Augmentation of the stable static travel range of electrostatically actuated slender nano-cantilevers by accounting for the influence of the van der Waals force

Abstract

The van der Waals (vdW) force, along with the electrostatic force and the first-order fringing field effect, act on the electrostatically actuated nano-cantilever (EANC) when the gap between the deformable electrode and the stationary electrode is less than 20 nanometres. Because of the vdW force, the EANC can undergo a pull-in phenomenon even without the electrostatic force when the nano-cantilever length exceeds its detachment length. The vdW force also results in a significant reduction in static pull-in instability parameters of the slender EANC compared to corresponding parameters obtained when this force is absent. This paper aims to augment the stable static travel range (i.e., the pull-in displacement) of the aforementioned EANC having a length close to its detachment length by varying the beam width. The beam width is assumed to vary in linear and parabolic manners and is controlled using a width variation parameter in each case. The governing equation of the Bernoulli-Euler beam theory and the Galerkin’s technique are utilised to obtain the weighted residual statement (GWRS). The GWRS is utilised to obtain static pull-in instability parameters of referential prismatic and variable-width EANCs. Pull-in instability parameters of variable-width EANCs, for various values of width variation parameters and the initial gap between electrodes, have been obtained. The aforementioned results have been validated with corresponding results obtained by three-dimensional finite element simulations performed using COMSOL Multiphysics®. Compared to the referential prismatic EANC, a significant augmentation in the pull-in displacement of the variable-width EANC has been obtained.