A new method of applying PLA coatings on the surface of magnesium alloy using the FDM technique

Abstract

The subject of the work was presented a new method of applying PLA (polylactide) coatings on the magnesium alloy's surface using the FDM (Fused Deposition Modeling) technique. The aim of this work was develop a low-temperature, low-waste coating method of Mg alloy surface with a polymer layer with a repeatable, predictable morphology according to a previously assumed model that uniformly covers a metal element using FDM technique (patent number: PL239348). Until now, polymer layers on Mg alloys have been produced mainly by spin coating or dip coating. Both spin coating and dip coating methods do not guarantee even coverage of element's surface, especially on the edges. In addition, the surface morphology is not reproducible because it cannot be influenced directly during the layering process. The advanced coating technology for magnesium alloys presented in the paper is intended to be used as a technology for the production of protective layers for short-term resorbable orthopedic implants. Therefore, the influence of the thickness on the cohesion of the coating in the Ringer's solution of the tested Mg alloy-PLA system was assessed. The 240 μm thick polylactide coating on Mg alloy retained its integrity for 12 days of immersion in Ringer's Solution at 37 °C.The probable mechanism of PLA coating damage was also presented. The adhesive strength of the PLA - Mg alloy system is about 9 MPa. The biocompatibility was assessed by direct grown and proliferation assay on tested materials of normal human dermal fibroblasts (NHDF) and osteosarcoma cancer cells (U2OS). The microscopic observations confirm, that the surface modification's with a PLA coatings on magnesium alloy improves the materials and make them a good candidate for further applications in regenerative medicine.