An asymmetric mode-localized mass sensor based on the electrostatic coupling of different structural modes with distributed electrodes

Mode-localized sensor with amplitude ratio as output metric has shown excellent potential in the field of micromass detection. In this paper, an asymmetric mode-localized mass sensor with a pair of electrostatically coupled resonators of different thicknesses is proposed. Partially distributed electrodes are introduced to ensure the asymmetric mode coupling of second- and third-order modes while actuating the thinner resonator by the distributed electrode. The analytical dynamic model is established by Euler–Bernoulli theory and solved by harmonic balance method (HBM) combined with asymptotic numerical method (ANM). Detailed investigations on the linear and nonlinear behavior, critical amplitude as well as the sensitivity of the sensor are performed. The sensitivity of the proposed sensor can be enhanced by about 20 times compared to first-order mode-localized mass sensors. By exploiting the nonlinearities while driving the device beyond the critical amplitude for the in-phase mode, the sensor performs a great improvement in sensitivity up to 1.78 times compared to linear case. The influence of the coupling voltage on the sensor performance is studied, which gives a good reference to avoid mode aliasing. Moreover, the effect of the length of driving electrode on sensitivity is investigated.