A comparative study of image analysis and porometry techniques for characterization of porous membranes

For porous membranes, characterization of a membrane’s key structural parameters, such as average and maximum pore size, pore size distribution, pore density, pore geometry, and surface roughness, is vital. The interplay between these parameters and membrane performance is detrimental for designing, evaluating, and developing the next generation of porous membranes. In this study, image analysis of scanning electron microscopy (SEM) micrographs is assessed as a technique to quantify such structural parameters. The focus of this work is on two open source software packages: ImageJ and Gwyddion. Comprehensive image analyses were carried out on three types of porous membranes: (i) phase inverted polyvinylidene fluoride, (ii) track-etched polycarbonate, and (iii) stretched polytetrafluoroethylene membranes. The information on key structural parameters acquired by image analysis was compared with data obtained from other established characterization methods. Based on current data, it was concluded that most membrane properties obtained by image analysis of micrographs were within acceptable accuracy, and consistent with other techniques except for surface roughness and pore size distribution. It was observed that optimum SEM micrograph’s magnification was essential to carry out an accurate image analysis. A major limitation of image analyses remains that they can only be carried out on surface pores. As such, they were found useful for characterizing membranes where surface pores define the overall pore size, geometry, and distribution.