Lateral Field Excited Acoustic Wave Devices: A new Approach to Bio-Interface Sensing

10 MHz AT-cut quartz crystals have been excited by placing two electrodes on one crystal surface. An electric field is generated, which is not only laterally confined in the plane of the quartz crystal disk, but also penetrates into the medium adjacent to the opposite bare sensor surface. Due to the mechanical and electrical nature of medium-sensor-interaction, access to additional physical material parameters is anticipated. Up to now the influence of an adjacent medium´s electrical and mechanical property changes on the sensor response has not been examined in detail for Lateral Field Excited (LFE) sensors. In order to determine these influences, the sensor impedance spectrum has been investigated while the sensor was exposed to liquid acoustic loads exhibiting varying permittivity and conductivity. The associated results will be discussed in terms of reorganization of the electric field distribution within the quartz.