Inverse colloidal crystal microfiltration membranes

Uniform pore size, high porosity membranes are important for applications such as microfiltration and ultrafiltration, as well as for use as membrane adsorbers. In this work, uniform pore size, high porosity microfiltration membranes were developed using three-dimensionally ordered macroporous templates. A membrane casting cell was designed for self-assembly of silica spheres into a colloidal crystal template. The resulting close-packed colloidal crystal was infiltrated with a reactive monomer solution. After polymerization, the silica spheres were etched away, resulting in an inverse colloidal crystal (ICC) membrane with high porosity and uniform pores that are highly interconnected. ICC membranes have been fabricated with a range of pore sizes and thicknesses. The membrane casting cell facilitates easy variation of membrane thickness. The membrane pore size is varied by changing the diameter of the silica spheres used to prepare the colloidal crystal template. By changing the composition of the reactive monomer solution, membranes have been fabricated with different hydrophilicities. Following synthesis, the ICC membranes were tested in a commercially available stirred cell. Particle fractionation was studied in normal flow filtration experiments. For bi-disperse particle suspensions, significant passage of particles smaller than the membrane pore size was observed if the ratio of large to small particles was around 14.