A novel method for monitoring mass-change response of piezoelectric-excited millimeter-sized cantilever (PEMC) sensors

We show that monitoring impedance at a fixed frequency near resonant frequency of a piezoelectric-excited millimeter-sized cantilever (PEMC) sensor provides equivalent measurement as the conventional approach of monitoring resonant frequency. Two sensing experiments are used to validate the proposed approach: density change and detection of a pathogen (E. coli O157:H7). The impedance approach is feasible because PEMC sensors exhibit modest Q-values of 30–60 at ∼900 kHz and typical biosensing response falls well below 5 kHz, a frequency band near resonant frequency where impedance is a linear function of frequency. The simpler impedance approach lends itself to high throughput applications where large number of sensor responses is to be monitored simultaneously.