This work describes the fabrication of self-standing, mechanically robust, polycrystalline (anatase) TiO2 nanotube array membranes of uniform pore size distribution. The membranes are made as flat sheets with thicknesses ranging from approximately 4.4 mu m to 1 mm. To evaluate biofiltration applications, we have used glucose, phenol-red, bovine serum albumin (BSA), and immunoglobulin (IgG) as model molecules for studying the diffusion characteristics through the nanotube array membranes. It is found that the natural log of the molecule diffusion coefficients scale linearly with molecular weight. To date, we have fabricated membranes up to 12.5cm(2), a size limited only by the processing equipment. Published by Elsevier B.V.