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Project

Ultra-High Performance MEMS Coupled Resonant Sensors Utilizing Its Bifurcation Points For Stiffness Detection Based On Parametric Pumping.

In recent years, interests in MEMS resonators have grown rapidly, thanks to the rapid development of microfabrication techniques, including vacuum packaging processes. MEMS resonators are employed as the key building block in a wide range of applications such as sensors[1]-[4], time references[5,6], and filters[7]-[10]. Among those applications, MEMS resonator-based sensors, such as resonant accelerometers [11]-[13] provide an exciting alternative to the existing capacitive accelerometers. Typically, a single-degree-of-freedom (1-DOF) resonator system is employed as the sensing element; however, it has a limited stiffness sensitivity, as well as a limited common-mode rejection ability. One approach to reach high sensitivity is to operate the resonator at the appropriate vibrational mode[13]. However, the higher-order modes may result in a reduced Q-factor, or a compromised signal-to-noise ratio (SNR). These could potentially diminish the advantages of higher/lower sensitivity. Recently, a new sensing scheme based on coupled resonator system, termed a mode localized sensor has emerged, demonstrating enormous potential in enhancing the sensitivity and common-mode rejection. Compared with the conventional frequency shift based sensing method of 1 DOF resonator, mode-localized sensors measure a drastic eigenstate or amplitude ratio shift, typically, 2-3 orders of magnitude higher than frequency shift [14]– [18]. However, mode localized sensors, still cannot effectively reduce the frequency noise floor, naturally, their stiffness resolution can not meet the high-resolution requirement for high-performance applications. Up to date, rather limited methods exist for enhancing the detection resolution of a MEMS resonator stiffness sensor. Recently, it is reported that mixed (i.e. electrical and mechanical) nonlinear behaviour of a MEMS resonator has been employed to improve the stiffness sensitivity[19]-[23]. However, The Duffing nonlinearity has become a great challenge for the MEMS resonators toward commercialization[23]-[24]. Although several techniques have been introduced to compensate Duffing nonlinearity, the structural fragility makes the inhibition effect not ideal[23]. In addition, modulating the resonator stiffness by parametric pumping can adjust the sensitivity of a resonator effectively[25]. However, the sensitivity depends on the structure itself, and the modal sensitivity of the resonator itself limits the improvement of the sensitivity. Further, the introduced parameter pump source with higher amplitude will result in a compromised SNR. Regarding the stiffness detection resolution, the high SNR effect in the bifurcation points can compensate for the degradation of noise performance induced by the parametric pumping modulation. To sum up, the combination of the Duffing nonlinear effect and the parameter pump of the resonant sensor is of great potential and worth exploring. In the proposed work, for the first time, a novel parametric pump in combination with the nonlinear operating interval in bifurcation points is proposed. The tunable nonlinearity frequency noise reduction based on MEMS resonator with parametric pump will be demonstrated. Parametric pumping should be able to overcome the Duffing nonlinearity by compensating the nonlinear frequency sensitivity meanwhile enhancing the frequency stability. This work will be a key element towards a high-performance sensor in the stiffness detection of physical quantities sensors, such as accelerometers, mass sensors, strain sensors, etc.

Date:29 Sep 2021 →  Today
Keywords:Parametric pump, Weakly-coupled resonators, Sensitivity enhancement, High-resolution, Frequency noise
Disciplines:Micro- and nanoelectromechanical systems
Project type:PhD project