Practical microsensors for fast, highly sensitive hydrogen gas detection were fabricated by combining silicon integral technology for MEMS microhotplate platform with newly developed technological, electrical, and electrolytic conditions for forming nanostructured porous-anodic-alumina-templated WO3 layer as the sensing material. The morphology-structure-property relationship for the nanostructured sensing layer was determined by scanning electron microscopy, X-ray diffraction, and through systematically investigating the sensor performance at various H-2 concentrations (5-1000 ppm) and operating temperatures (20-350 degrees C). The sensors showed superior sensitivity to hydrogen gas, with the lowest detection limit ever reported for WO3 semiconductors (5 ppm), the fast response and recovery times (2-3 min), and the best sensitivity at 150 degrees C, which was 100 times higher than that of a reference sensor having a smooth WO3 active film. The technology developed enables high-volume, low-cost, and low-power sensor-on-a-chip solution for a hydrogen-based energy economy where the use of highly sensitive and low-power-consuming devices is encouraged. Copyright (c) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.