Multi-parameter sensing in liquid using a lamb wave based microsensor

The characters of zero anti-symmetric (A₀) and zero symmetric modes (S₀) of Lamb wave sensor loaded with liquid were investigated and compared in the paper. It was found that due to the their different acoustic penetration depths inside the liquid the changes of the surface characteristics of the sensor and the characteristics of liquid near the surface can be identified respectively by combined A₀ and S₀ modes simultaneously. At the same time, the mass sensitivities of both A₀ mode and S₀ mode of a 2 mum Lamb wave sensor were demonstrated experimentally. It was proved that S₀ mode has higher sensitivity to surface mass changes and the mass sensitivity of the acoustic sensor can be improved further.