Near-Infrared-Responsive Poly(l-Lactic Acid)/poly(l-Lactide-Co-ε-Caprolactone) Shape-Memory Composites Reinforced With Photothermal Hybrid Nanoparticles for 4D Printing

Conventional poly( l -lactic acid) (PLLA) exhibits a relatively high switching temperature, limiting its on-demand actuation under mild biomedical conditions. Herein, poly( l -lactide-co-ε-caprolactone) (PLCL) was incorporated into PLLA to improve chain mobility and elasticity, and (MWCNTs–ZnO)@polydopamine nanoparticles (CZP) were introduced to construct a near-infrared (NIR)-responsive photothermal shape-memory system. The resulting PLLA/PLCL/CZP composites showed improved crystallinity, mechanical performance, and light-triggered actuation. At 1 wt% CZP, the film exhibited optimal tensile properties, with a tensile strength of 24.5 MPa and an elongation at break of 373%. Under 808 nm NIR irradiation, the composites rapidly recovered their original shape at approximately 55°C, enabling remote and mild-temperature actuation. Direct-ink-written 4D-printed scaffolds displayed high print fidelity and enhanced compressive properties, with 3 wt% CZP reaching a compressive strength of 5.2 MPa and a modulus of 0.6 MPa at 40% strain. The scaffolds showed shape-fixity ratios above 95% and recovery ratios above 80%. Biological evaluations revealed acceptable initial cell adhesion, concentration-dependent cytocompatibility, and antibacterial activity against E. coli and S. aureus . This work provides a tunable platform for NIR-triggered shape-memory actuation and programmable 4D-printed biomedical scaffolds.