Method for Characterizing Microscopic Void Structure in Porous Media

Transport of molecules and particles in porous media is ubiquitous in industrial and biophysical systems, where specific pore morphologies are utilized for selective filtering. Mass transport through porous media is commonly modeled at the macroscopic scale by abstracting the interior morphology of the medium into effective quantities that describe flow hindrance. While these methods are successful in predicting macroscopic properties such as permeability, they are not as well suited for modeling and predicting heterogenous transport, where the tortuous structural features of the material must be represented in detail. We have developed a method for obtaining a detailed quantitative structural description of void structures in a porous medium. Our method includes the construction and analysis of Voronoi diagrams, from which we determine a network of all possible void paths and their widths throughout the system. These networks can be further analyzed to determine the size-dependent migration rate of liquid-borne particles migrating through the material. We validate our results using Brownian dynamics simulations of tracer colloids of various sizes diffusing in the voids of a colloidal gel that show excellent agreement between predicted cutoff sizes and diffusive behavior.