1 3 Microsyst Technol DOI 10.1007/s00542-016-3264-x TECHNICAL PAPER Design of a capacitive MEMS double beam switch using dynamic pull-in actuation at very low voltage Hatem Samaali 1 · Fehmi Najar 2 Received: 26 November 2016 / Accepted: 28 December 2016 © Springer-Verlag Berlin Heidelberg 2017 1 Introduction Microelectromechanical systems (MEMS) switches has been developed and used in many radio frequency (RF) applications, including signal routing, matching networks, antenna switches, tunable filters and other high frequency applications. In telecommunication applications RF MEMS switches offer significant improvements to the RF charac- teristics such as low insertion loss at the ON state of the microswitch, high OFF-state isolation and better linearity over broad frequency range (Rebeiz 2003; Angira and Ran- gra 2015). Also RF MEMS switches need low power con- sumption to lead the microswitch to its ON or OFF state. Nevertheless they are limited by a high actuation volt- age and a switching time relatively high when compared with the equivalent semi-conductor switches (Rebeiz 2003; Samaali et al. 2015). Electromechanical actuation forces are used to drive the MEMS switches. In general, these forces use of the follow- ing transduction mechanisms: (1) piezoelectric deformation (Gross et al. 2003), electromagnetic force (Wright and Tai 1998), thermoelastic deformation (Girbau et al. 2003) and electrostatic force (Zavracky et al. 1997). Due to its simple structure and capability of implementation with integrated circuits (IC) the electrostatic transduction mechanism is the most prevalent candidate for MEMS switches actuation (Senturia 2007). However, this mechanism needs high actu- ation voltage and it generates high switching time. Several designs have been presented to reduce the actua- tion voltage of electrostatic MEMS switches. Peroulis et al. (2004) introduced a microswitch with a small capacitor gap and serpentine springs and an electrode on top of the actuated bridge, but this microswitch is hard to be modeled and fabricated. Also the proposed springs need large sur- face area (Khater et al. 2011). Cho et al. (2005) proposed Abstract This paper presents a design of a capacitive dou- ble beam MEMS microswitch based on dynamic pull-in actuation. The design consists of two suspended microbe- ams actuated by an electrostatic nonlinear force accounting for fringing field effect. The applied force controls the ON and the OFF states of the microswitch using a variable volt- age. We first develop a mathematical model for the MEMS microswitch, then we investigate the static behavior and use finite element analysis to validate the derived mathematical model. A comparison with classical single beam design is also done. The results show 32% reduction in the actuation voltage when double beam design is used. Dynamic analy- sis using combination of DC and AC signals is examined, the outcome presents significant reduction in the actuation voltage. We demonstrate that driving the microswitch using square wave signals gives several improvements to the per- formance such as large pull-in band, low actuation voltage and small switching time. Global stability analysis showed that, for the same applied voltage, square wave signals are more efficient to actuate the microswitch. The electrostatic switching energy is also studied, we show that this energy can be optimized for specific switching times. * Fehmi Najar fehmi.najar@ept.rnu.tn 1 Sousse National Engineering School, University of Sousse, BP 264, Sousse Erriadh 4023, Tunisia 2 Applied Mechanics and Systems Research Laboratory, Tunisia Polytechnic School, University of Carthage, BP 743, La Marsa 2078, Tunisia