Slavkovic Vukasin, Palic Nikola, Milenkovic Strahinja, Zivic Fatima, Grujovic Nenad
Faculty of Engineering, University of Kragujevac, 34000 Kragujevac, Serbia.
Materials (Basel). 2023 Jul 24;16(14):5186. doi: 10.3390/ma16145186.
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.
本研究针对不同型号的可生物降解形状记忆聚合物（SMP）支架展开。研究采用了一台基础的熔融沉积建模（FDM）/材料挤出（MEX）打印机，运用标准打印技术，并采用了一种新颖的、经过改良的四轴打印方法，以聚乳酸（PLA）聚合物作为打印材料进行对比。通过这种方式制造的4D打印生物可降解血管支架（BVS），由于打印方向的差异，能够实现高质量的表面，并且改善了机械性能——拉伸测试表明，与常规打印相比，使用四轴打印的试样在断裂伸长率方面提高了一倍，分别为8.15毫米和3.92毫米。此外，使用这种方法制造的支架在热机械编程后呈现出显著的形状恢复水平。为了测试形状记忆效应，在热机械编程后，采用了两种方法：一种方法是在温度箱内卸载试样后对其进行加热，另一种方法是在温水中加热。两种方法均使试样平均恢复到原始高度的99.7%，不过由于后一种情况下对试样的加热更为直接，因此在温度箱内的恢复时间（120秒）比在温水中的恢复时间（约3秒）更长。这表明，使用新提出的四轴打印进行4D打印是一种有效且有前景的技术，未来可用于制造由SMP制成的生物可降解结构。
