ABSTRACT
Actually, it is a challenge to optimize NEMS mass sensors in order to achieve high resolutions. Although the linear design optimization and mechanical transduction gain of the devices have been thoroughly studied, the drive power has always been a priori limited by the onset of nonlinearities. Indeed, driving the
cantilever at large oscillation amplitude leads to better signal to noise ratio (SNR) and, thus, simplifies the design of the electronic feedback loop. However, doing so in the nonlinear regime reduces the sensor performances since the frequency instability of a nonlinear resonator is proportional to its oscillation amplitude. Moreover, even when NEMS resonators are used as oscillators in closed-loop, a large part of noise mixing (Kaajakari et al., 2005b) due to nonlinearities drastically reduces their dynamic range and alters their detection limit. NEMS cantilevers are promising candidates for the new generation of physical, chemical and biological sensing. One reason for this is that they are commonly said to have a very large linear dynamic range compared to clamped-clamped nanoresonators, without any formal proof, quantitative comparison, or thorough study. Models for doubly clamped beams (Kacem et al., 2009, 2011b) cannot be easily adapted to cantilevers: indeed, their real specificity comes from their complex nonlinear dynamics including geometric and inertial nonlinearities. This partly explains why so little has been done about nonlinear dynamics of electrostatically actuated cantilevers.
