Casimir-driven Parametric Amplification of a MEMS Accelerometer*

In this work, we use the gradient of the attractive Casimir interaction existing between an Au-coated silicon plate and an Au-coated microsphere bonded to the proof mass of a commercial MEMS capacitive accelerometer to modulate the effective spring constant of the MEMS proof mass. By modulating this system parameter, the accelerometer output at resonance can be greatly amplified or de-amplified depending on the frequency and phase of modulation. The extraordinary distance dependence of the Casimir force (1/r³ for a sphere-plane geometry) leveraged with the parametric amplification results in a system capable of resolving sub pm changes in sphere-plate separation or sub pN changes in force. On top of that, the robust built-in signal processing in the MEMS circuitry provides low noise density of ~fN/√Hz. Such a highly sensitive device allows for further investigation into the not yet fully understood physics of Casimir cavities and also provides a versatile platform for conducting a variety of quantum metrology experiments.