Investigation of pull-in behaviors of a nanoswitch tuned by piezoelectric and flexoelectric effects

In this work, the static and dynamic pull-in behaviors of an electrostatically and piezoelectrically actuated nanoswitch are investigated. The nanoswitch is based on a cantilever nanobeam with a piezoelectric actuation layer attached. In the modeling, we consider the flexoelectric effect of the piezoelectric layer, the surface effect of the unimorph as well as the Casimir effect. The governing equation of the proposed model is derived using the Hamilton's principle and discretized by employing the Galerkin method. Firstly, the results of the proposed model are compared with the numerical and experimental data, providing the validity of this model. Then, simulations are performed to show the influence of flexoelectricity on the static pull-in voltage and pull-in deflection of the nanoswitch with a lead zirconate titanate (PZT-5H) and a polyvinylidene fluoride (PVDF) actuation layer, respectively. Results indicate that the flexoelectric effect plays a significant role in determining the static pull-in behaviors of the nanoswitch and such an effect is size-dependent at the nanoscale. Moreover, we show how the flexoelectric effect influences the unstable region of dynamic pull-in instability of the proposed nanoswitch. This work suggests that the flexoelectric effect of the piezoelectric layer can be used to tune the static and dynamic pull-in behaviors of a nanoswitch, which may guide the design and development of devices in the micro- and nano-electro-mechanical-systems (M/NEMS).