Compliant Parallel Motion Linkage Amplification Mechanism for Resonant Force/Acceleration Sensing

We report on the theoretical and experimental feasibility study of a resonant sensing device implementing a compliant, parallel linkage-type, force amplification architecture. The work is motivated by the development of resonant sensors and, particularly, of vibrating beam accelerometers (VBAs). A beam-type resonator is clamped at its two ends to two proof masses, each attached to the substrate using two links with pseudohinges. Due to the offset between the hinges, the links effectively operate as oblique linkages, allowing in- plane, parallel to the substrate, motion of the masses and resulting in significant amplification of the forces transferred by the masses to the resonator. This single-layer device of a simple, manufacturable, Manhattan geometry is distinguished by low parasitic compliance and allows an axial, lacking any bending, loading of the resonators. The design parameters and performance estimates of the devices are obtained using simple lumped reduced order (RO) models, combined with a detailed finite element (FE) analysis. The devices, fabricated from silicon-on-insulator (SOI) wafers were open-loop, operated in ambient air; the acceleration was emulated by applying an appropriately scaled electrostatic force acting on the masses and provided by gap-closing electrodes. A sensitivity of ≈2.1 Hz/V2 or ≈300 Hz/g, in the case of a nondifferential measurement and ≈4.39 Hz/V2 in case of a differential measurement, was registered in the experiments, consistently with the models' predictions. Our results indicate that the suggested architecture can be implemented for high-end robust inertial sensors.