A SAW immunosensor for operation in liquid using a SiO2 protective layer

The key to accessing the full potential of surface acoustic wave (SAW) sensors in liquid environments lies in a protection of the necessary electrode structures. In this work, we present a combination of a SiO2 protective layer on LiTaO3 substrate and an inductively coupled SAW device. For efficient insulation, the layer thickness has to be of the order of the acoustic wavelength. Thus, perturbation of the acoustic surface wave occurs and therefore the influence of the protective layer thickness on the acoustic wave parameters has been calculated. By choosing a suitable layer thickness, successful application in aqueous solutions is possible. As a promising application immunosensing capabilities are demonstrated.