Size-dependent pull-in phenomena in nonlinear microbridges

This paper investigates the deflection and static pull-in of microbridges based on the modified couple stress theory, a non-classic continuum theory able to predict the size effects for structures in micron and sub-micron scales. The beam is modeled using Euler–Bernoulli beam theory and the nonlinearities caused by mid-plane stretching have been considered. It is shown that modified couple stress theory predicts size dependent normalized deflection and pull-in voltage for microbeams while according to classical theory the normalized behavior of microbeams is independent of the size of the beam. According to results, when the thickness of the beam is in order of length scale of the beam material, the difference between the results given by modified couple stress theory and those predicted by classical theory is considerable.

► We study the size dependent behavior of electrostatically actuated microbridges.
► We used modified couple stress as a non-classical theory to capture the size effects.
► There is a gap between results of classical and non-classical theories in small scale.
► As the beam thickness increases, results converge to the results of classical theory.