Wireless sensor concepts

Surface and bulk acoustic wave (SAW and BAW) devices are suitable as passive wireless sensor elements, called SAW transponders or BAW sensors, for measuring physical quantities e.g. temperature, pressure or specific bio molecules even in liquids. But the sensitivity of the resonance frequency in liquids depends on the polarization of the acoustic wave and therefore shear wave polarizes surface or bulk acoustic waves are respectively needed. In the recent years different kinds of approaches of SAW transponders for sensor applications were published mainly based on piezoelectric materials designed for filter applications with longitudinal wave polarizations e.g. Rayleigh waves for SAW transponders or longitudinal waves for BAW sensors. A new approach is presented designing adapted piezoelectric materials with Metal-Organic-Vapor-Phase-Epitaxy (MOVPE) especially for sensor application and therefore with shear wave polarization of the acoustic waves in this work.