Insights into the mechanical properties of several triply periodic minimal surface lattice structures made by polymer additive manufacturing

Functional graded materials are gaining increasing attention in tissue engineering (TE) due to their superior mechanical properties and high biocompatibility. Triply periodic minimal surface (TPMS) has the capability to produce smooth surfaces and interconnectivity, which are very essential for bone scaffolds. To further enhance the versatility of TPMS, a parametric design method for functionally graded scaffold (FGS) with programmable pore size distribution is proposed in this study. Combining the relative density and unit cell size, the effect of design parameters on the pore size was also considered to effectively govern the distribution of pores in generating FGS. We made use of Gyroid to generate different types of FGS, which were then fabricated using selective laser melting (SLM), followed by investigation and comparison of their structural characteristics and mechanical properties. Their morphological features could be effectively controlled, indicating that TPMS was an effective way to achieve functional gradients which had bone-mimicking architectures. In terms of mechanical performance, the proposed FGS could achieve similar mechanical response under compression tests compared to the reference FGS with the same range of density gradient. The proposed method with control over pore size allows for effectively generating porous scaffolds with tailored properties which are potentially adopted in various fields.

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Modeling porous structures with fractal rough topography based on triply periodic minimal surface for additive manufacturing

Rapid Prototyping Journal ◽

10.1108/rpj-09-2015-0121 ◽

2017 ◽

Vol 23 (2) ◽

pp. 257-272 ◽

Cited By ~ 4

Author(s):

Zhijia Xu ◽

Qinghui Wang ◽

Jingrong Li

Keyword(s):

Additive Manufacturing ◽

Minimal Surface ◽

Surface Topography ◽

Porous Structures ◽

Fractal Surface ◽

Content Type ◽

Periodic Minimal Surface ◽

Triply Periodic ◽

Fractal Parameters ◽

Triply Periodic Minimal Surface

Purpose The purpose of this paper is to develop a general mathematic approach to model the microstructures of porous structures produced by additive manufacturing (AM), which will result in fractal surface topography and higher roughness that have greater influence on the performance of porous structures. Design/methodology/approach The overall shapes of pores were modeled by triply periodic minimal surface (TPMS), and the micro-roughness details attached to the overall pore shapes were represented by Weierstrass–Mandelbrot (W-M) fractal representation, which was integrated with TPMS along its normal vectors. An index roughly reflecting the irregularity of fractal TPMS was proposed, based on which the influence of the fractal parameters on the fractal TPMS was qualitatively analyzed. Two complex samples of real porous structures were given to demonstrate the feasibility of the model. Findings The fractal surface topography should not be neglected at a micro-scale level. In addition, a decrease in the fractal dimension Ds may exponentially make the topography rougher; an increase in the height-scaling parameter G may linearly increase the roughness; and the number of the superposed ridges has no distinct influence on the topography. Furthermore, the synthesis method is general for all implicit surfaces. Practical implications The method provides an alternative way to shift the posteriori design paradigm of porous media to priori design mode through numeric simulation. Therefore, the optimization of AM process parameters, as well as the porous structure, can be potentially realized according to specific functional requirement. Originality/value The synthesis of TPMS and W-M fractal geometry was accomplished efficiently and was general for all implicit freeform surfaces, and the influence of the fractal parameters on the fractal TPMS was analyzed more systematically.

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Investigation of the Functional Properties of Additively-Fabricated Triply Periodic Minimal Surface-Based Bone Scaffolds for the Treatment of Osseous Fractures

Volume 1: Additive Manufacturing; Advanced Materials Manufacturing; Biomanufacturing; Life Cycle Engineering; Manufacturing Equipment and Automation ◽

10.1115/msec2021-63413 ◽

2021 ◽

Author(s):

Abigail Chaffins ◽

Mohan Yu ◽

Pier Paolo Claudio ◽

James B. Day ◽

Roozbeh (Ross) Salary

Keyword(s):

Mechanical Properties ◽

Additive Manufacturing ◽

Fused Deposition Modeling ◽

Fused Deposition ◽

Bone Scaffolds ◽

Periodic Minimal Surface ◽

Triply Periodic ◽

Triply Periodic Minimal Surface ◽

Deposition Modeling

Abstract Fused deposition modeling (FDM), is a direct-write material extrusion additive manufacturing process, which has emerged as a method of choice for the fabrication of a wide range of biological tissues and structures. FDM allows for non-contact, multi-material deposition of a broad spectrum of functional materials for tissue engineering applications. However, the FDM process is intrinsically complex, consisting of a multitude of parameters as well as material-machine interactions, which may adversely influence the mechanical properties, the surface morphology, and ultimately the functional integrity of fabricated bone scaffolds. Hence, process optimization in addition to physics-based characterization of the FDM process would be inevitably a need. The overarching goal of this research work is to fabricate biocompatible, porous bone scaffolds, incorporating autologous human bone marrow mesenchymal stem cells (hBMSCs), for the treatment of osseous fractures, defects, and eventually diseases. The objective of this work is to investigate the mechanical properties of several triply periodic minimal surface (TPMS) bone scaffolds, fabricated using fused deposition modeling (FDM) additive manufacturing process. In this study, biocompatible TPMS bone scaffolds were FDM-deposited, based on a medical-grade polymer composite, composed of polyamide, polyolefin, and cellulose fibers (named PAPC-II). In addition, the experimental characterization of the TPMS bone scaffolds was on the basis of a single factor experiment. The compression properties of the fabricated bone scaffolds were measured using a compression testing machine. Furthermore, a digital image processing program was developed in the MATLAB environment to characterize the morphological properties of the fabricated bone scaffolds.

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