  We investigate the dynamics of a microelectromechanical (MEMS) self-sustained
oscillator supporting multiple resonating and interacting modes. In particular,
the interaction of the first four flexural modes along with the first torsional
mode are studied, whereby 1:2, 1:3, and 2:1 internal resonances occur. Even and
odd modes are induced to couple by breaking the longitudinal symmetry of the
structure. Self-oscillations are induced in the second flexural mode via a
gain-feedback loop, thereafter its frequency is pulled into a commensurate
frequency ratio with the other modes, enabling the oscillator to act as a
driver/pump for four modes simultaneously. Thus, by leveraging multiple
internal resonances, a five modes frequency-locked comb is generated.
