Mechanics of Three-Dimensional Printed Lattices for Biomedical Devices

Abstract

Advances in three-dimensional (3D) printing are enabling the design and fabrication of tailored lattices with high mechanical efficiency. Here, we focus on conducting experiments to mechanically characterize lattice structures to measure properties that inform an integrated design, manufacturing, and experiment framework. Structures are configured as beam-based lattices intended for use in novel spinal cage devices for bone fusion, fabricated with polyjet printing. Polymer lattices with 50% and 70% porosity were fabricated with beam diameters of 0.4–1.0mm, with measured effective elastic moduli from 28MPa to 213MPa. Effective elastic moduli decreased with higher lattice porosity, increased with larger beam diameters, and were highest for lattices compressed perpendicular to their original build direction. Cages were designed with 50% and 70% lattice porosities and included central voids for increased nutrient transport, reinforced shells for increased stiffness, or both. Cage stiffnesses ranged from 4.1kN/mm to 9.6kN/mm with yielding after 0.36–0.48mm displacement, thus suggesting their suitability for typical spinal loads of 1.65kN. The 50% porous cage with reinforced shell and central void was particularly favorable, with an 8.4kN/mm stiffness enabling it to potentially function as a stand-alone spinal cage while retaining a large open void for enhanced nutrient transport. Findings support the future development of fully integrated design approaches for 3D printed structures, demonstrated here with a focus on experimentally investigating lattice structures for developing novel biomedical devices.

Surface Quality of 3D-Printed Models as a Function of Various Printing Parameters

“…Whether the above findings can be transferred to different materials and printers with different functionalities should also be investigated. The already wide application range of 3D printing in medicine and dentistry and the continuing rapid development indicates that these technologies will continue to gain in importance in these fields [1,2,3].…”

“…Computer-assisted additive manufacturing has become increasingly useful in medical and dental applications [1,2,3,4,5]. Numerous 3D printers based on different technologies are commercially available [6]: PolyJet, ColorJet, and fused deposition modeling are comparatively expensive technologies, whereas printers based on digital light projection and stereolithography (SLA) printers are relatively inexpensive.…”

3D Printed Wavy Scaffolds Enhance Mesenchymal Stem Cell Osteogenesis

“…Thus, it has been widely utilized for fabricating custom designed bone scaffolds [24][25][26][27][28]. A wide range of 3D printing techniques have been used to fabricate 3D bone scaffolds, such as fused deposition modeling (FDM) [29][30][31][32], direct ink writing (DIW) [33,34], selective laser sintering and melting (SLS and SLM) [35], stereolithography (SLA) [36][37][38], continuous digital light processing (cDLP) [39,40], and inkjet printing [41,42]. These 3D printing technologies allow utilizing various 2 of 15 printable materials [43] and designs [44].…”

Mechanical and Biological Characterization of 3D Printed Lattices

“…These contrasting beam diameters were chosen since they enable adequate tuning of pore sizes for the chosen porosity ranges, and there is a need to test whether beam diameter size may influence the mechanical stiffness of lattices for each topology. 29 Fixed p samples had 3 • 3 • 3 patterning for mechanical testing or a topology-dependent patterning for the maximum unit cell number not to exceed 10 mm lattice length, to determine whether number of unit cells influenced elastic modulus. A 3 • 3 • 1 patterning with the single unit cell layer constructed parallel to the build platform (i.e., one unit cell height) was also fabricated by using fixed p samples for cell culture testing.…”