Abstract In this research, considering the nano-scale size-dependent theories, mechanical analysis and instability of nanoswitches that have been subjected to electrostatic field are performed. These nanoswitches are composite and consist of two materials. Based on nonlinear theories used for mechanical analysis of nanostructures as well as strain gradient theory, a size dependent model is proposed to investigate the instability and static behavior of nanoswitches. The bilayer nanoswitch is excited by an electrostatic field and its equations are determined based on the theory of nonlocal strain gradient theory. Using the Hamilton principle, the equation of motion is obtained and then dimensionslized, and the dimensionless parameters and length scale are determined. Non-dimensional equations are solved using finite element and analytical methods and the static response of the beam to electrostatic actuation is determined. In the finite element method, high-order beam elements in isoparametric coordinates are used, and in the analytical method, the combined Galerkin method and homotopy perturbation are used. Next, according to the obtained mechanical response, the system instability, that is the pull-in instability, is eva‎luated. The results show that considering the non-dimensional nonlocal parameters and the length scale parameter causes hardening in the static response and with increasing these parameters, instability occurs at higher voltages. Therefore, considering the theory of nonlocal strain gradient, the obtained static deformation is significantly reduced compared to the classical results.

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