Numerical Study on Parameters Affecting the Structure of Scaffolds Prepared by Freeze-Drying Method

Freeze-drying is one of the most used methods for preparing scaffolds and is very sensitive to the material and operational parameters such as nucleation temperature, thermal properties of the mold, cooling rate, set freezing point, and slurry height. In the present study, a Finite Element Method (FEM) based code was developed to investigate the effects of such parameters and to eventually predict the microstructure of the scaffold. Similar molds and cooling conditions used in various experimental studies were simulated and compared. The achieved pattern demonstrated how different thermal condition tailored scaffold microstructure. It was shown that nucleation temperature (Tn) was an effective parameter controlling the final structure of the scaffold and influenced pore sizes with different mold materials. Simulation results also showed that by decreasing the rate of cooling, the average pore sizes increased, and a quenching solution led to a randomly distributed pattern of pore sizes. It is also achieved that by increasing the set freezing temperature as well as the height of the solution the pore sizes increased more at the top of the mold. The thermal gradient also illustrated the orientation of the pore in a mold with the thick isolated wall was considerably uniform. This framework can be used to optimize the scaffold structure or any ice templating method.