Anodic aluminum oxide (AAO) membranes are chemically and thermally stable and inert, and can be produced with wide variety of pore size distribution. We report thin alumina nanoporous membranes (0.7-1 mu m thickness) with narrow pore size distribution (20-30 nm diameter) obtained by anodizing aluminum films that were deposited on silicon substrates for a biomolecule separation platform. We demonstrate the electrostatic sieving effect for separation of proteins with similar molecular weights with the thin nanoporous anodic aluminum oxide membranes. Without separate modification of the membrane surface, we have achieved high throughput (>10(-8) M cm(-2) s(-1)) and high selectivity (>42) for separation of bovine serum albumin (BSA) and bovine hemoglobin (BHb) at pH = 4.7, the isoelectric point of BSA. (C) 2009 Elsevier B.V. All rights reserved.