Abstract
Electrostatic MEMS transducer driven by repulsive force is an attractive possibility and has advantages of avoiding the pull-in instability, tuning the natural frequency, and achieving high sensitivity by applying high enough voltages. In this work, a “T”-shaped beam, which is formed by attaching a secondary beam perpendicular to a primary cantilever at the tip, is introduced and its nonlinear dynamics is analyzed. A reduced-order model is derived from mode shapes formed from electromechanical coupling effects respectively. Generalized forms of forced Mathieu equation of motion are derived, and then, dynamic behaviors are investigated through the theory of multiple scales. The resonant responses, including both primary and principal parametric resonances, reveal softening behavior originating from quadratic and cubic nonlinearities in the governing equation. The behavior of the T-beam is compared with traditional cantilever structure. The resonance under repulsive force demonstrates that the T-beam has several advantages over a traditional cantilever: Lower natural frequency but higher resonant responses can improve the signal-to-noise ratio; with an attached micropaddle, the T-beam has a larger surface for absorption of targeted analytes for mass sensing. We conclude that an electrostatic MEMS resonator with a “T”-shaped beam is potentially appropriate for the new generations of sensors and actuators.
Highlights
Capacitive sensing and actuation have been the most common method of transduction in MEMS transducers for the past few decades [1,2,3]
We introduce a MEMS resonator that uses a “T”-shape beam driven by repulsive force, of which the first advantage is to avoid pull-in instability; high enough voltages can be applied to the MEMS system to tune the center frequency
We investigate the feasibility of using repulsive electrode configuration to build a MEMS gas sensors
Summary
Capacitive sensing and actuation have been the most common method of transduction in MEMS transducers for the past few decades [1,2,3]. Larger surface area makes it possible for more molecules to adhere to the microstructure and more significant change in the mass and resonance frequency. We study the statics and dynamics of a gas sensor that employs repulsive electrode configuration. Because the beam goes further away from the bottom electrode when a DC voltage is applied on the side electrode, the effective gap between the moving and bottom electrodes increases [8] This provided more room for the vibration of the microstructure enabling it to have large stroke motion [8, 10, 22].
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