Date of Award
Doctor of Philosophy (PhD)
Computational Analysis and Modeling
Microcapsules play an important role in chemical, biomedical, and medical research. Of importance is their potential use as bio-sensors, as microreactors, and for drug delivery. In this dissertation, Computational Fluid Dynamics methodology is used to model the generation of droplets or cores (using alginate and oil) and to determine from the model process parameters needed for generating cores of homogeneous size for the manufacturing of microcapsules. Also, material diffusion through a microcapsule for controlled release is modeled based on finite difference methodology. The model was applied to experimental data on dextran release from microcapsules in order to estimate the diffusion coefficients in the core and wall of a microcapsule.
Results of the study showed that the velocities of alginate and oil and their ratio were considered as two important factors for determining droplet size. One can obtain the desired droplet size by adjusting these two factors. Also, it was observed that the properties of the two immiscible phases can influence the variance. A low viscosity of one of the phases (the non-oil phase) produced a small variance for droplet size. The flow channel was straight with a width of 100 micrometers. In future work, it would be of interest to determine if channel width and or geometry will have any effect on droplet size and variance.
Analysis of diffusivity estimates for the core and wall membrane from fitting the diffusion model to experimental data on the release of dextran from microcapsules over time revealed that only layer thickness had an effect on diffusivity in the core. The diffusivity for four layers was almost half of that for two layers of polyelectrolytes in the wall membrane. In the case of diffusivity in the microcapsule wall, both time and layer thickness had an effect. Diffusivity was larger for two layers of wall membrane thickness than for four or six layers and it was also larger for 12 hours than for 36 or 60 hours of loading time. There was no significant change in diffusivity beyond four layers or beyond 36 hours of loading time. In all cases, diffusivity in the wall membrane was considerably less than that in the core.
Wu, Xiaoshuo, "" (2007). Dissertation. 551.