Surface acoustic wave sensor for liquid-phase application

The surface acoustic wave with shear horizontal polarized displacement (SH-SAW) sensor fabricated on the 36YX.LiTaO₃ 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 fields such as food, medicine and environment, the development of a small sensor, which can measure characteristics of the liquid, is desired. The SH-SAW sensor satisfies such a demand. 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.