Lateral-field-excited (LFE) bulk acoustic wave sensors on langasite working on different operational modes are investigated and compared. Langasite LFE sensors on pure-LFE mode and pseudo-LFE mode are designed and fabricated. The sensitivities of the devices to changes in liquid electrical properties (e.g., conductivity or permittivity) and micro-mass changes on their surfaces were tested and compared. The experimental results show that compared with langasite pure-LFE devices, langasite pseudo-LFE devices have superior sensitivities to both liquid conductivity and liquid permittivity changes. For the micro-mass changes, the pure- LFE devices showed high sensitivity, whereas the pseudo-LFE devices do not, because they cannot resonate in air. On this basis, the physical interpretation of these results is discussed.
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