Mechanical and corrosion performance of biodegradable iron porous structures

Abstract

Biodegradable metals have gained attention in the field of bone repair, to be used as temporary bone implants. Among those metals, iron shows good biocompatibility properties, but has high stiffness when compared to bone and exhibits a low degradation rate. There are several approaches that may be applied to overcome those disadvantages. Porous materials have become important in the design of bone substitutes, since the porosity allows for a decrease in strength and for an increase in the degradation rate, due to their high surface areas. The aim of this work is to develop iron porous structures that lead to a mechanical and corrosion performance adequate for temporary implants. Three types of structures, with different relative densities and geometries, were studied: porous graded, cellular graded truss-lattices and a sort of random distribution of pores. The mechanical properties were evaluated through a finite-element analysis using the software NX Nastran. The degradation behaviour of the iron porous samples in a simulated body fluid environment was simulated using the software COMSOL. Results show that both mechanical and corrosion properties depend on the relative density and on the arrangement of pores. Moreover, structures with low relative density exhibit compressive strength values similar to the ones of human trabecular bone, showing degradation rates in the range established for ideal bone substitutes. This means that it is possible to match the iron properties to the ones required for biodegradable devices, by choosing adequate porous arrangements that tailor the mechanical and the corrosion behaviour.