Preparation and Evaluation of 4D-Printed Poly(L-lactic) Acid/Silk Fibroin Polymer Blends with Enhanced Mechanical Properties and Water-Induced Shape Memory Effects

The integration of water-induced shape memory polymers into 4D printing provides novel opportunities to create innovative intelligent medical devices. Herein, poly(L-lactic) acid (PLLA)/silk fibroin (SF) scaffolds with water-induced shape memory capabilities and enhanced mechanical properties are developed using direct-write 4D printing technology. By analyzing the influence of the content of SF on the rheological properties, apparent viscosity and volatile properties of the ink, and the direct writing process of PLLA/SF scaffolds is systematically investigated. Results reveal that the PLLA/SF-30 wt% scaffold with a 50% filling ratio achieves the optimal mechanical properties, a compressive strength of 12.27 MPa, and a compressive modulus of 2.01 MPa, which is 1.42 and 2.83 times that of pure PLLA scaffolds, respectively. Furthermore, the PLLA/SF-30 wt% scaffold exhibits good shape memory behavior in water at 40 °C, with a shape fixation ratio (R_f) of 94.6% and a shape recovery ratio (R_r) of 67.0%. A 4D-printed grabber made from PLLA/SF-30 wt% can successfully grasp objects weighing 10 times its own weight. These results provide important insights into the potential applications in healthcare, enhancing their promise for personalized medical devices.