Effect of the Interior Fill Percentage on the Deterioration of the Mechanical Properties of FFF-3D-Printed PLA Structures

Poly (lactic acid) (PLA), a biodegradable polymer, is widely used in medical applications, particularly for 3D-printed tissue engineering scaffolds. The fused filament fabrication (FFF) 3D printer is an available processing tool for PLA. The nozzle scan pattern and interior fill percentage (IFP) considerably influence the mechanical properties of formed structures and may have dominant effects on the rates at which the mechanical properties of PLA deteriorate. When the IFP is set to a low value, such as 80%, internal gaps form within the structure, leading to different deterioration patterns compared to structures formed under the IFP 100% condition. In this study, we fabricated test pieces with an FFF 3D printer using three different nozzle scan patterns. After immersing the test pieces in phosphate buffer saline (PBS) for up to 120 days, the water content was measured and the test pieces underwent tensile testing to determine the tensile strength, elastic modulus, and breaking energy. Both the deterioration rate and water uptake rate varied among the different nozzle scan patterns used for the fabrication. For the test pieces formed with internal gaps, the water uptake and deterioration proceeded in two stages. The deterioration rate of the structures with internal gaps was faster than that of the fully filled structures. The data obtained in this study will be useful for the design of PLA structures applied in tissue engineering.