In this work, surface effects, including surface elasticity, residual surface stress and surface piezoelectricity, are considered to study the electromechanical coupling (EMC) behaviour of piezoelectric nanowires (NWs) with the Euler-Bernoulli beam theory. Using the surface-layer-based model, explicit formula for EMC coefficient is derived. It is clearly observed that this coefficient is size-dependent and can be strongly enhanced when the geometric dimensions of NWs scale down. The static bending of a cantilever piezoelectric NW is also studied. The surface effects are found to significantly influence the stiffness and electric field distribution in the NW. The results indicate that surface effects play a significant role in the EMC and bending behaviours of piezoelectric nanobeam. This work is very helpful for understanding the size-dependent properties of nanostructured piezoelectric materials and improving the performance of the piezoelectric nanobeam-based devices in energy harvesting.
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