; no. 14; p. 5186
• Main Authors: Slavkovic, Vukasin, Palic, Nikola, Milenkovic, Strahinja, Zivic, Fatima, Grujovic, Nenad
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 01.07.2023; MDPI
• Subjects: 3-D printers; 4D printing; additive manufacturing (AM); Atherosclerosis; Chambers; Comparative analysis; Elongation; FDM 3D printing; Fused deposition modeling; Lactic acid; Load; Manufacturing; Mechanical properties; Methods; Polymers; Recovery time; Scaffolds; Shape effects; Shape memory; shape-memory materials (SMMs); Smart materials; smart materials (SM); Stent (Surgery); Stents; Tensile tests; thermo-mechanical testing; Three dimensional printing; additive manufacturing (AM); FDM 3D printing; biodegradable vascular stents (BVS); shape-memory materials (SMMs); biomedical devices; smart materials (SM); 4D printing; thermo-mechanical testing; material extrusion (MEX)
• DOI: 10.3390/ma16145186
• ISSN: 1996-1944

This study was conducted on different models of biodegradable SMP (shape-memory polymer) scaffolds. A comparison was conducted utilizing a basic FDM (fused deposition modeling)/MEX (material extrusion) printer with a standard printing technique and a novel, modified, four-axis printing method with a PLA (poly lactic acid) polymer as the printing material. This way of making the 4D-printed BVS (biodegradable vascular stent) made it possible to achieve high-quality surfaces due to the difference in printing directions and improved mechanical properties-tensile testing showed a doubling in the elongation at break when using the four-axis-printed specimen compared to the regular printing, of 8.15 mm and 3.92 mm, respectfully. Furthermore, the supports created using this method exhibited a significant level of shape recovery following thermomechanical programming. In order to test the shape-memory effect, after the thermomechanical programming, two approaches were applied: one approach was to heat up the specimen after unloading it inside temperature chamber, and the other was to heat it in a warm bath. Both approaches led to an average recovery of the original height of 99.7%, while the in-chamber recovery time was longer (120 s) than the warm-bath recovery (~3 s) due to the more direct specimen heating in the latter case. This shows that 4D printing using the newly proposed four-axis printing is an effective, promising technique that can be used in the future to make biodegradable structures from SMP.