We have successfully fabricated sub-100 nm nanogaps in Pd-Ni alloy thin films on an elastomeric substrate by simple stretching. The nanogaps-containing Pd-Ni films were utilized as hydrogen-sensing sponges and their performance was demonstrated to dominate over the performance of similar mobile thin films comprised of pure Pd in major aspects such as the response time, sensitivity in high H-2 concentrations, and H2 detection limit. Notably, Pd82.5Ni12.5 hydrogen sensing sponges showed ultra-high sensitive and reversible On-Off behaviors and low detection limit of similar to 100 ppm, which were attributed to the reduced nanogap width and the enhanced volume expandability of Pd-Ni lattice. The effects of Ni added to Pd and a search for an optimum Ni concentration were also systematically studied. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.