Internal Resonance Mismatch-Controlled Dissipative Bistability Collapse in Coupled Micromechanical Oscillators.

Nonlinear resonance governs the stability boundaries of high-Q micromechanical systems, but the collapse of Duffing bistability is usually limited by fixed intrinsic dissipation. Here we demonstrate internal resonance mismatch-controlled dissipative bistability collapse (DBC) in serially coupled micromechanical oscillators. By independently tuning an antiphase internal mode near a 1:2 internal resonance with a driven rotational mode, we activate a nonlinear energy-transfer pathway without directly changing the drive strength. Frequency responses and frequency-mismatch maps show that the high-amplitude Duffing branch collapses within a finite mismatch window around the near-zero internal-resonance condition, accompanied by a sharp downshift of the jump frequency and an approximately 80% reduction in stored vibration energy. Phase-resolved measurements reveal that the internal-mode resonance separates two phase domains, indicating a mismatch-controlled change in how internal-mode feedback is projected onto the driven-mode dynamics. Near the DBC transition, strong internal-mode excitation coincides with a favorable dissipative phase projection, maximizing phase-weighted internal-resonance feedback. Effective damping extraction and energy-balance modeling further show that the collapse is caused by the rapid growth of the internal resonance mediated dissipative contribution, rather than by intrinsic damping alone. These results establish internal resonance mismatch as an independent control axis for nonlinear dissipation engineering and reconfigurable micromechanical switching.