Sensitivity of a Lamb wave sensor with 2 microm AlN membrane

Area of Science:

• Materials Science
• Sensor Technology
• Acoustic Wave Devices

Background:

• The anti-symmetrical Lamb wave mode A0 offers high sensitivity to mass loading and minimal attenuation in liquids.
• Achieving high mass sensitivity in such sensors is contingent upon utilizing thin piezoelectric membranes.
• Existing sensors face challenges with temperature sensitivity, complicating accurate mass measurements.

Purpose of the Study:

• To develop a highly sensitive mass-loading sensor using thin piezoelectric membranes.
• To investigate the feasibility of using aluminum nitride (AlN) for fabricating these membranes.
• To address and mitigate the temperature sensitivity issue in acoustic wave sensors.

Main Methods:

• Fabrication of a 2-micrometer thick aluminum nitride (AlN) piezoelectric membrane.
• Utilizing the anti-symmetrical Lamb wave mode (A0) for mass detection.
• Implementing a dual-wave propagation design with perpendicular directions on the same membrane to differentiate temperature effects.

Main Results:

• The fabricated AlN membrane demonstrated a mass sensitivity of 200 cm²/g when in contact with a fluid.
• Experimental results showed distinct temperature sensitivities for different wave propagation directions.
• Mass sensitivity remained consistent across different propagation directions, enabling effective decoupling of mass and temperature influences.

Conclusions:

• Thin AlN piezoelectric membranes are effective for high-sensitivity mass loading detection in liquids.
• The proposed dual-wave propagation method successfully distinguishes mass loading from temperature variations.
• This approach enhances the practical applicability of acoustic wave sensors in environments with fluctuating temperatures.