Balanceable Coupled Piezoelectric NEMS Resonators

This project aims at designing, fabricating and characterising balanceable coupled NEMS resonators, in order to verify a theoretical model. In the field of sensing, coupled NEMS resonators benefit from an immensely increased sensitivity towards changes in mass or in stiffness as compared to single resonators, but they are limited by the fabrication imprecisions, which may yield unbalanced resonators. As mode localisation is crucial to maximise the sensitivity, the fabricated resonators need to be balanceable, which is here to be achieved through the reverse piezoelectric effect, with the application of a direct voltage on one of the clamped-clamped beam resonators. While the mathematical model predicted a large tunability of the resonant frequencies per unit voltage, the fabricated resonators presented a smaller tunability. In fact, it has been discovered that the resonators are bending out of the plane to varying extents depending on the voltage that is applied for tuning, which partially invalidates the mathematical model by introducing a countereffect. Coupled resonators have nevertherless been able to be balanced, in spite of a weaker response to tuning.