Fully Differential Actuation and Sensing in Piezoelectric Diaphragm Resonators for High Signal to Background Resonant Sensing

We report a successful realization of a self-actuating and self-sensing piezoelectric diaphragm resonator for sensing applications with high signal to background ratio (SBR). A fully differential electrode topology is designed for actuation of the diaphragm in the first flexural mode, and for simultaneously sensing the resulting vibrational response. The electrical (sense) outputs from the resonator (of radius
$1000~\mu \text{m}$
and thickness
$25~\mu \text{m}$
) in two different experimental arrangements — partial differential and fully differential — are compared with the mechanical vibration response obtained from a laser Doppler vibrometer. The effect of poling on electrical crosstalk for the fully differential operation is investigated. The resonator suffers from electrical crosstalk even in fully differential operation when characterized without poling the PZT thin film. The sense output from the resonator after poling, when actuated using a differential electrical input of 0.5 Vpp, is measured both in-air and in liquids of different densities. In the self-sensing mode, the peak output from the device at the first flexural mode resonance is 2-3 mV in different density liquids and ~9 mV in air. The resonator is also characterized as a resonant sensor for liquid density measurements. The sensitivity of the device is found to be 11.9 Hz/(kg/m
³
). The corresponding sensitivity in parts per million is calculated to be ~454 ppm/(kg/m3) with the resonance frequency in DI water (26.3 kHz) as the reference. [2020-0137]