Flexural plate wave sensors with buried IDT for sensing in liquids

Aluminum nitride (AlN) based flexural plate wave (FPW) sensors with buried interdigital transducers (IDTs) were designed, fabricated, and characterized with respect to their application as sensors operating in liquids. In the proposed device, the IDTs are designed as a buried electrode, and thus, are electrically shielded, enabling full immersion of the sensor into the liquid. The functionality of the proof-of-concept sensors was demonstrated by means of laser Doppler vibrometry and network analyzer measurements in air and water. The fabricated devices showed a mass sensitivity of 240 cm
²
/g for loading with de-ionized water which is in good agreement with the theoretically determined mass sensitivity.