Contactless electromagnetic switched interrogation of micromechanical cantilever resonators

Abstract

A principle for contactless interrogation of passive micromechanical resonator sensors is proposed, in which an external primary coil is electromagnetically air-coupled to a secondary coil connected to a conductive path on the resonator. The interrogation periodically switches between interleaved excitation and detection phases. During the excitation phase the resonator is driven into vibrations, while in the detection phase the excitation signal is turned off and the decaying oscillations are contactless sensed. The principle advantageously avoids magnetic properties required to the resonator, thereby ensuring compatibility with standard microfabrication processes. Results are reported on the successful implementation on a MEMS SOI microcantilever resonator working as a mass sensor for which the deposition and evaporation of a water droplet have been detected.