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Dissertation
Three degrees of freedom weakly coupled resonators used for mass measurement.
Authors: --- --- --- --- --- et al.
Year: 2016 Publisher: Liège Université de Liège (ULiège)

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Abstract

Objectives :
A three degrees of freedom (DOF) resonator was designed to measure stiffness perturbation. The task assigned to this master thesis was to study the existing chips and to create models in order to represent their response to tiny mass perturbation (virus, bacteria, ...). Based on those models, techniques to quantify mass perturbation will be proposed.

Modelization and measurement strategy :
Four modelized systems were characterized using the eigenvalue method. Those four systems are 2DOF and 3DOF, each of them with and without damping. The types of information obtained with those models are the resonant frequencies and the amplitude of mass movement in function of frequency.
In order to simulate the behavior of the MEMS (frequency response and time domain simulations), an electrical model was derived from the mechanical model. Since the values of the components are not common values that can be bought, it was necessary to adapt them to build the circuit by a scaling process. A huge drawback of RLC circuits is that they cannot have as high a quality factor as MEMS. That is why quartz crystals were used instead of RLC components.
Based on modelization process results, three main strategies to measure mass variation were investigated : frequency shifting, amplitude variation and amplitude ratio variation.

Conclusion :
Based on the different models, it is clear that MEMS are used for their very high Q factor. The quartz model has shown that complex coupled mechanical systems can be realized by using smaller systems electrically coupled. It was also proved that 3DOF systems have a better sensitivity than 2DOF but still have low sensitivity around no perturbation. At the end of the project, the MEMS was turned into a sensor by adding a feedback loop.


Book
Development of CMOS-MEMS/NEMS Devices
Authors: ---
ISBN: 3039210696 3039210688 Year: 2019 Publisher: MDPI - Multidisciplinary Digital Publishing Institute

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Abstract

Micro and nano-electro-mechanical system (M/NEMS) devices constitute key technological building blocks to enable increased additional functionalities within Integrated Circuits (ICs) in the More-Than-Moore era, as described in the International Technology Roadmap for Semiconductors. The CMOS ICs and M/NEMS dies can be combined in the same package (SiP), or integrated within a single chip (SoC). In the SoC approach the M/NEMS devices are monolithically integrated together with CMOS circuitry allowing the development of compact and low-cost CMOS-M/NEMS devices for multiple applications (physical sensors, chemical sensors, biosensors, actuators, energy actuators, filters, mechanical relays, and others). On-chip CMOS electronics integration can overcome limitations related to the extremely low-level signals in sub-micrometer and nanometer scale electromechanical transducers enabling novel breakthrough applications. This Special Issue aims to gather high quality research contributions dealing with MEMS and NEMS devices monolithically integrated with CMOS, independently of the final application and fabrication approach adopted (MEMS-first, interleaved MEMS, MEMS-last or others).]

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