▎ 摘　　要

Applying an external electric field on a graphene surface is an important way to improve the molecular adsorption capability of graphene, thus pull-in instability of suspended graphene sensors becomes a critical issue. Incorporating residual built-in strains, fringing fields and intermolecular forces, an electromechanical model is developed to characterize the nonlinear pull-in behaviors of suspended graphene-based sensors. The obtained results of pull-in voltages agree well with the reported experimental data. Moreover, the fracture failure of graphene sensors is initially compared to the pull-in failure. To avoid pull-in instability and fracture failure, critical formulas of axial pre-stress for zigzag-oriented and armchair-oriented graphene sensors are derived. It is demonstrated that axial pre-stress is an effective and controllable way to improve the pull-in stability of graphene sensors. Copyright (C) EPLA, 2019