The natural frequency and pull-in instability of clamped-clamped nano-actuators in the presence of a dielectric layer are analyzed. The influence of the presence of Casimir force, electrostatic force, fringing field effect, axial force, stretching effects and the size effect are taken into account. The governing equation of the dynamic response of the actuator is transformed in a non-dimensional form. The Galerkin decomposition method is employed to decompose the equations in time and space. Then, the obtained decomposed governing equations are solved numerically. The results show that the presence of the size effect and the axial force increases the natural frequency of the system. It is found that there is a unique value of the dielectric layer, in which the pull-in deflections of the nano-actuators are independent of the Casimir force, size effect and the axial loads. The advantage of this dielectric layer can be utilized in the design of nano-actuators and nano-sensors in the nanoscale. پرونده مقاله