A simple criterion for determining the static friction force between nanowires and flat substrates using the most-bent-state method

A simple criterion was developed to assess the appropriateness of the currently available models that estimate the static friction force between nanowires and substrates using the 'most-bent-state' method. Our experimental testing of the static friction force between Al₂O₃ nanowires and Si substrate verified our theoretical analysis, as well as the establishment of the criterion. It was found that the models are valid only for the bent nanowires with the ratio of wire length over the minimum curvature radius $\left(L/R_O\right)$ no greater than 1. For the cases with $L/R_O$ greater than 1, the static friction force was overestimated as it neglected the effect of its tangential component. (paper)