MEMS MULTI-DOF WEAKLY COUPLED RESONATOR BASED ON MODE LOCALIZATION FOR MASS CHANGE SENSING APPLICATIONS

This thesis comprehensively explores the potential of a 3-DOF mode localized weakly coupled resonator. A novel reversible method which exploits the usage of nanoparticles as well quantified mass changes is described. The mass sensitivity of the coupled resonator can be characterized accordingly. It has been demonstrated that a) the resonance amplitude ratio yields a sensitivity to mass changes around two times larger than amplitude change and around two orders of magnitude larger than frequency shift in air and b) nanoparticles as mass perturbation to characterize the MEMS mass sensors is an effective and cost-effective technique. These techniques can contribute to the development of MEMS mass resonant sensor in general.
Further investigations of the capability for 3-DOF coupled resonators have been carried out. A novel mass to stiffness transduction mechanism has been proposed. Hereby, a commercial QCM mass sensor is combined with a 3-DOF mode localized coupled resonator stiffness sensor. This approach can solve the problem that typical micromachined resonators suffer from performance degradation when operated in high damping environments such as air or liquids which results in a low quality factor. Consequently, this contributes an important step towards a practical biochemical sensor that can exploit the advantages of mode localized coupled resonators but works directly in contact with a liquid.
In addition to aforementioned points, this thesis describes several simulation models for the 3-DOF mode localized weakly coupled resonators. MATLAB, SIMULINK, COMSOL and equivalent circuit models are presented, which agree well with practical experiments. Furthermore, multiple device layouts of 3-DOF coupled resonator dedicated for biosensing purposes have been designed. Furthermore, a biochemical surface functionalization process is investigated, which is evolved subsequently to a general operation protocol.
Finally, a 2-DOF mode localized weakly coupled BAW disk resonator is studied, along with the interface electronic circuit and associated instrumentation. This research has the potential to put forward an alternation route for high Q coupled resonators that can operate in a highly damped environment, with the ultimate objective to result in a highly sensitive biosensor.