Improving Sensitivity of Resonant Sensor Systems Through Strong Mechanical Coupling

This paper reports on the first use of strongly coupled microresonators to improve the sensitivity of resonant sensing systems. To date, the research on coupled resonant sensors has concentrated on weakly coupled systems, which rely on the measurement of signal amplitudes. Strongly coupled resonant sensor systems, on the other hand, provide a frequency-shift output that results in improved accuracy, precision, and dynamic range. A system model is developed to investigate the effect of perturbations on the eigenvalues of resonator arrays. The model is used to study the system sensitivity to perturbations as the coupling strength between the resonators is increased and demonstrates a multi-fold increase in sensitivity for strong coupling. The developed theory is employed to design strongly coupled resonant sensor systems. Proof-of-concept devices were fabricated in a custom microfabrication process that allowed for inclusion of piezoresistors on structural layers. Experimental results were used to validate the theoretical model and demonstrated an improvement of more than 20% in sensitivity with moderate coupling ratios. This paper lays the foundation for the design of strongly coupled resonant sensor systems for single or multiple measurands. [2015-0186]