Ultrasensitive Sensing via Internal Resonance Induced Frequency Combs in Micromechanical Resonators

Operating microscale mechanical resonators in the nonlinear region has brought up abundant research activities. Among various nonlinear phenomena, internal resonance referring to energy exchange between different vibration modes in a resonant cavity has been theoretically and experimentally demonstrated with a great potential for improving the sensitivity performance compared to conventional frequency modulated resonant sensors. In particular, mechanical frequency combs induced by unstable internal resonance in which time-varying energy transfer between modes occurs, have emerged as alternative candidates for boosting the sensitivity. This work experimentally shows this by 1:6 internal resonance derived frequency comb spacing modulation in micromechanical resonators, revealing more than $30\times $ enhancement in response to temperature change compared to that in a regular resonator counterpart. Based on the nonlinear model developed in this work, the use of 1:6 internal resonance is key to attaining linear dependence of comb spacing against temperature variation. The results show a new paradigm for ultrasensitive sensing schemes. [2025-0036]