Overcoming limitations of nanomechanical resonators with simultaneous resonances

Dynamic stabilization by simultaneous primary and superharmonic resonances for high order nonlinearity cancellation is demonstrated with an electrostatically-actuated, piezoresistively-transduced nanomechanical resonator. We prove experimentally how the combination of both the third-order nonlinearity cancellation and simultaneous resonances can be used to linearly drive a nanocantilever up to very large amplitudes compared to fundamental limits like pull-in occurrence, opening the way towards resonators with high frequency stability for high-performance sensing or time reference

Sensitive detection of nonlinear nanomechanical motion using capacitive signal down-mixing for resonant NEMS-based sensors

International audienceNanoelectromechanical systems (NEMS) are emerging as strong candidates for a host of important applications in semiconductor-based technology and fundamental science. At this level of miniaturization, the electric characterization of capacitive NEMS is a challenge. In fact, the high-frequency signals are normally cut off due to the limited bandwidth of the readout circuitry dominated by stray capacitance between the large amplifier and the high impedance tunneling junction. In order to overcome such limitations, some methods have been suggested: using several amplifier stages, inserting an LC resonator, or the scanning tunneling microscopy down-mixing readout technique. Nevertheless, these methods are efficient only at oscillations below the critical amplitude due to nonlinearities which induce noise mixing. In the present paper, a new characterization technique for resonant NEMS based on capacitive down-mixing has been developed and applied to M&NEMS accelerometers. The considered method is highly sensitive and permits a simple tuning of the signal to nonlinearity ratio

From MEMS to NEMS: Modelling and characterization of the non linear dynamics of resonators, a way to enhance the dynamic range

International audienceThe resonant sensing technique is highly sensitive, has the potential for large dynamic range, good linearity, low noiseand potentially low power. The detection principle is based on frequency change that is induced by rigidity changes in theresonator. In order to compensate the loss of performances when scaling sensors down to NEMS, it proves convenient to find physical conditions in order to maximise the signal variations and to push the limits of the linear behavior. To do so, a comprehensive model including the main sources of nonlinearities is needed. In the present paper, a process, characterization methods and above all an original analytical model are presented.Le mode de détection fréquentielle a pour avantages d'être extrêmement sensible, a le potentiel d'avoir une large gamme dynamique, peu sensible au bruit, une large gamme de linéarité et une faible consommation électrique. Le principe de détection est basé sur le changement de la fréquence de résonance induit par une modification de la raideur du résonateur. Afin de compenser la détérioration des performances lorsqu'on réduit les tailles des résonateurs des MEMS au NEMS, il s'avère important de trouver des conditions physiques permettant de maximiser le signal de détection et pousser les limites du comportement linéaire. Pour cela, un modèle complet qui prend en compte toutes les sources principales des non-linéarités est nécessaire. Dans ce papier, un modèle analytique sur la dynamique non linéaire de micro et nanorésonateurs ainsi qu'une validation expérimentale sont présentés

Nonlinear dynamics of nanoelectromechanical cantilevers based on nanowire piezoresistive detection

International audienceThe nonlinear dynamics of in-plane nanoelectromechanical cantilevers based on silicon nanowire piezoresistive detection is investigated using a comprehensive analytical model that remains valid up to large displacements in the case of electrostatic actuation. This multiphysics model takes into account geometric, inertial and electrostatic nonlinearities as well as the fringing field effects which are significant for thin resonators. The bistability as well as multistability limits are considered in order to provide close-form expressions of the critical amplitudes. Third order nonlinearity cancellation is analytically inspected and set via an optimal DC drive voltage which permits the actuation of the NEMS beyond its critical amplitude. It may result on a large enhancement of the sensor performances by driving optimally the nanocantilever at very large amplitude, while suppressing the hysteresis

Nonlinear techniques for wide-bandwidth resonant energy harvesting

International audienceEnergy harvesting from motion is presently receiving great worldwide attention as a means to power autonomous systems. Conventional linear vibration energy harvesters are usually designed to be resonantly tuned to the ambient dominant frequency. They have a narrow operating bandwidth that limits their application in real-world environments where the ambient vibrations have their energy distributed over a wide spectrum of frequencies, with significant predominance of low frequency components and frequency tuning is not always possible due to geometrical/dynamical constraints

Computational and quasi-analytical models for non-linear vibrations of resonant MEMS and NEMS sensors

International audienceLarge-amplitude non-linear vibrations of micro- and nano-electromechanical resonant sensors around their primary resonance are investigated. A comprehensive multiphysics model based on the Galerkin decomposition method coupled with the averaging method is developed in the case of electrostatically actuated clamped-clamped resonators. The model is purely analytical and includes the main sources of non-linearities as well as fringing field effects. The influence of the higher modes and the validation of the model is demonstrated with respect to the shooting method as well as the harmonic balance coupled with the asymptotic numerical method. This model allows designers to investigate the sensitivity variation of resonant sensors in the non-linear regime with respect to the electrostatic forcing

Capteurs résonants M/NEMS et phénomènes non linéaires

Accessible via http://www.bruit.fr/flipbook/AT57/index.html#/10/Les capteurs résonants de type M/NEMS jouent et joueront un rôle essentiel dans les nouvelles technologies. Cependant leur comportement est souvent fortement non linéaire ce qui est préjudiciable à la précision de la mesure exigée. Les résonateurs M/NEMS analysés ont des comportements complexes combinant raidissements, assouplissements, instabilités latérales car régis par des larges déflexions, des excitations paramétriques, des couplages géométrique et électrique. Ces comportements nécessitent une conception soigneuse qui doit s'appuyer sur des modèles les plus simples possibles mais tout en gardant leur pertinence pour modéliser au mieux les différents phénomènes physiques en jeu

Pull-In Retarding in Nonlinear Nanoelectromechanical Resonators Under Superharmonic Excitation

International audienceIn order to compensate for the loss of performance when scaling resonant sensors down to NEMS, a complete analytical model, including all main sources of nonlinearities, is presented as a predictive tool for the dynamic behavior of clamped-clamped nanoresonators electrostatically actuated. The nonlinear dynamics of such NEMS under superharmonic resonance of an order half their fundamental natural frequencies is investigated. It is shown that the critical amplitude has the same dependence on the quality factor Q and the thickness h as the case of the primary resonance. Finally, a way to retard the pull-in by decreasing the AC voltage is proposed in order to enhance the performance of NEMS resonators

Nonlinear phenomena in nanomechanical resonators: mechanical behaviors and physical limitations

International audienceIn order to overcome the loss of performances issue when scaling resonant sensors down to NEMS, it proves extremely useful to study the behavior of resonators up to large displacements and hence high nonlinearities. A comprehensive nonlinear multiphysics model based on the Euler-Bernoulli equation which includes both mechanical and electrostatic nonlinearities in the case of a capacitive doubly clamped beam is presented. This purely analytical model captures all the nonlinear phenomena present in NEMS resonators electrostatically actuated including bistability, multistability which can lead to several physical limitations such as noise mixing, frequency stability deterioration as well as dynamic pull-in. Moreover, close-form expressions of the critical amplitudes and pull-in domain initiation amplitude are provided which can potentially serve for NEMS designers as quick design rules