Experimental Verification of Coupling Strength on the Mode-Localization in Single MEMS DETF Resonators and Its Application as a Force Sensor

This article presents an experimental verification of the mode-localization effect between the two tines of a single double-ended tuning fork (DETF) microelectromechanical systems (MEMS) resonator and its application in measuring forces in the micro-Newton range. The two tines of a DETF resonator are considered as individual resonators while coupling strength is tuned through a tines gap, which enables the DETF to operate either in two modes operational region or a modal overlap regime. Finite element method (FEM)-based simulations of DETF structures are performed to analyze the effect of the tines gap on mechanical coupling strength that shows the inverse relation. The DETF resonators with three different tine gaps of 20, 40, and 60 \, \mu m are experimentally evaluated and an open-loop frequency response is obtained. The experimental results show that two fundamental flexure modes occur at 41.7 and 42.75 kHz for 20 \, \mu m, 42.55 and 43.05 kHz for 40 \, \mu m, and a single mode at 44 kHz for 60 \, \mu m tines gap. This shows the operating region shift from two modes to a modal overlap operating region as the tines gap widens. The potential application of a single DETF as a force sensor has been investigated through experimental measurements, and the results revealed higher sensitivity, resolution, and dynamic range for a single-mode operating region.