Layer guided surface acoustic wave sensors using langasite substrates

The use of acoustic wave sensors for industrial applications is widespread. At present there are few sensors for assessing fluid properties which are capable of operating at temperatures in excess of 500degC. In this work we present surface acoustic wave devices fabricated on Langasite substrates as possible candidates for such sensors. Two port delay line devices are produced and investigated in terms of temperature and their ability to measure viscosity-density properties of liquids. Single port resonator devices are fabricated and a polymer guiding layer applied to enhance sensitivity. A sharp resonance is seen for a guiding layer thickness of 4.2 mum and the mass sensitivity is assessed by depositing layers of gold onto its surface. This sensitivity is found to 749 Hzmiddotng
^-1
middotcm
^-2
which is several orders of magnitude higher that that for a thickness shear mode device produced on the same substrate. By further developing these devices with particular focus on the reflector arrangement on the single port resonator devices, highly sensitive sensors for temperatures in excess of 900degC may be produced which will be suitable for use with automated data processing.