A mass-loading effect LiNbO3 SAW sensor

A mass-loading effect SAW sensor with a quadrate (3mm×3mm) mass-loading effect groove is presented. Its input and output IDTs have 40 pairs and 60 pairs of aluminum electrodes respectively. A photoresist layer is covered on the surface of LiNbO₃ substrate to protect the aluminum electrodes and to construct the quadrate groove in the center of the sonic path. The tiny loading mass in this groove leads into a tiny center frequency shift of the SAW sensor. The loading mass density can be obtained from the frequency shift and the sensitivity curve. This kind of SAW mass-loading effect sensor can be used in direct measurement and dual SAW sonic path comparative measurement. The input and output IDTs can be worked in direct mode and oscillator mode connected with a high gain wide band amplifier. The testing results show that this mass-loading effect sensor possesses a better sensitivity (S=21.2ng/ppm*cm² in direct sensing and S=3.82ng/ppm*cm² in comparative sensing) and a higher linearity (δ = Δ/Sav = 3.1%) than the previous report[3].