Electrostatic pull‑in instability for tweezer architectures

The work investigates the static pull-in instability of electrostatically actuated tweezers with tubular electrodes. At a critical voltage, named pull-in voltage, the attraction force between the two electrodes causes the unexpected pull-in of the tubular cantilevers, which defines the limit of the elastic region of the system, especially in the case of carbon-nano tubes (CNTs) applications. The work aims to evaluate the lower and upper bounds of pull-in parameters of a tweezer device with the use of an accurate analytical model which allows to calculate the critical voltage and deflection values of the system. In order to assess the accuracy of the analytical model, we built a prototype and measured the critical pull-in voltage for different geometrical configurations of the device. The experimental results confirm the analytical predictions, with a maximum relative difference between the experimental and analytical values of the pull-in voltage lower than 13%.