Study on the 4D printing performance of PFO occluder frames based on PLA/PEG filaments

This paper focuses on the study of factors influencing the performance of 4D-printed PFO occluder frames. First, polyethylene glycol (PEG, Mn = 2000) was used to blend and modify polylactic acid (PLA). At a PEG content of 15%, the glass transition temperature of the blend decreased from 74°C for pure PLA to 56°C, with a significant increase in hydrophilicity and the water contact angle decreased from 74° to 62°. Regarding mechanical properties, tensile strength decreased from 60.0 ± 1.8 MPa to 27.5 ± 1.2 MPa, while elongation at break increased substantially from 4.8 ± 0.8% to 300 ± 50.2%.When PEG content was increased to 25%, the glass transition temperature decreased to 58°C, hydrophilicity continued to enhance, and the contact angle decreased to 54°. At this point, tensile strength decreased to 15.6 ± 2.0 MPa, while elongation at break further increased to 432.5 ± 30.2%. Then, orthogonal + response surface experiments were conducted to optimize the FDM 4D printing process parameters, identifying fill rate as the key factor influencing the shape recovery rate and tensile strength of PLA parts. A regression model was established linking tensile strength to printing temperature, speed, and fill rate. Mechanical testing indicated that the 8-ligament occluder exhibited the best mechanical properties, while shape memory recovery rate tests showed that occluders made from PLA/PEG2K-25 filament had superior shape recovery rates compared to those made from PLA/PEG2K-15. The study demonstrates that through PEG modification of PLA and control of the 4D printing process, comprehensive optimization of the mechanical and shape memory properties of PFO occluder frameworks can be achieved.