In this work we demonstrate microfabricated thin alumina nanopore membranes as a platform for impedance sensing of DNA immobilization and hybridization. We develop a wafer-scale fabrication of free-standing alumina nanopore membranes with well controlled thickness, pore diameter and overall pore density. One 1 cm x 1 cm single chip contains an array of 69 membranes. Each membrane is 100 mu m x 100 mu m large and 2 mu m thick, with pore diameter of 120 nm. With low pore density of similar to 6 pores/mu m(2), nanopore resistance and membrane capacitance can be recognized clearly in the electrochemical impedance spectrum from 100 to 1 MHz. The total surface area can be further increased by the coating of silica nanoparticles with similar to 20 nm in diameter. During the immobilization of probe ssDNA to (3-glycidoxypropyl) trimethoxysilane functionalized surface, the nanopore resistance drops significantly by 80%, whereas the membrane capacitance increases less than 2%. After hybridization with complementary DNA, the nanopore resistance increases up to 10%. Non-complementary ssDNA has no obvious effect. The detection limit is 12.5 nM in phosphate-buffered saline (PBS) solution. (C) 2015 Elsevier B.V. All rights reserved.