The Effect of Nozzle Temperature and Indentation Load on the Mechanical Properties and In Vitro Degradation of 3D-Printed Polylactide for Biomedical Applications.

Three-dimensional (3D) printing has revolutionized the fabrication of complex, patient-specific biomedical components, with the mechanical performance of printed parts being highly dependent on processing parameters. This study, for the first time, investigated the combined effects of nozzle temperature and indentation load (0.1 kgf, 0.2 kgf, and 0.3 kgf) on the mechanical properties and in-vitro degradation behavior of fused deposition modelling (FDM)-printed polylactic acid (PLA). Specifically, this work aims to understand the indentation size effect on the hardness values of the investigated materials as applied load increases. PLA specimens were fabricated at nozzle temperatures of 200°C, 210°C, and 220°C and characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), hardness measurements, fracture toughness evaluation, impact testing, and in-vitro degradation in simulated physiological conditions. FTIR analysis confirmed that variations in nozzle temperature did not alter the chemical structure of PLA. SEM revealed improved interlayer fusion at 210°C and the onset of thermal degradation at 220°C. Mechanical testing demonstrated that hardness increased with nozzle temperature, with specimens printed at 210°C and 220°C exhibiting approximately 18% and 38% higher hardness, respectively, than those printed at 200°C, across all indentation loads. The highest hardness and fracture toughness were obtained at 220°C, whereas impact resistance was greatest at 200°C, highlighting a trade-off between stiffness and toughness. In-vitro degradation over 28 days resulted in a maximum weight loss of 0.28%, accompanied by an increase in solution pH from 7.4 to 8.9. Surface apatite formation following immersion confirmed the bioactive potential of the printed PLA scaffolds. These findings demonstrate that nozzle temperature significantly influences the microstructure, mechanical performance, and degradation behavior of FDM-printed PLA, providing valuable data for optimizing biodegradable scaffolds for biomedical applications.