Mechanically Bi-Stable In-Plane Switch with Dual-Stiffness Actuators

This paper presents an optimized mechanical multi-spring concept for electrostatic actuators, demonstrated in a lateral curved-electrode configuration for a mechanically interlocking bi-stable switch. The concept features a dual-stiffness mechanism where the actuator is operated in two regimes of different spring constants, which in contrast to conventional actuator mechanisms allows for independently optimizing both the deflection and the force provided during actuation. Further, the non-linear electrostatic force is optimally matched to the linear spring force by the design of the two stiffness regimes. A mechanically bi-stable switch with two separate dual-stiffness cantilevers and a interlocking mechanism has been designed and fabricated in a single photolithographic mask step. The evaluation of the prototype devices has successfully shown the advantages of the dual-stiffness actuator concept.