Investigation of the Effect of the Tortuous Pore Structure on Water Diffusion through a Polymer Film Using Lattice Boltzmann Simulations
Journal article, 2015
Understanding how the pore structure influences the mass
transport through a porous material is important in several applications, not
the least in the design of polymer film coatings intended to control drug release.
In this study, a polymer film made of ethyl cellulose and hydroxypropyl
cellulose was investigated. The 3D structure of the films was first experimentally
characterized using confocal laser scanning microscopy data and then
mathematically reconstructed for the whole film thickness. Lattice Boltzmann
simulations were performed to compute the effective diffusion coefficient
of water in the film and the results were compared to experimental data.
The local porosities and pore sizes were also analyzed to determine how the
properties of the internal film structure affect the water effective diffusion
coefficient. The results show that the top part of the film has lower porosity,
lower pore size, and lower connectivity, which results in a much lower effective
diffusion coefficient in this part, largely determining the diffusion rate
through the entire film. Furthermore, the local effective diffusion coefficients were not proportional to the local film porosity,
indicating that the results cannot be explained by a single tortuosity factor. In summary, the proposed methodology of combining
microscopy data, mass transport simulations, and pore space analysis can give valuable insights on how the film structure affects
the mass transport through the film.
Lattice Boltzmann method
transport through a porous material