By exerting bending stresses on a metal surface, we show that in-plane tensile stresses can effectively promote CuO nanowire (NW) formation by significantly increasing the NW growth density during the oxidation of copper. It is found that the improved NW growth is associated with decreased size of oxide grains and increased number of grain boundaries in the underlying Cu2O and CuO layers. These results are attributed to the effect of in-plane tensile stresses that result in fine grain structures in the underlying oxide layers, which facilitates the outward diffusion of Cu ions for enhanced oxide NW growth. (C) 2011 Elsevier B. V. All rights reserved.