Ultrabroadband Microresonators with Geometrically Nonlinear Stiffness and Dissipation

In the areas of micro- and nanoresonant sensing, energy harvesting, and signal processing, the ability to provide resonance over a broad frequency bandwidth is a persistent goal. One strategy for a broadband resonator that researchers focus on is to exploit the relatively large-amplitude response of micro- and nanoresonators operating in the geometrically nonlinear dynamic regime. Geometric nonlinearity is well known to have a hardening effect on the resonance curve, thereby generating a broadband resonance, the bandwidth of which is limited by the linearized resonant frequency (lower bound) and the drop-down bifurcation frequency (upper bound). With everything else kept constant, increasing the drop-down bifurcation frequency in the frequency response of a nonlinear resonator enhances the broadband resonance. Here, the ultrabroadband resonance of microresonators with geometrically nonlinear stiffness is investigated and validated experimentally. Specifically, a microresonator with a cubic stiffness nonlinearity is excited at its base and, as the excitation amplitude approaches a critical level, a sudden and significant increase in the resonant bandwidth of the fundamental bending mode is observed. The significant implications of this nonlinear phenomenon in sensing, signal processing, and other applications at the microscale are discussed.