Multiple shear wave roundtrips liquid sensor by c-axis parallel oriented ZnO film/silica glass pipe structure

We demonstrated the multiple roundtrips of shear horizontal (SH) waves using IDT/c-axis parallel-oriented (112̅0) ZnO film/silica glass pipe structure for a high-sensitive liquid sensor. Forth roundtrip was observed in the time response of acoustic waves. The insertion loss of the first lap consisted of two frequency components at 131 MHz and 160-350 MHz. IDT/c-axis parallel-oriented ZnO film/silica glass cylinder structure was also fabricated, but multiple roundtrips were not occurred. Therefore, we considered the waves propagating in the pipe structure as plate type waves, not surface acoustic waves. In addition, the liquid loading characteristics of the pipe structure sensor were measured by immersing inside or outside of the pipe in liquid. Because the insertion loss increases in the pipe structure with pure water loading were relatively small, we can conclude that the waves were SH-type plate wave. Liquid property detections using both outside and inside of the pipe structure sensor are expected.