Mechanical behavior of scaffold-like structures: research of relationships between properties and geometry

Scaffolds are structures used to support the growth of cells in order to replace damaged parts of tissues. They are typically simple structures with a porous arrangement, which allows cells adhesion, but also the flow of the biological fluid. The scaffold geometry and structure are, however, defined by the specific application and customized according to the pathology and the patient. Based on their functions, scaffolds are characteristically made of biocompatible and often biodegradable materials. A deep knowledge of the properties of the scaffold, and their peculiarities, is essential for a correct design. This work aims at analyzing whether the mechanical behavior of a typical scaffold structure could be described by referring to properties intrinsic to the system (independent on the geometry/size), or a geometry/size dependence should be taken into account. Only in the former case, the structure could be treated as an effective "3D material", so that scaffold design could be easily produced and its performance predicted. In order to explore this aspect, scaffold-like structures made of poly(lactic acid) have been manufactured using a Fused Deposition Modelling 3D printing machine. Several specimens with different sizes have been fabricated and their mechanical stiffness and strength measured. The results show that concerning the mechanical strength the structure behaves as a "3D material", whereas for the stiffness a size dependence is observed.