Comb-Drive Over Plate-Drive: A Superior Force-to-Damping Ratio Unlocking High-Performance Electromagnetic-Induction MEMS Magnetometers

To identify a more cost-effective electrostatic actuation method for a high-performance MEMS magnetometer with electromagnetic-induction sensing, this study compares the performance differences of MEMS magnetometers with electrostatic parallel-plate and comb structures. Both MEMS magnetometers share an identical resonance architecture, which is coupled by two long beams operating at the opposite motion mode along the direction perpendicular to the long beam. Through theoretical analyses and experimental tests of the two-type devices under atmospheric and low-pressure environments, it is found that comb driving has a superior force-to-damping ratio and hence facilitates the realization of low power consumption, high sensitivity and high resolution for the electromagnetic-induction MEMS magnetometer. Especially under the atmosphere, the measured sensitivity and resolution of the comb-type device (∼135.2 mV/mT, ∼8.2 μT) are around 12.5 times higher than that of the plate-type (∼10.8 mV/mT, ∼107 μT) at the same driving voltages (Vd=15 V,Va=1 V). Under the ∼30-Pa environment, the comb-type device holds on to its favorable position (∼1.5 fold) in the sensitivity and resolution (∼39.7 mV/mT, ∼5.5 μT) compared with the plate-type (∼27.1 mV/mT, ∼8.4 μT) at the same driving voltages (Vd=15 V,Va=25 mV). Wherein the plate-type device reaches its ultimate performance under the linear resonance state. By contrast, the comb-type device has a wider linear resonance range (Vd=15 V,Va=100 mV), whose sensitivity and resolution are improved to ∼162.8 mV/mT and ∼1.3 μT. Overall, these findings not only highlight comb driving as an advantageous choice but also provide optimization instructions for electromagnetic-induction MEMS magnetometers.