Structural design and analytical study of a new polysilicon tunable microactuator for measurement of different resonance frequencies

Abstract

This paper presents a novel MEMS tunable resonator that draws inspiration from the folded beam structure in its comb drive resonator design. Conventional electrostatic comb-drive resonators commonly employ folded-beam suspensions to achieve linearity and reduce system stiffness. The proposed design incorporates eight zigzag-shaped meander springs to support the comb finger structure, featuring two central anchors. The objective of this design is to introduce zigzag-shaped nested-folded beam suspensions to the comb parts, thereby reducing the tuning voltage and sensor size. The governing equations are provided to calculate the support springs’ stiffness, and a comparative analysis is conducted to evaluate the stiffness of the proposed design against other parameters. The mathematical analysis demonstrates that Zigzag Nested-Folded beams result in a decreased resonance frequency and a softened electrostatic spring under applied DC voltage. The integration of zigzag-shaped nested-folded beam flexures enables MEMS resonator devices to exhibit reduced stiffness, leading to a lower pull-in voltage. The resonator design and simulation are performed using Intellisuite and SolidWorks software. Results indicate that the resonant frequency of the proposed tunable comb-drive resonator, equipped with 26 finger pairs and a movable part displacement of 21 μm, is reduced by 66% from the original frequency of 2.420 kHz when a tuning voltage of 59 V is applied. Simultaneously, the corresponding effective stiffness decreases by 66% from the initial value of 0.72 N m−1. This compact resonator occupies an area of approximately 1.058×278 (μm)2, demonstrating a smaller size compared to previous works.