Facile and Scalable Fabrication of High-Performance Polylactide-Based Medical Microparts through Combining the Microinjection Molding Intense Shear Stress Field and Annealing Strategy

Abstract

The second surgery for removing metallic internal fixation devices causes unbearable pain to orthopedic patients. Fortunately, poly(L-lactic acid) (PLLA), a bioabsorbable aliphatic polyester, has exhibited certain advantages in practical application due to its degradation over time in vivo with a minimal inflammatory response. However, the use of a PLLA bone screw for repairing defective bones is actually limited by the difficulty in realizing the balance between stiffness and toughness in current products. Herein, we report a novel strategy to fabricate the microbone screw from a blend of PLLA and poly[(butylene succinate)-co-adipate] (PBSA) by adopting the combination of the microinjection molding process featured with an intensive shear stress field and the subsequent annealing strategy. Accordingly, the hybrid shish-kebab structures consisting of flexible PBSA fibers attached by well-aligned lamellar crystals of PLLA could be generated, which prove to be able to overcome the difficulties well in keeping the balance between stiffness strength and toughness of the regular PLLA microparts. Thanks to the above-formed unique hybrid shish−kebab structures, the bone-mimicking PLLA/PBSA (90/10) blend material not only possesses excellent ductility (elongation at break of 51%) but also exhibits high stiffness (Young's modulus of 2.32 GPa) and balanced tensile strength (61.2 MPa). Moreover, the flexural measurements show that the fabricated PLLA/PBSA microbone screw also possesses good flexural properties (comparable flexural strength and much better toughness) compared to that of the pure PLLA bone screw. The strategy proposed in this work for fabrication of the PLLA-based microbone screw could be industrially scalable and shows good application prospects.

Analysis of Weld Lines in Micro-Injection Molding

“…The thickness value changed when analyses were conducted at the weld line location: in that position, the thickness was 0.45 mm. The tensile strength measurements were performed at 30 • C [17]. The set maximum load was 8 N, with a load rate of 1 N/min.…”

Performance Enhancement of PLA-Based Blend Microneedle Arrays through Shish-Kebab Structuring Strategy in Microinjection Molding

“…Microinjection molding has gained much attention among these processing methods due to its excellent molding accuracy and high processing efficiency [ 4 , 5 ], thus making it easy to be industrialized. Many polymer components and devices applied in the medical field, such as transnasal inhalers, vascular clips, bone screws and microneedles [ 6 , 7 , 8 ], generally require the precision manufacturing (good replication accuracy) and processing efficiency so as to achieve good economic benefits. Obviously, the microinjection molding strategy could exhibit significant advantages in the manufacturing of micro medical devices.…”

“…In order to realize the creation of the shish-kebab crystalline structures in the PLA/PPDO blend system, it is first necessary to make PPDO uniformly dispersed in the PLA matrix. Then, taking advantage of the strong shear force field during processing, the PPDO dispersed phases could be in situ fibrillated along the flow direction to form the highly oriented fibrillar structure [ 6 , 25 ] which could possibly act as shish during crystallization and then be advantageous to the shish-kebab crystallization formation. As we know, extrusion and injection molding are the two well-known polymer processing techniques featured with shear force field.…”

SLS 3D Printing To Fabricate Poly(vinyl alcohol)/Hydroxyapatite Bioactive Composite Porous Scaffolds and Their Bone Defect Repair Property

“…The bioactive ceramics, especially hydroxyapatite (HA), are the most popular bone substitute materials because of their similarity to the mineralized composition in human hard tissues as well as their good biocompatibility, osteoconductivity, and potential osteoinductivity. − Compounding of HA and biodegradable polymers can provide significant improvements in biological and mechanical properties. − The synthetic polymers such as poly­(l-lactic acid) (PLA) , and polycaprolactone (PCL) , have been extensively studied for various biomedical applications. However, the poor cell adhesion due to their hydrophobicity limits further application of these materials.…”

“…7−9 Compounding of HA and biodegradable polymers can provide significant improvements in biological and mechanical properties. 10−12 The synthetic polymers such as poly(l-lactic acid) (PLA) 13,14 and polycaprolactone (PCL) 15,16 have been extensively studied for various biomedical applications. However, the poor cell adhesion due to their hydrophobicity limits further application of these materials.…”