Generation of Electromechanical Frequency Combs in Fluid Media with a Parametrically Driven Capacitive Microresonator

The generation of electromechanical frequency combs in both air and liquid environments using a capacitive microresonator array is presented in this paper. In contrast to frequency-comb generation in purely mechanical resonators, we show that the damping-dependent threshold for comb generation can be reduced by parametrically coupling a resonant electrical circuit to the mechanical resonator. A one-dimensional lumped parameter model of the proposed system is presented and semianalytical solutions are developed to investigate the parameters influencing frequency-comb formation under various oper-ating conditions. The results obtained with numerical simulations are experimentally validated using a commercially available microelectromechanical resonator, and frequency combs with a repetition rate sensitive to the force on the mechanical resonator are generated with a single electrical drive in air and in a liquid-filled microfluidic channel. In contrast to prior work on electromechanical frequency combs, this work represents a simple yet robust approach to generating stable combs, thereby enabling its practical use in applications, such as gas sensing and microfluidics.