An experimental analysis of electrostatically vibrated array of polysilicon cantilevers

Abstract

Micromechanical cantilevers are one of the most fundamental and widely studied structures in micro-electromechanical systems. Dynamic response of such cantilevers has long been an interesting subject to researchers and different analytical and experimental approaches have been reported to determine it. Theoretical estimation of different damping mechanisms have been reported over years which are relevant particularly in studying the dynamics of the micro-mechanical structures. Most properties and functionalities of the MEMS devices are invariably dependant on the dynamic response of the devices, which in turn depends on the quality factor of the devices or in other words the overall damping present in the system. This paper presents a thorough experimental analysis of vibration characteristics of micro-mechanical cantilevers of different dimensions. Arrays of polysilicon micro-cantilevers of different dimensions have been designed and fabricated using surface micromachining process. The beams are resonated by electrostatic actuation and their vibration characteristics have been observed using Laser Doppler Vibrometer. Also a thorough analysis of modal behaviour of the beams is presented using analytical approach and finite element method based simulation. Different damping mechanisms have been critically reviewed and a semianalytical estimation of the overall damping is presented. The results are compared with experimental values.

The use of strain sensors in an experimental modal analysis of small and light structures with free–free boundary conditions

“…The second possibility is to fix a smaller structure to the base in one position and excite it with a noncontact device in another position. The noncontact excitation can be achieved by a magnetostrictive actuator that excites a small ferromagnetic target fastened to the structure (Wilson and Bogy, 1996), the interference of ultrasound frequencies in air (Huber et al, 2006), pressurized air (Vanlanduit et al, 2007;Farshidi et al, 2010) and magnetostriction of the structure itself (Chakraborty et al, 2010), etc. Attaching masses to the structure changes the dynamical response and the free-free boundary conditions are still not possible.…”