Surface acoustic wave sensor for liouid-phase application

The surface acoustic wave with shear horizontal polarized displacement (SH-SAW) sensor fabricated on the 36YX.LiTO3 crystal can measure both mechanical and electrical properties in liquid without any selective films. Especially, the electrical characteristics of the liquid (permittivity and conductivity) can be detected at a high sensitivity because of the high electromechanical coupling coefficient of the substrate. In the fields such as food, medicine and environment, the development of the small sensor is desired which can measure characteristics of the liquid. The SH-SAW sensor satisfies such demand, which we have investigated since 1987. In this report, the detection principles and measurement examples are described. As application examples, enzyme-immobilized biosensor, liquid identification (taste sensor), and identification of ion species by using flow sensing system are presented.