An Analysis of Stepped Trapezoidal Shaped Microcantilever beams for MEMS based Devices

Akarapu, Ashok and Gangele, Aparna and Pal, Prem and Pandey, Ashok Kumar (2018) An Analysis of Stepped Trapezoidal Shaped Microcantilever beams for MEMS based Devices. Journal of Micromechanics and Microengineering. ISSN 0960-1317

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Abstract

Microcantilever beam has been most widely used mechanical element in the design and fabrication of MEMS/NEMS based sensors and actuators. In this work, we have proposed a new design of microcantilever beam based on stepped trapezoidal shaped microcantilever. Single, double, triple and quadruple stepped trapezoidal shaped microcantilever beams along with the conventional rectangular shaped microcantilever beam were analysed experimentally, numerically and analytically. The microcantilever beams were fabricated from silicon dioxide material using wet bulk micromachining in 25 wt% TMAH. Length, width and thickness of the microcantilever beams are fixed as 200, 40 and 0.96 μm, respectively. Laser vibrometer is utilized to measure the resonance frequency and Q-factor of the microcantilever beams in vacuum as well as in ambient conditions. Furthermore, a finite element analysis software, ANSYS is employed to numerically analyse the resonance frequency, maximum deflection, and torsional end rotation of all designs of microcantilever beam. Analytical and numerical resonance frequencies are found to be in good agreement with experimental resonance frequencies. In stepped trapezoidal shaped microcantilever beams with increasing number of steps Q-factor, maximum deflection and torsional end rotation were improved, whereas the resonance frequency was slightly reduced. Nevertheless, the resonance frequency is higher than the basic rectangular shaped microcantilever beam. The observed quality factor, maximum deflection and torsional end rotation for quadruple stepped trapezoidal shaped microcantilever are 38%, 41% and 52%, respectively, higher than those of conventional rectangular shaped microcantilever beam. Furthermore, for the applied concentrated mass of 1 picogram on cantilever surface, a greater shift in frequency is obtained for all designs of stepped trapezoidal shaped microcantilever beams compared to conventional rectangular microcantilever beam.

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