Nonlinear dynamics of in-plane ring resonator for mass sensing

Mass sensing using MEMS is crucial for detecting minute changes in mass with high sensitivity, enabling applications in environmental monitoring, medical diagnostics, and chemical detection. However, fluid damping in these environments is relatively high and can lead to reduction of the quality factor and sensitivity of these sensors. In this paper, we present a rotating ring resonator for mass sensing applications and investigate its nonlinear dynamics and bifurcation. The ring is supported by four slender beams and subjected to rotational base excitation. The shift in the nonlinear bifurcation point on the frequency response curve is used for mass sensing, which is significant because the device exhibits multiple nonlinear bifurcation points. The structure is designed and modelled to vibrate in a rotational in-plane mode, to provide lower damping and higher quality factor compared to cantilever-based mass sensors that operate in a translational out-of-plane mode. Moreover, the structure exhibits nonlinear resonance zones within the super harmonic regime, enabling mass detection at a particular fraction of the primary resonance zone. At lower excitation amplitudes, the linear response dominates, and the device also allows mass detection in the linear regime via resonance frequency shifts.