Modeling the static response and pull-in instability of CNT nanotweezers under the Coulomb and van der Waals attractions

• Instability of CNT nanotweezers is investigated using a nano-scale continuum model.
• Three different approaches are employed to solve the governing equation.
• The maximum stable arm length and the minimum gap between the arms are determined.
• van der Waals force reduces the instability deflection and voltage of the nanotweezers.
• van der Waals force might be neglected for a wide range of real applications.

In this paper, the static response and pull-in instability of nanotweezers fabricated from carbon nanotubes (CNT) are theoretically investigated considering the effects of the Coulomb electrostatic and van der Waals molecular attractions. For this purpose, a nanoscale continuum model is employed to obtain the nonlinear constitutive equation of this nano-device. The van der Waals attraction is computed from the simplified Lennard-Jones potential. In order to solve the nonlinear constitutive equation of the nanotweezers, three different approaches, e.g. developing a lumped parameter model, applying the analytical modified Adomian decomposition (MAD) and using a commercial numerical integration routine, are employed. The obtained results are in good agreement with experimental measurements as reported in the literature. As a case study, we have investigated a freestanding nanotweezer and have determined the detachment length and minimum initial gap. Furthermore, range of dominancy of the molecular attraction has been discussed.