title: Instability analysis of torsional MEMS/NEMS actuators under capillary force.
abstract: The static and dynamic instabilities of a torsional MEMS/NEMS actuator caused by capillary effects are studied, respectively. An instability number, eta, is defined, and the critical gap distance, g(cr), between the mainplate and the substrate is derived. According to the values of eta and g, the instability criteria of the actuator are presented. The dimensionless motion equation of the MEMS/NEMS torsional actuator is derived when it makes nonlinear oscillation under capillary force. The qualitative analysis of the nonlinear equation is made, and the phase portraits are presented on the phase plane. In addition, the bifurcation phenomena in the system are also analyzed.
authors.affiliation: Department of Mechanics, Tianjin University, Tianjin 300072, People's Republic of China.
authors.forename: Jian-Gang
authors.initials: JG
authors.lastname: Guo
authors.forename: Li-Jun
authors.initials: LJ
authors.lastname: Zhou
authors.forename: Ya-Pu
authors.initials: YP
authors.lastname: Zhao