Laser Melt Infiltration of UHMWPE into the Binary Coatings of Strontium Apatite and Colloidal Silica

Abstract

Medical-grade ultrahigh molecular weight polyethylene (UHMWPE) is the material of choice for sliding surfaces in various articular joint implants owing to its excellent biocompatibility and superior physical properties, such as an exceptionally low coefficient of friction and excellent durability. However, the bioinert nature of UHMWPE limits its extended use in rapidly advancing medical fronts. In this study, bioactive surface modifications of UHMWPE were addressed using a newly developed laser-melt infiltration technique. UHMWPE was coated with binary mixtures of strontium apatite and colloidal silica particles and irradiated using a 30 W CO2 laser to reach the maximum temperature of 150 ± 5 °C. UHMWPE melts infiltrated the porous matrices of the coatings by capillary force and formed surface-selective composite materials between them. Capillary rise heights were evaluated by observing the uplift of the substrate after the selective dissolution of the coating substances and were found to be much higher than the estimated values based on the Lucas–Washburn equation. This finding suggests that the melt viscosity of UHMWPE confined within the nanopores might be significantly lower than that measured at macroscopic scales. Both strontium and silicate ions are known osteo-inductive factors, and their concentrations eluted from the binary coatings were substantially higher than those found in the single coatings.