Polylactic acid (PLA) is a biodegradable polymer material used as a material for medical devices, because PLA breaks down in the body and doesn’t need to be removed. Injection molding methods have been used for the processing of PLA. On the other hand, processing methods using fused filament fabrication (FFF) 3D printers have attracted attention in recent years. Using FFF 3D printers, it is possible to create medical devices that are optimally tailored for each patient. When we apply PLA in medical devices, data on mechanical properties related to degradability are essential. In previous studies, test pieces were made micro-size to enable efficient testing, making it impossible to attach extensometers and calculate accurate strain. In this study, we used digital image correlation (DIC) to calculate the accurate strain of PLA test piece and evaluated their mechanical properties related to degradability. PLA test pieces were fabricated using an FFF 3D printer and immersed in saline before tensile tests. As a result, the maximum tensile stress and breaking energy decreased after 90 days of immersion. On the other hand, no significant change was observed in the tensile elastic modulus after 210 days of immersion. When comparing the strain calculated from the displacement of the testing machine's crosshead and the strain calculated by DIC, there was a large difference between them. It became clear that this difference had a significant impact on the evaluation of mechanical properties of PLA. The tensile elastic modulus calculated by DIC was close to previously known values, demonstrating that accurate strain measurements using DIC are available for evaluating the mechanical properties of micro-size PLA test pieces.
HORIBE et al. (Wed,) studied this question.