In-liquid characterization of high order out-of-plane modes in piezoelectric square plates

In this work, we study the modes of vibration for various aluminium nitride-actuated square microplates. We combine electrical and optical techniques to fully characterize the modes of vibration in different media, with special attention to the modes with the highest quality factor. An electronic speckle pattern interferometry technique is used for a full 3D detection of the movement of the microplates, allowing a precise identification of the modal shape, even under liquid immersion. The electrical characterization was carried out with an impedance analyser. Quality factors as high as 6700 were obtained in vacuum, and as high as 155 in isopropanol, for a high order out-of-plane mode. The effective excitation of these modes is made possible by a proper design of the electrode layout.