Force balanced chip scale gravimeter achieving record low self noise of 0.1 μGal/√Hz

Abstract

Micro-electro-mechanical systems (MEMS) gravimeters are emerging as promising next-generation tools to overcome the high costs and large dimensions of conventional gravimeters. However, persistent sensitivity limitations have hindered their practical adoption. This paper presents a pioneering force-balanced MEMS gravimeter with enhanced sensitivity, achieved using quasi-zero-stiffness (QZS) springs and an arrayed capacitive displacement sensor. A novel two-step tuning method, combining saturated-ions enhanced lateral plasma thinning and thermo-mechanical coupling, precisely adjusts the QZS state and attains optimal sensitivity in displacement transducers, successively. The gravimeter achieves a resonant frequency of 0.6 Hz and a self-noise of 0.1 μGal/√Hz at 0.14 Hz, setting a new benchmark for MEMS gravimeters. To address bandwidth constraints imposed by the ultra-low resonant frequency, an electromagnetic feedback control module is introduced, expanding the bandwidth to 108 Hz. A 45-day Earth tide observation demonstrated a residual standard deviation of 2.3 μGal, reflecting exceptional long-term stability. This MEMS gravimeter breaks through sensitivity and bandwidth barriers, offering a compact, cost-effective solution for next-generation gravimetry.