Laser-assisted surface patterning of magnesium with silver nanoparticles: synthesis, characterization and modelling

Surface patterning of biocompatible materials may improve cell adhesion, infiltration and proliferation. Magnesium is a biocompatible metal which has bioresorption capability, as well as a low elastic modulus. This unique combination of properties has attracted researchers to develop biodegradable magnesium devices. In this work, the patterning of magnesium with silver nanoparticles printed by the laser-assisted maskless microdeposition (LAMM) process was studied. The geometry and microstructure of the printed silver patterns and the diffusion zone at the Mg/Ag interface were studied using profilometry, scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS) and transmission electron microscopy (TEM). The TEM analysis suggested that some intermetallic particles may form at the interface during laser sintering. The penetration curve of the Ag-Mg diffusion couple was obtained using EDS analysis. A finite element model is developed to simulate the LAMM process of silver nanoparticles on magnesium substrates. The model included a thermal analysis for determining the temperature history throughout the process, coupled with a diffusion model for evaluating compositional profiles across the interface. A comparison of the predicted profiles with the EDS results showed that the modelling and the experimental results qualitatively match. The analysis of SEM micrographs of the sintered nanoparticles, in light of the thermal modelling results, suggested that a minimum laser heat input was required for effective sintering of the nanoparticles.