Elsevier

Biomaterials

Volume 32, Issue 29, October 2011, Pages 6875-6882
Biomaterials

Leading opinion
Minimal surface scaffold designs for tissue engineering

https://doi.org/10.1016/j.biomaterials.2011.06.012Get rights and content

Abstract

Triply-periodic minimal surfaces are shown to be a more versatile source of biomorphic scaffold designs than currently reported in the tissue engineering literature. A scaffold architecture with sheetlike morphology based on minimal surfaces is discussed, with significant structural and mechanical advantages over conventional designs. These sheet solids are porous solids obtained by inflation of cubic minimal surfaces to sheets of finite thickness, as opposed to the conventional network solids where the minimal surface forms the solid/void interface. Using a finite-element approach, the mechanical stiffness of sheet solids is shown to exceed that of conventional network solids for a wide range of volume fractions and material parameters. We further discuss structure–property relationships for mechanical properties useful for custom-designed fabrication by rapid prototyping. Transport properties of the scaffolds are analyzed using Lattice-Boltzmann computations of the fluid permeability. The large number of different minimal surfaces, each of which can be realized as sheet or network solids and at different volume fractions, provides design flexibility essential for the optimization of competing design targets.

Section snippets

Mechanical properties at 50% volume fraction

It is the main result of this article that, as demonstrated by Fig. 3, minimal surface sheet solids consistently are considerably stiffer than minimal surface network solids of the same volume fraction and built from the same material. For φ = 50% and ν0=0.2, we find bulk moduli in the range [0.29; 0.31] for sheet solids, and [0.22; 0.25] for network solids.

The mechanical properties of the scaffolds were computed using a voxel-based finite-element method scheme (similar to the approach of ref.

Discussion

We have discussed two types of biomorphic scaffolds based on triply-periodic minimal surfaces, termed network solids and sheet solids, and their mechanical properties. While network solids have received considerable attention in the mechanical and tissue engineering literature [11], [13], [14], [15], sheet solids, at least those based on minimal surfaces, have only recently been suggested as scaffold designs for tissue engineering [23].

As the key result of this article, we have shown that, at

Conclusion

This article makes the case for a more prominent role of geometric considerations in the design process of artificial bone scaffolds. The first step toward an optimal functional scaffold is the informed choice of the geometric structure, which is the principal determinant of its physical properties. Owing to advances in rapid prototyping technology, this step is increasingly decoupled from the choice of specific chemical and biological material parameters. This recognition highlights the

Acknowledgments

We thank Robert Magerle (Chemnitz) for pointing out the analogy to solid struts and hollow pipes; we also thank Mahyar Madadi (Canberra) and Ruggero Gabbrielli (Bath) for helpful comments and discussions on the subject of the article. GEST and SK acknowledge financial support through the Deutsche Forschungsgemeinschaft (DFG) under grant SCHR1148/2-1. KM gratefully acknowledges the support of the Cluster of Excellence ‘Engineering of Advanced Materials’ within the Exzellenzinitiative of the DFG.

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    Editor’s Note: This paper is one of a newly instituted series of scientific articles that provide evidence-based scientific opinions on topical and important issues in biomaterials science. They have some features of an invited editorial but are based on scientific facts, and some features of a review paper, without attempting to be comprehensive. These papers have been commissioned by the Editor-in-Chief and reviewed for factual, scientific content by referees.

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