Mass sensor using mode localization in two weakly coupled MEMS cantilevers with different lengths: Design and experimental model validation

This paper presents a sensor using the mode localization phenomenon to detect a mass perturbation. It is composed of two cantilevers with different lengths and connected by a coupling beam. The short cantilever is electrostatically actuated and by changing the applied DC voltage, we can reduce its stiffness and reach the veering point, which corresponds to a balanced system. This principle allows us to overcome the manufacturing defect which perturbs the initial system. An analytical model using the Euler-Bernoulli beam theory is developed for the design. The equation of the continuous system is discretized with the Galerkin method and simulations are performed. The designed device composed of polysilicon coupled microbeams is then fabricated with the Multi-User MEMS Processes and an experimental investigation is carried out. Three devices with different coupling are considered with a length ratio of 0.98. This ratio is suitable to reach the veering point by using a DC balancing voltage around the half of the pull-in voltage. The comparison between theoretical and experimental results shows a good agreement for each device. (C) 2019 Elsevier B.V. All rights reserved.