SAW sensor for liquid chromatography using 2-port resonator

The propagation characteristics of surface acoustic waves (SAW) along a solid surface vary considerably depending on the ambient environment. Therefore, SAW devices are used as sensors in a variety of fields. In particular, surface acoustic waves propagating in the shear horizontal (SH) mode only possess components for which particle displacements are parallel to the surface, which means that, even in a liquid, they propagate without loss of energy. Sensors that utilize such waves are thus suitable for sensing the characteristics of liquids. A flow-type liquid sensor using a 2-port SH-SAW resonator was constructed and used to measure properties, such as electrical characteristics, density and viscosity, of various liquids. Results of measurements using this liquid flow sensing system on a variety of liquids are presented. Finally, this sensing system is demonstrated to be an effective sensor in liquid chromatography, due to its small size, enabling measurement on a very small amount of liquid, and its highly stable operation.