Numerical Analysis of Nanotube Based NEMS Devices

A non-linear analysis of nanotube based nano-electromechanical systems (NEMS) is presented. Singly and doubly clamped nanotubes under electrostatic actuation are examined by solving nonlinear elastic equations. The analysis emphasizes the importance of nonlinear effects, such as finite kinematics (i.e. large deformations) and charge concentrations at the tip of singly clamped nanotubes, in the prediction of the pull-in voltage of the device, a key design parameter. We show that nonlinear kinematics results in an important increase in the pull-in voltage of doubly clamped nanotube devices, but that it is negligible in the case of singly clamped devices. Likewise, we demonstrate that charge concentration at the tip of singly clamped devices results in a significant reduction in pull-in voltage. By comparing numerical results to analytical predictions, closed form formulas derived elsewhere are verified. The results reported in this work are particularly useful in the characterization of the electro-mechanical properties of nanotubes as well as in the optimal design of nanotube based NEMS devices.