While resonant frequency-based sensors have emerged as a mature technology for detection of miniscule properties in micromechanical systems, an uncompensated resonant frequency variation make such sensors not only sensitive to the measurand, but also to other undesirable perturbations to the system \[1\]. In this work, a novel transduction scheme of a sensor design based on the mode localization phenomena of a weakly coupled resonator system is described. Indeed, researchers have shown that two-weakly coupled, symmetric resonators can improve the sensitivity by more than 2 order of magnitude compared to their SDOF counterpart by measuring the change in the amplitude ratio of the coupled resonators \[2\]–\[4\]. The high sensitivity of weakly coupled resonators is owed to a phenomenon known as eigenvalue veering, wherein two natural frequencies of a system come close as a system parameter (e.g., stiffness) is varied and instead of crossing each other, they veer away. In the so-called frequency veering region, the eigenmodes of the weakly coupled system are highly sensitive to minute parametric changes, thus provide an effective transduction scheme to detect small scale physical quantities. Here, we show that when the weakly-coupled resonator system is highly asymmetric, the system provides two transduction channels: one that is insensitive to perturbations to the system and another that is highly sensitive to external perturbations as shown in Figure 1. The insensitive and sensitive transduction channels are in the forms of a non-varying and varying eigenmode of the dynamic system, respectively and the non-varying eigenmode of the system can be utilized for unambiguous determination of the measurand in a micromechanical sensor. A comprehensive dynamic study of the proposed system is presented. These characteristics of mode localization in a highly-asymmetric weakly-coupled system are valuable for the design and control of other resonator-based sensors. The practical significance of such a system was demonstrated in a previous work through an atomic force microscopy (AFM) cantilever system which consisted of two structurally dissimilar microbeams weakly coupled to each other \[5\]. The importance of the weak coupling of the beams in the proposed AFM probe for the intended functionality is also presented as shown in Figure 2.


A New Multi-Modal Sensing Strategy Based on a Highly-Asymmetric and Weakly-Coupled Resonator System

Division / Sponsors: 
Design Engineering Division and Computers & Information In Engineering Division


Paper Proceedings: https://asmedigitalcollection.asme.org/IDETC-CIE/IDETC-CIE2020/volume/83907

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