Pseudo-LFE sensors with different electrode configurations on X-cut LiNbO3

In the present study, several 4.5 MHz X-cut LiNbO₃ LFE devices working on pseudo-LFE mode with different electrode configurations, including the dual-gap electrode, single-turn Archimedes spiral electrode, and two-turn symmetric spiral electrode, were fabricated and tested. Two common single-gap electrode LFE devices with different gap distance are also fabricated for comparison. All devices were tested in glycerol-water and isopropanol-water solutions and their resonant frequencies were recorded and analyzed. The result shows that the pseudo-LFE devices with the dual-gap electrode, single-turn Archimedes spiral electrode, and two-turn symmetric spiral electrode have a much higher sensitivity to the permittivity change of liquid than single-gap electrode LFE device. Theoretical analysis for these phenomena is given.