Impedance change as an alternate measure of resonant frequency shift of piezoelectric-excited millimeter-sized cantilever (PEMC) sensors

We establish that monitoring impedance at a fixed frequency near the initial resonant frequency of piezoelectric-excited millimeter-sized cantilever (PEMC) sensors is superior than using resonant frequency or impedance measurements at resonance for monitoring sensor response. Density change experiments were conducted and the three monitoring approaches were compared with respect to the obtained signal, noise level and signal-to-noise ratio. Monitoring impedance at fixed frequency approach exhibited a significantly larger response and superior signal-to-noise ratio than resonant frequency or impedance at resonant frequency monitoring approaches. The impedance approach is simpler compared to the conventional resonant frequency monitoring method and is effective for applications that require simultaneous monitoring of multiple sensors.