Preparation Of PLA-based Remote Drive Shape Memory Composites By 4D Printing And Their Properties

With the growing demand for healthy living by patients,the medical industry has put forward more stringent requirements for the biosecurity and versatility of biomedical devices.The emergence of 4D printing has brought breakthroughs to achieve the construction of relatively complex,personalized and high-precision intelligent devices,of which fused deposition modeling(FDM)is one of the most used printing technologies.Polylactic acid(PLA)is the most commonly used FDM printing materials,with good biocompatibility,degradability and excellent shape memory properties.However,the shape memory properties of PLA are often triggered by heating,and the single drive limits its application as a shape memory polymer in the biomedical field.Polydopamine(PDA)has excellent biocompatibility and degradability,and its conjugated structure provides absorption in the near-infrared region in a wide band.By blending PDA particles to the PLA matrix,it can give the near-infrared remote drive performance of the part,and at the same time change the surface wettability of the part,which can improve its application potential in the biomedical field.In this paper,the FDM process parameters with optimal shape memory performance and mechanical properties were determined by research.Specimens with 80% filling rate and grating angle of 45°/-45° have the best comprehensive performance and can be achieved 90% shape recovery within 20 s and highest tensile strength(57.1 MPa).Based on the best process parameters,the effects of different coating conditions on the thickness of PDA coating were studied,and increasing the DA concentration,prolonging the impregnation time and increasing the number of impregnation times could increase the coating thickness of PDA coated PLA.At the concentration of 2mg/ml DA,the coating time was 6h,and two coating times,the PDA content on the spline was still small,and the shape recovery rate was less than 50%.PDA-SA-SP particles with high carboxylate group content in the system were prepared by adjusting the oxidation conditions,which had excellent near-infrared absorption and hydrophilicity,and had a low agglomeration tendency.The addition of PDA-SA-SP to the PLA matrix by melting blending can improve the fluidity of the composite,and the molding processing temperature decreases with the increase of PDA amount,among which the temperature range of the single screw extrusion zone is 170°C-175°C,FDM printing nozzle temperature is 175°C-190°C.In addition,the addition of PDA-SA-SP can improve the surface wettability of composites and facilitate cell adhesion in tissue engineering.Composites with PDA additions of 3 wt% have the best light-driven shape memory and can reach 70% shape recovery rate within 300 s,increasing the laser power can further reduce the spline shape recovery time to 180 s.