Design and Mechanical Testing of 3D Printed Hierarchical Lattices Using Biocompatible Stereolithography

Abstract

<jats:p>Emerging 3D printing technologies are enabling the rapid fabrication of complex designs with favorable properties such as mechanically efficient lattices for biomedical applications. However, there is a lack of biocompatible materials suitable for printing complex lattices constructed from beam-based unit cells. Here, we investigate the design and mechanics of biocompatible lattices fabricated with cost-effective stereolithography. Mechanical testing experiments include material characterization, lattices rescaled with differing unit cell numbers, topology alterations, and hierarchy. Lattices were consistently printed with 5% to 10% lower porosity than intended. Elastic moduli for 70% porous body-centered cube topologies ranged from 360 MPa to 135 MPa, with lattices having decreased elastic moduli as unit cell number increased. Elastic moduli ranged from 101 MPa to 260 MPa based on unit cell topology, with increased elastic moduli when a greater proportion of beams were aligned with the loading direction. Hierarchy provided large pores for improved nutrient transport and minimally decreased lattice elastic moduli for a fabricated tissue scaffold lattice with 7.72 kN/mm stiffness that is suitable for bone fusion. Results demonstrate the mechanical feasibility of biocompatible stereolithography and provide a basis for future investigations of lattice building blocks for diverse 3D printed designs.</jats:p>

Utilization of Carbon Nanotubes in Manufacturing of 3D Cartilage and Bone Scaffolds

“…Therefore, it allows the creation of a construct that closely resembles native tissue. This is a crucial aspect, both in terms of mechanical support and for proper cellular function because, as was mentioned earlier, the local environment inside the tissue affects every aspect of cellular behavior such as metabolism, proliferation, and migration [ 125 , 126 ].…”

Polymer 3D Printing Review: Materials, Process, and Design Strategies for Medical Applications

“…Numerous 3D-printed biocompatible materials have been recently investigated for use as bone tissue scaffolds, with several methacrylic/acrylic-based materials included as examples in Table 1 [ 9 , 16 , 17 ]. These materials were printed with varied resin curing processes and all demonstrated similar elastic moduli around 1500 MPa to 2000 MPa, with some dependency on build orientation.…”

“…In direct laser writing, ultraviolet light is directed towards a vat of photosensitive resin to form solid layers with a moving build platform ( Figure 3 B). Resin curing also occurs in polyjet printing, with the deposition of ink/resin on a surface with subsequent ultraviolet curing [ 9 , 17 ]. Powder 3D printing relies on fusing powders of a selected material using lasers in selective laser sintering [ 46 , 47 ] ( Figure 3 C) or by chemical means in binder jetting.…”

“…Hierarchical strategies are a more sophisticated approach to producing architected materials for improved mechanics [ 78 ], and are demonstrated in Figure 4 A for a tissue scaffold application [ 14 ]. Hierarchical architected materials have a moderately decreased elastic moduli and a highly increased nutrient transportation capability due to larger pores introduced by the hierarchy [ 17 ], therefore providing potential performance improvements for tissue scaffolds in regenerative medicine applications.…”

“…The Figure 1 schematic highlights a hierarchical tissue scaffold constructed from beam-based unit cells with interconnected considerations in materials, process, and design for ensuring appropriate mechanical and biological functioning [ 17 ]. In this example, a design strategy for mimicking the hierarchical structure of bone largely drove the need for a suitable printing process and material selection to support the application.…”