Surface transformation of bioactive glass in bioreactors simulating microgravity conditions. Part II: numerical simulations

The effects of simulated microgravity on the surface modification of bioactive glass (BG) in solution were studied using a numerical method. Models were developed for estimating the mass transfers of different chemical species from the surface of bioactive glass particles (microcarriers) suspended in the rotating liquid medium of a NASA-designed high aspect ratio vessel (HARV) bioreactor and on the bottom surface of a static vial. The concentration profiles resulting from chemical reactions and ionic transports were ascertained. Numerical results for the transport under simulated microgravity in the HARV and at normal gravity in the static vial were compared. These results were also compared with those of experiments to verify the enhancement of the reaction kinetics under simulated microgravity conditions. The experimental and numerical studies confirm that simulated microgravity conditions lead to the quick achievement of bioactive glass surface modification.