Ultralow Loss Torsion Micropendula for Chipscale Gravimetry

We explore a new class of chipscale torsion pendula formed by Si_{3}N_{4} nanoribbon suspensions. Owing to their unique heirarchy of gravitational, tensile, and elastic stiffness, the devices exhibit damping rates of ∼10  μHz and parametric gravity sensitivities near that of an ideal pendulum. The suspension nonlinearity can also be used to cancel the pendulum nonlinearity, paving the way toward fully isochronous, high Q pendulum gravimeters. As a demonstration, we study a 0.1 mg, 32 Hz micropendulum with a damping rate of 16  μHz, a thermal acceleration sensitivity of 2×10^{-9}g_{0}/sqrt[Hz] (g_{0}=9.8  m/s^{2}), and a parametric gravity sensitivity of 5  Hz/g_{0}. We record Allan deviations as low as 2.5  μHz at 100 seconds, corresponding to a bias stability of 5×10^{-7}g_{0}. We also demonstrate a 100-fold cancellation of the pendulum nonlinearity. In addition to inertial sensing, our devices are well suited to proposed searches for new physics exploiting low-loss micro- to milligram-scale mechanical oscillators.