Displacement Measurement With a Self-Sensing MEMS Electrostatic Drive

This letter outlines a simultaneous actuation and displacement sensing technique applied to a microelectromechanical system (MEMS) electrostatic drive. Using the same electrostatic drive for both actuation and sensing allows more die space to be dedicated to the electrostatic drive, increasing the effective transduction efficiency of both functions and simplifying the mechanical design. Displacement sensing is performed with capacitive measurement implemented by incorporating the drive into an LC oscillator. This provides the mapping from displacement-to-capacitance to frequency-to-voltage. The technique was applied to a MEMS nanopositioner and the sensor exhibited no dynamics over the bandwidth of the device. The sensitivity of the sensor was 0.7551 V μm^-1 and had a displacement noise floor of 0.00836 nm_rms/√Hz.